Vasopressin and angiotensin receptors of the medial septal area of the brain in the control of thirst and salt appetite induced by vasopressin in water-deprived and sodium-depleted rats

In this study we investigated the influence of d(CH2)5-Tyr (Me)-AVP (A1AVP) and [Adamanteanacatyl1,D-ET-D-Tyr2, Val4, aminobutyril6,A8,9]-AVP (A2AVP), antagonists of V1 and V2 arginine8-vasopressin (AVP) receptors, respectively, as well as the effects of losartan and CGP42112A, antagonists of angiotensin II (ANGII) AT1 and AT2, receptors, respectively, on water and 0.3 M sodium intake induced by water deprivation or sodium depletion (furosemide treatment) and enhanced by AVP injected into the medial septal area (MSA). A stainless steel cannula was implanted into the medial septal area (MSA) of male Holtzman rats AVP injection enhanced water and sodium intake in a dose-dependent manner. Pretreatment with V1 antagonist injected into the MSA produced a dose-dependent reduction, whereas prior injection of V2 antagonist increased, in a dose-dependent manner, the water and sodium responses elicited by the administration of AVP. Both AT1 and AT2 antagonists administered into the MSA elicited a concentration-dependent decrease in water and sodium intake induced by AVP, while simultaneous injection of the two antagonists was more effective in decreasing AVP responses. These results also indicate that the increase in water and sodium intake induced by AVP was mediated primarily by MSA AT1 receptors.