カエル舌咽神経の相動性味覚応答に関与する複数受容部位

― 交叉順応法による研究 ―

抄録

The frog glossopharyngeal nerve elicits phasic responses to various taste stimuli applied to the tongue after a rinse of 1mM NaCl. The difference in the receptor sites for various taste stimuli eliciting phasic responses in the frog glossopharyngeal nerve was investigated by using a cross-adaptation method. Cross-adaptation experiments were carried out as follows. First, one stimulus was applied to the tongue and was followed by another stimulus after the response to the first stimulus had declined. The cross-adaptation experiments were carried out between pairs of four basic taste substances, four bitter substances and three chloride-salts. The results obtained suggest that four basic taste substances (quinine-HCl, NaCl, saccharin and acetic acid) stimulate different receptor sites. The response to one of the bitter substances (quinine-HCl, denatonium, caffeine and theophylline) applied secondarily was decreased by another bitter substance applied first, but reduction in the response to the second stimulus depended on the types of bitter substances applied first. This was also true in cross-adaptation experiments between pairs of three salts (NaCl, KCl and NH_4Cl). However, quinine-HCl and salts did not share a receptor mechanism with each other. The present results suggest that there are different receptor sites responsible for phasic responses to various taste substances and that some receptors interact with other receptors. The sites responsible for adaptation to taste stimulation are discussed.