SYNAPSE 21:169-176 (1995) Superoxide Radicals Mediate the Biochemical Effects of Methylenedioxymethamphetamine (MDMA)' Evidence From Using CuZn- Superoxide Dismutase Transgenic Mice JEAN LUD CADET, BRUCE LADENHEIM, HIROSHI HIRATA, RICHARD B. ROTHMAN, $YED ALI, ELAINE CARLSON, CHARLES EPSTEIN, AND TIMOTHY H. MORAN Molecular Neuropsychiatry (J.L.C., B.L., H.H.) and Clinical Psychopharmacology (R.B.R.) Sections, NIH / NIDA, Intramural Research Programs, Baltimore, Maryland 21224; Neurochernistry Laboratory, National Center for Toxicological Research, Jefferson, Arkansas 72079 (S.A.); Department of Pediatrics, University of California, San Francisco, California 94143 (E.C., C.E.); and Department of Psychiatry and Behavioral Sciences, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205 (7_.H.M.) KEY WORDS Transgenic mice, Superoxide dismutase, MDMA, Neurotoxicity, Free radicals, Dopamine, Striatum, Ecstasy ABSTRACT The subacute andlong-term biochemical effects ofmethylenedioxymeth- amphetamine (MDMA) were assessed in homozygous and heterozygous transgenic (Tg) mice that carry the complete sequence of the human copper-zinc (CuZn) superoxide dismutase (SOD) gene. Non-transgenic (Non-Tg) mice showed significant decreased in striatal dopamine (DA) and dihydroxyphenylacetic acid (DOPAC) levels both at 24 h and at 2 weeks after a single injection ofMDMA (50 mg/kg). Heterozygous SOD-Tg mice showed DA depletion only at the 24 h time point. In contrast, homozygous SOD-Tg mice show no DA or DOPAC depletion at either the 24h or at the 2 week time points. Moreover, three injections ofMDMA (50 mg/kg) given 24 h apart also caused marked reduction of striatal DAand DOPAC in Non-Tg mice when these substances were measured 2 weeks after the last MDMA injection. That injection schedule also caused small decreases in DA levels in the heterozygous animals but no changes in the homozygous mice;DOPAC levels were not affected in the heterozygous nor in the homozygous SOD-Tg mice. Fur- thermore, the multiple injection schedule caused significant decreases inDAand DOPAC in female Non-Tg mice but not in the two strains of transgenic mice. Neither the single dose nor the multiple dose schedule ofMDMA injections affected striatal serotonin (5- HT) and 5-hydroxyindoleacetic acid (5-HIAA) levels in any of the three strains of mice. These results support previous observations that MDMA-induced biochemical effects are observed in the DA systems of mice, whereas these effects are seen in the 5-HT systems of rats. The present observations also document for the first time arole for the production of superoxide radicals in these effects of MDMA. These mice are an important toolfor dissecting pathways involved in drug-induced neurotoxicity. ©1995 Wiley-Liss, Inc.* INTRODUCTION duced during electron transport in the mitochondria Oxidative stress and oxygen free radicals are thought (Boveris and Chance, 1973). In addition, endoplasmic toplay an important role inboth the acute and chronic reticulum and peroxisomes, as well as nuclear and plasma membranes generate oxygen-based radicals effects ofa number of neurotoxic processes. These in- (Freeman and Crapo, 1982). Cells protect themselves clude administration of some drugs and radiation-in- duced injury, as well as oxygen-induced injury to the against reactive oxygen intermediates (ROI) by using central nervous system (Ames et al., 1993; Cadet, 1988; see Janssen et al., 1993 fora comprehensive review). Superoxide radicals and hydrogen peroxide are pro- Received December 12, 1994; accepted in revised form April 11, 1995. .,, © 1995 WILEY-LISS, INC. *This article is a US Government work and, as such, is in the public domain in the UnitedStates ofAmerica.