| Research Abstract |
The presence of chorea gravidarum and oral contraceptives induced-dyskinesia suggests that estrogen may intensify the function of central dopamine (DA). In experimental animals too, estrogens have been reported to modulate the function of central DA neurons. Administration of large doses of estrogens has been reported to increase the duration of stereotypy, a behavior characteristic of striatal DA receptor stimulation in vivo. Stereotypy duration was reduced in guinea pig after ovariectomy. However the precise mechanism of the interaction between estrogens and the function of central DA neurons is still poorly understood. To examine the interactions between estrogen and central dopamine (DA) neurons. Eight-week-old female Sprague-Dawley rats were divided into 3 groups : Ovariectomized rats (OVX group, N=10) ; OVX rats with estradiol (E2) treatment (20 mug estradiol valerate, i. p. , twice a week for 8 weeks) (OVX + E2 group, N=10) ; and Sham-operation control rats with vehicle injectio
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n (Sham group, N=10). Spontaneous locomotor movements were observed. Concentration of DA and its metabolites at the striatum, the nucleus accumbens, and the cerebral cortex were measured by high performance liquid chromatography. At the striatum, the changes in extracellular DA concentration after the injection of methamphetamine (MA ; 0.2mg/kg, i. p.) were determined by in vivo microdialysis. Spontaneous locomotor movements decreased in OVX group but E2 treatment reversed to the levels of Sham group. No significant differences were observed in the concentrations of DA and its metabolites at the three sites of brain among the three groups. The basal output of DA was lower in the OVX group than the other two groups. Extracellular DA concentration after MA administration at the striatum was also lower in the OVX group than the Sham group. However no significant differences were observed in DA concentration between the OVX + E2 group and Sham group. Based on these results, we conclude that estrogen enhances the DA release at the striatum in rats. Less
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