GLOSSOPHARYNGEAL NERVE TRANSECTION DOES NOT COMPROMISE THE SPECIFICITY OF TASTE-GUIDED SODIUM APPETITE IN RATS

The chorda tympani nerve (CT) has been shown to be critical in the sod ium-specific drinking behavior of sodium-depleted rats, but the role o f other gustatory nerves and the contribution of the major salivary gl ands remain to be elucidated. In this study, rats received either bila teral section of the CT (CTX) or the glossopharyngeal nerve (GLX), ext irpation of the sublingual and submaxillary salivary glands (DSAL), or sham surgery. After recovery, rats were sodium depleted with furosemi de and tested for their licking responses to 0.05 and 0.3 M NaCl, KCl, CaCl2, and NH4Cl, as well as distilled water in an automated gustomet er. Rats that received GLX maintained a specific sodium appetite compa rable to controls despite denervation of similar to 64% of the taste b uds. In contrast, compared with control rats, CTX and DSAL rats had al tered response profiles, showing much smaller differences in licking t o NaCl relative to the other stimuli. This was accompanied by a substa ntially lower lick rate in DSAL rats, raising the possibility that gen eral licking impairments contributed to the decreased NaCl responsiven ess in these rats. These findings imply that the CT, but not the gloss opharyngeal nerve, is necessary for the maintenance of normal sodium-s pecific, taste-guided behavior under sodium deplete conditions.