Amiloride does not block taste transduction in the mudpuppy, necturus maculosus

Activity of the glossopharyngeal nerve was recorded with bipolar silver wire electrodes while taste stimuli were applied to the lingual surface in anesthetized mudpuppies. Taste stimuli were injected into a continuous stream of distilled water which was running over the tongue, KCl, CaCl₂ and LiCl₂ and 0.4 M elicited brisk responses, as did HCl at 0.2 M and quinine at 6 x 10^-4 M. Sucrose, glucose and saccharin did not elicit responses. Twenty amino acids were surveyed for their ability to evoke a response at 0.04 M: l-arginine, l-valine, l-phenylalanine, l-tryptophan, l-tyrosine, l-glutamic acid, l-lysine and histidine always evoked responses, whereas other amino acids either did not evoke responses or only occasionally evoked responses. The supernatants from solutions of minced worms and minnows and Purina Trout Chow were effective taste stimuli. Pre-adapting the tongue to Ringer's solution by running a continuous stream of Ringer's solution over it eliminated responses to quinine and decreased responses to NaCl. Pre-adapting the tongue to 10^-4 to 10^-3 M amiloride, a potent sodium channel blocker, did not alter the responses to NaCl, LiCl, or other taste stimuli.