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 V₂-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-, V₂- and V_1a/V₂-AVP selective antagonists and AT₁- and AT₂-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 V₂-antagonists reduced, whereas prior injection of the V_1a/V₂-antagonist induced a decrease in the MAP that remained below the baseline. Both AT ₁- and AT₂-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 V₂-AVP and AT₁and AT₂-Ang II receptors in the MSA in the regulation of MAP.