In vitro assay of contractile activities of spastic canine basilar artery and its surrounding blood clot.

A prolonged vasospasm was produced in the canine basilar artery by injection of fresh autogenous arterial blood into the chiasmatic cistern. Homogenates of lyophilized blood clot around the spastic artery, were made, and their contractile activities were studied in vitro. The homgenates of the lyophilized spastic arteries usually induced a dose dependent sustained contraction, whereas those of the lyophilized normal arteries often produced a dose-dependent transient contraction, and those of the lyophilized blood clot induced a dose-dependent transient or sustained contraction. The initial maximum contractions produced by the homogenates of the lyophilized normal and spastic arteries were significantly different in their values, suggesting the presence of a vasoactive agent in the spastic artery itself. Preliminary pharmacological analysis of the vasoactive agent was attempted using methysergide and phentolamine.