Sodium specificity of salt appetite in Fischer-344 and Wistar rats is impaired by chorda tympani nerve transection

Abstract

Unlike other rat strains, the sodium-replete Fischer-344 (F344) strain shows no innate preference for NaCl and displays more aversive and fewer ingestive oral motor responses to orally infused NaCl when tested in sodium balance. Despite these differences, F344 rats show an increase in preference for NaCl in response to sodium depletion. The present study was designed to determine whether the salt appetite of sodium-depleted F344 rats is cation specific and whether such selectivity is mediated in part by an intact chorda tympani nerve. Sodium-depleted (10 mg furosemide) F344 (n = 13) and Wistar (n = 16) rats were permitted repeated access to nine stimuli (water, and 0.05 and 0.3 M NaCl, KCl, NH4Cl, and CaCl2), presented randomly in 10-s trials. One-half of the rats had their chorda tympani nerve sectioned (CTX). Under conditions of sodium depletion, both strains discriminated NaCl from other chloride salts. CTX significantly impaired the selectivity of the licking behavior in both strains, suggesting that sodium-specific licking is partially mediated by anterior tongue taste receptors. These findings suggest that both sodium-depleted F344 and Wistar rats are comparable in their abilities to recognize NaCl, to distinguish it from other salts, and to respond selectively to it, despite the fact that sodium-replete F344 and Wistar rats differ greatly in their NaCl preference.