C-FOS INDUCTION IN THE RAT NUCLEUS OF THE SOLITARY TRACT BY INTRAORALQUININE INFUSION DEPENDS ON PRIOR CONTINGENT PAIRING OF QUININE AND LITHIUM-CHLORIDE

Intraoral infusions of sucrose or saccharin induce c-Fos-like immunore activity (c-FLI) in the intermediate nucleus of the solitary tract (iN TS) of rats after acquisition of a conditioned taste aversion (CTA). T he induction of c-FLI in the iNTS may be a consequence of the shift in behavioral response from ingestive to aversive behaviors that charact erize acquisition and expression of a CTA. To test this hypothesis, ra ts were intraorally infused with 0.3 mM quinine sulfate, an aversive t aste, 1. prior to conditioning, 2. after 3 noncontingent (unpaired) in fusions of quinine and toxic lithium chloride (LiCl) injections, 3. af ter conditioning with 3 contingent pairings of quinine and LiCl, and 4 . after extinction with repeated unpaired infusions of quinine. Intrao ral infusions of quinine induced c-FLI in the iNTS only after acquisit ion of a CTA against quinine; quinine failed to induce c-FLI in the iN TS of unconditioned, noncontingently treated, or extinguished rats. Th e pattern of c-FLI in the iNTS induced by expression of a CTA against quinine was quantitatively and anatomically similar to that elicited b y sucrose in rats expressing a CTA against sucrose. We conclude that a versive responses per se are not sufficient to induce c-FLI in the iNT S. Furthermore, contingent pairing of quinine and LiCl does not cause a shift in behavioral response from palatable, ingestive behaviors to aversive behaviors as in acquisition of a CTA against sucrose. Thus, w e also conclude that a shift in behavior from ingestive to aversive re sponses is not required for increased c-FLI expression in the iNTS dur ing CTA expression. Therefore, the induction of c-FLI in the iNTS duri ng expression of a CTA may be correlated with neuronal processes speci fic to acquisition and expression of a CTA. Copyright (C) 1996 Elsevie r Science Inc.