Profile of MDMA Self-Administration from a Large Cohort of Rats: MDMA Develops a Profile of Dependence with Extended Testing

About half of a large sample of rats learned to self-administer MDMA, taking an average of 16 daily sessions before meeting the initial criterion. When the dose was reduced, the rats increased their responding in a compensatory manner. Over an additional 14 days of self-administration, daily intake rose from 8.5 to 15.25 mg/kg. These results indicate that MDMA acts as a reliable reinforcer for roughly half of rats, and that acquiring self-administration requires more sessions than is typical for other abused drugs.

Study at a glance

Abstract

The present study provides a profile of acqui- sition and maintenance of self-administration of +/-3,4- methylenedioxymethamphetamine (MDMA) obtained from a large cohort of rats tested during a 2 year period. Of the 128 rats, 49% self-administered 1.0 mg/kg/infusion MDMA to an initial criterion within a 25 day cut-off period. The number of test sessions required to meet this initial criterion was normally distributed around an average of 15.9 days and responding increased in a compensatory manner when the dose was decreased. In a subgroup of rats that self-administered MDMA for an additional 14 days intake increased from 8.5 to 15.25 mg/kg/day. Thus, under these conditions, MDMA is a reliable reinforcer for about half of a large sample of rats, responding is dose-dependent and acquisition of self-administration for these sensitive rats requires more test sessions than is typically used for studies examining self-administration of other drugs of abuse.