Relaxant effect of calcitonin gene-related peptide on cerebral arterial spasm induced by experimental subarachnoid hemorrhage in dogs.

This study examines the relaxant effect of calcitonin gene-related peptide (CGRP), a 37-amino acid peptide with a potent vasodilator action, on cerebral arterial spasm after subarachnoid hemorrhage (SAH). The spasm was induced by injecting autologous arterial blood percutaneously into the cisterna magna in adult mongrel dogs. The single-injection model of SAH was produced by injection of 1.0 ml/kg body weight of blood (on Day 0), and the double-injection model involved two successive injections of 0.5 ml/kg body weight of blood made 48 hours apart (on Day 0 and Day 2). On vertebral angiograms, arterial narrowing of the major cerebral arteries was most prominent on Day 3 after SAH in the single-injection model and on Day 7 in the double-injection model. When 10(-10) mol/kg of CGRP was administered intracisternally in the single-injection model on Day 3, the diameter of the spastic cerebral arteries, as determined by angiography, recovered to normal. After intracisternal administration of 10(-11) to 2 X 10(-10) mol/kg of CGRP on Day 7 in double-injection models, spastic cerebral arteries dilated in a dose-dependent manner. The dilatory effect of CGRP continued for a few hours after administration. The results suggest that CGRP injected intracisternally may reverse cerebral arterial spasm after SAH.