Effect of diabetic peripheral neuropathy on peripheral neurotoxicity induced by local anesthetics in rats

Abstract

Objective To evaluate the effect of diabetic peripheral neuropathy on peripheral neurotoxicity induced by local anesthetics in rats. Methods Sixty healthy adult male SPF Sprague-Dawley rats, aged 6 weeks, weighing 150-180 g, were divided into either control group(n=18)or diabetic peripheral neuropathy group(n=42)using a random number table.The rats were fed a high-fat and high-sucrose diet for 8 weeks, and streptozotocin(STZ)30 mg/kg was injected intraperitoneally to induce diabetes mellitus which was confirmed by blood glucose level≥16.7 mmol/L.The mechanical paw withdrawal threshold to von Frey filament stimulation and thermal paw withdrawal threshold were measured.The decrease in reaction thresholds to thermal and mechanical stimuli(changing from sensitivity to insensitivity)was observed after STZ injection.At 4 weeks after STZ injection, the rats showing a marked hyperalgesia served as early diabetic group.At 8 weeks after STZ injection, the rats showing a marked insensitivity to pain served as late diabetic group.Experiments were carried out in early or late diabetic rats, and ordinary Sprague-Dawley rats of the same age were used as control group.Left sciatic nerve block was performed with 2% lidocaine 0.2 ml.Before the sciatic nerve block and at 1 week after the sciatic nerve block, the nerve conduction velocity of the left sciatic nerve and F-wave minimal latency were measured, and the sciatic nerve block time was recorded. Results Compared with the baseline before block, the nerve conduction velocity was significantly decreased, and the F-wave minimal latency was prolonged in late diabetic rats(P<0.05). Compared with control group, the sciatic nerve block time was significantly prolonged in late diabetic group(P<0.05). Conclusion Diabetic peripheral neuropathy aggravates peripheral neurotoxicity induced by local anesthetics in rats. Key words: Diabetes mellitus; Neuralgia; Lidocaine; Sciatic nerve