Effect of repeated administration of MDMA on the levels of CB1 receptor protein in the brain in wild-type mice on the 1st and 7th day of MDMA withdrawal (10 mg/kg, i.p., daily for 7 days). (a) The levels of CB1 receptor protein in the hippocampus, prefrontal cortex, and striatum were measured. Data represent the mean±SEM (n=8–11). (b) Effect of repeated administration of AM251 (3.2 mg/kg) with MDMA on MDMA-induced up-regulation of CB1 receptor protein expression in the hippocampus. Open and closed bars indicate vehicle- and repeated MDMA-treated group. Data represent the mean±SEM (n=5–11). ***p<0.001 vs vehicle-treated mice; ##p<0.01 vs MDMA-treated mice. Vehicle means results for mice administered saline.