Vasopressin and angiotensin receptors of the medial septal area in the control of mean arterial pressure induced by vasopressin.

Introduction: Brain arginine( 8)-vasopressin (AVP), through the V(1a)- and V(2)-receptors, is essential for the maintenance of mean arterial pressure (MAP). Central AVP interacts with the components of the renin-angiotensin system, which participate in MAP regulation. This study aimed to determine the effects of V(1a)-, V(2)- and V(1a)/V(2)-AVP selective antagonists and AT(1)- and AT(2)-angiotensin II (Ang II) selective antagonists on the MAP induced by AVP injected into the medial septal area (MSA) of the brain.

Materials And Methods: Male Holtzman rats with stainless steel cannulae implanted into the MSA were used in experiments. Direct MAP was recorded in conscious rats.

Results: AVP administration into the MSA caused a prompt and potent pressor response in a dose-dependent fashion. Pretreatment with the V(1a)- and V(2)-antagonists reduced, whereas prior injection of the V(1a)/V(2)-antagonist induced a decrease in the MAP that remained below the baseline. Both AT(1)- and AT(2)-antagonists elicited a decrease, while simultaneous injections of two antagonists were more effective in decreasing the MAP induced by AVP.

Conclusion: These results indicate there is a synergism between the V(1a)- and V(2)-AVP and AT(1)and AT(2)-Ang II receptors in the MSA in the regulation of MAP.