Method for evaluating MDMA self-administration in mice

SORIA G, ROBLEDO P, BALERIO G. AND MALDONADO R.

Brighton, UK

Workshop; International Workshop on New Advances in the Understanding and treatment of Addiction; 2002

METHOD FOR EVALUATING MDMA SELF-ADMINISTRATION IN MICE Soria G, Robledo P, Balerio G, Maldonado R Laboratori Neurofarmacologia. Departament de Ciències Experimentals i de la Salut. Universitat Pompeu Fabra. Barcelona. Spain. MDMA (d,l,1-3,4-methylenedioxymethamphetamine) is a popular recreationally drug used among young people. Although its use is increasing in the last years, there are few studies concerning the abuse potential of MDMA. The purpose of this study was to investigate the rewarding properties of MDMA in mice by using an intravenous self-administration paradigm. Mice were first deprived of food to 95% of their initial weight. Five days after starting food deprivation mice were trained in operant chambers to nose-poke for food pellets under a FR1 schedule of reinforcement with a 10 sec time-out period and in 60 min sessions with a maximum of 100 pellets available. Food restriction was maintained only during this food training period.  When mice maintained a stable response rate for 3 consecutive days with less than 15% variability, they were implanted with chronic indwelling jugular vein catheters. Mice were then trained to self-administer cocaine (1 mg/kg/injection). The drug was initially available under a FR1 response schedule of intravenous injection. Each self-injection was followed by a 30 sec time-out period, and each session lasted 60 min allowing a maximum of 50 injections per session. When animals maintained 80% of stability on FR1, the schedule of reinforcement was changed to FR3. Once stable responding was achieved, cocaine was substituted for saline until extinction was observed. Finally, saline was substituted by MDMA (1 mg/kg/injection) under the same experimental conditions.