Calcitonin gene-related peptide (CGRP) has been shown to be a potent vasorelaxant. We tested the interaction of CGRP with angiotensin II (Ang II) in conscious, unrestrained Wistar rats. Rat CGRP (rCGRP, 0.1 and 1.0 nmol/kg per min) dose-dependently lowered mean arterial blood pressure and increased the heart rate. The effects continued throughout the infusion period of 30 min. Moreover, rCGRP significantly attenuated the pressor responses to Ang II (100 ng/kg per min). High-dose rCGRP (1.0 nmol/kg per min) almost abolished the pressor action of Ang II, and a much higher dose of Ang II (1000 ng/kg per min) was needed to restore the pre-infusion pressure. Plasma renin activity was dose-dependently increased by rCGRP, but was attenuated by simultaneous Ang II infusion. Rat CGRP also increased the plasma aldosterone concentration, as did Ang II. These results suggest that CGRP may have a neuromodulatory role in cardiovascular regulation.