Abstract
Estrogens were found to exert a biphasic effect on the density of serotonin receptors in the female rat brain: an acute reduction in serotonin receptor density throughout the brain is followed 48 to 72 hr later by a selective increase in those brain regions known to contain estrogen receptors--hypothalamus, preoptic area, and amygdala. The acute reduction in serotonin receptor density can be mimicked by estradiol in vitro. We conclude that estradiol may have a fast, direct effect on brain membranes to modify serotonin receptor availability, while exerting a slow effect on the same receptors through an interaction with intracellular estrogen receptors in those brain regions that contain them. The observation that female sex hormones are involved in the regulation of serotonin receptors may have important implications in the understanding of female sexual behavior in the female rat and in the understanding of hormone-linked emotional disturbances in women.