FUNCTIONAL EVIDENCE THAT THE CENTRAL RENIN-ANGIOTENSIN SYSTEM PLAYS AROLE IN THE PRESSOR - RESPONSE INDUCED BY CENTRAL INJECTION OF CARBACHOL

We investigated the effects of losartan, an AT(1)-receptor blocker, an d ramipril, a converting enzyme inhibitor, on the presser response ind uced by angiotensin II (ANG II) and carbachol (a cholinergic receptor agonist). Male Holtzman rats (250-300 g) with a stainless steel cannul a implanted into the lateral ventricle (LV) were used. The injection o f losartan (50 nmol/l mu l) into the LV blocked the presser response i nduced by ANG II(12 ng/l mu l) and carbachol (2 nmol/l mu l). After in jection of ANG II and carbachol into the LV, mean arterial pressure (M AP) increased to 31 +/- 1 and 28 +/- 2 mmHg, respectively, Previous in jection of losartan abolished the increase in MAP induced by ANG II an d carbachol into the LV (2 +/- 1 and 5 +/- 2 mmHg, respectively), The injection of ramipril (12 ng/l mu l) prior to carbachol blocked the pr esser effect of carbachol to 7 +/- 3 mmHg, These results suggest an in teraction between central cholinergic pathways and the angiotensinergi c system in the regulation of arterial blood pressure.