Different neuroprotective responses of Ginkgolide B and bilobalide, the two Ginkgo components, in ischemic rats with hyperglycemia

Ginkgo biloba extracts show neuroprotective effects during cerebral ischemia, but with various components, the mechanisms of action remain unclear. In this study, we tested the effects of Ginkgolide B (GB) and bilobalide (BB) on normoglycemic and hyperglycemic rats subjected to transient cerebral ischemia. Rats were administered p.o. with different Ginkgo components GB (6 mg/kg) or BB (6 mg/kg) once daily for 7 days. Hyperglycemia was made by jugular vein infusion of glucose and transient middle cerebral artery occlusion/reperfusion was induced by a suture insertion technique. Results showed that both GB and BB exerted neuroprotection under normoglycemia, as determined by infarct volume and neurological deficit scores. Yet, BB showed less protective effects during hyperglycemic cerebral ischemia. Cerebral blood flow (CBF) was evaluated during occlusion and the first hour of reperfusion. BB but not GB caused acute increase in CBF after reperfusion, especially in hyperglycemia. Reactive oxygen species and malondialdehyde levels were reduced by GB in both models but BB were not effective in reactive oxygen species or malondialdehyde control in hyperglycemia ischemic rats. These results suggested that CBF plays crucial roles during early stage of reperfusion in the presence of hyperglycemia. Administration of compound that improves CBF may have little effect in hyperglycemic stroke.