Amiloride sensitivity of chorda tympani response to NaCl in Fischer 344 and Wistar rats

Abstract

Fischer 344 (F-344) rats fail to prefer NaCl solutions to water at any concentration and avoid NaCl solutions preferred by other strains, including Wistar rats. Behavioral and electrophysiological responses of the mammalian gustatory system to NaCl have been shown to depend on a sodium transport system that is specifically blocked by lingual application of the sodium-transport blocker amiloride. The present study examined whether strain differences exist between F-344 and Wistar rats in the amiloride sensitivity of the chorda tympani (CT) electrophysiological response to NaCl. Whole nerve CT recordings were obtained from adult F-344 and Wistar rats during chemical stimulation of the anterior tongue. Responses to NaCl solutions ranging from 0.01 to 1.0 M were examined both before and after pretreatment with amiloride hydrochloride. Integrated whole nerve responses to NaCl solutions were expressed relative to the response to 0.5 M NH4Cl. Strain differences in the response to NaCl solutions emerged, with F-344 animals showing a significantly larger amplitude of the tonic response to NaCl, relative to NH4Cl, than Wistars. F-344 rats were also more sensitive to the sodium-channel blocker amiloride. These results suggest that strain differences in amiloride sensitive signals mediated by the CT nerve may contribute to the NaCl aversion displayed by F-344 rats.