Effects of amiloride on gustatory neural responses to salts in the frog

摘要

In frogs, the glossopharyngeal nerve (GL) innervates taste receptors on almost the entire tongue. The mandibular branch (MBF) and palatine branch (PN) of the facial nerve innervate taste receptors on a very small area at the base of the tongue and on the palate, respectively. In the present study, effects of amiloride, an epithelial sodium channel blocker, on the tonic responses of the GL, MBF and PN in frogs to NaCl, LiCl, KCl and CaCl_2 were investigated. In three nerves, amiloride at 0.5 M NaCl, 0.5 M LiCl and 0.3 M KCl, whereas it almost completely inhibited the response to 1.0 mM CaCl_2. Amiloride may exert and inhibitory action on the response to CaCl_2 by a competitive antagonism between Ca~(2+) and a monovalent cation of amiloride, because the response to Ca~(2+) is competitively inhibited by other cations such as Na~+ and Mg~(2+). The lack of inhibitory effect of amiloride on the responses in the GL, MBF and PN to NaCl suggests that amiloride-sensitive sodium channels in the apical membrane of taste receptor cells are not involved in sodium taste transduction in frogs.