Cerebrovascular effects of topically applied serotonin in the cat

Abstract

The problem of neurologic symptoms in subarachnoid hemorrhage is discussed. Cerebral vasospasm is presented as one of the etiologic mechanisms of these symptoms. Serotonin (5-hydroxytryptamine) is an active vasoconstrictor substance present in blood platelets and is apparently released whenever platelets are disrupted during clotting. Serotonin was applied topically to major cerebral arteries and the cortex of cats. Prolonged localized spasm of these arteries was observed. Marked blanching of the treated cortex was also seen. Small quantities of serum from clotted blood caused vasospasm comparable to that caused by serotonin. Fresh blood did not cause vasospasm. While undoubtedly there are other mechanical, neurogenic, and possibly chemical factors, it is postulated that serotonin liberated from the platelets of extravasated blood may play a significant role in the pathogenesis of cerebral vasospasm following rupture of an intracranial aneurysm.