Pituitary gonadotropin-releasing hormone receptors during the rat estrous cycle

The binding of [6-alanine]gonadotropin-releasing hormone to pituitary plasma membranes increased threefold between metestrus and early proestrus in female rats. Receptor numbers fell rapidly on the afternoon of proestrus coincident with the preovulatory gonadotropin surge. The numbers of receptors for gonadotropin-releasing hormone were positively correlated with concentrations of estradiol in serum; this pattern may be a necessary component of increased pituitary sensitivty to gonadotropin-releasing hormone observed during proestrus.