Effect of 5-HT2B receptor inhibition on MDMA-induced conditioned place preference in mice.

<p><b>A</b>) Repeated i.p. injection of MDMA 10 mg/kg induced CPP in WT mice compared to saline injection, but this effect was absent in 5-HT_2B^−/− mice. However, repeated injection of a high dose of MDMA (30 mg/kg) induced CPP in WT as well as in 5-HT_2B^−/− mice. Data (means±SEM, <i>n</i> = 8 per group) were analyzed by two-way ANOVA with genotype and treatment as main factors, revealing a significant interaction, <i>F</i>(2, 41) = 3.93, p<0.05, a main effect of treatment <i>F</i>(2, 41) = 11.67, p<0,001 but no effect of genotype <i>F</i>(1, 41) = 0.27, ns. Bonferroni tests were used for post-hoc comparisons. In all cases, p<0.05 was considered statistically significant; **p<0.01 compared to saline-treated mice. <b>B</b>) After an initial extinction of the CPP (12 days) in WT mice, MDMA (10 mg/kg) re-exposure induced reinstatement of CPP. MDMA-induced reinstatement was not observed in RS127445-pretreated mice. Data (means±SEM, <i>n</i> = 10−20 per group) were analyzed by one-way ANOVA. Dunnetts tests were used for post-hoc comparisons. The null hypothesis was rejected at the p<0.05 level; *p<0.05 **p<0.01 compared to saline-treated mice.