Ovarian steroid manipulation of the antidipsogenic and thermogenic responses of rats to central administration of prostaglandin E1.
Intracerebroventricular (icv) injection of prostaglandin E1 (PGE1) increases arterial pressure, suppresses water intake, and elevates core temperature of rats. Treatment of ovariectomized rats with estradiol or progesterone results in an attenuation of the pressor response to PGE1. This work addressed the effects of daily subcutaneous injection of estradiol (1 microgram), progesterone (5 mg), or oil vehicle on the antidipsogenic and thermogenic response to icv PGE1 of ovariectomized rats. The change of core temperature induced by the PGE treatment was significantly correlated with antidipsogenesis for ovariectomized rats receiving daily oil injections. Although neither the suppression of water intake nor the increase of core temperature in response to icv PGE1 was affected significantly by ovarian steroid treatment, the linear relation between the thermogenic and antidisogenic actions of the icv PGE1 was abolished by either estradiol or progesterone administration. Thus, although the pressor, antidipsogenic, and thermogenic effects of icv PGE1 tend to occur in concert, they may be differentially affected by ovarian steroid administration, which suggests that the mechanisms underlying these varied effects of icv PGE1 may be independent.