[Reversal of experimental cerebral vasospasm by neuropeptides]

Changes in the density of cerebroarterial nerve fibers containing calcitonin gene-related peptide (CGRP) and vasoactive intestinal polypeptide (VIP)-like substance, as well as changes in dilatory responses of isolated cerebral arteries to these neuropeptides, after subarachnoid hemorrhage (SAH) were examined in dogs. Moreover, the effects of these neuropeptides to the experimentally produced cerebral arterial spasm were also examined in dogs. SAH was produced by a single injection of fresh autologous arterial blood (1 ml/kg body weight) or double injection of arterial blood (0.5 ml/kg body weight, 48 hours apart) into the cisterna magna. Constriction of basilar artery was most prominent on Day 3 in the single injection model, and on Day 7 in the double injection model. The density of nerve fibers with CGRP-or VIP-like immunoreactivity (LI) was markedly decreased during 7-14 days or 3-7 days after SAH. Vasodilatory actions of CGRP and VIP to isolated basilar artery in vitro were markedly impaired during acute stage of post-SAH period and significantly enhanced during chronic stage of post-SAH period. Intracisternal bolus injection of 10(-10) mol/kg CGRP completely reversed cerebral arterial constriction on Day 3 of single injection SAH model, and intracisternal injection of 10(-11) to 2 x 10(-10) mol/kg CGRP reversed cerebral vasospasm dose-dependently. Intraarterial injection of CGRP could not reversed cerebral arterial constriction. The effects of VIP was much weaker than CGRP.