Enhancement of gustatory neural response to salts following adaptation of frog tongue to quinine-HCI.

After a frog tongue was adapted to 0.001 M quinine-HCl(Q-HCl), a change in the gustatory neural responses to salts was investigated. The initial phasic response to a variety of salt solutions such as 0.1 M NaCl, KCl, LiCl, MgCl2 and CaCl2 was greatly potentiated as a result of the Q-HCl adaptation. A weaker enhancement of the response to salts was observed after the tongue was adapted to deionized water, compared with the control response to salts during Ringer adaptation. Therefore, the Q-HCl-induced enhancement of salt responses is due to the summated effect of Q-HCl solute and water solvent. Concerning the enhancing mechanism of Q-HCl, it is postulated that the membrane potential of some salt-sensitive taste cells will be displaced in the hyperpolarizing direction during the Q-HCl adaptation, and that large depolarization, which may be related to the enhanced nerve response, will be produced by applying salts after Q-HCl.