Abstract
Microinjection of angiotensin II (ANG II) into the subfornical organ (SFO) caused drinking in ovariectomized (OVX) female rats that were treated with either propylene glycol (PG) vehicle or estradiol benzoate (EB). The amount of water intake elicited by the ANG II injection was significantly greater in the PG-treated than in the EB-treated animals. In both groups, previous injections of either dizocilpine (MK801), a N-methyl-D-asparatate (NMDA) antagonist, or 6-cyano-7-nitroquinoxaline-2,3-dion (CNQX), a non-NMDA antagonist, into the median preoptic nucleus (MnPO) resulted in the significant attenuation of the drinking response to ANG II, whereas similar injections of saline vehicle into the MnPO was without effect. These results show the involvement of glutamatergic projections from the SFO to the MnPO in the elicitation of drinking response ANG II activation of the SFO, and suggest that the elicitation of drinking response may be mediated through both NMDA and non-NMDA receptor mechanisms in the MnPO. Our data further imply that the circulating estrogen may act to attenuate the glutamatergic SFO inputs to the MnPO. [J Physiol Sci. 2008;58 Suppl:S139]
