IN-SITU TIGHT-SEAL RECORDINGS OF TASTE SUBSTANCE-ELICITED ACTION CURRENTS AND VOLTAGE-GATED BA CURRENTS FROM SINGLE TASTE BUD CELLS IN THE PEELED EPITHELIUM OF MOUSE TONGUE

We investigated the taste responses of single taste-bud cells (TBCs) i n mice by applying stimuli only on receptor membranes acclimated to de ionized water under tight-seal cell-attached voltage-clamp conditions, while their basolateral membranes were irrigated with a physiological saline solution. For this irrigation, we developed a new method: a pe eled-tongue epithelium with TBCs mounted on a recording chamber where the peeled epithelium separated the irrigating solutions for each memb rane as it separated in situ. Although no quinine-elicited action pote ntials had been reported, TBCs elicited a long-lasting train of biphas ic currents derived from the action potentials in response to 10 mM qu inine, in addition to responses to 10 mM HCl, or 200 mM NaCl dissolved in deionized water. These results indicate that quinine as well as HC l and NaCl depolarizes TBCs and generate action potentials. Under whol e-cell recording conditions, TBCs generated action potentials, and vol tage-gated currents such as LVA and HVA Ca currents, TTX-sensitive Na currents, and TEA/4-AP-sensitive K currents on depolarization. These v oltage-gated channels were shown to exist predominantly on the basolat eral membranes. We discussed the receptor mechanisms and the role of t aste substance-elicited action potentials. (C) 1997 Elsevier Science B .V.