INTERACTION OF VASOPRESSIN AND ANGIOTENSIN-II IN CENTRAL CONTROL OF BLOOD-PRESSURE AND THIRST

It is now well recognized that systemically released angiotensin II (A ng II) and arginine vasopressin (AVP) act in concert in regulation of blood pressure and water-electrolyte balance. Numerous studies have al so demonstrated that centrally applied Ang II and AVP cause significan t alterations of the cardiovascular functions and body fluid balance. Moreover, it has been established that Ang II and AVP are released in the central nervous system during cardiovascular and osmotic disorders and that the cardiovascular regions of the brainstem and the osmoregu latory regions of the forebrain are extensively innervated by the angi otensinergic and vasopressinergic neurons. Some evidence indicates tha t the angiotensinergic and vasopressinergic system may interact in the central blood pressure control, although the significance of this int eraction may differ in various species. Recently, attempts have been m ade to find out whether centrally released Ang II and AVP may play a r ole in the regulation of the cardiovascular system under physiological and pathophysiological conditions. With regard to this, the available evidence strongly suggests that the both systems may be involved in r egulation of blood pressure under baseline conditions. In addition, th e vasopressinergic system appears to be involved in the adjustment of cardiovascular functions to hypovolemia, whereas its role in regulatio n of blood pressure during the osmotic disorders is less clear. Regula tion of blood pressure and heart rate by centrally released AVP under baseline conditions, during hypovolemia and in osmotic disorders is si gnificantly altered in the spontaneously hypertensive rats. It is now well established that centrally applied Ang II and Ang III are potent dipsogenic compounds. There also is evidence that AVP may enhance the osmotic thirst. However, the physiological role of brain-derived AVP a nd Ang II in the control of water intake awaits further examination. T he available evidence from rat studies does not give support to a sign ificant cooperation between central angiotensinergic and vasopressiner gic system in regulation of water intake.