The 5-hydroxytryptamine antagonist ketanserin inhibits the vasoconstrictor activity of per-operative CSF, from subarachnoid haemorrhage patients, on isolated tissues.

Peri-aneurysmal CSF was obtained at operation from 13 patients with subarachnoid haemorrhage from ruptured intracranial aneurysms. The 5-hydroxytryptamine antagonist ketanserin inhibited contractions of isolated human intracranial arteries, elicited by this CSF. The presence of 5-HT in CSF was confirmed by high performance liquid chromatography. The use of ketanserin in the therapy of postoperative cerebral vasospasm is discussed.