Human α-calcitonin gene-related peptide (CGRP)-(8–37), but not-(28–37), inhibits carotid vasodilator effects of human α-CGRP in vivo

Human α-calcitonin gene-related peptide-(8–37) alone (up to doses of 30 nmol kg −1 min −1) had no significant effects on blood pressure, heart rate or common or internal carotid haemodynamics, although it caused significant, reversible, inhibition of the hypotensive, tachycardic, and common and internal carotid vasodilator effects of human α-CGRP (0.03 nmol kg −1min −1) in conscious, Long Evans rats. Human α-CGRP-(28-37) up to doses of 300 nmol kg −1 min −1 had no cardiovascular effects itself and did not influence responses to human α-CGRP. These results are consistent with the carotid haemodynamic effects of human α-CGRP being due largely to activation of the CGRP 1-receptor subtype.