Gustatory deafferentation and desalivation: effects on NaCl preference of Fischer 344 rats

The chorda tympani nerve (CT) appears to be particularly responsive to NaCl stimulation of the tongue. However, in most strains of rat, bilateral transection of the CT (CTX) results in little alteration of salt preference. The Fischer 344 (F344) strain of rat is unusual in its lack of preference for any concentration of salt. We recently reported a dramatic change from aversion to preference for salt in F344 rats after CTX. The present studies further explored this alteration in salt preference of F344 rats with an expanded range of NaCl concentrations. Additionally, the specificity of the CT in mediating F344 salt aversion was examined by testing NaCl preference after glossopharyngeal nerve (GL) transections, combined CT and GL deafferentation, and partial desalivation. Comparison with Wistar rats revealed that salt preference of F344 CTX rats followed a typical preference/aversion pattern across a range of NaCl concentrations. Studies of GL section, either alone or combined with CT sectioning, indicated that F344 rats' aversion was dependent on the integrity of the CT and not the GL. Removal of sublingual and submaxillary salivary glands did not lead to preference changes similar to those after CTX, indicating that the effects of CTX are not secondary to desalivation. Overall, the findings point to signals from the CT as playing a primary role in the NaCl aversion displayed by the intact F344 rat.