Alteration of dopamine metabolism in different brain regions of the rabbit by estradiol and tamoxifen.
Tamoxifen citrate, a mixed estrogen agonist-antagonist, and estradiol 17-beta administered separately for 14 days significantly reduced dopamine and dihydroxyphenylacetic acid in the cortex and hypothalamus regions of the brain in immature female rabbits. In addition to these areas, estradiol also reduced dopamine and dihydroxyphenylacetic acid in the striatum but tamoxifen treatment significantly reduced only dihydroxyphenylacetic acid concentration in the striatum. When estradiol and tamoxifen were injected together, dopamine and dihydroxyphenylacetic acid concentrations were reduced only in the cortex. Specific binding of [3H]spiperone to dopamine receptors was significantly increased by both estradiol and tamoxifen in the hypothalamus but only tamoxifen increased dopamine binding in the striatum. A low dose of tamoxifen, either alone or in combination with estradiol, increased uterine weight, but a higher dose of tamoxifen was neither an estrogen agonist nor antagonist. These studies indicate that estradiol and tamoxifen alter dopamine metabolism in the various regions of brain differentially. The estrogen agonist activity of tamoxifen does not correspond to antidopaminergic action of estradiol in the striatum.
D015102:3,4-Dihydroxyphenylacetic Acid / Q000032:analysis; D000818:Animals; D001921:Brain / Q000378:metabolism*; D002540:Cerebral Cortex / Q000032:analysis; D003342:Corpus Striatum / Q000032:analysis; D004298:Dopamine / Q000032:analysis / Q000378:metabolism*; D004958:Estradiol / Q000494:pharmacology*; D005260:Female; D007031:Hypothalamus / Q000032:analysis; D009638:Norepinephrine / Q000032:analysis; D011817:Rabbits; D013629:Tamoxifen / Q000494:pharmacology*
D013629:Tamoxifen; D015102:3,4-Dihydroxyphenylacetic Acid; D004958:Estradiol; D004298:Dopamine; D009638:Norepinephrine