Inhibition by dipyridamole of cerebral vasospasm induced in vitro by whole blood

This study evaluates the effect of dipyridamole, an inhibitor of platelet aggregation, on cerebral artery contraction induced in vitro by the addition of whole blood. Whole fresh arterial blood added to isolated rabbit basilar artery bathed in a physiological buffer produces a sustained contraction in vessels observed for 60 minutes. Significant dose-dependent inhibition of contraction was observed when dipyridamole was added to the vessel bath. This effect was not influenced by preincubating cerebral vessels with aspirin, an inhibitor of prostaglandin synthesis. It is suggested that inhibition of whole blood-induced cerebral artery contraction by dipyridamole does not result from potentiation of cerebral vessel prostaglandin pathways, but possibly from a direct effect on platelets.