Investigation of the dose-dependent antivasospasmic effect of Ginkgo biloba extract (EGb 761) in experimental subarachnoid hemorrhage.

Many drugs with possible effects against the vasospasm that occurs following a subarachnoid hemorrhage continue to be investigated with great enthusiasm. Among these drugs, the effect of Ginkgo biloba extract (EGb 761) on vasospasm has not been studied extensively. A model of vasospasm was constructed using 30 selected Sprague-Dawley rats. There were four groups in this study: Group I were the untreated control group; vasospasm was induced in Group II, but no treatment was administered; and Groups III and IV experienced vasospasm before being treated with 45 and 90 mg/kg per day EGb 761, respectively. In Group I, the luminal structures of the arteries were normal; the mean vessel lumen area, based on the number of microm(2) units counted in the lumen, was 4931 units. In Group II, signs of inflammation were observed, as well as marked luminal constriction and increase in the thickness of the vessel wall; the mean vessel lumen area was 235 units (p<0.001 vs Group I). In Group III, the endothelial lining was the same as in Group I; the mean luminal area was 4336 units. In Group IV, inflammation occurred as in Group II and the luminal radius was clearly narrowed; the mean luminal area was 131 units (p<0.001 vs Group I). When Ginkgo biloba extract was administered at a dose of 45 mg/kg per day in an experimental vasospasm model, it was effective against vasospasm. However, this effect disappeared at a dose of 90 mg/kg per day.