Interaction of vasopressin and angiotensin II in central control of blood pressure and thirst.

It is now well recognized that systemically released angiotensin II (Ang II) and arginine vasopressin (AVP) act in concert in regulation of blood pressure and water-electrolyte balance. Numerous studies have also demonstrated that centrally applied Ang II and AVP cause significant 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 osmoregulatory regions of the forebrain are extensively innervated by the angiotensinergic and vasopressinergic neurons. Some evidence indicates that the angiotensinergic and vasopressinergic system may interact in the central blood pressure control, although the significance of this interaction may differ in various species. Recently, attempts have been made to find out whether centrally released Ang II and AVP may play a role 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 regulation of blood pressure under baseline conditions. In addition, the vasopressinergic system appears to be involved in the adjustment of cardiovascular functions to hypovolemia, whereas its role in regulation of blood pressure during the osmotic disorders is less clear. Regulation of blood pressure and heart rate by centrally released AVP under baseline conditions, during hypovolemia and in osmotic disorders is significantly 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 and Ang II in the control of water intake awaits further examination. The available evidence from rat studies does not give support to a significant cooperation between central angiotensinergic and vasopressinergic system in regulation of water intake.