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

[³H]Prazosin was found to bind to sites on guinea pig brain membranes with α₁-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 α₁-receptors, although limitations of the methodology employed do not completely rule out this possibility.