Effects of hyperbaric oxygen postconditioning of microglia on activation in rats model of neuropathic pain

Abstract

Objective To investigate the antinociceptive effect of hyperbaric oxygen(HBO) on activation of microglia in rats with neuropathic pain (NP) produced by chronic constriction injury of the sciatic nerve.Methods Twenty four healthy male Sprague-Dawley rats were randomly divided into four groups (n=6):Sham group (group S),CCI group (group C),2.0 ATA HBO post-conditioning group (group H2.0) and 2.5ATA HBO post-conditioning group (group H2.5).Group CCI,group H2.0 and group H2.5 were received the surgery of the chronic constriction injury.One day later,surgery HBO of 2.0 ATA and 2.5 ATA was given respectively by hyperbaric oxygen cabin once a day for seven days.The mechanical withdrawal threshold (MWT) and thermal withdrawal latency (TWL) of rats in each group were measured respectively 1 h after the surgery every day.The rats were killed after 7 days when MWT and TWL had already been measured.The lumbar segment L4-5 of the spinal cord was removed.Immunohistochemical technique was used to detect the activation of microglias in the spinal cord.Results Compared with group S,MWT and TWL were significantly decreased and the activation of microglias in the spinal cord was significantly enhanced after surgery in group C(P＜0.05).Compared with group C,MWT and TWL were significantly increased and the activation of microglias in the spinal cord was significantly inhibited after surgery in group H2.0 and H2.5 (P＜0.05).There was no significant difference in the activation of spinal microglias between group H2.0 and H2.5.Conclusions HBO post-conditioning may produce the antinociceptive effect by inhibiting activation of spinal microglias in rats model of neuropathic pain. Key words: Hyperbaric oxygen; Neuropathic pain; Microglia; Antinociception