Effect of intracisternal and intravenous calcitonin gene-related peptide on experimental cerebral vasospasm in rabbits.

We investigated the vasodilatory effect of intracisternal (i.c.) and intravenous (i.v.) administration of calcitonin gene-related peptide (CGRP) on arterial narrowing after experimental subarachnoid hemorrhage (SAH). Forty-one rabbits were divided into five groups: control (normal animals); SAH plus i.c. infusion of vehicle; SAH plus i.c. infusion of CGRP; SAH plus i.v. infusion of vehicle; SAH plus i.v. infusion of CGRP. In all but the control group, either CGRP (100 ng/kg/min) or vehicle solution was infused for two hours immediately prior to sacrifice by perfusion-fixation. A morphometric technique was employed to measure the luminal diameter of rabbit basilar arteries two days after SAH. The diameter of the basilar arteries in either the i.c. or i.v. CGRP groups was significantly greater than that of the respective vehicle group (i.c., p < 0.001; i.v., p < 0.01). Although there was no significant difference in systemic arterial blood pressure after infusion between the i.c. vehicle and i.c. CGRP groups, i.v. CGRP caused significant hypotension. Our results suggest that exogenous CGRP has some therapeutic potential for arterial narrowing after SAH not only by intrathecal application, but also by systemic use.