Estrogen attenuates the drinking response induced by activation of angiotensinergic pathways from the lateral hypothalamic area to the subfornical organ in female rats.

The present study was carried out to investigate whether estrogen modulates the drinking response induced by activation of angiotensinergic neural pathways from the lateral hypothalamic area (LHA) to the subfornical organ (SFO) in the female rats. Microinjection of ANG II (10(-10) M, 0.2 microl) into the LHA caused drinking in 17 out of 26 ovariectomized (OVX) female rats that were treated with propylene glycol (PG) vehicle and in 18 out of 28 OVX female rats that were treated with estrogen benzoate (EB). In both groups, previous injections of the ANG II antagonist saralasin (Sar, 10(-10) M, 0.2 microl) into the SFO significantly attenuated the water intake caused by the ANG II injection, suggesting that the ANG II-induced drinking response may be mediated by the angiotensinergic LHA projections to the SFO. Injections of ANG II (10(-10) M, 0.2 microl) into the SFO elicited drinking in all the animals that demonstrated the drinking response to ANG II injected into the LHA. The amount of water intake caused by either the injection of ANG II into the LHA or the SFO was significantly greater in the PG-treated than in the EB-treated animals. These results suggest that the circulating estrogen may act to attenuate the dipsogenic response induced by activation of the angiotensinergic pathways from the LHA to the SFO.