Reserpine and cerebral vasospasm.

Cerebral vasospasm was produced in the dog basilar artery by topically applied five-day-old clotted autologous blood, but not by freshly drawn blood. The spasm was reversed by methysergide, an antiserotonin agent. However, vasospasm was not produced by five-day-old clotted autologous blood from dogs pretreated with reserpine. This suggests platelet serotonin or a similar, unidentified substance as the vasospastic element in dog blood responsible for experimental vasospasm from topically applied whole blood. Other experimental data support these findings.