Facilitation of estrogen-induced receptivity through metyrapone administration in ovariectomized rats

Previously it has been established that adrenalectomy facilitates lordosis in estrogen-primed ovariectomized female rats and that corticosterone administration restores lordosis to preadrenalectomy levels. The present study examined the effects of an inhibitor of the synthesis of corticosterone, metyrapone, upon lordosis in ovariectomized females. In Experiment 1, chronic administration of moderate doses of metyrapone was found to facilitate lordosis. In Experiment 2, a single metyrapone administration at various doses and time intervals before testing had a mild facilitatory effect on lordosis. Experiment 3 compared the effects of metyrapone on ovariectomized and adrenalectomized-ovariectomized females. The absence of a facilitatory effect in adrenalectomized females suggests that the drug's effect on lordosis is mediated by its established inhibitory effects on 11 beta-hydroxylation in the adrenal. These data are consistent with indications that corticosterone titer modulates female receptivity.