EVIDENCE THAT ANGIOTENSIN-(1-7) PLAYS A ROLE IN THE CENTRAL CONTROL OF BLOOD-PRESSURE AT THE VENTROLATERAL MEDULLA ACTING THROUGH SPECIFIC RECEPTORS

In this study we determined which angiotensin receptors may mediate th e cardiovascular effects elicited by angiotensin-(1-7) [Ang-(1-7)] in the rostral ventrolateral medulla (RVLM) and caudal presser area (CPA) of the ventrolateral medulla (VLM) of anesthetized rats. Furthermore the role of endogenous angiotensins in these areas was also investigat ed. The presser effect produced by unilateral microinjection of Ang-(1 -7) into the RVLM or CPA was not modified by either the AT(1) receptor antagonist, DuP 753 or by the AT(2) receptor antagonist, CGP 42112A, but was completely blocked by the Ang-(1-7) selective antagonist, A-77 9. In contrast, the presser effect produced by microinjection of angio tensin II (Ang II) was completely blocked by DuP 753 but was not chang ed by CGP 42112A or A-779. Bilateral microinjection of A-779 into the RVLM or CPA produced a significant fall in mean arterial pressure and heart rate. Microinjection of DuP 753 produced a presser effect compar able to bilateral injection of vehicle. These results indicate that, a lthough Ang II acts in the VLM through an AT(1) receptor subtype, the cardiovascular effects produced by microinjection of Ang-(1-7) into th e RVLM and CPA are mediated by a specific angiotensin receptor (AT(5)? ). Furthermore, our data provide evidence that endogenous Ang-(1-7) pa rticipates at the VLM in the neural control of arterial blood pressure .