Characteristics of [3H]prazosin binding to guinea pig brain alpha-adrenergic receptors: effects of estradiol and progesterone.

[3H]Prazosin was found to bind to sites on guinea pig brain membranes with alpha 1-adrenergic receptor characteristics. Treatment of ovariectomized guinea pigs with estradiol benzoate (EB) or EB followed by progesterone (P) did not affect [3H]prazosin binding to membranes from hypothalamus, preoptic area, amygdala or cerebral cortex. When added to the incubation mixture of the assay, estradiol, P, and other steroids decreased [3H]prazosin binding but only at high concentrations. These results do not support the idea that estrogen and progestin influence reproductive physiology through effects on brain alpha 1-receptors, although limitations of the methodology employed do not completely rule out this possibility.