Functional Role of α-Calcitonin Gene-Related Peptide in the Regulation of the Cardiovascular System

It remains unknown whether the extent of vasoactive response to exogenous calcitonin gene-related peptide (CGRP) varies among different regional vascular beds. It is also unclear whether endogenous CGRP plays a functional role in regulating basal vascular activity. To address these two issues, experiments were conducted in 27 anesthetized rats instrumented with a carotid flow probe and catheters in a jugular vein, left ventricle (LV), and femoral artery, and in 6 conscious dogs, chronically instrumented with LV pressure gauge, aortic and atrial catheters, and ascending aortic, coronary, carotid, and renal flow probes. In both species, administration of human α-CGRP (0.1–0.5 μg/kg, i.v.) induced a dose-dependent peripheral vasodilation that was completely abolished by pretreatment with α-CGRP[8-37] (30 μg/kg/min, i.v.), a competitive antagonist of CGRP receptors. Regional blood flow measured by the radioactive microsphere technique in rats showed that the α-CGRP (0.3 μg/kg, i.v.)-induced increase in blood flow was greater ( p p