Modulation of corticosterone does not affect the acquisition or expression of ethanol-induced conditioned place preference in DBA/2J mice

Several recent studies have implicated the stress hormone corticosterone in modulating the rewarding properties of abused drugs, including amphetamine and ethanol. The present experiments examined a role for corticosterone in modulating the rewarding effects of ethanol in the place conditioning paradigm. Male DBA/2J mice were subjected to a Pavlovian conditioning procedure in which a distinctive floor stimulus (CS+) was paired four times with ethanol (2 g/kg). On intervening days, a different floor stimulus was paired with saline (CS -). In the first experiment, the steroid synthesis inhibitor, aminoglutethimide (AMG), administered prior to conditioning trials with ethanol, did not alter the acquisition of place preference. However, during conditioning trials, ethanol-stimulated locomotor activity in the AMG- treated group was significantly higher relative to the vehicle-treated group, suggesting that corticosterone may normally inhibit ethanol-stimulated activity. Plasma corticosterone levels in AMG-treated mice were significantly lower than in vehicle-treated mice, showing that AMG effectively suppressed corticosterone release on CS+ trials. The second experiment examined the effect of AMG on the expression of conditioned ethanol place preference. AMG administration prior to the preference test did not alter the magnitude of ethanol place preference. Corticosterone levels in the AMG-treated groups were significantly reduced relative to vehicle-treated groups, which showed a higher level of corticosterone during the preference test. These findings show that manipulation of corticosterone levels in a physiological range does not alter the acquisition or expression of ethanol-induced conditioned place preference in DBA/2J mice.