Abstract
Quinine-sensitive units (Q-units) of the frog glossopharyngeal nerve respond to chloride-salts such as NaCl and choline Cl (Ch-Cl). Q and chloride-salts are quite different taste substances. Q-units show only a phasic response. In the present study, we investigated the specificity of and similarities between taste reception of Q and that of chloride salts. Anesthetized bullfrogs were used. Antidromic impulses of single Q-units were recorded from a single fungiform papilla that had been drawn into a suction electrode during chemical stimulation of adjacent papillae. The taste stimuli were delivered through a fine tube positioned close to the suction electrode. An electrical surge (onset of stimulus) appeared when the first drop of stimulant reached the tongue surface. The time between the onset of stimulus and appearance of the first impulse were measured as the latency of taste response. The latency decreased and the frequency of impulses increased with increasing concentrations of Q or Ch-Cl. In each Q-unit, the relation between the latency and the frequency of impulses elicite by Q at 0.001-1.0 mM are identical to that elicited by Ch-Cl at 1-500 mM, suggesting that Q and Ch-Cl use the same transduction pathway. However, Q-units could be excited by Ch-Cl after being desensitized by Q. It appears that Q and Ch-Cl interact with different receptor sites. The present results suggested that Q and Ch-Cl act on different receptors and use a common transduction pathway. [J Physiol Sci. 2007;57 Suppl:S100]
