Abstract
Amiloride has been suggested to inhibit responses to a variety of taste stimuli, including salty, sweet, and sour (acid). To test for the involvement of amiloride-sensitive Na
+ channels in the transduction of acid stimuli, fungi-form taste receptor cells were examined using patch-clamp techniques. Approximately one-half of all cells had amiloride-sensitive Na
+ currents (I
Na) with a K
i value near 0.2 μM amiloride. After blocking voltage-gated conductances, cells having amiloride sensitivity were tested for responses to acid stimuli. Over three-fourths of cells showed an inward proton current (I
H
+
) with an extrapolated reversal potential near approximately +150 mV, which was completely blocked by amiloride (30 μM). Treatment of isolated taste cells with argininee-vasopressin caused equivalent increases in both I
Na and I
H
+
; each effect was mimicked by 8-Br-cAMP. Taken together, these results indicate that protons permeate amiloride-sensitive Na
+ channels in hamster fungiform taste cells and contribute to acid transduction.
