TEMPERATURE AND AMILORIDE ALTER TASTE NERVE RESPONSES TO NA+, K+, ANDNH4+ SALTS IN RATS

The effects of adaptation/stimulus temperature (25 degrees C vs. 35 de grees C) on taste nerve responses to salt stimulation and amiloride su ppression 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, (NH 4)(2)SO4, and ammonium acetate (NH4Ac) mixed with or without 100 mu M amiloride hydrochloride at 25 degrees C and 35 degrees C. Taste nerve responses to all Na+ and NH4+ salts, but not K+ salts, were significan tly smaller at 25 degrees C than at 35 degrees C. Amiloride significan tly suppressed taste nerve responses to all salts (Na+ salts > K+ salt s > NH4+ salts); amiloride suppression of Na+ and NH4+ salts was signi ficantly greater at 25 degrees C than at 35 degrees C. Benzamil-HCl, a more potent Na+ channel blocker compared to amiloride, strongly suppr essed taste nerve responses to NaCl and KCl, but not to NH4Cl. Amilori de and benzamil suppression of NaCl responses were similar; however, a miloride suppressed KCl responses more than did benzamil. The results suggest that: (1) amiloride-sensitive Na+ channels are involved to var ying degrees in the transduction of sodium and potassium salt taste, a nd (2) amiloride may inhibit membrane proteins other than passive Nachannels during stimulation with potassium and ammonium salts.