1 Administration of 3,4-methylenedioxymethamphetamine (MDMA or`ecstasy') to several species results in a long lasting neurotoxic degeneration of 5-hydroxytryptaminergic neurones in several regions of the brain. We have now investigated whether this degeneration is likely to be the result of free radicalinduced damage. 2 Free radical formation can be assessed by measuring the formation of 2,3-and 2,5-dihydroxybenzoic acid (2,3-DHBA and 2,5-DHBA) from salicylic acid. An existing method involving implantation of a probe into the hippocampus and in vivo microdialysis was modi®ed and validated. 3 Administration of MDMA (15 mg kg 71 , i.p.) to Dark Agouti (DA) rats increased the formation of 2,3-DHBA (but not 2,5-DHBA) for at least 6 h. Seven days after this dose of MDMA, the concentration of 5-hydroxytryptamine (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) was reduced by over 50% in hippocampus, cortex and striatum, re¯ecting neurotoxic damage. There was no change in the concentration of dopamine or 3,4-dihydroxyphenylacetic acid (DOPAC) in the striatum. 4 p-Chloroamphetamine (PCA), another compound which produces a neurotoxic loss of cerebral 5-HT content, when given at a dose of 5 mg kg 71 also signi®cantly increased the formation of 2,3-DHBA (but not 2,5-DHBA) in the dialysate for over 4.5 h. post-injection starting 2 h after treatment. 5 In contrast, fen¯uramine administration (15 mg kg 71 , i.p.) failed to increase the 2,3-DHBA or 2,5-DHBA concentration in the dialysate. A single fen¯uramine injection nevertheless also markedly decreased the concentration of 5-HT and 5-HIAA in the hippocampus, cortex and striatum seven days later. 6 When rats pretreated with fen¯uramine (15 mg kg 71 , i.p.) seven days earlier were given MDMA (15 mg kg 71 , i.p.) no increase in 2,3-DHBA was seen in the dialysate from the hippocampal probe. This indicates that the increase in free radical formation following MDMA is occurring in 5-HT neurones which have been damaged by the prior fen¯uramine injection. 7 Administration of the free radical scavenging agent a-phenyl-N-tert-butyl nitrone (PBN; 120 mg kg 71 , i.p.) 10 min before and 120 min after an MDMA (15 mg kg 71 , i.p.) injection prevented the acute rise in the 2,3-DHBA concentration in the dialysate and attenuated by 30% the long term damage to hippocampal 5-HT neurones (as indicated by a smaller MDMA-induced decrease in both the concentration of 5-HT and 5-HIAA and also the binding of [ 3 H]-paroxetine). 8 These data indicate that a major mechanism by which MDMA and PCA induce damage to 5-hydroxytryptaminergic neurones in rat brain is by increasing the formation of free radicals. These probably result from the degradation of catechol and quinone metabolites of these substituted amphetamines. In contrast, fen¯uramine induces damage by another mechanism not involving free radicals; a proposal supported by some of our earlier indirect studies. 9 We suggest that these di erent modes of action render untenable the recent suggestion that MDMA will not be neurotoxic in humans because ...

1 The ecacy of the free radical trapping agent NXY-059 in reducing the infarct volume following both transient and permanent focal ischaemia has been examined in rats. 2 In the transient ischaemia model, rats were subjected to a 2 h occlusion of the middle cerebral artery (MCA). Intravenous infusion of NXY-059 (1, 10 and 30 mg kg 71 h) for 21.75 h starting 2.25 h after the occlusion, produced a dose-dependent decrease in both neurological impairment and the histologically measured infarct volume (a mean 59% decrease at 10 mg kg 71 h). 3 In the permanent ischaemia model, animals were injected (s.c.) with a loading dose of NXY-059 of 32.5, 53.8 or 75.4 mg kg 71 and osmotic minipumps were implanted which had been primed to deliver respectively 30, 50 or 70 mg kg 71 h. When treatment was initiated 5 min after MCA occlusion there was a dose dependent protection of both cortical and sub-cortical tissue (cortex: 63% at the mid-range dose). Protection was related linearly to plasma concentration (plasma unbound NXY-059 concentration at 1 h: 37+16 mmol l 71 at the mid-range dose). 4 When the mid range dose was administered between 5 min ± 4 h after MCA occlusion, a marked and statistically signi®cant protection was seen at all time points (44% protection in cortex at 4 h). 5 These data demonstrate the substantial neuroprotective ecacy of NXY-059 at plasma concentrations that can be achieved clinically and indicate that NXY-059 also has a therapeutic window of opportunity that is clinically relevant.

1 It has been reported that co-administration of¯uoxetine with 3,4-methylenedioxymethamphetamine (MDMA,`ecstasy') prevents MDMA-induced degeneration of 5-HT nerve endings in rat brain. The mechanisms involved have now been investigated. 4 A signi®cant cerebral concentration of¯uoxetine plus nor¯uoxetine was detected over the 7 days following¯uoxetine administration. The¯uvoxamine concentration had decreased markedly by 24 h. 5 Pretreatment with¯uoxetine (10 mg kg 71 , 62) failed to alter cerebral MDMA accumulation compared to saline pretreated controls. 6 Neither¯uoxetine or¯uvoxamine altered MDMA-induced acute hyperthermia. 7 These data demonstrate that¯uoxetine produces long-lasting protection against MDMA-induced neurodegeneration, an e ect apparently related to the presence of the drug and its active metabolite inhibiting the 5-HT transporter. Fluoxetine does not alter the metabolism of MDMA or its rate of cerebral accumulation.