MDMA (Ecstasy) damages the fine serotonergic axons that connect the raphe nucleus to the striatum, a disruption previously inferred but not directly observed in living animals. Using manganese-enhanced magnetic resonance imaging (MEMRI) in rats, the study tracked manganese ions injected into the raphe nucleus as they traveled along neural pathways. Eight days after repeated MDMA injections (5 mg/kg daily for six days), MEMRI showed reduced signal enhancement in the medial forebrain bundle and striatum, indicating disrupted axonal transport. Immunohistological staining confirmed a loss of serotonin transporters. The findings provide direct in vivo evidence that MDMA causes axonal damage in these serotonergic projections.
Chronic MDMA use damages serotonin transporters (SERT) in the brain, which is linked to addiction and impaired decision-making. In rats, the cough suppressant dextromethorphan (DM) partially reversed this damage: co-administration with MDMA restored SERT binding by about 23% after 14 days compared to MDMA alone. Behavioral tests showed that MDMA-induced reward and hyperactivity were associated with lower SERT activity, and DM helped restore both SERT levels and serotonin fiber density. The findings suggest DM may protect against MDMA's neurotoxic effects on the brain's reward and motivation circuits.