In the present study, we investigated the involvement of the brain renin-angiotensin system in the effects of central cholinergic stimulation on blood pressure in conscious, freely moving normotensive rats. In the first step, we determined the effects of intracerebroventricular (icv) choline (50, 100 and 150 mug) on blood pressure. Choline increased blood pressure in a dose-dependent manner. In order to investigate the effects of brain renin-angiotensin: system blockade on blood pressure increase induced by choline (150 mug, icy), an angiotensin-converting enzyme inhibitor, captopril (25 and 50 mug, icy), was administered 3 min before choline. Twenty-five mug captopril did not block the presser effect of choline, while 50 mug captopril blocked it significantly. Our results suggest that the central renin-angiotensin system may participate in the increase in blood pressure induced by icy choline in normotensive rats.