Adolescent male rats given 10 mg/kg of MDMA every 2 hours for 6 hours showed decreased serotonin content in the amygdala and increased anxiety-like behavior ten days later, compared to controls given saline. In the elevated plus-maze, treated rats made fewer entries into unprotected arms and showed less rearing, indicating heightened anxiety. No significant changes in dopamine or its metabolites were observed. The findings suggest that MDMA exposure during adolescence can cause lasting serotonin depletion and anxiety-like effects, similar to those seen in adult rats.
Adolescent mice pre-exposed to ethanol, MDMA, or both showed increased rewarding effects from a low dose of MDMA in a conditioned place preference model. Pre-exposure did not alter acquisition of place preference induced by a higher MDMA dose, but the preference was more persistent in mice pre-exposed to MDMA or ethanol plus the higher MDMA dose. After extinction, reinstatement occurred with lower priming doses in pre-exposed groups. Pre-treatment also caused long-term changes in brain monoamine levels, including dopamine turnover and serotonin metabolites, depending on the dose used. The findings suggest that adolescent exposure to ethanol and MDMA may enhance the addictive properties of MDMA.