Off-depolarization and off-hyperpolarization after termination of quinine-HCl stimulation in frog taste cells

Off-responses in frog taste cells evoked by a Ringer rinse following 1 mM quinine-HCI (Q-HCl) stimulation were investigated with an intracellular recording technique. Three types of off-responses were found; a transient off-depolarization, a rebound-type off-depolarization and a transient off-hyperpolarization. The time to peak and duration of off-responses were in the order of rebound type-off-depolarization > transient off-depolarization > transient off-hyperpolarization. The reversal potential for the rebound-type off-depolarization existed in more positive level than the resting potential. The reversal potential for the transient off-depolarization was around 0 mV, and that for the transient off-hyperpolarization was -58 mV. These three off-responses in frog taste cells may be initiated by an increase in permeability of the apical receptive membrane to Na+, K+ and CI-. A kind of principal ion is dependent on off-response types.