CA2+-DEPENDENT CHLORIDE CONDUCTANCE IN NECTURUS TASTE CELLS

This report describes the occurrence and localization of a Ca2+-dependent chloride conductance in taste cells of Necturus maculosus. Lingual epithelium from Necturus was removed with blunt dissection and mounted in a modified Ussing chamber which allowed individual taste cells to be impaled with intracellular micropipettes. Solutions in the mucosal and serosal chambers could be changed independently and the properties of apical and basolateral membranes tested separately. Action potentials in taste cells, elicited by brief depolarizing current pulses passed through the intracellular recording microelectrode, provided an accurate description of whether voltage-dependent conductances had been blocked or unmasked by the experimental conditions. We found that Ca2+ influx during the action potential triggers a prolonged depolarization due to Ca2+-dependent conductance changes, particularly in the presence of TEA to block repolarizing K+ currents. This afterdepolarization could last up to 7 sec and is due, in part, to a Ca2+-dependent Cl- conductance. Other Ca2+-dependent channels such as Ca2+-dependent K+ channels or nonselective cation channels may also contribute to the afterpotential. Calcium-dependent conductance channels were situated on apical and basolateral membranes of the taste cells. We speculate that Ca2+-dependent Cl- channels may play a role in discriminating chloride salts from salts of other anions and may help shape receptor cell responses elicited by taste stimuli.