Experimental cerebral vasospasm after subarachnoid hemorrhage. Participation of adrenergic nerves in cerebral vessel wall.

Distribution and morphology of nerves in basilar-artery-induced vasospasm were investigated electronmicroscopically. Small cored vesicles were transformed, decreased and disappeared gradually after development of vasospasm induced by blood-CSF mixture incubated 5--10 days. These changes were not induced by fresh arterial blood, lysed platelets in saline and mechanical stimulation. In the portion with severe vasospasm induced by incubated blood-CSF mixture, nerve distribution was rich and uniform in all portions of the adventitia. In the portion with slight vasospasm, nerves were extremely scanty in the innermost area of the adventitia, within 10 mu from the outer edge of the media. The severity of experimental vasospasm became definitely lighter and the duration shorter after bilateral cervical sympathectomy. These findings indicate that nerves, especially the adrenergic axon in the innermost area of the adventitia, may play an important role on the genesis of late vasospasm. The difference in nerve distribution may be a factor influencing individual differences in frequency or severity of vasospasm.