Pressor responses to central angiotensin II, prostaglandin E1 and prostaglandin E2. Effects of ovarian steroids.

The effects of ovarian steroids on baseline blood pressure and on changes of mean arterial pressure in response to centrally administered angiotensin II, prostaglandin E1, and prostaglandin E2 were examined. Ovariectomized rats treated with estradiol or progesterone showed no change of resting blood pressures relative to oil-treated, ovariectomized controls. Intracerebroventricular injections of prostaglandin E1, prostaglandin E2 or angiotensin II produced significant elevations of arterial pressure of oil-treated rats. Either estradiol or progesterone treatment significantly attenuated pressor responses to prostaglandin E1 but not to prostaglandin E2 or angiotensin II injections. The duration of the blood pressure increase of estradiol-treated rats in response to angiotensin II was reduced when the animals did not have access to drinking water during the pressure monitoring session but not when water was available. These results suggest that the effects of ovarian steroids in modulating pressor responses are dependent on the particular factors which initiate the pressure increases. Possible mechanisms underlying this ovarian-steroid action are discussed.