Modulation of brain and pituitary dopamine receptors by estrogens and prolactin

Abstract

1. Ovariectomized rats were treated for 2 weeks with 17β-estradiol (0.0002–100 μg/day). [ 3H] spiperone striatal dopamine receptor binding was maximally increased by 30% after 0.05 μg/day of 17β-estradiol and a similar increase is observed at higher doses. By contrast, plasma prolactin concentrations of these rats are unchanged after 0.05 μg/day and increased after 100 μg/day. A chronic estradiol treatment at very low doses (0.0002–0.001 μg/day) leads to increases in pituitary dopamine receptor binding while plasma prolactin levels are unchanged. At higher doses (1–100 μg/day) binding is decreased and plasma prolactin concentrations are elevated. 2. [ 3H]spiperone striatal dopamine receptor binding is elevated in lactating female rats compared to intact or ovariectomized female rats. 3. Anterior pituitary dopamine receptor concentrations fluctuate during the estrous cycle while striatal dopamine receptors are unchanged. 4. An injection of 30 ng of estradiol, which reproduces the estradiol proestrus surge, leads as in proestrus, to a decrease of anterior pituitary dopamine receptors.