Amiloride-insensitive units of the chorda tympani nerve are necessary for normal ammonium chloride detectability in the rat.

Abstract

In spite of its common use as a standard stimulus in peripheral nerve recordings, relatively little is known about the psychophysics of NH-sub-4Cl taste. Rats' detection threshold for this salt was tested under a variety of conditions, including amiloride (100 muM) treatment and bilateral chorda tympani (CT) nerve transection. Detectability was measured with a 2-lever operant discrimination procedure used previously to measure detection thresholds for NaCl and KCl. Although NH-sub-4Cl and KCl appear to share a common taste quality and transduction mechanism, the logistic function and threshold for NH-sub-4Cl were found to be more similar to those of NaCl than to those of KCl. Like that of KCl, however, the detection threshold for NH4Cl increased significantly with CT transection (0.54 log-sub-1-sub-0 units, p < .004), but not with amiloride adulteration. This finding supports the hypothesis that the CT is necessary for normal salt detection regardless of stimulus, and suggests that amiloride does not appreciably impact responses to nonsodium salts at the behavioral level.