4-Hydroxytamoxifen attenuates methamphetamine-induced nigrostriatal dopaminergic toxicity in intact and gonadetomized mice Yu-Min Kuo,* Hsiang-Hua Chen, Chih-Chang Shieh,à Kuo-Pin Chuang,à Chianfang G. Cherng§ and Lung Yu  *Department of Cell Biology and Anatomy,  Institute of Behavioral Medicine and àDepartment of Microbiology and Immunology, National Cheng Kung University College of Medicine, Tainan, Taiwan §Psychological Research Center, Chinese Air Force Academy, Kangshan, Taiwan Abstract The present study was undertaken to assess the ability of 4-hydroxytamoxifen (4-OHT) to alter methampheta- mine-induced nigrostriatal dopaminergic toxicity. Three daily doses of 4-OHT (6 lg/day) effectively attenuated metham- phetamine-induced nigrostriatal dopamine depletions in both sexes of intact and gonadectomized C57BL/6 J mice. 4-OHT alone did not alter the dopamine content levels in the striatum. Both male and female mice exhibited similar Cu, Zn-super- oxide dismutase protein levels in the striata whether after gonadectomy or 4-OHT treatment. Furthermore, basal body temperature and methamphetamine-induced hyperthermia were not affected by 4-OHT treatment in either sex of mice. Using a lucigenen-derived chemiluminescence assay, we found that 4-OHT by itself can serve as a potent superoxide anion radical scavenger in vitro. The protective effects of 4-OHT against methamphetamine-induced nigrostriatal dopamine depletion can be, in part, due to its antioxidative characteristics. The free radical-scavenging ability of 4-OHT calls for further investigations for its uses in clinical practice. Keywords: anti-estrogen, antioxidation, dopamine, neuro- toxicity, striatum. J. Neurochem. (2003) 87, 1436–1443. A methamphetamine (MA) dosing paradigm has been consistently shown to produce nigrostriatal dopaminergic pathologies, including dopaminergic terminal degenerations and decreases in dopamine (DA) content level, DA transporter binding sites, and tyrosine hydroxylase activity in rodent models (Wagner et al. 1979; Wagner et al. 1980; Ricaurte et al. 1982; Sonsalla et al. 1996; Fleckenstein et al. 1997; Yu and Liao 2000a). There is, however, a sex difference in the susceptibility to the MA-induced nigro- striatal DA depletion. The magnitude of the MA-induced dopaminergic toxicity was lower in females as compared with males in two strains of mice (Wagner et al. 1993; Yu and Wagner 1994; Yu and Liao 2000a). Several lines of evidence showed that hormones modulated various neuro- toxin-induced striatal dopaminergic toxicities (Dluzen et al. 1996; Dluzen 1997; Miller et al. 1998). We have demon- strated that estradiol, at physiological doses, effectively attenuated MA-induced DA depletion in female mice (Yu and Liao 2000b). Surprisingly, tamoxifen, with an anti-estrogenic activity, was reported to serve as a neuroprotectant against such DA neurotoxicity in female and male mice (Dluzen et al. 2001; Dluzen and McDermott 2002). Furthermore, 4-hydroxytamoxifen (4-OHT), a major metabolite of tamoxifen and selective estrogen receptor antagonist, potentiated the protective effects of estradiol against the MA-induced nigrostriatal DA depletion (Yu et al. 2002a). These results, taken together, suggest that at least part of the neuroprotective effects exerted by tamoxi- fen and 4-OHT might be via an estrogen receptor- independent pathway. Received April 4, 2003; revised manuscript received July 1, 2003; accepted August 28, 2003. AddresscorrespondenceandreprintrequeststoL.Yu,NationalCheng Kung University College of Medicine, Institute of Behavioral Medicine, 1 University Road, Tainan 70101, Taiwan. E-mail: lungyu@mail.ncku.edu.tw Abbreviations used: LDCL, lucigenin-derived chemiluminescence; 4-OHT, 4-hydroxytamoxifen; s.c., subcutaneously; SOD, superoxide dismutase. Journal of Neurochemistry , 2003, 87, 1436–1443 doi:10.1046/j.1471-4159.2003.02089.x 1436 Ó 2003 International Society for Neurochemistry, J. Neurochem. (2003) 87, 1436–1443