Visual evoked potentials and optic nerve histopathology in normal and diabetic rats and effect of ginkgo biloba extract.

The purpose of this study was to test the possible therapeutic role of ginkgo biloba extract on the impairment of visual function and pathological histology of the optic nerve caused by early diabetes. Ginkgo biloba extract entraps oxygenated free radicals and is also a strong inhibitor of the platelet activation factor (PAF). For this purpose, VEP recordings and optic nerve histopathology were studied on alloxan diabetic and normal Swiss albino rats in four experimental groups. The VEP recordings showed no statistical significance between diabetic and normal rats. However, the amplitudes were significantly increased in diabetic animals with ginkgo biloba extract compared with the diabetics, supposing an impression of axonal protection. But the amplitude values were decreased in normal rats treated with the same extract compared with normal animals, assuming a toxic activity. Optic nerve ultrastructural findings also confirmed these VEP changes. It was concluded that this extract could be encouraging for human clinical trials of diabetes.