Effects of extract of Ginkgo biloba on cognitive function and apoptosis of hippocampus neuronal cells in type 1 diabetic rats

AIM:To investigate the protective mechanism of extract of Ginkgo biloba (EGB) on apoptosis of hippocampus neuronal cells in type 1 diabetic encephalopathic rats. METHODS:Thirty-six male Sprague-Dauley rats were divided into 3 groups:control group,diabetic group and EGB-treated group. Streptozotocin was injected intraperitoneally to the animals in later two groups to induce diabetes. The rats in EGB-treated group were injected intraperitoneally with EGB,and the same volume of normal saline was injected to the rats in other groups. At the end of the 12th week,the spatial learning and memory abilities of rats in each group were examined by Morris water maze test. Blood glucose and serum insulin concentration were measured. The neuron densities in hippocampus were measured by Image-Pro Plus 6.0 software. The expressions of Bax,Bcl-2,caspase-3 were assayed by Western blotting and immunohistochemistry. RESULTS:Compared to control group,the level of blood glucose (P0.01),the protein expression of Bax (P0.01) and caspase-3 (P0.01) in hippocampus neuronal cells,and the ratio of Bax/Bcl-2 (P0.01) and the escape latency (P0.01) in diabetic group,were significantly increased,while the serum insulin concentration (P0.01),the neuronal density (P0.05) in CA1,CA2 hippocampal regions and the platform searching score (P0.01) were significantly deceased. After treated with EGB,the serum insulin concentration (P0.05),the neuronal density (P0.05) in CA1,CA2 hippocampal regions and the platform searching score (P0.01) were significantly increased,while the level of blood glucose (P0.01),the protein expression of Bax (P0.05),caspase-3 (P0.05) in hippocampus neuronal cells,the ratio of Bax/Bcl-2 (P0.01) and the escape latency (P0.05) were significantly deceased than those in diabetic group. The protein expression of Bcl-2 in hippocampus neuronal cells did not alter in any experimental rats. CONCLUSION:EGB improves the spatial learning and memory capacity in diabetic rats by decreasing the expression of Bax,Bax/Bcl-2 ratio and down-regulating caspase-3 to reduce neurocyte apoptosis and increase the neuron density in CA1,CA2 hippocampal regions,suggesting that effective regulation of neuron apoptosis associated genes may be one of the mechanisms for EGB to treat diabetic encephalopathy.