ROLE OF PARAVENTRICULAR NUCLEUS IN CONTROL OF BLOOD-PRESSURE AND DRINKING IN RATS

The present investigation examined the abilities of angiotensin (ANG) II and III to produce increases in blood pressure and drinking when microinfused into the paraventricular nucleus (PVN) of the hypothalamus of the Sprague-Dawley rat. Dose-dependent elevations in systemic blood pressure and heart rate were measured to both ANG II and III in the anesthetized rat, with ANG II more potent than ANG III at the two highest doses examined. Pretreatment with the specific ANG receptor antagonist [Sar1,Thr8]ANG II (sarthran), blocked subsequent ANG II- and III-induced elevations in blood pressure, suggesting that these responses were dependent on the activation of ANG receptors. A similar analysis in awake rats yielded nearly equivalent results. A final experiment demonstrated that microinfusions of ANG II and III into the PVN produced drinking in a dose-dependent manner, with greater consumption to ANG II than ANG III. Again, sarthran was found to block the dipsogenic response. Histological examination revealed that the location of the injection site was linked to the character of the ANG-dependent response. These data suggest that the PVN may play a critical role in mediating central ANG effects on body water homeostasis and blood pressure regulation. Furthermore, it appears that subnuclei of the PVN may participate differentially in ANG-mediated actions.