1. Themeanrestingmembranepotentialofrattaste cells is - 36 mVunderadap-
tation of the tongue to 41.4 mMNaCI and - 50mV under water adaptation.
2. The shapes ofreceptor potentials ofrattastecells inresponsetothe four
basic tastestimuli(0.5MNaCI, 0.02 M Q-HCI, 0.01 MHCl, and0.5 M
sucrose)are classified into three types, namely (1) a depolarization
alone, (2) a depolariza- tion preceded by a transient hyperpolarization,
and (3) a hyperpolarization alone. No regenerative spike potentials are
evoked in rat taste cells by chemical stimuli. The amplitude of rat
taste cell responses increases with increasing concentrationofthe taste
stimulus. Mostofthe rat taste cells show a multiple sensitivity in that
single cells respond to various combinations of the four basic taste
stimuli with depolarizations or hyperpolarizations. 3. The rise and fall
times of depolarizing responses to 0.5 M NaCI are much shorter than
those of depolarizing responses to the other three stimuli. The fall
time of depolarization evoked by 0.01 M HCI is the longest. The rise and
fall times of all hyperpolarizing responses are shorter than those of
all de- polarizing responses.