Specificity of Glossopharyngeal Nerve Responses to Astringent Compounds in Xenopus

Astringent compounds were applied to oral epithelium of theclawed toad, Xenopus laevis, and rapidly rising and highly sensitiveresponses could be recorded from the whole glossopharyngealnerve, but not at all from the trigeminal nerve. The responseto 10 mM tannic acid decreased progressively with repetitiveapplication. These responses to tannic acid, however, recoveredcompletely by treating with chemicals capable of forming stronghydrogen and hydrophobic bonds. These chemical bondings aregenerally recognized as a model for polyphenol (tannin)-proteininteractions based on physico-chemical measurements in vitro.The high affinities of these chemicals for tannic acid may beeffective in releasing both bonds in the interaction of tannicacid with the receptor molecules. Our results provide in vivoevidence for this model. Chem. Senses 21: 459–465, 1996.