Abstract
RATIONALE: In some rats, the hormone corticosterone is reinforcing. High novelty-seeking rats (high responders, HR) self-administered corticosterone at a much higher rate than low novelty-seeking rats (low responders, LR) do [Piazza PV, Deroche V, Deminiere JM, Maccari S, Le Moal M, Simon H, Corticosterone in the range of stress-induced levels possesses reinforcing properties: implications for sensation-seeking behaviors, Proc Natl Acad Sci USA 1993;90:11738-42]. While previous studies demonstrated that corticosterone reinforces nose poking in a self-administration paradigm, no studies to date have examined whether corticosterone is rewarding. OBJECTIVE: Using the conditioned place preference (CPP) paradigm, we examined the rewarding effects of corticosterone in HR and LR rats. METHODS: Male Sprague-Dawley rats were classified into HR and LR groups based on their locomotor activity in a novel environment. Subsequently, independent groups of HR and LR rats underwent CPP for corticosterone (0, 2.5 or 10 mg/kg; i.p.) or cocaine (12 mg/kg; i.p). CPP for cocaine was used as a positive control. RESULTS: While cocaine produced a strong CPP in both HR and LR rats, corticosterone failed to produce either preference or aversion in both phenotypes. CONCLUSION: Corticosterone is neither rewarding nor aversive in either behavioral phenotype.