Protective Effect and Potential Mechanism of Ginkgo biloba Extract EGb 761 on STZ‐induced Neuropathic Pain in Rats

Diabetes induced neuropathic pain is recognized as one of the most difficult types of pain to treat with conventional analgaesics. EGb 761 is a standardized extract of Ginkgo biloba that has analgaesic and antiinflammatory properties and modulatory effects on key pain‐related molecules. We examined the effect of EGb 761 on streptozotocin (STZ)‐induced neuropathic pain behaviours and assessed its mechanism of action. Streptozotocin (20 mg/kg i.p for 5 days) was administered to induce experimental diabetes. Pain hypersensitivity to radiant heat was measured using the Dynamic Plantar Aesthesiometer to test the pain threshold. Diabetic rats exhibited mechanical allodynia and thermal hyperanalgaesia after the third week of STZ injection and concomitantly increased thiobarbituric acid reactive substance and nitric oxide concentration. The antioxidant enzymes level of superoxide dismutase and catalase was markedly reduced in STZ‐diabetic rats (p < 0.05). Systemic administration of EGb 761 (25, 50 and 100 mg/kg), starting after the third week following STZ injection, dose‐dependently reversed STZ‐induced thermal hyperanalgaesia and mechanical allodynia. Moreover, it reduced oxidonitrosative stress and concomitantly restored the level of antioxidant enzymes (p < 0.05) as compared with untreated diabetic rats. These results suggest that EGb 761 attenuated STZ‐induced neuropathic pain behaviours by inhibiting oxidative and nitrosative stress and may constitute a new approach for treatment of painful diabetic neuropathy. Copyright © 2012 John Wiley & Sons, Ltd.