Prolactin inhibits pituitary luteinizing hormone-releasing hormone receptors in the rat.

Abstract

Pituitary LHRH receptors were studied in intact immature and mature female rats as well as in adult castrated animals of both sexes under experimental conditions leading to marked alterations of plasma PRL levels. Implantation of three anterior pituitary glands under the kidney capsule on the morning of estrus prevented the increase in pituitary LHRH receptor content measured 3 days later on the morning of expected proestrus. Pituitary implants slightly decreased pituitary LHRH receptor levels in ovariectomized adult rats while simultaneous treatment with 17β-estradiol (E2; 1 μg daily) markedly potentiated the inhibitory effect of pituitary implants and led to much higher plasma PRL concentrations. Although pituitary implants alone had no effect on plasma gonadotropin levels, they potentiated the inhibitory effect of E2 on both plasma LH and FSH on both plasma LH and FSH on both plasma LH and FSH levels. Treatment with the dopaminergic agonist 2α-bromoergocryptine (CB-154) completely reversed the inhibito...