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

I 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 BW50IC67, 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 BW50IC67 antagonized 5-HT induced cerebral arterial spasm.3 BW50IC67 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.