Estrogen reduces acute striatal dopamine responses in vivo to the neurotoxin MPP+ in female, but not male rats

The effects of in vivo estrogen treatment upon MPP+-induced dopamine (DA) r elease were determined using in vivo microdialysis in female and male mts. Ovariectomized female rats were implanted or not with an estrogen pellet (0 .1 mg, 17 beta estradiol) and subjected to microdialysis 6 days later. Afte r baseline DA release was determined, 5 mM MPP+ was infused through the mic rodialysis probe for one 20-min interval. Perfusion resumed with normal med ium for the duration of the experiment. A significant attenuation of MPP+-i nduced DA release was obtained in estrogen-treated females. One week later, striatal DA and dihydroxyphenylacetic acid (DOPAC) concentrations were det ermined for the lesioned and non-lesioned striata of each animal. MPP+ infu sion significantly decreased striatal DA concentrations, however, there was no effect of estrogen treatment on striatal DA depletion. This experiment was repeated using orchidectomized male rats treated with 0, 0.1, or 5 mg e stradiol. In contrast to the females, no differences in MPP+-induced DA rel ease were seen among these males, and there was no significant effect of th e varying estrogen treatments on striatal DA or DOPAC concentrations. These results demonstrate that in vivo estrogen treatment attenuates MPP+-induce d striatal DA release in gonadectomized female, but not male, rats. (C) 200 0 Elsevier Science B.V. All rights reserved.