ROLE OF ANGIOTENSIN-II AND VASOPRESSIN RECEPTORS WITHIN THE SUPRAOPTIC NUCLEUS IN WATER AND SODIUM-INTAKE INDUCED BY THE INJECTION OF ANGIOTENSIN-II INTO THE MEDIAL SEPTAL AREA

In this study we investigated the effects of the injection into the su praoptic nucleus (SON) of non-peptide AT1- and AT2-angiotensin II (ANG II) receptor antagonists, DuP753 and PD123319, as well as of the argi nine-vasopressin (AVP) receptor antagonist d(CH2)(5)-Tyr(Me)-AVP, on w ater and 3% NaCl intake induced by the injection of ANG io II into the medial septal area (MSA). The effects on water or 3% NaCl intake were assessed in 30-h water-deprived or in 20-h water-deprived furosemide- treated adult male rats, respectively. The drugs were injected in 0.5 mu l over 30-60 s. Controls were injected with a similar volume of 0.1 5 M NaCl. Antagonists were injected at doses of 20, 80 and 180 nmol. W ater and sodium intake was measured over a 2-h period. Previous admini stration of the AT1 receptor antagonist DuP753 into the SON decreased water (65%, N = 10, P<0.01) and sodium intake (81%, N = 8, P<0.01) ind uced by the injection of ANG II (10 nmol) into the MSA. Neither of the se responses was significantly changed by injection of the AT2-recepto r antagonist PD 123319 into the SON. On the other hand, while there wa s a decrease in water intake (45%, N = 9, P<0.01), ANG II-induced sodi um intake was significantly increased (70%, N = 8, P<0.01) following i njection of the V1-type vasopressin antagonist d(CH2)(5)-Tyr(Me)-AVP i nto the SON. These results suggest that both AT I and V1 receptors wit hin the SON may be involved in water and sodium intake induced by the activation of ANG II receptors within the MSA. Furthermore, they do no t support the involvement of MSA AT2 receptors in the mediation of the se responses.