Previous work from our laboratory has shown prevention of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced striatal dopamine (DA) depletion in mice by 17β-estradiol, progesterone, and raloxifene. Dehydroepiandrosterone (DHEA), a neurosteroid, was shown to have neuroprotective activities in various paradigms of neuronal death but its effect in vivo in mice on MPTP toxicity has not been reported. We investigated the effects of 17β-estradiol (2 μg/day) and DHEA (3 mg/day) for 5 days before and after an acute treatment of four MPTP (10 mg/kg) injections in male C57Bl/6 mice. Striatal DA concentrations and its metabolites dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) were measured by HPLC. MPTP mice that received 17β-estradiol or DHEA had striatal DA, DOPAC, and HVA concentrations comparable to intact animals and higher than striatal DA, DOPAC, and HVA levels in saline-MPTP-treated mice. MPTP treatment led to an increase of striatal DA turnover (assessed with the HVA/DA ratio); DHEA and 17β-estradiol prevented this increase. 17β-Estradiol did not affect striatal DA and metabolites concentrations in intact mice in this paradigm. Furthermore, in the substantia nigra DHEA and 17β-estradiol prevented the MPTP-induced dopamine transporter and tyrosine hydroxylase mRNA decreases measured by in situ hybridization. Therefore, DHEA such as 17β-estradiol is active in preventing the catecholamine-depleting effect of MPTP and our results suggest that this involves neuroprotection of DA neurons. Synapse 47:10–14, 2003. © 2002 Wiley-Liss, Inc.