The response characteristics of rat taste cells to four basic taste stimuli.

1. The shapes of receptor potentials of rat taste cells in response to the four basic taste stimuli (0.5 M NaCl, 0.02 M quinine-HCl (Q-HCl), 0.01 M HCl and 0.5 M sucrose) were classified into three types, i.e. (1) a depolarization alone, (2) a depolarization preceded by a transient hyperpolarization and (3) hyperpolarization alone. 2. The rise and fall times of depolarizing responses to NaCl were much shorter than those to the other three stimuli. The fall time of depolarization evoked by HCl was the longest. The rise and fall times of all hyperpolarizing responses were shorter than those of all depolarizing responses. 3. The input resistance of taste cells decreased during depolarizations elicited by NaCl stimulation, but increased during depolarizations and hyperpolarizations elicited by stimulation with Q-HCl, HCl and sucrose. 4. The taste stimulus-induced input resistance change returned faster to the control in the order of NaCl greater than sucrose greater than Q-HCl greater than HCl when the stimulus was rinsed from the tongue. 5. From these response characteristics the rat taste cells responding to each of the four basic taste stimuli are largely divided into two types, low-sensitive taste cell and high-sensitive taste cell.