Calcitonin gene-related peptide (CGRP) causes redistribution of blood flow in humans

In normal human subjects (n = 6), blood flow in the common carotid artery, assessed with an ultrasonic duplex-scanning unit, was increased up to 152% of basal levels by 60-min infusions of human calcitonin gene-related peptide I (alpha CGRP) 80 pmol.kg-1.h-1, but it was not affected by 20 pmol.kg-1.h-1 CGRP or 88 pmol.kg-1.h-1 human calcitonin. In the superior mesenteric artery, on the other hand, blood flow was reduced by 80 pmol.kg-1.h-1 CGRP to 58% of the basal level, but not by 20 pmol.kg-1.h-1 CGRP or with 88 pmol.kg-1.h-1 calcitonin. Blood flow in the abdominal aorta remained largely unchanged under the same conditions. Skin blood flow, assessed by a laser Doppler unit, was increased up to 682% of the basal level by 80 pmol.kg-1.h-1 CGRP, but not by 20 pmol.kg-1.h-1 CGRP or calcitonin. Thus CGRP increased regional blood flow to the brain and the skin at the expense of the gastrointestinal tract.