Tamoxifen diminishes methamphetamine-induced striatal dopamine depletion in intact female and male mice

It has been demonstrated that the nigrostriatal dopaminergic system of male mice is more sensitive to the neurotoxic effects of methamphetamine (MA), The basis for this difference can be related to oestrogen, which has the capacity to function as a neuroprotectant against neurotoxins that target the nigrostriatal dopaminergic system. We examined the effects of the anti-oestrogen, tamoxifen (TMX), upon MA-induced neurotoxicity of the nigrostriatal dopaminergic system in intact female and male CD-1 mice. Striatal dopamine concentrations of TMX-treated female and male mice receiving MA were significantly greater than mice receiving MA alone. In female, but not male, mice, oestrogen treatment also resulted in greater striatal dopamine concentrations compared to mice receiving MA alone. Interestingly, male mice treated with oestrogen were particularly sensitive to the acute toxic effects of MA and displayed no evidence of nigrostriatal neuroprotection. The dihydroxyphenylacetic acid/dopamine ratios following MA for female and male mice treated with TMX or females treated with oestrogen were significantly reduced compared to MA-treated mice and oestrogen + MA-treated male mice. No differences among the treatment groups were obtained for dopamine in the hypothalamus or olfactory bulb. These data demonstrate that TMX treatment of intact female and male mice diminishes striatal dopamine depletions to the nigrostriatal dopaminergic neurotoxin, MA. Oestrogen also displayed this capacity when administered to female, but accentuated acute toxicity in male mice. These effects are relatively specific for the nigrostriatal dopaminergic system. Such data suggest that TMX can function as a nigrostriatal dopaminergic neuroprotectant against MA-induced neurotoxicity in intact female and male mice.