Electrical responses to frog taste cells to chemical stimuli

1. Cells inside a fungiform papilla of the frog tongue were impaled with a glass capillary micro-electrode filled with 3 M-KCl. Cells considered to be taste cells showed a resting potential of about -35 mV and an input resistance of 17 Momega on the average. 2. Application of chemical stimuli such as salts, acids and quinine produced a sustained depolarization in a taste cell, the magnitude of depolarization being dependent on the stimulus concentration. Water and weak NaCl solution yielded a hyperpolarization. The thresholds for depolarization as well as the concentration-response relationships for various chemical stimuli in taste cells are in approximate agreement with those determined from the glossopharyngeal nerve responses. 3. The magnitude of depolarization produced by 0-1 M-NaCl and 0-03 M-CaCl2 was dependent on the membrane potential level and reduced linearly with a rise in the latter. However, depolarizations generated by 0-001 M-HDl and 0-02 M quinine changed little in magnitude by a membrane potential change over a wide range. 4. During depolarizations induced by NaCl and KCl a marked reduction in the input resistance of a cell was observed, the amount of the reduction depending on the stimulus concentration. The reduction was also produced by CaCl2 and HCl, but it is small compared with those by NaCl and KCl. Quinine produced an increase in the resistance associated with a depolarization. Water and weak NaCl solution produced an increase in the resistance associated with hyperpolarization. 5. The receptive mechanisms for various kinds of chemical stimuli are discussed in relation to changes in the membrane potential and the membrane conductance of taste cells.