Effects of hyperbaric oxygen on pain-related behaviours and expression levels of nitric oxide synthase in rats with neuropathic pain

doi:10.3969/j.issn.1002-7386.2016.18.012

Abstract：Objective To investigate the effects of hyperbaric oxygen ( HBO) on pain-related behaviours and expression levels of nitric oxide synthase in rats with neuropathic pain.Methods Thirty-two male Sprague Dawley rats were randomly divided into four groups; sham operation group ( group S), sciatic nerve ligation group ( CCI group), HBO pretreatment group (pre-HBO group) and HBO post-treatment group (post-HBO group),with 8 rats in each group.The baseline mechanical withdrawal thresholds ( MWT) were measured one day before CCI for all the rats.The pain-related behaviours were observed on 1d,2d,3d,7d,14d,21d,28d after CCI,and MWT was also measured.Moreover the numbers of nNOS, eNOS and iNOS positive neurons in cornu dorsale medullae spinalis were calculated on 28d after CCI.Results There was no significant difference in MWT before CCI among the 4 groups ( P >0.05).The MWT in pre-HBO group, post-HBO group and CCI group in every time point was significantly lower than that in group S ( P <0.05),moreover,the decrease degree in CCI group was the most obvious ( P <0.05).The MWT in pre-HBO group and post-HBO group in every time point was significantly higher than that in CCI group ( P <0.05).As compared with those in group S,the numbers of nNOS and iNOS positive neurons in CCI group,pre-HBO group and post-HBO group on 28d after CCI were significantly increased ( P <0.05).The numbers of nNOS and iNOS positive neurons in CCI group were significantly higher than those in pre-HBO group and post-HBO group ( P <0.05).However there were no significant differences in numbers of eNOS positive neurons among 4 groups ( P >0.05).Conclusion HBO has preventive and therapeutic effects on neuropathic pain,which can relieve pain, and its action mechanism may be correlated to the decrease of the expresion levels of NOS.