Role of the endocannabinoid system in MDMA intracerebral self‐administration in rats

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Abstract
I.c.v. self‐administration of MDMA (0.01–2 μg per infusion), alone and in combination with CP 55,940 (0.4 μg infusion−1), was studied on an operant responding procedure. On the basis of individual preference for one of two levers, developed during training, rats were allowed to self‐administer vehicle from the preferred lever and MDMA from the other. Pressings on the MDMA associated‐lever, except for the maximal unit dose, progressively increased. The combination of CP 55,940 with MDMA (1 μg infusion−1) reduced the number of drug‐associated lever pressings compared to the single drugs. Pre‐treatment with SR 141716A (0.5 mg kg−1 i.p.), 15 min before each daily session, significantly increased MDMA self‐administration. These findings suggest that MDMA self‐administration is under endogenous tonic control by the endocannabinoid system.British Journal of Pharmacology (2002) 136, 1089–1092. doi:10.1038/sj.bjp.0704825