MDMA ("ecstasy") exhibits an anxiogenic-like activity in social encounters between male mice.

Recent studies have suggested that 3,4-methylenedioxymethamphetamine (MDMA; "ecstasy"), a synthetic amphetamine derivative, might exhibit an anxiogenic-like activity in rodents. In this work, we examined the effects of MDMA (1, 8 and 15 mg kg(-1), i.p.) on social encounters between male mice using an ethopharmacological approach. Likewise, we compared the behavioural profile of MDMA with that induced by FG 7142 (15 mg kg(-1), i.p.), an anxiogenic benzodiazepine receptor ligand. Individually housed mice were exposed to anosmic standard opponents 30 min after drug administration, and the encounters were videotaped and evaluated using an ethologically based analysis. MDMA (8 and 15 mg kg(-1)) produced a behavioural pattern characterized by a marked decrease of aggression (threat and attack) as well as social investigation, body care and digging behaviours, without affecting immobility. Moreover, avoidance/flee and defence/submission behaviours were significantly increased by the drug. A very similar behavioural profile was observed in FG 7142-treated animals. Overall, these findings might indicate that MDMA has anxiogenic-like properties in male mice.