Effects of hyperbaric oxygen treatment on expression of nerve growth factor in spinal cord of rats with neuropathic pain

Objective To evaluate the effect of hyperbaric oxygen (HBO) treatment on the expression of nerve growth factor (NGF) in the spinal cord of rats with neuropathic pain (NP).Methods Thirty healthy male Sprague-Dawley rats,aged 8-10 weeks,weighing 270-300 g,were randomly divided into 5 groups (n =6 each) using a random number table:sham operation group (group S),group NP,pure oxygen group (group O),treatment with HBO at 2.5 atmosphere absolute group (group H2.5) and treatment with HBO at 3.0 atmosphere absolute group (group H3.0).The animals were anesthetized with intraperitoneal 10％ chloral hydrate 300 mg/kg.NP was induced by chronic constrictive injury.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.HBO treatment was performed with the corresponding atmosphere absolute once a day for 7 consecutive days starting from 1 day after operation in H2.5 and H3.0 groups.The mechanical paw withdrawal threshold (MWT) and thermal paw withdrawal latency (TWL) were measured on 3,5,7 and 14 days after operation.The animals were sacrificed after the last measurement of pain threshold,and the lumbar segments of the spinal cord were removed to detect the expression of NGF by immuno-histochemistry and Western blot analysis.Results Compared with group S,MWT was significantly decreased,TWL was shortened,and the expression of NGF was up-regulated at each time point after operation in NP and O groups.Compared with group NP,MWT was significantly increased,TWL was prolonged,and the expression of NGF was up-regulated at each time point after operation in H2.5 and H3.0 groups,and no significant change was found in MWT,TWL and expression of NGF in group O.Compared with group H2.5,the expression of NGF was significantly down-regulated,and no significant change was found in MWT and TWL in group H3.0.Conclusion The mechanism by which HBO treatment mitigates NP is related to up-regulation of the expression of NGF in the spinal cord of rats. Key words: Hyperbaric oxygen;  Neuralgia;  Nerve growth factor;  Spinal cord