title: c-Fos induction in the rat nucleus of the solitary tract by intraoral quinine infusion depends on prior contingent pairing of quinine and lithium chloride.
abstract: Intraoral infusions of sucrose or saccharin induce c-Fos-like immunoreactivity (c-FLI) in the intermediate nucleus of the solitary tract (iNTS) of rats after acquisition of a conditioned taste aversion (CTA). The induction of c-FLI in the iNTS may be a consequence of the shift in behavioral response from ingestive to aversive behaviors that characterize acquisition and expression of a CTA. To test this hypothesis, rats were intraorally infused with 0.3 mM quinine sulfate, an aversive taste, 1. prior to conditioning, 2. after 3 noncontingent (unpaired) infusions of quinine and toxic lithium chloride (LiCl) injections, 3. after conditioning with 3 contingent pairings of quinine and LiCl, and 4. after extinction with repeated unpaired infusions of quinine. Intraoral infusions of quinine induced c-FLI in the iNTS only after acquisition of a CTA against quinine; quinine failed to induce c-FLI in the iNTS of unconditioned, noncontingently treated, or extinguished rats. The pattern of c-FLI in the iNTS induced by expression of a CTA against quinine was quantitatively and anatomically similar to that elicited by sucrose in rats expressing a CTA against sucrose. We conclude that aversive responses per se are not sufficient to induce c-FLI in the iNTS. 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, we also conclude that a shift in behavior from ingestive to aversive responses is not required for increased c-FLI expression in the iNTS during CTA expression. Therefore, the induction of c-FLI in the iNTS during expression of a CTA may be correlated with neuronal processes specific to acquisition and expression of a CTA.
authors.affiliation: E. W. Bourne Behavioral Research Laboratory, Department of Psychiatry, Cornell University Medical College, White Plains, NY 10605, USA. tah2@cornell.edu
authors.forename: T A
authors.initials: TA
authors.lastname: Houpt
authors.forename: J M
authors.initials: JM
authors.lastname: Philopena
authors.forename: T H
authors.initials: TH
authors.lastname: Joh
authors.forename: G P
authors.initials: GP
authors.lastname: Smith
mesh_terms: D000818:Animals; D002452:Cell Count / Q000187:drug effects; D003213:Conditioning, Psychological / Q000187:drug effects*; D018021:Lithium Chloride / Q000494:pharmacology*; D008297:Male; D016760:Proto-Oncogene Proteins c-fos / Q000187:drug effects*; D011803:Quinine / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D017552:Solitary Nucleus / Q000187:drug effects*
chemical_list: D016760:Proto-Oncogene Proteins c-fos; D011803:Quinine; D018021:Lithium Chloride