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Albertino BIGIANI

Professore Ordinario
Dipartimento di Scienze Biomediche, Metaboliche e Neuroscienze sede ex-Sc. Biomediche


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Pubblicazioni

2023 - Effect of kokumi taste-active γ-glutamyl peptides on amiloride-sensitive epithelial Na+ channels in rat fungiform taste cells [Articolo su rivista]
Bigiani, Albertino; Rhyu, Meera
abstract

Kokumi taste-active compounds enhance salty taste perception. In animal models, sodium (salt) detection is mediated by the amiloride-sensitive epithelial sodium channel, ENaC. This ion channel works as a sodium receptor in the so-called sodium-taste cells. It is not known whether kokumi taste substances are able to affect the activity of functional ENaCs in these cells. Here, we use the patch-clamp technique to study the effect of kokumi-active tripeptides, glutathione (GSH) and γ-glutamyl-valyl-glycine (EVG), on the ENaC-mediated membrane current in rat fungiform sodium-taste cells. GSH and EVG reduced slightly this current and the effect disappeared in the presence of amiloride, a specific ENaC blocker. No effect on membrane current was detected in other taste cells (Type II and Type III cells) that do not express functional ENaC. Our findings suggest that the enhancing effect of kokumi taste-active γ-glutamyl peptides on salt reception is not explained by an increase in the activity of ENaC.


2022 - Changes of the biophysical properties of voltage-gated Na+ currents during maturation of the sodium-taste cells in rat fungiform papillae [Articolo su rivista]
Bigiani, Albertino; Tirindelli, Roberto; Bigiani, Lorenzo; Mapelli, Jonathan
abstract

Taste cells are sensory receptors that undergo continuous turnover while they detect food chemicals and communicate with afferent nerve fibers. The voltage-gated sodium current (INa ) is a key ion current for generating action potentials in fully differentiated and chemo-sensitive taste cells, which use electrical signaling to release neurotransmitters. Here we show that, during the maturation of rat taste cells involved in salt detection (sodium cells), the biophysical properties of INa , such as voltage dependence of activation and inactivation, change significantly. Our results help understand how taste cells gain electrical excitability during turnover, a property critical to operate as chemical detectors that relay sensory information to nerve fibers.


2022 - Long-Term Synaptic Plasticity Tunes the Gain of Information Channels through the Cerebellum Granular Layer [Articolo su rivista]
Mapelli, Jonathan; Boiani, Giulia Maria; D’Angelo, Egidio; Bigiani, Albertino; Gandolfi, Daniela
abstract

A central hypothesis on brain functioning is that long-term potentiation (LTP) and depression (LTD) regulate the signals transfer function by modifying the efficacy of synaptic transmission. In the cerebellum, granule cells have been shown to control the gain of signals transmitted through the mossy fiber pathway by exploiting synaptic inhibition in the glomeruli. However, the way LTP and LTD control signal transformation at the single-cell level in the space, time and frequency domains remains unclear. Here, the impact of LTP and LTD on incoming activity patterns was analyzed by combining patch-clamp recordings in acute cerebellar slices and mathematical modeling. LTP reduced the delay, increased the gain and broadened the frequency bandwidth of mossy fiber burst transmission, while LTD caused opposite changes. These properties, by exploiting NMDA subthreshold integration, emerged from microscopic changes in spike generation in individual granule cells such that LTP anticipated the emission of spikes and increased their number and precision, while LTD sorted the opposite effects. Thus, akin with the expansion recoding process theoretically attributed to the cerebellum granular layer, LTP and LTD could implement selective filtering lines channeling information toward the molecular and Purkinje cell layers for further processing.


2021 - Modeling Neurotransmission: Computational Tools to Investigate Neurological Disorders [Articolo su rivista]
Gandolfi, Daniela; Boiani, Giulia Maria; Bigiani, Albertino; Mapelli, Jonathan
abstract

The investigation of synaptic functions remains one of the most fascinating challenges in the field of neuroscience and a large number of experimental methods have been tuned to dissect the mechanisms taking part in the neurotransmission process. Furthermore, the understanding of the insights of neurological disorders originating from alterations in neurotransmission often requires the development of (i) animal models of pathologies, (ii) invasive tools and (iii) targeted pharmacological approaches. In the last decades, additional tools to explore neurological diseases have been provided to the scientific community. A wide range of computational models in fact have been developed to explore the alterations of the mechanisms involved in neurotransmission following the emergence of neurological pathologies. Here, we review some of the advancements in the development of computational methods employed to investigate neuronal circuits with a particular focus on the application to the most diffuse neurological disorders.


2021 - The effects of the general anesthetic sevoflurane on neurotransmission: an experimental and computational study [Articolo su rivista]
Mapelli, J.; Gandolfi, D.; Giuliani, E.; Casali, S.; Congi, L.; Barbieri, A.; D'Angelo, E.; Bigiani, A.
abstract

The brain functions can be reversibly modulated by the action of general anesthetics. Despite a wide number of pharmacological studies, an extensive analysis of the cellular determinants of anesthesia at the microcircuits level is still missing. Here, by combining patch-clamp recordings and mathematical modeling, we examined the impact of sevoflurane, a general anesthetic widely employed in the clinical practice, on neuronal communication. The cerebellar microcircuit was used as a benchmark to analyze the action mechanisms of sevoflurane while a biologically realistic mathematical model was employed to explore at fine grain the molecular targets of anesthetic analyzing its impact on neuronal activity. The sevoflurane altered neurotransmission by strongly increasing GABAergic inhibition while decreasing glutamatergic NMDA activity. These changes caused a notable reduction of spike discharge in cerebellar granule cells (GrCs) following repetitive activation by excitatory mossy fibers (mfs). Unexpectedly, sevoflurane altered GrCs intrinsic excitability promoting action potential generation. Computational modelling revealed that this effect was triggered by an acceleration of persistent sodium current kinetics and by an increase in voltage dependent potassium current conductance. The overall effect was a reduced variability of GrCs responses elicited by mfs supporting the idea that sevoflurane shapes neuronal communication without silencing neural circuits.


2021 - The origin of saltiness: oral detection of NaCl [Articolo su rivista]
Bigiani, Albertino
abstract

Salt (NaCl) is an essential nutrient for it allows maintaining a stable level of Na+ in the extracellular fluid. This condition is required by many physiological processes, which would be otherwise compromised by sodium deficiency. To recognize salt in food and beverages, we rely on specific chemical detectors provided by taste and somatosensory systems in the oral cavity. Activation of these detectors elicits the sensation of saltiness. Here I will use a model, based on animal research, as a conceptual framework to help understand the mechanisms of salt detection in humans.


2020 - Does ENaC Work as Sodium Taste Receptor in Humans? [Articolo su rivista]
Bigiani, Albertino
abstract

Taste reception is fundamental for the proper selection of food and beverages. Among the several chemicals recognized by the human taste system, sodium ions (Na+) are of particular relevance. Na+ represents the main extracellular cation and is a key factor in many physiological processes. Na+ elicits a specific sensation, called salty taste, and low-medium concentrations of table salt (NaCl, the common sodium-containing chemical we use to season foods) are perceived as pleasant and appetitive. How we detect this cation in foodstuffs is scarcely understood. In animal models, such as the mouse and the rat, the epithelial sodium channel (ENaC) has been proposed as a key protein for recognizing Na+ and for mediating preference responses to low-medium salt concentrations. Here, I will review our current understanding regarding the possible involvement of ENaC in the detection of food Na+ by the human taste system.


2020 - Gustatory dysfunctions in COVID-19 patients: possible involvement of taste renin-angiotensin system (RAS) [Articolo su rivista]
Bigiani, Albertino
abstract


2020 - How to Minimize the Impact of Pandemic Events: Lessons From the COVID-19 Crisis [Articolo su rivista]
Bigiani, Lorenzo; Bigiani, Stefano; Bigiani, Albertino
abstract

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is responsible for the current pandemic of coronavirus disease 2019 (COVID-19). This pandemic is characterized by a high variability in death rate (defined as the ratio between the number of deaths and the total number of infected people) across world countries. Several possible explanations have been proposed, but it is not clear whether this variability is due to a single predominant factor or instead to multiple causes. Here we addressed this issue using multivariable regression analysis to test the impact of the following factors: the hospital stress (defined as the ratio between the number of infected cases and the total number of hospital beds), the population median age, and the quality of the National Health System (NHS). For this analysis, we chose countries of the world with over 3000 infected cases as of April 1, 2020. Hospital stress was found to be the crucial factor in explaining the variability of death rate, while the others had negligible relevance. Different procedures for quantifying cases of infection and death for COVID-19 could affect the variability in death rate across countries. We therefore applied the same statistical approach to Italy, which is divided into 20 Regions that share the same protocol for counting the outcomes of this pandemic. Correlation between hospital stress and death rate was even stronger than that observed for countries of the world. Based on our findings and the historical trend for the availability of hospital beds, we propose guidelines for policy-makers to properly manage future pandemics.


2020 - Inhibitory Plasticity: From Molecules to Computation and Beyond [Articolo su rivista]
Gandolfi, Daniela; Bigiani, Albertino; Porro, Carlo Adolfo; Mapelli, Jonathan
abstract

Synaptic plasticity is the cellular and molecular counterpart of learning and memory and, since its first discovery, the analysis of the mechanisms underlying long-term changes of synaptic strength has been almost exclusively focused on excitatory connections. Conversely, inhibition was considered as a fixed controller of circuit excitability. Only recently, inhibitory networks were shown to be finely regulated by a wide number of mechanisms residing in their synaptic connections. Here, we review recent findings on the forms of inhibitory plasticity (IP) that have been discovered and characterized in different brain areas. In particular, we focus our attention on the molecular pathways involved in the induction and expression mechanisms leading to changes in synaptic efficacy, and we discuss, from the computational perspective, how IP can contribute to the emergence of functional properties of brain circuits.


2020 - Salt Taste [Capitolo/Saggio]
Bigiani, Albertino
abstract

Our ability to detect salt (NaCl) in food and beverages (salt taste) depends on the activity of taste cells, biological sensors localized in the oral cavity. Salt taste is mainly due to sodium ions and has a huge impact on our lifestyle by guiding food preferences. The use of animal models has allowed us to decipher the mechanisms used by taste cells to recognize Na+. It is now known that at least two parallel signaling routes exist in most mammals, including humans. One is called the amiloride-sensitive (AS) pathway because it relies on a specific molecular receptor to detect Na+, the epithelial sodium channel (ENaC), which is highly sensitive to the blocking effect of amiloride, a diuretic drug. This pathway is extremely selective in detecting Na+ over other cations. The other one is called amiloride-insensitive (AI) pathway because is not affected by amiloride. This mechanism is not selective for Na+, and can detect a variety of cations. The molecular receptor(s) for this pathway, however, is (are) still unknown. In rodents, AS pathway is crucial for recognizing Na+ and underlies preference responses to low-moderate concentrations of NaCl in water. On the contrary, the AI pathway is preferentially recruited when NaCl concentrations are high and it mediates rejection responses. Psychophysical studies indicate that salt taste is a very complex sensory activity in humans, which hardly can be reduced to only two separate signaling pathways. Besides the actual concentration of Na+ in the saliva, which represents the stimulus for taste cells, other factors may contribute substantially to modify what we actually perceived as salty. The positive hedonic tone of salt taste may lead to sodium overconsumption, a risk factor for the development of hypertension. Understanding salt taste mechanisms represents the prerequisite to improve food products and therefore our health.


2020 - Salt Taste, Nutrition, and Health [Articolo su rivista]
Bigiani, Albertino
abstract


2020 - Scattering Compensation for Deep Brain Microscopy: The Long Road to Get Proper Images [Articolo su rivista]
Pozzi, Paolo; Gandolfi, Daniela; Porro, Carlo Adolfo; Bigiani, Albertino; Mapelli, Jonathan
abstract

Multiphoton microscopy is the most widespread method for preclinical brain imaging when sub-micrometer resolution is required. Nonetheless, even in the case of optimal experimental conditions, only a few hundred micrometers under the brain surface can be imaged by multiphoton microscopy. The main limitation preventing the acquisition of images from deep brain structures is the random light scattering which, until recently, was considered an unsurmountable obstacle. When in 2007 a breakthrough work by Vellekoop and Mosk [1] proved it is indeed possible to compensate for random scattering by using high resolution phase modulators, the neuro-photonics community started chasing the dream of a multiphoton microscopy capable of reaching arbitrary depths within the brain. Unfortunately, more than 10 years later, despite a massive improvement of technologies for scattering compensation in terms of speed, performances and reliability, clear images from deep layers of biological tissues are still lacking. In this work, we review recent technological and methodological advances in the field of multiphoton microscopy analyzing the big issue of scattering compensation. We will highlight the limits hampering image acquisition, and we will try to analyze the road scientists must tackle to target one of the most challenging issue in the field of biomedical imaging.


2019 - Molecular and Cellular Mechanisms Underlying Somatostatin-Based Signaling in Two Model Neural Networks, the Retina and the Hippocampus [Articolo su rivista]
Cammalleri, Maurizio; Bagnoli, Paola; Bigiani, Albertino
abstract

Neural inhibition plays a key role in determining the specific computational tasks of different brain circuitries. This functional “braking” activity is provided by inhibitory interneurons that use different neurochemicals for signaling. One of these substances, somatostatin, is found in several neural networks, raising questions about the significance of its widespread occurrence and usage. Here, we address this issue by analyzing the somatostatinergic system in two regions of the central nervous system, the retina and the hippocampus. By comparing the available information on these structures, we have identified common motifs in the action of somatostatin that may explain its involvement in such diverse circuitries. The emerging concept is that somatostatin-based signaling, through conserved molecular and cellular mechanisms, allows neural networks to operate correctly.


2018 - Use of a 3D floating sphere culture system to maintain the neural crest-related properties of human dental pulp stem cells [Articolo su rivista]
Pisciotta, Alessandra; Bertoni, Laura; Riccio, Massimo; Mapelli, Jonathan; Bigiani, Albertino; Noce, Marcella La; Orciani, Monia; de Pol, Anto; Carnevale, Gianluca
abstract

Human dental pulp is considered an interesting source of adult stem cells, due to the low-invasive isolation procedures, high content of stem cells and its peculiar embryological origin from neural crest. Based on our previous findings, a dental pulp stem cells sub-population, enriched for the expression of STRO-1, c-Kit, and CD34, showed a higher neural commitment. However, their biological properties were compromised when cells were cultured in adherent standard conditions. The aim of this study was to evaluate the ability of three dimensional floating spheres to preserve embryological and biological properties of this sub-population. In addition, the expression of the inwardly rectifying potassium channel Kir4.1, Fas and FasL was investigated in 3D-sphere derived hDPSCs. Our data showed that 3D sphere-derived hDPSCs maintained their fibroblast-like morphology, preserved stemness markers expression and proliferative capability. The expression of neural crest markers and Kir4.1 was observed in undifferentiated hDPSCs, furthermore this culture system also preserved hDPSCs differentiation potential. The expression of Fas and FasL was observed in undifferentiated hDPSCs derived from sphere culture and, noteworthy, FasL was maintained even after the neurogenic commitment was reached, with a significantly higher expression compared to osteogenic and myogenic commitments. These data demonstrate that 3D sphere culture provides a favorable micro-environment for neural crest-derived hDPSCs to preserve their biological properties.


2017 - Activation of the CREB/c-Fos pathway during long-term synaptic plasticity in the cerebellum granular layer [Articolo su rivista]
Gandolfi, Daniela; Cerri, Silvia; Mapelli, Jonathan; Polimeni, Mariarosa; Tritto, Simona; Fuzzati-Armentero, Marie-Therese; Bigiani, Albertino; Blandini, Fabio; Mapelli, Lisa; D’Angelo, Egidio
abstract

The induction of long-term potentiation and depression (LTP and LTD) is thought to trigger gene expression and protein synthesis, leading to consolidation of synaptic and neuronal changes. However, while LTP and LTD have been proposed to play important roles for sensori-motor learning in the cerebellum granular layer, their association with these mechanisms remained unclear. Here, we have investigated phosphorylation of the cAMP-responsive element binding protein (CREB) and activation of the immediate early gene c-Fos pathway following the induction of synaptic plasticity by thetaburst stimulation (TBS) in acute cerebellar slices. LTP and LTD were localized using voltage-sensitive dye imaging (VSDi). At two time points following TBS (15 min and 120 min), corresponding to the early and late phases of plasticity, slices were fixed and processed to evaluate CREB phosphorylation (P-CREB) and c-FOS protein levels, as well as Creb and c-Fos mRNA expression. High levels of P-CREB and Creb/c-Fos were detected before those of c-FOS, as expected if CREB phosphorylation triggered gene expression followed by protein synthesis. No differences between control slices and slices stimulated with TBS were observed in the presence of an N-methyl-Daspartate receptor (NMDAR) antagonist. Interestingly, activation of the CREB/c-Fos system showed a relevant degree of colocalization with long-term synaptic plasticity. These results show that NMDAR-dependent plasticity at the cerebellum input stage bears about transcriptional and post-transcriptional processes potentially contributing to cerebellar learning and memory consolidation.


2017 - Calcium Homeostasis Modulator 1-Like Currents in Rat Fungiform Taste Cells Expressing Amiloride-Sensitive Sodium Currents. [Articolo su rivista]
Bigiani, Albertino
abstract

Salt reception by taste cells is still the less understood transduction process occurring in taste buds, the peripheral sensory organs for the detection of food chemicals. Although there is evidence suggesting that the epithelial sodium channel (ENaC) works as sodium receptor, yet it is not clear how salt-detecting cells signal the relevant information to nerve endings. Taste cells responding to sweet, bitter, and umami substances release ATP as neurotransmitter through a nonvesicular mechanism. Three different channel proteins have been proposed as conduit for ATP secretion: pannexin channels, connexin hemichannels, and calcium homeostasis modulator 1 (CALHM1) channels. In heterologous expression systems, these channels mediate outwardly rectifying membrane currents with distinct biophysical and pharmacological properties. I therefore tested whether also salt-detecting taste cells were endowed with these currents. To this aim, I applied the patch-clamp techniques to single cells in isolated taste buds from rat fungiform papillae. Salt-detecting cells were functionally identified by exploiting the effect of amiloride, which induces a current response by shutting down ENaCs. I looked for the presence of outwardly rectifying currents by using appropriate voltage-clamp protocols and specific pharmacological tools. I found that indeed salt-detecting cells possessed these currents with properties consistent with the presence, at least in part, of CALHM1 channels. Unexpectedly, CALHM1-like currents in taste cells were potentiated by known blockers of pannexin, suggesting a possible inhibitory action of this protein on CALMH1. These findings indicate that communication between salt-detecting cells and nerve endings might involve ATP release by CALMH1 channels.


2016 - Electrophysiology of Sodium Receptors in Taste Cells [Articolo su rivista]
Bigiani, Albertino
abstract

Sodium intake is important to maintain proper osmolarity and volume of extracellular fluid in vertebrates. The ability to find sources of sodium ions for managing electrolyte homeostasis relies on the activity of the taste system to sense salt. Several studies have been performed to understand the mechanisms underlying Na+ reception in taste cells, the peripheral detectors for food chemicals. It is now generally accepted that Na+ interacts with specific ion channels in taste cell membrane, called sodium receptors. As ion channels, these proteins mediate transmembrane ion fluxes (that is, electrical currents) during their operation. Thus, a lot of information on the functional properties of sodium receptors has been obtained by using electrophysiological techniques. Here, I review our current knowledge on the biophysical and physiological features of these receptors obtained by applying the patch-clamp recording techniques to single taste cells.


2016 - Heterosynaptic GABAergic plasticity bidirectionally driven by the activity of pre- and postsynaptic NMDA receptors [Articolo su rivista]
Mapelli, Jonathan; Gandolfi, Daniela; Vilella, Antonietta; Zoli, Michele; Bigiani, Albertino
abstract

Dynamic changes of the strength of inhibitory synapses play a crucial role in processing neural information and in balancing network activity. Here, we report that the efficacy of GABAergic connections between Golgi cells and granule cells in the cerebellum is persistently altered by the activity of glutamatergic synapses. This form of plasticity is heterosynaptic and is expressed as an increase (long-term potentiation, LTPGABA) or a decrease (long-term depression, LTDGABA) of neurotransmitter release. LTPGABA is induced by postsynaptic NMDA receptor activation, leading to calcium increase and retrograde diffusion of nitric oxide, whereas LTDGABA depends on presynaptic NMDA receptor opening. The sign of plasticity is determined by the activation state of target granule and Golgi cells during the induction processes. By controlling the timing of spikes emitted by granule cells, this form of bidirectional plasticity provides a dynamic control of the granular layer encoding capacity.


2016 - Nicotine and the taste allure for salty food [Articolo su rivista]
Bigiani, Albertino
abstract

Smoking has been recognized as one agent that may decrease the effectiveness of the gustatory system to detect salt (Na+) in foodstuffs. As a consequence, smokers tend to ingest saltier foods than nonsmokers. An increase in sodium intake has been associated with hypertension: thus, smoking may concur to the development of hypertension by impairing salt perception. Understanding the mechanisms underlying the action of smoking on salty taste represents the premise to design proper intervention aiming at restoring normal sensitivity to sodium in smokers. I addressed this issue by studying the effect of nicotine, one of the main components of tobacco smoke, on the sodium detection mechanism in rat taste cells. Electrophysiological analysis of these cells revealed that long-term exposure to nicotine reduced the ion current mediated by the Epithelial Sodium Channel (ENaC), one of the sodium receptors occurring in taste cells. As to the molecular mechanism responsible for such a current decrease, data were consistent with a reduction in the number of functional ENaCs in the membrane of taste cells. Therefore, nicotine reduces the capability of taste cells to respond to sodium ions. This might explain, at least in part, why smokers tend to use salt more abundantly when flavoring their food: they are just boosting the sensory information to be relayed to the brain.


2015 - Amiloride-sensitive sodium currents in fungiform taste cells of rats chronically exposed to nicotine. [Articolo su rivista]
Bigiani, Albertino
abstract

Many studies have demonstrated that chronic exposure to nicotine, one of the main components of tobacco smoke, has profound effects on the functionality of the mammalian taste system. However, the mechanisms underlying nicotine action are poorly understood. In particular no information is available on the chronic effect of nicotine on the functioning of taste cells, the peripheral detectors which transduce food chemicals into electrical signals to the brain. To address this issue, I studied the membrane properties of rat fungiform taste cells and evaluated the effect of long-term exposure to nicotine on the amiloride-sensitive sodium currents (ASSCs). These currents are mediated by the epithelial sodium channels (ENaC) thought to be important, at least in part, in the transduction of salty stimuli. Patch-clamp recording data indicated that ASSCs in taste cells from rats chronically treated with nicotine had a reduced amplitude compared to controls. The pharmacological and biophysical analysis of ASSCs revealed that amplitude reduction was not dependent on changes in amiloride sensitivity or channel ionic permeability, but likely derived from a decrease in the activity of ENaCs. Since these channels are considered to be sodium receptors in taste cells, my results suggest that chronic exposure to nicotine hampers the capability of these cells to respond to sodium ions. This might represent a possible cellular mechanism underlying the reduced taste sensitivity to salt typically found in smokers.


2015 - The effect of desflurane on neuronal communication at a central synapse [Articolo su rivista]
Mapelli, Jonathan; Gandolfi, Daniela; Giuliani, Enrico; Prencipe, FRANCESCO PIO; Pellati, Federica; Barbieri, Alberto; D'Angelo, Egidio; Bigiani, Albertino
abstract

Although general anesthetics are thought to modify critical neuronal functions, their impact on neuronal communication has been poorly examined. We have investigated the effect induced by desflurane, a clinically used general anesthetic, on information transfer at the synapse between mossy fibers and granule cells of cerebellum, where this analysis can be carried out extensively. Mutual information values were assessed by measuring the variability of postsynaptic output in relationship to the variability of a given set of presynaptic inputs. Desflurane synchronized granule cell firing and reduced mutual information in response to physiologically relevant mossy fibers patterns. The decrease in spike variability was due to an increased postsynaptic membrane excitability, which made granule cells more prone to elicit action potentials, and to a strengthened synaptic inhibition, which markedly hampered membrane depolarization. These concomitant actions on granule cells firing indicate that desflurane re-shapes the transfer of information between neurons by providing a less informative neurotransmission rather than completely silencing neuronal activity.


2014 - The effect of anesthesia on neuronal communication [Poster]
Mapelli, Jonathan; Giuliani, Enrico; Gandolfi, D.; Congi, L.; Barbieri, Alberto; D'Angelo, E.; Bigiani, Albertino
abstract

One challenging aspect in the analysis of neuronal circuits is the lack of quantitative and objective measurements of network activity to be translated into functional states. For example, the clinical assessment of the consciousness state in a brain-injured, unresponsive patient can be hardly analyzed at the cellular and network level. General anesthesia employs different classes of molecules to modulate at various levels neuronal functional states. General anesthetics (GA) are known to progressively and selectively reduce consciousness, perception and motor control. In this work we have investigated in a simplified neuronal circuit the effect of GA on information transfer. The Shannon mutual information (MI) was used to evaluate how much the neuron response reflected the input stimuli versus its intrinsic variability, providing a statistical tool to dissect the contribution of spike timing to neural information transmission. The cerebellum granule cell (GrC), due to its limited number of excitatory inputs, can be used to calculate the Mutual Information (MI) and its variation during a perturbed state (e.g. under anesthesia). The MI was experimentally assessed by detecting action potentials elicited in response to specific inputs through whole-cell patch-clamp recordings in rat acute cerebellar slices (P18-24). In order to test the action of the application of GA, GABAergic currents elicited by inhibitory afferent connections were recorded. The action of GA (in particular Sevoflurane and Desflurane) increased (+120%) post-synaptic inhibitory currents (IPSCs) in less than 10 sec and was fully recovered in 30 sec. Furthermore, the action of GA was to markedly reduce the MI measured in control condition (-57.4%). This control condition was fully recovered after removal the anesthetics, therefore leaving unaltered neuronal activity. This approach will be applied to larger circuits and investigated with other techniques (e.g. Multielectrode array recordings or cellular imaging), moreover different concentration of anesthetics could lead to the identification of multiple functional states.


2012 - The effects of volatile halogenated anesthetics on information flow at the cerebellum input stage [Abstract in Rivista]
Mapelli, Jonathan; Gandolfi, D.; Giuliani, Enrico; Barbieri, Alberto; D'Angelo, E.; Bigiani, Albertino
abstract

The cerebellum is of crucial importance for sensory-motor integration and is also involved in cognitive processing. Blended anesthesia employs different molecules whose mechanisms of action are not fully understood. Among these, sevoflurane and desflurane are currently used in clinic for maintenance of general anesthesia. In this work, we have tested how anesthetics affect the flow of excitatory information transmitted by cerebellum granule cells (GCs). It is in fact still unknown the way the neuronal network activity is modulated during anesthesia. Whole-cell patch clamp recordings from GCs were performed in current-clamp mode in rat cerebellar slices. The bath application of sevoflurane (8%), on one hand dramatically reduced the total number of synaptically evoked spikes (-79%±10; n=4), on the other hand, the first spike latency and the temporal precision were increased (+23%±5; +32%±5 respectively). Furthermore, the spike timing data were used to estimate how anesthetics can modulate information transmission through the measure of Mutual Information (MI). Preliminary results show that the effect of sevoflurane perfusion was to reduce up to the 80% (n=4, p<0.05) the MI measured in control condition. Interestingly, the control condition was fully recovered after the removal of the anesthetic. These evidences indicate that anesthetics perfusion can potentially affect the cerebellar network which is fundamental for sensory-motor integration, memory formation and consolidation.


2011 - Functional diversity of taste cells. A review [Articolo su rivista]
Bigiani, Albertino; Prandi, Simone
abstract

Our ability to sense chemicals occurring in food and beverages relies on the operation of specialized epithelial cells called taste cells, found as clusters (taste buds) mainly in the oral cavity. Unlike other sensory cells, such as hair cells in the cochlea, taste cells differ from each other in terms of structural features. At least three main morphotypes are now recognized in mammalian taste buds: Type I, Type II and Type III. Each of them displays specific membrane properties (i.e. ion channels and receptors) as well as intracellular signalling pathways. Some of themare electrically excitable (Type II and Type III), whereas Type I seems to subserve a glial‐like role. They also differ in theway they communicatewith nerve terminals: apparently, only Type III cells seem to be able to relay directly information via synaptic contacts, whereas the other types of cells may communicate through less specializedmechanisms, including ATP release through non‐conventional synapses.What is then thesignificance of these three cell types in the context of taste reception? Although it is not yet possible to draw any definitiveconclusion, the emerging view is that functional diversity of taste cells might represent the basis for a ‘sensory processing’circuitry designed to detect chemicals, as a whole.


2011 - Gusto e olfatto [Capitolo/Saggio]
Bigiani, Albertino
abstract

Testo di Fisiologia rivolta agli studenti universitari di corsi di laurea differenti, dalle Scienze Biologiche alle Biotecnologie, alle Scienze Naturali, alla Farmacia e alla Medicina.


2011 - Palytoxin induces cell lysis by priming a two-step process in MCF-7 cells [Articolo su rivista]
Prandi, Simone; Sala, GIAN LUCA; Bellocci, Mirella; Alessandrini, Andrea; P., Facci; Bigiani, Albertino; Rossini, Gian Paolo
abstract

The cytolytic action of palytoxin (PlTX) was recognized long ago, but its features have remained largely undetermined. We used biochemical, morphological, physiological and physical tools, to study the cytolytic response in MCF-7 cells, as our model system. Cytolysis represented a stereotyped response induced by addition of isotonic phosphate buffer (PBS) to cells that had been exposed to PlTX, after toxin removal and under optimal and sub-optimal experimental conditions. Cytolysis was sensitive to osmolytes present during cell exposure to PlTX but not in the course of the lytic phase. Fluorescence microscopy showed that PlTX caused cell rounding and rearrangement of the actin cytoskeleton. Atomic force microscopy (AFM) was used to monitor PlTX effects in real time, and we found that morphological and mechanical properties of MCF-7 cells did not change during toxin exposure, but increased cell height and decreased stiffness at its surface were observed when PBS was added to PlTX-treated cells. The presence of an osmolyte during PlTX treatment prevented the detection of changes in morphological and mechanical properties caused by PBS addition to toxin-treated cells, as detected by AFM. By patch-clamp technique, we confirmed that PlTX action involved the transformation of the Na+,K+-ATPase into a channel, and found that cell membrane capacitance was not changed by PlTX, indicating that the membrane surface area was not greatly affected in our model system. Overall, our findings show that the cytolytic response triggered by PlTX in MCF-7 cells includes a first phase, that is toxin-dependent and osmolyte-sensitive, priming cells to lytic events taking place in a separate phase, that does not require the presence of the toxin and is osmolyte-insensitive, but is accompanied by marked reorganization of actin-based cytoskeleton and altered mechanical properties at the cell’s surface. A model of the two step process of PlTX-induced cytolysis is presented.


2011 - Palytoxin action on the Na+,K+-ATPase and the disruption of ion equilibria in biological systems [Articolo su rivista]
Rossini, Gian Paolo; Bigiani, Albertino
abstract

Palytoxin-group toxins (PlTX) exert their potent biological activity by altering mechanisms of ion homeostasis in excitable and non-excitable tissues. This review will describe major aspects that led to the relatively early identification of the Na+,K+-ATPase as the molecular target and receptor of the toxin in sensitive systems. The importance of this pump in the normal functioning of animal cells has driven extensive investigative efforts. The recognized molecular mechanism of action of PlTX involves its binding to the extracellular portion of alpha subunits of this plasma membrane protein, which converts an enzyme carrying ions against their concentration gradient at the expense of chemical energy (ATP) into a non-selective cation channel, allowing passive flow of ions following their concentration gradients. More recent findings have indicated that PlTX would interfere with the normal strict coupling between inner and outer gates of the pump controlling the ion access to the Na+,K+-ATPase, allowing the gates to be simultaneously open. The ability of PlTX to make internal portions of the Na+,K+-ATPase accessible to relatively large molecules has been exploited to characterize the structure-function relationship of the pump, leading to a better understanding of its ion translocation pathway. Thus, forty years from the isolation of this potent marine biotoxin, a considerable understanding of its mode of action and of its potential as a research tool have been achieved and are the basis for promising future advancement in the characterization of biological systems and their alteration by PlTX.


2010 - Fondamenti di Anatomia, Lineamenti di Istologia e Fisiologia [Monografia/Trattato scientifico]
Palumbo, Carla; Rezzani, R.; DE POL, Anto; Bigiani, Albertino
abstract

Il volume è rivolto agli Studenti delle Professioni Sanitarie e contiene la trattazione omnicomprensiva dell'Anatomia umana normale, dell'Istologia (ad essa propedeutica) e della Fisiologia (ad essa conseguente). E' un testo di Anatomia e Istologia funzionale adatto allo studio di tre discipline fondamentali che offre, nell'ambito della formazione nelle Professioni Sanitarie, un quadro complessivo dei livelli organizzativi e funzionali del corpo umano, nella spiegazione dell'espletamento delle complesse e sofisticate funzioni dell'organismo.


2009 - Proteomic analysis reveals multiple patterns of response in cells exposed to a toxin mixture [Articolo su rivista]
Sala, GIAN LUCA; Ronzitti, Giuseppe; M., Sasaki; H., Fuwa; T., Yasumoto; Bigiani, Albertino; Rossini, Gian Paolo
abstract

We have used proteomic analyses to probe the responses induced by a pair of marine biotoxins, okadaic acid (OA) and gambierol (GB), added alone or in combination to a cultured cell line, and carried out a preliminary investigation into the possible interactions between toxins possessing two different molecular mechanisms of action at a cellular level. When MCF-7 cells were treated with OA, we found that cellular levels of thirty proteins were significantly affected, including several isoforms of non-phosphorylated and phosphorylated hsp 27, as well as enzymes involved in the maintenance of nucleoside triphosphate pools and the control of redox states of the cell. When we repeated our analysis using GB, nine proteins were significantly affected, including some isoforms of non-phosphorylated hsp 27, as well as semenogelin-1, myosin-7 and the ATP synthase subunit δ. The combined addition of OA and GB to MCF-7 cells, in turn, affected fourteen proteins, including some isoforms of non-phosphorylated and phosphorylated hsp 27, as well as myosin-7, the ATP synthase subunit δ, and enzymes involved in the control of redox states of the cell. If components affected by either OA or GB, as well as by the combined treatment, were classified according to the detected changes, two sets of data were obtained, including the components whose levels were found affected by the combined treatment, regardless of the effect observed after addition of only one agent, and those that had been found affected in cells that had been challenged with only one toxin, but not when cells had been subjected to the combined treatment. Multiple patterns of responses to the toxin mixture were recorded in the two sets, consisting of both independent and interacting actions, among which we detected synergistic, similar and antagonistic effects.


2009 - Proteomic analyses for the characterization of toxicity pathways and their interactions in human cells: learning from marine biotoxins [Capitolo/Saggio]
Sala, GIAN LUCA; Ronzitti, Giuseppe; Bellocci, Mirella; M., Sasaki; H., Fuwa; T., Yasumoto; Bigiani, Albertino; Rossini, Gian Paolo
abstract

The analysis of molecular families by “omic” approaches is increasingly used in investigations onto signaling pathways. We have exploited proteomic analyses to probe the molecular responses of living systems exposed to marine biotoxins, and found that these components cause changes in the levels of expression of many proteins in MCF-7 cells. By an integration of different means of protein detection and analysis, we observed changes in molecular components that reveal the involvement of complex sets of covalent modifications of hsp 27 in the signaling pathways responsible for the death response of MCF-7 cells exposed to okadaic acid. The integration of results obtained by complementary analytical techniques and means of analyte detection facilitates a better exploitation of proteomic approaches.


2008 - Daytime melatonin treatment influences food-carrying (hoarding) behavior in rats. [Articolo su rivista]
Scalera, Giuseppe; Benassi, Carlo; Bigiani, Albertino
abstract

Objective. Three experiments were performed to verify whether melatonin (MEL) may influence hoarding behavior in rats. This hypothesis was supported by the consideration that leptin treatment decreases food hoarding in hamsters and that an inverse relation exists between plasma leptin concentration and MEL treatment. Methods. Male Sprague-Dawley rats housed individually and kept on 12h:12h light-dark cycle were used. First experiment was performed to check whether a bimodal distribution of food hoarding scores exists in rats, and to select two groups of high (HH-rats) or low (LH-rats) hoarding. Second experiment was designed to verify whether MEL treatment modifies food-hoarding, while the third one was performed to investigate whether MEL treatment was able to modify the reciprocal relation between leptin and MEL plasma concentration. Results. In rats the hoarding tendency fell into a bimodal distribution and the plasma leptin concentration was significantly higher in HH-rats than LH-rats. When MEL was injected, circulating concentration of leptin was decreased in both HH-rats and LH-rats and such MEL treatment significantly increased the number of pellets hoarded by LH-rats but not that hoarded by HH-rats. Conclusions. MEL influences the food-hoarding in rats either directly, or indirectly by the MEL and leptin reciprocal interaction. Our results support the hypothesis that the endocrine system either directly, by the action of one or more combined hormones (MEL, leptin), or indirectly via its actions on neural substrates determines, at least in part, food-hoarding of rats.


2007 - Fisiologia: Un approccio integrato, 3° ediz. [Traduzione di Libro]
L., Agnati; Bigiani, Albertino; C., Franzini; Lui, Fausta
abstract

Negli anni trascorsi dalla precedente edizione, la fisiologia e la medicina hanno continuato la loro rapida evoluzione. Man mano che gli scienziati acquisiscono nuove conoscenze dei processi biologici fondamentali, le loro scoperte sono tradotte in nuovi trattamenti medici e in suggerimenti pe mantenerre lo stato di salute. In questa edizione abbiamo continuato ad aggiornare e a focalizzare i temi di base e i concetti di fisiologia per aiutare gli studenti a stabilire un modello mentale su come funziona il corpo umano.


2007 - Localization of amiloride-sensitive sodium current and voltage-gated calcium currents in rat fungiform taste cells [Articolo su rivista]
Bigiani, Albertino; Cuoghi, Valeria
abstract

Recent studies have shown that taste cells transducing bitter, sweet, and umami stimuli do not possess high-threshold voltage-gated calcium channels required for synaptic transmission at conventional synapses, suggesting some sort of signal processing inside taste buds prior to the activation of nerve endings. To evaluate whether this is a general paradigm for the physiology of taste reception, we studied the transduction pathway underlying the detection of sodium ions (salty stimulus). In laboratory rodents, Na(+) is thought to be transduced, at least in part, through amiloride-sensitive sodium channels (ASSCs). Therefore we used the patch-clamp techniques to analyze the occurrence pattern of amiloride-sensitive sodium currents and voltage-gated calcium currents (both low-voltage-activated T-type current and high-voltage-activated L-type current) among taste cells in rat fungiform papillae. Because taste cells turnover, we focused our attention on cells possessing large voltage-gated sodium currents, a sign of "mature" cells. We found that cells expressing functional ASSCs either did not possess any calcium currents or exhibited only T-type calcium currents, which is believed to play a role in repetitive firing. On the contrary, cells lacking functional ASSCs were endowed with L-type calcium currents, which are thought to mediate calcium influx required for neurotransmitter exocytosis. Therefore our data suggest that sodium-detecting cells are unlikely to use conventional synaptic communication to transfer taste information to nerve endings. Our findings on sodium taste detection support the recent model of taste transduction, involving separate groups of taste cells: chemosensitive cells and cells forming conventional synapses.


2007 - Long-term effects of nicotine on rat fungiform taste buds [Articolo su rivista]
Tomassini, Silvia; Cuoghi, Valeria; Catalani, E; Casini, G; Bigiani, Albertino
abstract

Nicotine, an alkaloid found in tobacco smoke, has been recognized as capable of inducing changes in taste functionality in conditions of chronic exposure. The mechanisms underlying these sensory alterations, however, are currently unknown. We addressed this issue by studying the long-term effects of nicotine on the anatomical features of taste buds, the peripheral end-organs of taste, in rat fungiform papillae. Nicotine was administered to rats via drinking water over a period of 3 weeks, which represents a standard method to achieve chronic drug exposure in laboratory animals. We found that prolonged administration of nicotine induced a significant reduction in the size of fungiform taste buds, without affecting their total number on the rat tongue. Morphometric measurements as well as evaluations of taste cell membrane capacitance suggested that the reduced size of taste organs was determined by a decrease in the number of cells per taste bud. In addition, chronic treatment with nicotine caused an increase in the relative density of cells expressing gustducin, a specific G protein alpha-subunit found in some taste cells and involved in bitter/sweet transduction. Interestingly, changes in the expression pattern of gustducin turned out to be more pronounced in periadolescent/adolescent than in adult rats. As a whole, our data indicate that long-term nicotine administration induces significant changes in the anatomical properties of taste buds in rat fungiform papillae. These changes could have a profound impact on the sensory information relayed to the brain; therefore, they may be responsible, at least in part, for the alterations in taste functionality observed during chronic nicotine exposure, a condition found in regular smokers.


2007 - Sapid solutions and food intake in repeated dehydration andrehydration periods in rats [Abstract in Atti di Convegno]
Scalera, Giuseppe; Benassi, Carlo; Bigiani, Albertino
abstract

Experiments were performed to ascertain whether food intakein thirsty rats is influenced by palatability of solutions andwhether the availability of food during tests influences tastepreference, acceptance, and total fluid intake. In five groups ofrats, 2-bottle preference (Experiment 1) and 1-bottle acceptancetests (Experiment 2) in either 12, 24, 36, 48 h water deprived ratswere performed; food was available during tests. Results showedthat food availability during tests did not affect taste preferenceand acceptance. In Experiment1, after 36, 48 h water deprivation,rats drinking either NaCl or sucrose, they ate less food than ratsdrinking either HCl, quinine, or water. In Experiment 2, ratsdrinking NaCl as the only source of fluid ate significantly lessfood than all other groups. Two different post-ingestive effects(energetic; osmotic) may explain the same behavior for intake ofsucrose or NaCl solutions. Since rats drinking either sucrose orNaCl ate less food but drank more fluid, they had a fluid/foodratio significantly higher than that of rats drinking either water,quinine, or HCl; these latters ate more food but drank less fluid.Taste, together with other factors, might inhibit or enhance theamount of fluid and food intake required to restore body weightand body fluid osmolality at the end of dehydration. Duringrecovery periods, overeating is necessary to restore body mass,Na+ and electrolytes; overdrinking corrects imbalance producedby excessive eating. In conclusion, food and fluid intake appearssignificantly related each other, even in dehydrated rats.


2006 - Activation of the cholinergic anti-inflammatory pathway reduces NF-kappa B activation, blunts TNF-alpha production, and protects against splanchnic artery occlusion shock [Articolo su rivista]
D., Altavilla; Guarini, Salvatore; A., Bitto; Mioni, Chiara; Giuliani, Daniela; Bigiani, Albertino; G., Squadrito; L., Minutoli; Fs, Venuti; F., Messineo; V., De Meo; Bazzani, Carla; F., Squadrito
abstract

The cholinergic anti-inflammatory pathway has not yet been studied in splanchnic artery occlusion (SAO) shock. We investigated whether electrical stimulation (STIM) of efferent vagus nerves suppresses the inflammatory cascade in SAO shock. Animals were subjected to clamping of the splanchnic arteries for 45 min, followed by reperfusion. This surgical procedure resulted in an irreversible state of shock (SAO shock). Sham-operated animals were used as controls. Two minutes before the start of reperfusion, rats were subjected to bilateral cervical vagotomy (VGX) or sham surgical procedures. Application of constant voltage pulses to the caudal vagus ends (STIM: 5 V, 2 ms, 6 Hz for 15 min, 5 min after the beginning of reperfusion) increased survival rate (VGX + SAO + Sham STIM = 0% at 4 h of reperfusion; VGX + SAO + STIM = 90% at 4 h of reperfusion), reverted the marked hypotension, inhibited I kappa B alpha liver loss, blunted the augmented nuclear factor-kappa B activity, decreased hepatic tumor necrosis factor (TNF)-alpha mRNA (VGX + SAO + Sham STIM = 1.0 +/- 1.9 TNF-alpha/ glyceraldehyde-3-phosphate dehydrogenase ratio; VGX + SAO + STIM = 0.3 +/- 0.2 TNF-alpha/glyceraldehyde-3-phosphate dehydrogenase ratio), reduced plasma TNF-alpha (VGX + SAO + Sham STIM = 118 +/- 19 pg/mL; VGX + SAO + STIM = 39 +/- 8 pg/mL), ameliorated leukopenia, and decreased leukocyte accumulation, as revealed by means of myeloperoxidase activity in the ileum (VGX + SAO + Sham STIM = 7.9 +/- 1 U/g tissue; VGX + SAO + STIM = 3.1 +/- 0.7 U/g tissue) and in the lung (VGX + SAO + Sham STIM = 8.0 +/- 1.0 U/g tissue; VGX + SAO + STIM = 3.2 +/- 0.6 U/g tissue). Chlorisondamine, a nicotinic receptor antagonist, abated the effects of vagal stimulation. Our results show a parasympathetic inhibition of nuclear factor-kappa B and TNF-alpha in SAO shock.


2006 - Effect of ciguatoxin 3C on voltage-gated Na+ and K+ currents in mouse taste cells [Articolo su rivista]
Ghiaroni, Valeria; Scalera, Giuseppe; H., Fuwa; M., Inoue; M., Sasaki; K., Miyazaki; Rossini, Gian Paolo; M., Hirama; T., Yasumoto; Bigiani, Albertino
abstract

The marine dinoflagellate Gambierdiscus toxicus produces highly lipophilic, polycyclic ether toxins that cause a seafood poisoning called ciguatera. Ciguatoxins (CTXs) and gambierol represent the two major causative agents of ciguatera intoxication, which include taste alterations (dysgeusiae). However, information on the mode of action of ciguatera toxins in taste cells is scarce. Here, we have studied the effect of synthetic CTX3C (a CTX congener) on mouse taste cells. By using the patch-clamp technique to monitor membrane ion currents, we found that CTX3C markedly affected the operation of voltage-gated Na+ channels but was ineffective on voltage-gated K+ channels. This result was the exact opposite of what we obtained earlier with gambierol, which inhibits K+ channels but not Na+ channels. Thus, CTXs and gambierol affect with high potency the operation of separate classes of voltage-gated ion channels in taste cells. Our data suggest that taste disturbances reported in ciguatera poisoning might be due to the ability of ciguatera toxins to interfere with ion channels in taste buds.


2006 - Fisiologia: molecole, cellule e sistemi [Monografia/Trattato scientifico]
A. M., Angioy; Bardoni, Rita; Bigiani, Albertino; M., Brunelli; A., Contestabile; M., Crispino; E., D'Angelo; F., Franciolini; E., Fugassa; S., Fulle; A., Giuditta; R., Levi; M. G., Lionetto; V., Lombardi; E., Macchi; D., Negrini; P., Paggi; S., Palmero; A., Peres; M., Piccolino; C., Poggesi; G., Rispoli; P., Rossi; V. F., Sacchi; T., Schettino; R., Serio; G., Valenti; Vellani, Vittorio; A., Zaza
abstract

Questo libro nasce con l’intento di offrire agli studenti dei Corsi universitari di carattere biomedico uno strumento di riferimento per lo studio dei meccanismi alla base del funzionamento degli esseri viventi, in particolare nel regno animale: l’attenzione è principalmente rivolta ai processi fondamentali e unificanti dei fenomeni fisiologici, quelli che costituiscono le basi, di solito molecolari e cellulari, di funzioni fisiologiche anche apparentemente lontane tra loro. Poiché questo libro è destinato agli studenti di Corsi di Laurea differenti, dalle Scienze biologiche alle Biotecnologie, ma anche di Scienze naturali e Farmacia, si è ritenuto utile includere anche capitoli di fisiologia dei sistemi.La sequenza degli argomenti si articola dal livello molecolare e cellulare, per considerare successivamente le interazioni fra le cellule e concludersi con la trattazione dei più importanti organi e sistemi d’organo. Questa progressione dal microscopico al macroscopico segue una logica inversa rispetto alla cronologia della storia dell’indagine dei processi fisiologici, che è naturalmente partita molti secoli fa dallo studio del funzionamento degli apparati e degli organi più evidenti e considerati maggiormente importanti. La progressiva comprensione dei meccanismi di funzionamento e il parallelo sviluppo tecnologico degli strumenti d’indagine hanno facilitato nel corso del tempo dei processi a livelli via via più nascosti e microscopici per trovare una spiegazione soddisfacente dell’evento macroscopico. Laddove questo approccio è riuscito ad addentrarsi fino al livello molecolare si è constatato che molte funzioni macroscopiche, a prima vista significativamente diverse tra loro, si basano in realtà su processi microscopici molto simili. Per questo motivo ci è sembrato preferibile trattare inizialmente una serie di processi elementari che vengono successivamente ritrovati in azione per contribuire alla realizzazione di funzioni fisiologiche complesse.A loro volta i processi fisiologici elementari, a livello molecolare e cellulare, si basano sulle leggi della fisica, della chimica e della biologia molecolare e cellulare. Queste nozioni costituiscono un’indispensabile base propedeutica per lo studio della fisiologia e non sono normalmente contenute nei testi di fisiologia. Per comodità del lettore, tuttavia, sono stati inclusi alcuni capitoli che sintetizzano alcuni punti fondamentali delle discipline fisiche, chimiche e biologiche di particolare interesse in fisiologia.La grande variabilità dei programmi degli insegnamenti che fanno riferimento alla fisiologia – e la diversa estensione e importanza che nelle diverse Università viene a essi data – ha consigliato di impostare il libro in modo da facilitarne un utilizzo in una certa misura “personalizzato”. Così, accanto a un percorso base, contenente tutti gli argomenti più classici trattati in modo rigoroso, ma senza eccessivi approfondimenti, sono presenti parti differenziate, che potranno essere utilizzate secondo le necessità degli indirizzi di studio. Il testo in corpo ridotto riguarda approfondimenti non strettamente necessari alla preparazione di base. I riquadri trovano spazio nei diversi capitoli, per consentire approfondimenti specifici in aree diverse: biofisica molecolare (per le Classi di Biotecnologie e di Scienze Biologiche con indirizzi cellulari o di Neuroscienze), fisiologia comparata (per le Classi di Scienze naturali e di Scienze biologiche con indirizzi naturalistici), ricerca applicata (Biotecnologie e Farmacia), area storica (destinata a tutti coloro che sono interessati a conoscere la storia delle idee sul funzionamento degli esseri viventi e del corpo umano in particolare, una storia di grandissimo interesse scientifico, filosofico e umano, che può essere tracciata fin dai primordi delle civiltà conosciute).


2006 - I neuropeptidi melanocortinici nell’approccio cardioprotettivo contro il danno da ischemia e da riperfusione [Articolo su rivista]
Mioni, C.; Giuliani, Daniela; Bazzani, Carla; Zaffe, Davide; Botticelli, A. R.; Bigiani, Albertino; Lodi, Renzo; Guarini, Salvatore
abstract

In questi ultimi anni abbiamo documentato che dosi nanomolari di melanocortine (neuropeptidi appartenenti al gruppo ACTH/MSH) hanno la capacità di attenuare in modo significativo, nel ratto, il danno conseguente ad ischemia/riperfusione miocardica e ad occlusione coronarica permanente, Dai nostri dati emerge che le melanocortine, previa stimolazione di recettorimelanocortinici MC3 localizzati nel sistema nervoso centrale, durante l’episodio ischemico innescherebbero l'attivazione di una via vagale efferente cardioprotettiva. La tappa finale di tale via cardioprotettiva sembra essere rappresentata dall’attivazione di recettori muscarinici periferici. I nostri dati suggeriscono che le melanocortine potrebbero fornire il potenziale per lo sviluppo di una nuova classe di farmaci per un approccio innovativo alla patologia ischemica cardiaca.


2005 - A dynamic population of excitable cells: the taste receptor cells [Articolo su rivista]
Ghiaroni, Valeria; Fieni, Francesca; F., Silvestri; Pietra, Pierangelo; Bigiani, Albertino
abstract

N/A


2005 - A simulative model for the analysis of conduction properties of ion channels based on first-principle approaches [Articolo su rivista]
F., Affinito; Brunetti, Rossella; Jacoboni, Carlo; E., Piccinini; M., Rudan; Bigiani, Albertino; P., Carloni
abstract

The calculation of free-energy profiles in proteins, and, more specifically, in ion channels, is a challenge for modern numerical simulations due both to the convergence problems associated with the electrostatics of the environment and to the difficulties in modeling the fields acting on the permeating ions. The present study is aims at comparing three different simulation techniques available in the literature on a nanometric channel protein chosen as a test case, with the purpose of establishing their real predictivity and limits.


2005 - Activation of an efferent cholinergic pathway produces strong protection against myocardial ischemia/reperfusion injury in rats [Articolo su rivista]
Mioni, C.; Bazzani, Carla; Giuliani, Daniela; Altavilla, D.; Leone, S.; Ferrari, Anna; Minutoli, L.; Bitto, A.; Marini, H.; Zaffe, Davide; Botticelli, Ar; Iannone, Anna; Tomasi, Aldo; Bigiani, Albertino; Bertolini, Alfio; Squadrito, F.; Guarini, Salvatore
abstract

Objective: A vagus nerve-mediated, brain cholinergic protective mechanism activated by melanocortin peptides is operative in conditions of circulatory shock; moreover, there is anatomical evidence of dual vagal-cardiac efferent pathways in rats, which could play different roles in controlling heart function. Therefore, we investigated the role and functional mechanism of such vagal efferent pathway(s) in an experimental model of ischemic heart disease. Design: Randomized experimental study. Setting: Research laboratory. Subjects: Adult Wistar rats of either sex. Interventions: After bilateral cervical vagotomy (with or without pretreatment with atropine), efferent vagal fibers were electrically stimulated in rats subjected to coronary artery occlusion (5 mins) followed by reperfusion (5 mins). Other rats (intact, vagotomized, or pretreated with atropine) were treated with nanomolar doses of melanocortin peptides. Measurements and Main Results: Electrical stimulation of efferent vagal fibers (5 V, 2 msecs,1-9 Hz, for the whole period of ischemia/reperfusion) strongly reduced the high incidence of severe arrhythmias and lethality, reduced the increase in free radical blood levels and left-ventricle histologic alterations, and augmented the extracellular signal-regulated kinase activation. Treatment with the melanocortin peptides adrenocorticotropin and gamma(2)-melanocyte-stimulating hormone (162 nmol/kg intravenously or 16.2 nmol/kg intracerebroventricularly, during coronary occlusion) produced the same protective effects of electrical stimulation and with the same muscarinic acetylcholine receptor-dependent mechanism, seemingly through brain activation (mediated by melanocortin MC3 receptors, as previously described) of such efferent vagal pathway. Conclusions: The present results give evidence for the identification of a protective, melanocortin-activated, efferent vagal cholinergic pathway, operative in conditions of myocardial ischemia/reperfusion. These data suggest that melanocortins and pertinent compounds able to activate such a pathway could provide the potential for development of a new class of drugs for a novel approach to management of ischemic heart disease.


2005 - Fisiologia: Un approccio integrato, 2° ediz. [Traduzione di Libro]
L., Agnati; Bigiani, Albertino; C., Franzini; Lui, Fausta
abstract

Vi sono oggi opportunità straordinarie per un proficuo studio delle funzioni del corpo umano. Questo dipende dal fatto che non solo beneficiamo di secoli di studi compiuti da fisiologi che hanno costruito un corpus di conoscenze sulle funzioni dell'organismo umano, ma anche dal fatto che negli anni '70 vi sono stati progressi nel campo della biologia cellulare e molecolare così spettacolari che gli studenti talvolta guardano alla fisiologia come a una materia 'morta', in cui non resta più nulla da scoprire. In effetti, un tempo si pensava che decodificando l'intero genoma umano avremmo avuto la chiave del segreto della vita. Tuttavia, questa visione riduzionista della biologia ha i suoi limiti. Gli organismi viventi sono molto più di una semplice somma di parti, e scoprire le sequenze di geni e proteine in un laboratorio di biologia molecolare non sempre ci chiarisce il loro significato biologico in vivo. Ora, alle soglie del XXI secolo, i biologi molecolari chiedono aiuto ai fisiologi per la comprensione della funzione delle molecole nell'organismo in toto. L'integrazione della funzione a tutti i livelli, dalla molecola all'organismo vivente, è compito precipuo dei fisiologi.


2005 - Glutamate receptors in taste receptor cells [Capitolo/Saggio]
Bigiani, Albertino
abstract

N/A


2005 - How proteins come together in the plasma membrane and function in macromolecular assemblies - Focus on receptor mosaics [Articolo su rivista]
Agnati, Luigi Francesco; D., Guidolin; Genedani, Susanna; S., Ferre; Bigiani, Albertino; As, Woods; K., Fuxe
abstract

Some theoretical aspects on structure and function of proteins have been discussed previously. Proteins form multimeric complexes, as they have the capability of binding other proteins (Lego property) resulting in multimeric complexes capable of emergent functions. Multimeric proteins might have either a genomic or a postgenomic origin. Proteins spanning the plasma membrane have been analyzed by considering the effects of the microenvironment in which the protein is embedded. In particular, the different effects of the hydrophilic (extracellular and intracellular) versus the lipophilic (intramembrane) environment have been considered. These aspects have been discussed in the framework of membrane microdomains, in particular, the so-called rafts. In alpha-helix proteins the individual peptide dipoles align to produce a macrodipole crossing the entire membrane. This macrodipole has its positive (extracellular) pole at the N-terminal end of the helix and its negative (intracellular) pole at the C-terminal end. This arrangement has been analyzed in the framework of the counter-ion atmosphere, that is, the formation of a cloud of small ions bearing an opposite charge. Excitable cells reverse their resting potential during the all-or-none action potentials. Hence, the extracellular side of the plasma membrane becomes negative with respect to the intracellular side. This change of polarization affects also the direction and magnitude of the alpha-helix dipole in view of the fact that there is a displacement of the counter ions. The oscillation in the intensity of the dipole caused by the action potentials opens the possibility of an interaction among dipoles by electromagnetic waves.


2005 - Inhibition of voltage-gated potassium currents by gambierol in mouse taste cells [Articolo su rivista]
Ghiaroni, Valeria; M., Sasaki; H., Fuwa; Rossini, Gian Paolo; Scalera, Giuseppe; T., Yasumoto; Pietra, Pierangelo; Bigiani, Albertino
abstract

Ciguatera is a food poisoning caused by toxins of Gambierdiscus toxicus, a marine dinoflagellate. The neurological features of this intoxication include sensory abnormalities, such as paraesthesia, heightened nociperception, and also taste alterations. Here, we have evaluated the effect of gambierol, one of the possible ciguatera toxins, on the voltage-gated ion currents in taste cells. Taste cells are excitable cells endowed with voltage-gated Na+, K+, and Cl- currents (I-Na, I-K, and I-Cl, respectively). By applying the patch-clamp technique to single cells in isolated taste buds obtained from the mouse vallate papilla, we have recorded such currents and determined the effect of bath-applied gambierol. We found that this toxin markedly inhibited I-K in the nanomolar range (IC50 of 1.8 nM), whereas it showed no significant effect on I-Na or I-Cl even at high concentration (1 mu M). The block of I-K was irreversible even after a 50-min wash. In addition to affecting the current amplitude, we found that gambierol significantly altered both the activation and inactivation processes of I-K. In conclusion, unlike other toxins involved in ciguatera, such as ciguatoxins, which affect the functioning of voltage-gated sodium channels, the preferred molecular target of gambierol is the voltage-gated potassium channel, at least in taste cells. Voltage-gated potassium currents play an important role in the generation of the firing pattern during chemotransduction. Thus, gambierol may alter action potential discharge in taste cells and this could be associated with the taste alterations reported in the clinical literature.


2005 - KCNK channels in taste cells: possible new chemical sensors? [Capitolo/Saggio]
Ghiaroni, Valeria; Pattabiraman, P; Fieni, Francesca; Domenici, L; Bigiani, Albertino
abstract

N/A


2005 - Noise properties of single open ion channels: an atomistic computational approach [Relazione in Atti di Convegno]
F., Affinito; E., Piccinini; Bigiani, Albertino; Brunetti, Rossella; Jacoboni, Carlo; AND M., Rudan
abstract

This paper presents the first results of a computational analysis of the noise associated with ion current in single open ion channels. This analysis is performed by means of a coupled Molecular Dynamics-Monte Carlo approach able to simulate the conduction process on the basis of all microscopic information today available from protein structural data and atomistic simulations. The case of potassium ions permeating the KcsA channel is considered in the numerical calculations. The obtained results evidence a noise spectrum different from what is theoretically predicted for uncorrelated ion-exit events (Poisson noise), confirming the existence of correlation in ion motion within the channel.


2005 - Pheromone reception in mammals [Articolo su rivista]
Bigiani, Albertino; C., Mucignat Caretta; G., Montani; R., Tirindelli
abstract

Pheromonal communication is the most convenient way to transfer information regarding gender and social status in animals of the same species with the holistic goal of sustaining reproduction. This type of information exchange is based on pheromones, molecules often chemically unrelated, that are contained in body fluids like urine, sweat, specialized exocrine glands, and mucous secretions of genitals. So profound is the relevance of pheromones over the evolutionary process that a specific peripheral organ devoted to their recognition, namely the vomeronasal organ of Jacobson, and a related central pathway arose in most vertebrate species. Although the vomeronasal system is well developed in reptiles and amphibians, most mammals strongly rely on pheromonal communication. Humans use pheromones too; evidence on the existence of a specialized organ for their detection, however, is very elusive indeed. In the present review, we will focus our attention on the behavioral, physiological, and molecular aspects of pheromone detection in mammals. We will discuss the responses to pheromonal stimulation in different animal species, emphasizing the complicacy of this type of communication. In the light of the most recent results, we will also discuss the complex organization of the transduction molecules that underlie pheromone detection and signal transmission from vomeronasal neurons to the higher centers of the brain. Communication is a primary feature of living organisms, allowing the coordination of different behavioral paradigms among individuals. Communication has evolved through a variety of different strategies, and each species refined its own preferred communication medium. From a phylogenetic point of view, the most widespread and ancient way of communication is through chemical signals named pheromones: it occurs in all taxa, from prokaryotes to eukaryotes. The release of specific pheromones into the environment is a sensitive and definite way to send messages to other members of the same species. Therefore, the action of an organism can alter the behavior of another organism, thereby increasing the fitness of either or both. Albeit slow in transmission and not easily modulated, pheromones can travel around objects in the dark and over long distances. In addition, they are emitted when necessary and their biosynthesis is usually economic. In essence, they represent the most efficient tool to refine the pattern of social behaviors and reproductive strategies.


2004 - A simulative method for the analysis of conduction properties of ion channels based on first-principle approaches [Relazione in Atti di Convegno]
Affinito, F.; Bigiani, A.; Brunettii, R.; Carloni, P.; Jacoboni, C.; Piccinira, E.; Rudan, M.
abstract


2004 - Adrenocorticotropin reverses hemorrhagic shock in anesthetized rats through the rapid activation of a vagal anti-inflammatory pathway [Articolo su rivista]
Guarini, Salvatore; Cainazzo, Maria Michela; Giuliani, Daniela; Mioni, Chiara; D., Altavilla; H., Marini; Bigiani, Albertino; Ghiaroni, Valeria; M., Passaniti; Leone, Sheila; Bazzani, Carla; Ap, Caputi; F., Squadrito; Bertolini, Alfio
abstract

Objective: Several melanocortin peptides have a prompt and sustained resuscitating effect in conditions of hemorrhagic shock. The transcription nuclear factor kB (NF-kB) triggers a potentially lethal systemic inflammatory response, with marked production of tumor necrosis factor-alpha (TNF-alpha), in hemorrhagic shock. Here we investigated whether the hemorrhagic shock reversal produced by the melanocortin ACTH-(1-24) (adrenocorticotropin) depends on the activation of the recently recognized, vagus nerve-mediated, brain cholinergic anti-inflammatory pathway. Methods and results: Anesthetized rats were stepwise bled until mean arterial pressure (MAP) atabilized at 20-25 turn Hg. The severe hypovolemia was incompatible with survival, and all saline-treated animals died within 30 min. In rats intravenously (i.v.) treated with ACTH-(1-24), neural efferent activity along vagus nerve (monitored by means of a standard system for extracellular recordings) was markedly increased, and the restoration of cardiovascular and respiratory functions was associated with blunted NF-kB activity and with decreased TNF-alpha mRNA liver content and TNF-alpha plasma levels. Bilateral cervical vagotomy, pretreatment with the melanocortin MC4 receptor antagonist HS014, atropine sulfate or chlorisondamine, but not with atropine methylbromide, prevented the life-saving effect of ACTH-(1-24) and the associated effects on NF-kB activity and TNF-alpha levels. HS014 and atropine sulfate prevented, too, the ACTH-(1-24)-induced increase in neural efferent vagal activity, and accelerated the evolution of shock in saline-treated rats. Conclusions: The present data show, for the first time, that the melanocortin ACTH-(I -24) suppresses the NF-kB-dependent systemic inflammatory response triggered by hemorrhage, and reverses shock condition, by brain activation (in real-time) of the cholinergic anti-inflammatory pathway, this pathway seeming to be melanocortin-dependent. (C) 2004 European Society of Cardiology. Published by Elsevier B.V. All rights reserved.


2004 - Functional correlates of somatostatin receptor 2 over-expression in the retina of mice with genetic deletion of somatostatin receptor 1 [Articolo su rivista]
Bigiani, Albertino; P., Petrucci; Ghiaroni, Valeria; M., Dal Monte; A., Cozzi; Hj, Kreienkamp; D., Richter; P., Bagnoli
abstract

Somatostatin-14 (SRIF) and its receptors (sst(1-5)) are found in the mammalian retina. However, scarce information is available on the role of the somatostatinergic system in retinal physiology. We have recently used gene-knockout technology to gain insights into the function of sst(1) and sst(2) receptors in the mouse retina. The sst(1) receptor localizes to SRIF-containing amacrine cells, whereas the sst(2) receptor localizes to several retinal cell populations including rod bipolar cells (RBCs). Molecular data indicate that, in retinas with deletion of the sst(1) receptor (sst(1) KO), sst(2) receptors become overexpressed in concomitance with an increased level of retinal SRIF. To test whether this up-regulation of sst(2) receptors correlates with altered sst(2) receptor physiology, we studied the effect Of sst(2) receptor activation on potassium current (I-K) in isolated RBCs and glutamate release in retina explants. Both I-K and glutamate release are known to be negatively modulated by sst(2) receptors in the mammalian retina. We used octreotide, a SRIF analogue, to activate selectively sst(2) receptors. Patch-clamp recordings from isolated RBCs indicated that the sst(2) receptor-mediated inhibition Of I-K was significantly larger in sst(1) KO than in control retinas. In addition, HPLC measurements of glutamate release in sst(1) KO retinal explants demonstrated that the sst(2) receptor-mediated inhibition of K+-evoked glutamate release was also significantly larger than in control retinas. As a whole, these findings indicate that the overexpression Of sst(2) receptors in sst(1) KO retinas can be correlated to an enhanced function Of sst(2) receptors. The level of expression Of sst(2) receptors may therefore represent a key step in the regulation Of sst(2) receptor-mediated responses, at least in the retina.


2004 - Sull'identificazione di una via colinergica anti-shock fisiologica e dipendente dalle melanocortine. [Articolo su rivista]
Bazzani, Carla; Cainazzo, Maria Michela; Giuliani, Daniela; Mioni, Chiara; Leone, Sheila; Pagliai, Francesca; Ghiaroni, Valeria; Bigiani, Albertino; Altavilla, D.; Squadrito, F.; Bertolini, Alfio; Guarini, Salvatore
abstract

Da tempo abbiamo documentato che dosi nanomolari di melanocortine (peptidi appartenenti al gruppo ACTH/a-MSH) hanno un pronto effetto salvavita, indipendente dal surrene, sia nell'animale che nell'uomo in condizioni di shock circolatorio. Recentemente abbiamo dimostrato che, in condizioni di shock emorragico, il sistema nervoso centrale (SNC) modula rapidamente la risposta infiammatoria sistemica attraverso l attivazione di una via colinergica anti-infiammatoria mediata dal nervo vago e che l'azione salvavita delle melanocortine è dovuta all'attivazione di tale via, con inibizione dell’attivazione del fattore di trascrizione nucleare NF-kB a livello epatico e diminuzione dei livelli di "tumour necrosis fictor-" (TNF-) mRNA epatico e TNF- circolante. Le nostre ricerche hanno anche dimostrato che la via colinergica anti-infiammatoria coinvolge (come tappa iniziale) l'attivazione di recettori melanocortinici MC4, localizzati nel SNC e (come principale tappa finale) recettori nicotinici periferici molto probabilmente localizzati sui macmfagi epatici. I nostri dati suggeriscono che questa rapida via salvavita potrebbe essere fisiologica e melanocortined-dipendente, con ovvie ed importanti implicazioni cliniche.


2004 - Taste and smell: From molecular biology to behaviour [Articolo su rivista]
Angelin, B.; Baxter, J.; Bergstrom, G.; Bigiani, A.; Blundell, J.; Buck, L.; Bufe, B.; Drevon, C.; Doving, K.; Garza, C.; Hall, G.; Hanson, L. A.; Hernell, O.; Hill, D.; James, P.; Kauer, J. S.; Katz, S.; Keverne, B.; Lin, D.; Lofstedt, C.; Mustaparta, H.; Norum, K.; Rolls, E.; Rosenberg, I.; Ryba, N.; Rossner, S.; Savic-Berglund, I.; Storm, D. R.; Stubbs, J.; Talamo, B.
abstract


2004 - Taste buds [Capitolo/Saggio]
Bigiani, Albertino
abstract

N/A


2003 - Apical and basal neurones isolated from the mouse vomeronasal organ differ for voltage-dependent currents [Articolo su rivista]
Fieni, Francesca; Ghiaroni, Valeria; R., Tirindelli; Pietra, Pierangelo; Bigiani, Albertino
abstract

The mammalian vomeronasal organ (VNO) contains specialized neurones that transduce the chemical information related to pheromones into discharge of action potentials to the brain. Molecular and biochemical studies have shown that specific components of the pheromonal transduction systems are segregated into two distinct subsets of vomeronasal neurones: apical neurones and basal neurones. However, it is still unknown whether these neuronal subsets also differ in other functional characteristics, such as their membrane properties. We addressed this issue by studying the electrophysiological properties of vomeronasal neurones isolated from mouse VNO. We used the patch-clamp technique to examine both the passive membrane properties and the voltage-gated Na+, K+ and Ca2+ currents. Apical neurones were distinguished from basal ones by the length of their dendrites and by their distinct immunoreactivity for the putative pheromone receptor V2R(2). The analysis of passive properties revealed that there were no significant differences between the two neuronal subsets. Also, apical neurones were similar to basal neurones in their biophysical and pharmacological properties of voltage-gated Na+ and K+ currents. However, we found that the density of Na+ currents was about 2-3 times greater in apical neurones than in basal neurones. Consistently, in situ hybridization analysis revealed a higher expression of the Na+ channel subtype III in apical neurones than in basal ones. In contrast, basal neurones were endowed with Ca2+ currents (T-type) of greater magnitude than apical neurones. Our findings indicate that apical and basal neurones in the VNO exhibit distinct electrical properties. This might have a profound effect on the sensory processes occurring in the VNO during pheromone detection.


2003 - Channels as taste receptors in vertebrates [Articolo su rivista]
Bigiani, Albertino; Ghiaroni, Valeria; Fieni, Francesca
abstract

Taste reception is fundamental for proper selection of food and beverages. Chemicals detected as taste stimuli by vertebrates include a large variety of substances, ranging from inorganic ions (e.g., Na+, H+) to more complex molecules (e.g., sucrose, amino acids, alkaloids). Specialized epithelial cells, called taste receptor cells (TRCs), express specific membrane proteins that function as receptors for taste stimuli. Classical view of the early events in chemical detection was based on the assumption that taste substances bind to membrane receptors in TRCs without permeating the tissue. Although this model is still valid for some chemicals, such as sucrose, it does not hold for small ions, such as Na+, that actually diffuse inside the taste tissue through ion channels. Electrophysiological, pharmacological, biochemical, and molecular biological studies have provided evidence that indeed TRCs use ion channels to reveal the presence of certain substances in foodstuff. In this review, we focus on the functional and molecular properties of ion channels that serve as receptors in taste transduction.


2003 - Efferent vagal fibre stimulation blunts nuclear factor-kappa B activation and protects against hypovolemic hemorrhagic shock [Articolo su rivista]
Guarini, Salvatore; D., Altavilla; Mm, Cainazzo; Giuliani, Daniela; Bigiani, Albertino; H., Marini; G., Squadrito; L., Minutoli; Bertolini, Alfio; R., Marini; Eb, Adamo; Fs, Venuti; F., Squadrito
abstract

Background-We investigated whether electrical stimulation (STIM) of efferent vagus nerves may suppress nuclear factor (NF)-kappaB activation and the inflammatory cascade in hemorrhagic (Hem) shock. Methods and Results-Rats were subjected to bilateral cervical vagotomy (VGX) or sham surgical procedures. Hem shock was induced by intermittent withdrawing of blood until mean arterial pressure stabilized within the range of 35 to 40 mm Hg. Application of constant voltage pulses to the caudal vagus ends (STIM; 5 V, 2 ms, 1 Hz for 12 minutes, 5 minutes after mean arterial pressure stabilization) increased survival time (VGX+Hem+Sham STIM=38+/-3 minutes; VGX+Hem+STIM>180 minutes), reverted the marked hypotension (VGX+Hem+Sham STIM=33+/-3 mm Hg; VGX+Hem+STIM=66+/-5 mm Hg), inhibited IkappaBalpha liver loss, and blunted the augmented NF-kappaB activity, decreased hepatic tumor necrosis factor (TNF)-alpha mRNA (VGX+Hem+Sham STIM=1.42+/-0.5 amount of TNF-alpha m-RNA; VGX+Hem+STIM=0.51+/-0.2 amount of TNF-alpha mRNA), and reduced plasma TNF-alpha (VGX+Hem+Sham STIM=190+/-24 pg/mL; VGX+Hem+STIM=87+/-15 pg/mL). Chlorisondamine, a nicotinic receptor antagonist, abated the effects of vagal stimulation. Conclusions-Our results show a parasympathetic inhibition of NF-kappaB by which the brain opposes NF-kappaB activation in the liver and modulates the inflammatory response during acute hypovolemic hemorrhagic shock.


2003 - Electrophysiological heterogeneity in a functional subset of mouse taste cells during postnatal development [Articolo su rivista]
Ghiaroni, Valeria; Fieni, Francesca; Pietra, Pierangelo; Bigiani, Albertino
abstract

Taste cells in adult mammals are functionally heterogeneous as to the expression of ion channels. How these adult phenotypes are established during postnatal development, however, is not yet clear. We have addressed this issue by studying voltage-gated K+ and Cl- currents (I-K and I-Cl, respectively) in developing taste cells of the mouse vallate papilla. I-K and I-Cl underlie action potential waveform and firing properties, and play an important role in taste transduction. By using the patch clamp technique, we analyzed these currents in a specific group of cells, called Na/OUT cells and thought to be sensory. In adult mice, three different electrophysiological phenotypes of Na/OUT cells could be detected: cells with I-K (K cells); cells with both I-K and I-Cl (K+Cl cells); and cells with I-Cl (Cl cells). In contrast, at early developmental stages (2-4 postnatal days, PD) there were no Cl cells, which appeared at PD 8. Our findings indicate a mechanism that contributes to building-up the functional heterogeneity of mammalian taste cells during the postnatal development.


2003 - Ion conductances in supporting cells isolated from the mouse vomeronasal organ [Articolo su rivista]
Ghiaroni, Valeria; Fieni, Francesca; R., Tirindelli; Pietra, Pierangelo; Bigiani, Albertino
abstract

The vomeronasal organ (VNO) is a chemosensory structure involved in the detection of pheromones in most mammals. The VNO sensory epithelium contains both neurons and supporting cells. Data suggest that vomeronasal neurons represent the pheromonal transduction sites, whereas scarce information is available on the functional properties of supporting cells. To begin to understand their role in VNO physiology, we have characterized with patch-clamp recording techniques the electrophysiological properties of supporting cells isolated from the neuroepithelium of the mouse VNO. Supporting cells were distinguished from neurons by their typical morphology and by the lack of immunoreactivity for Ggamma8 and OMP, two specific markers for vomeronasal neurons. Unlike glial cells in other tissues, VNO supporting cells exhibited a depolarized resting potential (about -29 mV). A Goldman-Hodgkin-Katz analysis for resting ion permeabilities revealed indeed an unique ratio of P-K:P-Na:P-Cl = 1:0.23:1.4. Supporting cells also possessed voltage-dependent K+ and Na+ conductances that differed significantly in their biophysical and pharmacological properties from those expressed by VNO neurons. Thus glial membranes in the VNO can sustain significant fluxes of K+ and Na+, as well as Cl+. This functional property might allow supporting cells to mop-up and redistribute the excess of KCl and NaCl that often occurs in certain pheromone-delivering fluids, like urine, and that could blunt the sensitivity of VNO neurons to pheromones. Therefore vomeronasal supporting cells could affect chemosensory transduction in the VNO by regulating the ionic strength of the pheromone-containing medium.


2002 - Electrophysiology of Necturus taste cells [Articolo su rivista]
Bigiani, Albertino
abstract

Taste buds are sensory end organs that detect chemical substances occurring in foodstuffs and relay the relative information to the brain. The mechanisms by which the chemical stimuli are converted into biological signals represent a central issue in taste research, Our understanding of how taste buds accomplish this operation relies on the detailed knowledge of the biological properties of taste bud cells-the taste cells-and of the functional processes occurring in these cells during chemostimulation. The amphibian Necaturus maculosus (mudpuppy) has proven to be a very useful model for Studying basic cellular processes of vertebrate taste reception, some of which are still awaiting to be explored in mammals. The main advantages offered by Necturus are the large size of its taste cells and the relative accessibility of its taste buds, which can therefore he handled easily for experimental manipulation,;. In this review, I summarize the functional properties of Necturus taste cells studied with electrophysiological techniques (intracellular recordings and patch-clamp recordings). My focus is on ion channels in taste cells and on their role in signal transduction, as well as on the functional relationships among the cells inside Necturus taste buds, This information has revealed to be well suited to Outline some of the general physiological processes occurring during taste reception in vertebrates, including mammals, and may represent a useful framework for understanding how taste buds work. (C) 2002 Elsevier Science Ltd. All rights reserved.


2002 - Postnatal development of membrane excitability in taste cells of the mouse vallate papilla [Articolo su rivista]
Bigiani, Albertino; R., Cristiani; Fieni, Francesca; Ghiaroni, Valeria; P., Bagnoli; Pietra, Pierangelo
abstract

The mammalian peripheral taste system undergoes functional changes during postnatal development. These changes could reflect age-dependent alterations in the membrane properties of taste cells, which use a vast array of ion channels for transduction mechanisms. Yet, scarce information is available on the membrane events in developing taste cells. We have addressed this issue by studying voltage-dependent Na+, K+, and Cl- currents (I-Na, I-K, and I-Cl, respectively) in a subset of taste cells (the so-called Na/OUT cells, which are electrically excitable and thought to be sensory) from mouse vallate papilla. Voltage-dependent currents play a key role during taste transduction, especially in the generation of action potentials. Patch-clamp recordings revealed that I-Na, I-K, and I-Cl were expressed early in postnatal development. However, only I-K and I-Cl densities increased significantly in developing Na/OUT cells. Consistent with the rise of I-K density, we found that action potential waveform changed markedly, with an increased speed of repolarization that was accompanied by an enhanced capability of repetitive firing. In addition to membrane excitability changes in putative sensory cells, we observed a concomitant increase in the occurrence of glia-like taste cells (the so called leaky cells) among patched cells. Leaky cells are likely involved in dissipating the increase of extracellular K+ during action potential discharge in chemosensory cells. Thus, developing taste cells of the mouse vallate papilla undergo a significant electrophysiological maturation and diversification. These functional changes may have a profound impact on the transduction capabilities of taste buds during development.


2002 - Vagus nerve stimulation blunts NF-kB activation and protects against hypovolemic hemorrhagic shock [Abstract in Rivista]
Altavilla, D.; Cainazzo, Maria Michela; Bazzani, Carla; Bigiani, Albertino; Squadrito, F.; Minutoli, L.; Bertolini, Alfio; Guarini, Salvatore
abstract

Vagus nerve stimulation blunts NF-kB activation and protects against hypovolemic hemorrhagic shock


2001 - Amiloride-sensitive sodium currents in identified taste cells of the frog [Articolo su rivista]
Bigiani, Albertino
abstract

Sodium ions occurring in food are thought to be detected, at least in part, through specific amiloride-sensitive, sodium channels (ASSCs) localized in taste receptor cells. Cells within taste buds are morphologically heterogeneous, and include taste receptor cells and other cells that could perform a support or even transduction role. It is not known whether subsets of the taste bud cells express ASSCs, and whether the properties of these channels are similar. By applying the patch-clamp technique to morphologically distinct cells, the supporting wing cells, isolated from the frog taste disk, I have found functional ASSCs that are moderately sensitive to amiloride (Ki 3-4 muM) and which are distinctly lower in affinity for amiloride than reported frog taste receptor cells (K-i 0.2 muM). These results support the hypotheses of the existence of distinct, functional ASSCs in different cell morphotypes, at least in frog taste organs. Neuro Report 12:1315-1321


2001 - Modulation of potassium current and calcium influx by somatostatin in rod bipolar cells isolated from the rabbit retina via sst(2) receptors [Articolo su rivista]
C., Petrucci; V., Resta; Fieni, Francesca; Bigiani, Albertino; P., Bagnoli
abstract

Somatostatin (somatotropin release-inhibiting factor, SRIF) receptor subtypes are expressed by several retinal neurons, suggesting that SRIF acts at multiple levels of the retinal circuitry, although functional data on this issue are scarce. Of the SRIF receptors, the sst(2A) isoform is expressed by rod bipolar cells (RBCs) of the rabbit retina, and in isolated RBCs we studied the role of sst, receptors in modulating both K+ current (I-K) and the intracellular free [Ca2+] ([Ca2+](i)) using both voltage-clamp and Ca2+-imaging techniques. SRIF and octreotide (a SRIF agonist that binds to sst(2) receptors) inhibited that component of I-K corresponding to the activation of large-conductance, Ca2+- and voltage-dependent K+ channels (I-BK) and reduced the K+-induced [Ca2+](i) accumulation, suggesting that SRIF effects on I-BK may have been secondary to inhibition of Ca2+ channels. Octreotide effects on I-BK or On [Ca2+](i) accumulation were prevented by RBC treatment with L-Tyr(8)-Cyanamid 154806, a novel sst(2) receptor antagonist, indicating that SRIF effects were mediated by sst(2) receptor activation. The present data indicate that SRIF may modulate the information flow through second-order retinal neurons via an action predominantly at sst(2) receptors, contribute to the proposition that SRIF be added to the growing list of retinal neuromodulators, and suggest that one of its possible roles in the retina is to regulate transmitter release from RBCs.


2001 - Mouse taste cells with glialike membrane properties [Articolo su rivista]
Bigiani, Albertino
abstract

Taste buds are sensory structures made up by tightly packed, specialized epithelial cells called taste cells. Taste cells are functionally heterogeneous, and a large proportion of them fire action potentials during chemotransduction. In view of the narrow intercellular spaces within the taste bud, it is expected that the ionic composition of the extracellular fluid surrounding taste cells may be altered significantly by activity. This consideration has led to postulate the existence of glialike cells that could control the microenvironment in taste buds. However, the functional identification of such cells has been so far elusive. By using the patch-clamp technique in voltage-clamp conditions, I identified a new type of cells in the taste buds of the mouse vallate papilla. These cells represented about 30% of cells patched in taste buds and were characterized by a large leakage current. Accordingly, I named them Leaky cells. The leakage current was carried by K+, and was blocked by Ba2+ but not by tetraethylammonium (TEA). Other taste cells, such as those possessing voltage-gated Na+ currents and thought to be chemosensory in function, did not express any sizeable leakage current. Consistent with the presence of a leakage conductance, Leaky cells had a low input resistance (similar to0.25 G Omega). In addition, their zero-current (resting) potential was close to the equilibrium potential for potassium ions. The electrophysiological analysis of the membrane currents remaining after pharmacological block by Ba2+ revealed that Leaky cells also possessed a Cl- conductance. However, in resting conditions the membrane of these cells was about 60 times more permeable to K+ than to Cl-. The resting potassium conductance in Leaky cells could be involved in dissipating rapidly the increase in extracellular K+ during action potential discharge in chemosensory cells. Thus Leaky cells might represent glialike elements in taste buds. These findings support a model in which specific cells control the chemical composition of intercellular fluid in taste buds.


1998 - Electrophysiological characterization of a putative supporting cell isolated from the frog taste disk [Articolo su rivista]
Bigiani, Albertino; A., Sbarbati; F., Osculati; Pietra, Pierangelo
abstract

Chemosensory cells in vertebrate taste organs have two obvious specializations: an apical membrane with access to the tastants occurring in food, and synapses with sensory axons. In many species, however, certain differentiated taste cells have access to the tastants but lack any synaptic contacts with axons, and a supportive rather than chemosensory function has been attributed to them. Until now, no functional data are available for these taste cells. To begin to understand their role in taste organ physiology, we have characterized with patch-clamp recording techniques the electrophysiological properties of a putative supporting cell-the so-called wing cell-isolated from frog taste disks. Wing cells were distinguished from chemosensory elements by the presence of a typical, sheet-like apical process. Their resting potential was approximately -52 mV, and the average input resistance was 4.8 G Omega. Wing cells possessed voltage-gated Na+ currents sensitive to TTX, and an inactivating, voltage-gated K+ current sensitive to TEA. Current injections elicited single action potentials but not repetitive firing. We found no evidence for voltage-gated Ca2+ currents under various experimental conditions. Amiloride-sensitive Na+ channels, thought to be involved in Na+ chemotransduction, were present in wing cells. Many of the membrane properties of wing cells have been also reported for chemosensory taste cells. The presence of ion channels in wing cells might be suggestive of a role in controlling the microenvironment inside the taste organs or the functioning of chemosensory cells or both. In addition, they might participate directly in the sensory transduction events by allowing loop currents to flow inside the taste organs during chemostimulation.


1997 - Responses to glutamate in rat taste cells [Articolo su rivista]
Bigiani, Albertino; R. J., Delay; N., Chaudhari; S. C., Kinnamon; S. D., Roper
abstract

We studied taste transduction in sensory receptor cells. Specifically, we examined the actions of glutamate, a significant taste stimulus, on the membrane properties of taste cells by applying whole cell patch-clamp techniques to cells in rat taste buds isolated from foliate and vallate papillae. In 55 of 91 taste cells, bath-applied glutamate, at concentrations that elicit taste responses in the intact animal (10-20 mM), produced one of two different responses when the cell membrane was held near its presumed resting potential, -85 mV. ''Sustained'' glutamate responses were observed in the majority of taste cells (51 of 55) and consisted of an outward current (reduction of the maintained inward current). Sustained glutamate responses were voltage dependent, were decreased by membrane depolarization, and were accompanied by a reduction in membrane conductance, An analysis of the reversal potential of sustained responses in different ionic conditions and the effect of ion substitutions suggested that the currents were carried by cations. The data suggest that sustained responses are mediated by the closure of nonselective cation channels. Ocher taste cells (4 of 55) responded to glutamate with a transient inward current-so-called ''transient'' responses. Transient glutamate responses were voltage dependent and Na+ dependent, and appeared to be generated by nonspecific cation channels activated by glutamate. L(+)-2 amino-di-phosphonobutyric acid (L-AP4), a specific agonist of a metabotropic glutamate receptor (mGluR4) recently identified in rat taste cells and believed to be involved in taste transduction, mimicked the sustained glutamate responses. These findings indicate that glutamate, at concentrations at or slightly above threshold for taste in rats, produces two different membrane currents. The properties of these two responses suggest that there may be two different sets of nonspecific cation channels in taste cells, one closed by glutamate (sustained response) and the other opened (transient response). Our findings on the effect of L-AP4 suggest that the sustained response is the membrane mechanism mediating, at least in part, taste transduction for glutamate.


1996 - Membrane properties and cell ultrastructure of taste receptor cells in Necturus lingual slices [Articolo su rivista]
Bigiani, Albertino; Dj, Kim; Sd, Roper
abstract

Whole cell patch-clamp recordings and electron micrographs were obtained from cells in Necturus taste buds in lingual slices to study their membrane properties and to correlate these properties with cell ultrastructure. 2. Two different populations of taste receptor cells could be identified: one type possessed voltage-gated Na+ and K+ (noninactivating) currents (group 1 cells); the other type possessed only K+ (inactivating) currents (group 2 cells). 3. The zero-current (''resting'') potential (V-0) and whole cell resistance (R(0)) of these two types of taste cells differed significantly. For group 1 cells, on average, V-0 = -75 mV and R(0) = 24.6 G Omega, and for group 2 cells, V-0 = -49 mV and R(0) = 48.9 G Omega. The difference in R(0) was not explained completely by differences in cell sizes, suggesting that intrinsic membrane properties differed between the taste cell populations. 4. Cells injected with biocytin were inspected with the electron microscope after tissues were reacted with diaminobenzidine. The majority (14 of 16) of cells with voltage-gated Na+ and K+ currents (group 1 cells) were characterized by abundant rough endoplasmic reticulum and dense granular packets in the apical process. These are features of dark cells. All the cells that only possessed K+ currents (group 2 cells) were characterized by well-developed smooth endoplasmic reticulum and an absence of granular packets. These features characterize Light cells. 5. These findings indicate that there is a good, although not exact, correlation between electrophysiological properties and cell morphotype in Necturus taste bud cells. All dark cells possessed Na+ and K+ currents and thus would be expected to be capable of generating action potentials. Most light cells only possessed outward K+ currents and thus would be incapable of generating action potentials.


1995 - Estimation of the junctional resistance between electrically coupled receptor cells in Necturus taste buds [Articolo su rivista]
Bigiani, Albertino; Sd, Roper
abstract

Junctional resistance between coupled receptor cells in Necturus taste buds was estimated by modeling the results from single patch pipette voltage clamp studies on lingual slices. The membrane capacitance and input resistance of coupled taste receptor cells were measured to monitor electrical coupling and the results compared with those calculated by a simple model of electrically coupled taste cells. Coupled receptor cells were modeled by two identical receptor cells connected via a junctional resistance. On average, the junctional resistance was similar to 200-300 M Omega. This was consistent with the electrophysiological recordings. A junctional resistance of 200-300 M Omega is close to the threshold for Lucifer yellow dye-coupling detection (similar to 500 M Omega). Therefore, the true extent of coupling in taste buds might be somewhat greater than that predicted from Lucifer yellow dye coupling. Due to the high input resistance of single taste receptor cells (>1 G Omega), a junctional resistance of 200-300 M Omega assures a substantial electrical communication between coupled taste cells, suggesting that the electrical activity of coupled cells might be synchronized.


1995 - The lingual slice preparation, isolated taste cells, and dye injections in Necturus maculosus (mudpuppies) [Capitolo/Saggio]
Bigiani, Albertino; EWALD D., A; Roper, S. D.
abstract

The lingual slice preparation in taste researcj has been extensively used for the amphibian, Necturus maculosus. In this chapter we will describe the experimental procedures that we have developed for this preparation.


1994 - Reduction of electrical coupling between Necturus taste receptor cells, a possible role in acid taste [Articolo su rivista]
Bigiani, Albertino; S. D., Roper
abstract

Cytoplasmic acidification in taste receptor cells is thought to be involved, at least in part, in acid taste transduction. Since in taste buds about 20% of the receptor cells are electrically coupled, we have tested whether reduction in intracellular pH affects these lateral synaptic interactions. By applying the patch clamp technique to a slice preparation of Necturus lingual epithelium, we found that electrical coupling between taste receptor cells was strongly reduced by cytoplasmic acidification. Therefore, electrical coupling in taste buds might be modified during acid stimulation.


1993 - Identification of electrophysiologically distinct cell subpopulations in Necturus taste buds [Articolo su rivista]
Bigiani, Albertino; Roper, S. D.
abstract

We used the patch clamp technique to record from taste cells in thin transverse slices of lingual epithelium from Necturus maculosus. In this preparation, the epithelial polarity and the cellular organization of the taste buds, as well as the interrelationships among cells within the taste bud, were preserved. Whole-cell recording, combined with cell identification using Lucifer yellow, allowed us to identify distinct subpopulations of taste cells based on their electrophysiological properties. Receptor cells could be divided in two groups: one group was characterized by the presence of voltage-gated Na+, K+, and Ca2+ currents; the other group was characterized by the presence of K+ currents only. Therefore, receptor cells in the first group would be expected to be capable of generating action potentials, whereas receptor cells in the second group would not. Basal taste cells could also be divided into two different groups. Some basal cells possessed voltage-gated Na+, K+, and Ca2+ conductances, whereas other basal cells only had K+ conductance. In addition to single taste cells, we were able to identify electrically coupled taste cells. We monitored cell-cell coupling by measuring membrane capacitance and by observing Lucifer yellow dye coupling. Electrical coupling in pairs of dye-coupled taste receptor cells was strong, as indicated by experiments with the uncoupling agent 1-octanol. Electrically coupled receptor cells possessed voltage-gated currents, including Na+ and K+ currents. The electrophysiological differentiation among taste cells presumably is related to functional diversifications, such as different chemosensitivities.


1992 - Olfactory sensitivity to amino acids in the juvenile stages of the European eel Anguilla anguilla (L.) [Articolo su rivista]
Crnjar, R.; Scalera, Giuseppe; Bigiani, Albertino; Tomassini Barbarossa, I.; Magherini, Pc; Pietra, P.
abstract

Scanning electron micrograph observations of the olfactory mucosa from both unpigmented glass eel(GE)andpigmentedelvers(EL)ofthe Europeaneel, AnguilluunguiNa(L.),revealed the presence of various cell types; amongst these, the ciliated and microvillous ones are likely to possess a chcmosensory function. Recording of underwater electro-olfactograms (EOGs) showed that various amino acids (glycine, L-alanine, L-valine, L-leucine, L-asparagine, L-glutamine and Lmethionine) are effective stimulants for the olfactory mucosa. Dose response curves of stimulus concentrations v. EOG amplitudesfit regression linesat both GEand ELstages. Leucine wasmore stimulatory at the GE than at the ELstage. The stimulatory effect ofthe other six amino acids tested was similar at both developmental stages. The possible role of olfactory sensitivity in animal behaviour at different developmental stages is discussed.


1991 - Mediation of responses to calcium in taste cells by modulation of a potassium conductance [Articolo su rivista]
Bigiani, Albertino; Roper, S. D.
abstract

Calcium salts are strong taste stimuli in vertebrate animals. However, the chemosensory transduction mechanisms for calcium are not known. In taste buds of Necturus maculosus (mud puppy), calcium evokes depolarizing receptor potentials by acting extracellularly on the apical ends of taste cells to block a resting potassium conductance. Therefore, divalent cations elicit receptor potentials in taste cells by modulating a potassium conductance rather than by permeating the cell membrane, the mechanism utilized by monovalent cations such as sodium and potassium ions.


1990 - Reduction in extrasynaptic acetylcholine sensitivity of axotomized anterior pagoda neurones in the leech [Articolo su rivista]
Bigiani, Albertino; Pellegrino, M.
abstract

1. The effects of axotomy on the sensitivity of the leech anterior pagoda (AP) neurone to acetylcholine (ACh) and carbamylcholine (CCh) have been studied 1-5 days after axon interruption. 2. Hyperpolarizing responses to ionophoretically applied ACh and CCh have been recorded intracellularly from desheathed cell bodies of normal and axotomized neurones. The electrical properties of the membrane have also been measured in the same neurones. 3. Axotomy produced a progressive loss of sensitivity to both ACh and CCh with a similar percentage reduction. 4. No significant changes have been found in the time to peak and in the reversal potential of the responses to agonists, or in the number of drug molecules needed to combine with a single receptor to produce a response. 5. Interruption of nerve roots and connectives which do not contain the AP axon did not induce the alterations of ACh sensitivity observed after axotomy. 6. It is concluded that the loss of ACh sensitivity following axotomy is due to a reduction in density of functional ACh receptors (AChRs).


1989 - DISTRIBUTION AND FUNCTION OF THE ANTENNAL OLFACTORY SENSILLA IN CERATITIS-CAPITATA WIED (DIPTERA, TRYPETIDAE) [Articolo su rivista]
Bigiani, Albertino; Scalera, Giuseppe; Crnjar, R; Barbarossa, It; Magherini, Pier Cosimo; Pietra, Pierangelo
abstract

Vedi articolo


1989 - Morphology and EAG mapping of the antennal olfactory receptors in Dacus oleae [Articolo su rivista]
Crnjar, R.; Scalera, G.; Liscia, A.; Angioy, A. M.; Bigiani, A.; Pietra, P.; Barbarossa, I. T.
abstract

EAGs were recorded from various locations on the flagellar surface of the antennae of the olive fly Dacus oleae stimulated with compounds of behavioural significance to this species. This information was compared with data on the typology and distribution patterns of the olfactory sensilla. Results showed that: a) 3 types of olfactory sensilla are present on the antennae: long basiconica, short grooved basiconica and trichodea; b) 1‐hexanol, ethanol and volatiles belonging to the oily fraction of the olive pulp are the strongest stimuli, while those of the water fraction are little or not effective; c) EAG amplitude values vary as a function of the recording location on the flagellar surface; d) a significant correlation was found, for 2 stimuli of the oily fraction, between EAG amplitude and population density of long sensilla basiconica, thus suggesting this type as specifically responding to these substances. Morphologie des antennes de Dacus oleae et localisation de leurs récepteurs olfactifs par électroantennogramme Des EAG ont été obtenus en différents points de la surface de flagelles d'antennes de la mouche de l'olive, stimulées par des substances ayant une signification pour le comportement de cette espèce. Ces informations ont été comparées avec les données tirées de la typologie et de la distribution des sensilles olfactives. Les résultats mettent en évidence: a) 3 types de sensilles: longue basiconique, basiconique à petit sillon et trichodes; b) les stimuli les plus puissants de la pulpe sont l'1‐hexanol, l'éthanol et les substances volatiles solubles dans l'huile, tandis que les substances hydrosolubles sont peu ou pas actives; c) une ampleur de l'EAG variant en fonction du lieu d'enregistrement sur la surface du flagelle; d) une corrélation significative pour 2 stimuli liposolubles entre l'amplitude de l'EAG et la densité des longues sensilles basiconiques, ce qui suggère une réaction spécifique de ce type de récepteur à ces substances. 1989 The Netherlands Entomological Society