title: Contribution of corticosterone to cued versus contextual fear in rats.
abstract: Several studies have suggested a positive relationship between circulating corticosterone levels and contextual conditioning. However, a positive relationship between circulating corticosterone levels and cued conditioning has also been reported. This study further investigates the relationship between corticosterone and fear conditioning by modulating the predictive value of contextual and discrete tone cues in separate groups of rats. In a first experiment in which training parameters were chosen to induce strong conditioning (five foot-shocks), we used a correlational approach and investigated whether post-training corticosterone levels were related to subsequent expression of contextual and/or tone fear. In a second experiment, in which training parameters were chosen to induce lower conditioning (one and two foot-shocks), we investigated whether a post-training corticosterone injection enhanced the consolidation of contextual and/or tone conditioning. In the first experiment, the highest post-training corticosterone levels were obtained in rats trained with paired tones and shocks. Post-training corticosterone levels tended to be positively correlated with freezing scores during the tone-fear test and were negatively correlated with freezing scores during training although not during the context-fear test. In the second experiment, a post-training injection of corticosterone (3mg/kg) had no effect on subsequent freezing to contextual cues and to a tone that did not predict shock, whereas it was efficient in increasing fear conditioned to a predictive tone. Globally, these results suggest that the predictive value of the conditioned stimulus may be the main determinant of the facilitatory action of acutely enhanced corticosterone in fear conditioning.
authors.affiliation: Centre de Neurosciences Intégratives et Cognitives, UMR 5228, CNRS, Université Bordeaux 1, Bâtiment B2, Avenue des Facultés, F-33405 Talence Cedex, France. a.marchand@cnic.u-bordeaux1.fr
authors.forename: Alain R
authors.initials: AR
authors.lastname: Marchand
authors.forename: Alexandra
authors.initials: A
authors.lastname: Barbelivien
authors.forename: Alexandre
authors.initials: A
authors.lastname: Seillier
authors.forename: Karine
authors.initials: K
authors.lastname: Herbeaux
authors.forename: Alain
authors.initials: A
authors.lastname: Sarrieau
authors.forename: Monique
authors.initials: M
authors.lastname: Majchrzak
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001245:Association Learning / Q000502:physiology*; D003214:Conditioning, Classical / Q000502:physiology*; D003345:Corticosterone / Q000097:blood* / Q000502:physiology; D003463:Cues; D004777:Environment; D005239:Fear / Q000502:physiology*; D046352:Freezing Reaction, Cataleptic / Q000502:physiology*; D008297:Male; D051381:Rats; D020318:Rats, Long-Evans
chemical_list: D003345:Corticosterone