Noradrenergic modulation of hypothalamic progestin receptors in female guinea pigs is specific to the ventromedial nucleus.

The concentration of estrogen-induced cytosolic progestin receptors (CPRs) in the hypothalamus of alpha 1-noradrenergic antagonist-treated female guinea pigs is reduced relative to non-drug-treated controls. The present study determined where within the hypothalamus this reduction occurs. Ovariectomized, estradiol-treated guinea pigs were given either the alpha 1-noradrenergic antagonist prazosin or vehicle. Microdissected brain regions were assayed for CPR levels. Prazosin caused a selective relative decrease in CPR levels of the ventromedial nucleus of the hypothalamus. No significant effects of prazosin were seen in other hypothalamic or preoptic area nuclei.