Temperature and amiloride alter taste nerve responses to Na+, K+, and NH+4 salts in rats.

The effects of adaptation/stimulus temperature (25 degrees C vs. 35 degrees C) on taste nerve responses to salt stimulation and amiloride suppression were assessed in rats. We measured the integrated responses of the chorda tympani nerve to 500 mM concentrations of NaCl, Na2SO4, sodium acetate (NaAc), KCl, K2SO4, potassium acetate (KAc), NH4Cl, (NH4)2SO4, and ammonium acetate (NH4Ac) mixed with or without 100 microM amiloride hydrochloride at 35 degrees C. Taste nerve responses to all Na+ and NH4+ salts, but not K/ salts, were significantly smaller at 25 degrees C than at 35 degrees C. Amiloride significantly suppressed taste nerve responses to all salts (Na+ salts > K+ salts > NH4+ salts); amiloride suppression of Na+ and NH4+ salts was significantly greater at 25 degrees C than at 35 degrees C. Benzamil-HCl, a more potent Na+ channel blocker compared to amiloride, strongly suppressed taste nerve responses to NaCl and KCl, but not to NH4Cl. Amiloride and benzamil suppression of NaCl responses were similar; however, amiloride suppressed KCl responses more than did benzamil. The results suggest that: (1) amiloride-sensitive Na+ channels are involved to varying degrees in the transduction of sodium and potassium salt taste, and (2) amiloride may inhibit membrane proteins other than passive Na+ channels during stimulation with potassium and ammonium salts.