The mechanisms involved in the long-lasting neuroprotective effect of fluoxetine against MDMA ('ecstasy')-induced degeneration of 5-HT nerve endings in rat brain

1 It has been reported that co-administration of fluoxetine with 3,4-methyl enedioxymethaniphetamine (MDMA. 'ecstasy') prevents MDMA-induced degenerati on of 5-HT nerve endings in rat brain. The mechanisms involved have now bee n investigated. 2 MDMA (15 mg kg(-1), i.p.) administration produced a neurotoxic loss of 5- HT and 5-hydroxyindoleacetic acid (5-HIAA) in cortex, hippocampus and stria tum and a reduction in cortical [H-3]-paroxetine binding 7 days later. Fluo xetine (10 mg kg(-1), i.p., x 2, 60 min apart) administered concurrently wi th MDMA or given 2 and 4 days earlier provided complete protection, and sig nificant protection when given 7 days earlier. Fluvoxamine (15 mg kg(-1), i .p., x 2, 60 min apart) only produced neuroprotection when administered con currently. 3 Fluoxetine (10 mg kg(-1), x 2) markedly increased the K-D and reduced the B-max of cortical [H-3]-paroxetine binding 2 and 4 days later. The B-max w as still decreased 7 days later, but the KD was unchanged. [H-3]-Paroxetine binding characteristics were unchanged 24 h after fluvoxamine (15 mg kg(1) , x 2). 4 A significant cerebral concentration of fluoxetine Plus norfluoxetine was detected over the 7 days following fluoxetine administration. The fluvoxam ine concentration had decreased markedly by 24 h. 5 Pretreatment with fluoxetine (10 mg kg(-1), x 2) failed to alter cerebral MDMA accumulation compared to saline pretreated controls. 6 Neither fluoxetine or fluvoxamine altered MDMA-induced acute hyperthermia . 7 These data demonstrate that fluoxetine produces long-lasting protection a gainst MDMA-induced neurodegeneration. an effect apparently related to the presence of the drug and its active metabolite inhibiting the 5-HT transpor ter. Fluoxetine does not alter the metabolism of MDMA or its rate of cerebr al accumulation.