Objective.To investigate the effects of Ginkgo biloba extracton cer ebral vasospasmafter subarachnoid hemorrhageand its influence on n itric oxideand endothelin-l .Methods.Noncraniotomy models of SAH in Wistar rats were used and animals were divided into sham-operated group

SAH group

saline-treated group and EGb-treated group.Diameter of basilar a rtery was measured.Regional cerebral blood flow

NO and ET-1levels in blood

and calcium content in brain tissue within24hours after SAH were dete cted.Pathological examination of hippocampus CA1sub-field was also performed .Results.Sham operation did not alter the above parameters.Induction of SAH l ed to a marked spasm of basilar artery.rCBF decreased obviously and consecutive ly within24hours after SAH.Meanwhile NO level in serum decreased

ET-1level in plasma and calcium content in brain tissue significantly in-creased.Pyra midal cells in hippocampus CA1subfield were severely damaged.EGb significantly antago-nized the pathological alterations of the above parameters.Conclusion .Alterations of NO

and ET-1play an important role in the development of CV S after SAH.EGb exerts its protective effects on CVS by inhibitng the above pat hological alterations.