Elevation of Striatal Dopamine Receptors by Estrogen: Dose and Time Studies

Abstract

Administration to male rats of a single dose of 17 beta-estradiol valerate (8-500 micrograms/rat) or implantation of a pellet containing 17 beta-estradiol (0.5-50 mg/rat) increased serum 17 beta-estradiol levels in a dose-dependent relationship when measured on the sixth day after administration. At the same time, after these doses, the serum rat prolactin (rPRL) levels were doubled and the striatal 3,4-dihydroxyphenylethylamine (DA, dopamine) receptor densities were increased 20%. A single dose of 17 beta-estradiol valerate of 4 micrograms/rat or less did not alter serum 17 beta-estradiol or rPRL levels or the striatal DA receptor density. After the single injection of 17 beta-estradiol valerate (125 micrograms/rat) the serum 17 beta-estradiol levels peaked at 1 day, the serum rPRL levels peaked at 2 days, and the striatal DA receptor density elevation peaked from 4 to 8 days. Implantation of a pellet containing 17 beta-estradiol (25 mg/rat) produced a constant elevation of serum 17 beta-estradiol levels from 1 to 10 days. Whereas the serum rPRL levels were continuously elevated about two-fold, the densities of the striatal DA receptors were increased significantly by 20-25% only from 4 to 8 days after pellet implantation. These results indicate that striatal DA receptor density rises and returns to control levels during the constant elevation of serum 17 beta-estradiol and rPRL levels.(ABSTRACT TRUNCATED AT 250 WORDS)