Effects of acute social stress on the conditioned place preference induced by MDMA in adolescent and adult mice

Social defeat stress reduces the rewarding effects of MDMA in adult male mice, but not in adolescents. Adult mice exposed to social defeat before each MDMA conditioning session did not develop a conditioned place preference at either 1.25 or 10 mg/kg doses, indicating decreased sensitivity to MDMA reward. Social defeat did not alter the motor or anxiogenic effects of MDMA. Adult defeated mice had higher corticosterone levels than controls and adolescent mice. Social stress had no behavioral effects in adolescent mice, suggesting age-dependent vulnerability.

Study at a glance

Abstract

Exposure to social defeat stress increases the rewarding effects of psychostimulants in animal models, but its effect on 3,4-methylenedioxymethylamphetamine (MDMA) reward has received little attention. In the present study, we evaluated the influence of social defeat on the rewarding effects of MDMA in adolescent [postnatal day (PND) 29-40] and adult (PND 50-61) male mice using the conditioned place preference paradigm. Experimental mice were exposed to social defeat in an agonistic encounter before each session of conditioning with 1.25 or 10 mg/kg of MDMA. The effects of social defeat on corticosterone levels and the motor or the anxiogenic effects of MDMA were also evaluated. Mice exposed to social defeat during adulthood did not show conditioned place preference after conditioning with either dose of MDMA. Conversely, social defeat did not affect the anxiogenic and motor effects of MDMA. Adult mice exposed to social defeat showed higher levels of corticosterone than their controls and adolescent mice. Social stress did not induce behavioural effects in adolescent mice. Our results show that stress induced by social defeat decreases the sensitivity of adult mice to the rewarding effects of MDMA.