Ginkgo biloba Leaf Extract (EGb761) Combined with Neuroprotective Agents Reduces the Infarct Volumes of Gerbil Ischemic Brain

Abstract

Ginkgo biloba exerts many pharmacological actions. It possesses antioxidant properties, the ability of neurotransmitter/receptor modulation and antiplatelet activation factor. This research is designed to investigate the neuroprotective effects of long-term treatment with EGb761 (a standard form of the extract of Ginkgo biloba leaf) in combination with MgSO 4, FK506, or MK-801 on the infarct volume of male gerbils' brain induced by unilateral middle cerebral artery occlusion (MCAO). Thirty-five gerbils fed a standard diet were intragastrically given water or EGb761 (100 mg/kg/day) for one week. Five randomized groups were established: control ( n = 7), EGb 761 ( n = 8), EGb 761 + MgSO 4 ( n = 7), EGb 761 + FK 506 ( n = 7), and EGb 761 + MK -801 ( n = 6). The three drug-combination groups were injected with MgSO 4 (90 mg/kg), FK506 (0.5 mg/kg), or MK-801 (1 mg/kg), respectively 30 min before MCAO. Gerbils were anesthetized and craniectomized to expose the right middle cerebral artery (MCA). The right MCA was constricted with an 8-0 suture to produce a permanent ligation for 24 hours. Postmortem infarct volumes were determined by quantitative image analysis of 2,3,5-triphenyltetrazolium chloride (TTC)-stained brain sections. Results showed that the total infarct volumes of the four treated groups either EGb761 alone or in combination with drugs were lower than the control group by 36.1% (EGb761 alone), 40.3% ( EGb 761 + MgSO 4), 35.3% ( EGb 761 + FK 506), and 56.4% ( EGb 761 + MK -801), respectively ( p < 0.01). The main affected areas of the brain in the four treated groups were significantly focused between 4 and 6 mm from the frontal pole, when compared to the control group ( p < 0.01). All animals in the five groups had infarctions in both cortex and subcortex. These results indicate that long-term pre-treatment of EGb761 administered either alone or in combination with drugs significantly effective neuroprotection on infarct volume in gerbil ischemic brains.