Chorda tympani section decreases the cation specificity of depletion-induced sodium appetite in rats

Abstract

Rats depleted of sodium by diuretic treatment were tested for their ability to respond selectively to NaCl after chorda tympani nerve (CTn) section (CTX). A variety of chloride salts (NaCl, KCl, NH4Cl, CaCl2) at two concentrations (0.05 and 0.3 M) were presented semirandomly to sodium-deplete rats in repeated single-stimulus trials (10 s). The responses of sodium-depleted surgical control rats (n = 8) were highly cation specific. These rats licked substantially more for both sodium stimuli than for any other chloride salt. On the other hand, the licking responses of CTX sodium-depleted rats (n = 8) were less cation selective. These rats licked NaCl and 0.05 M KCl at comparable rates. For both NaCl concentrations, CTX rats had significantly lower lick rates than controls. In addition, the difference between the lick rate for NaCl and that for the other salts was much greater for control rats than for CTX rats. Although CTn section did not entirely eliminate the high levels of responsivity to NaCl observed in the intact sodium-depleted rat, it did substantially compromise the selectivity of the behavior, which suggests that the input of the CTn is critical for taste-guided sodium specific behaviors.