Aetiology of cerebral arterial spasm following subarachnoid haemorrhage: evidence against a major involvement of 5-hydroxy-tryptamine in the production of acute spasm.

1 Acute cerebral arterial spasm was produced in baboons by intracisternal injection of blood or 5-hydroxytryptamine (5-HT). Blood induced spasm was not antagonized by the potent 5-HT antagonist BW501C67, but 5-HT induced cerebral arterial spasm was largely antagonized. 2 Blood platelets from baboons were isolated and aggregated in vitro with adenosine diphosphate (ADP) and 5-HT. 5-HT induced platelet aggregation was abolished by BW501C67 in vitro. It was also abolished after intracisternal administration of the drug. Thus it is concluded that BW501C67 antagonized 5-HT induced cerebral arterial spasm. 3 BW501C67 also failed to antagonize contractions produced by human cerebrospinal fluid, serum and platelet extracts on the isolated human basilar artery, the isolated rat fundus and aorta. 4 These results suggest that the role of 5-HT in the aetiology of human cerebral spasm may be minimal.