Role of spinal NADPH oxidase in development and maintenance of neuropathic pain in rats

Abstract

Objective To evaluate the role of spinal nicotinamide-adenine dinucletide phosphate(NADPH)oxidase in the development and maintenance of neuropathic pain(NP)in rats. Methods Twenty-four pathogen-free healthy male Sprague-Dawley rats, aged 200-250 g, were divided into 3 groups(n=8 each)using a random number table: sham operation group(S group), NP group and NADPH oxidase inhibitor group(NI group). The left sciatic nerve was exposed but not ligated in group S. The left sciatic nerve was exposed and 4 loose ligatures were placed on the sciatic nerve at 1 mm intervals with 4-0 silk thread to establish the NP model in group NP.In group NI, the NP model was established at 3 days after intrathecal catheterization, and NADPH oxidase inhibitor 5 μg/10 μl was injected intrathecally once a day for 7 consecutive days starting from 30 min before operation.The mechanical paw withdraw threshold(MWT)was measured at 1 day before operation and 1, 3, 5 and 7 days after operation.The rats were sacrificed at 8 days after operation, and the spinal cord was removed for determination of NeuN positive cells(by immuno-histochemistry)and expression of NADPH oxidase(by Western blot). Results Compared with group S, the MWT at each time point after operation and ratio of NeuN positive cells at 8 days after operation were significantly decreased in NP and NI groups, the expression of NADPH oxidase was up-regulated in group NP, and the expression of NADPH oxidase was down-regulated in group NI(P<0.05). Compared with group NP, the MWT at each time point after operation and ratio of NeuN positive cells at 8 days after operation were significantly increased, and the expression of NADPH oxidase was down-regulated in group NI(P<0.05). Conclusion Up-regulated expression of spinal NADPH oxidase is involved in the development and maintenance of NP in rats. Key words: Spinal cord; NADPH oxidase; Neuralgia