Temperature dependence of amiloride-sensitive and -insensitive components of rat taste nerve response to NaCl

The temperature dependence of the rat taste response to NaCl was examined by measuring the chorda tympani activities in response to NaCl solution of varying temperatures before and after amiloride treatment. The response to NaCl was composed of 3 components: component I which was not suppressed by amiloride and components II and III which were suppressed by amiloride. Components I, II and III show maximal responses around 30, 30 and 10 degrees C, respectively. The response to NaCl at 10 degrees C was composed mostly of amiloride-sensitive component (component III). Magnitude of the amiloride-insensitive component (I) was greatly affected by variation of anion species. The amiloride-sensitive component II also showed anion influence but the influence was different from that for component I. Another amiloride-sensitive component (III) showed practically no anion influence. Threshold concentrations of the components were 0.1 mM for component I, 3 mM for component II and 0.3 mM for component III. Equilibrium potentials of Na+ at the threshold concentrations across the apical membrane of taste cells were calculated to be -120.2 mV for component I, -31.4 mV for component II and -85.4 mV for components III. Thus the equilibrium potentials of Na+ at the thresholds for components I and III were more negative than the resting potentials reported, which suggested that an increase in permeabilities of Na+ through receptor sites (or channels) for these components will lead to hyperpolarization, not depolarization of taste cells.