Stimulus-induced currents in isolated taste receptor cells of the larval tiger salamander

Gustatory receptor cells, isolated from the lingual epitheliumof larval tiger salamanders (Ambystoma tigrinum), possess avariety of voltage- and ion-dependent conductances, includinga transient Na⁺ -current (I_Na), a voltage-gated Ca²⁺ -current(I_A). a transient K₊ -current (I_A), a delayed rectifier K⁺ -current(I_K), and a Ca₂₊ -activated K₊ -current (I_K(Ca))- By use ofwhole-cell and excised-patch tight-seal recording techniques,we examined the effects of taste stimuli on the conductancesof taste cells from the tiger salamander. Depolarizing receptorpotentials elicited by NaCl were associated with slow, gradedinward currents which were composed of amiloride-sensitive andtetrodoxin-(TTX)-sensitive components. Potassium chloride producedmaintained inward currents, which usually showed both phasicand tonic components and were only partially blocked by tetraethylammoniumchloride (TEA). Citric and acetic acids elicited slow depolarizationsin taste cells. Under voltage-clamp, acids produced graded inwardcurrents which were composed of two components: one attributableto a transient block of voltage-dependent K₊ -channels and asmaller component which may have resulted from an increasedconductance to cations. Quinine hydrochloride elicited slowdepolarization of taste cells which was associated with a slowlydeveloping maintained inward current under voltage-clamp. Quininesuppressed both voltage-dependent inward and outward currents.In some taste cells, L-arginine elicited small outward currentswhich were attributable to an increase in K₊ conductance. Inother cells, L-arginine produced a decrease in voltage-dependentoutward currents and generated depolarizations associated withinward currents. These results indicate that several independentmechanisms, including amiloride-sensitive Na₊ -channels, andstimulus modulation of voltage-dependent K₊ -channels, are involvedin taste cell responses to chemical stimuli. More than one mechanismis typically present in a single cell. ³Present address: Department of Physiology, Tokyo Medical andDental University, 5-45 Yushima 1-chome, Bunkyo-ku, Tokyo 113,Japan