Effect of Microglia Activation on Neuropathic Pain in Rat SNI Model

Objective To investigate the effect of microglia on neuropathic pain in rat model of spared nerve injury (SNI). Methods Sixty-four SD rats were randomly assigned to 4 groups: sham operation group (Sh group),SNI model group (SNI group),40 mg/kg minocyline group (Mb group),and 10 mg/kg minocyline group (Ms group). The rats in Mb and Ms groups were intraperitoneally injected with minocyline twice daily,beginning from 1 day before nerve transection and lasting for 7 days. The mechnical withdraw threshold (MWT) and thermal withdraw duration (TWD) were recorded 1 day before surgery and 1,3,5,7,and 14 days after surgery. The expression of OX-42 in spinal microglia was detected by immunofluorescence. Results MWL decreased and TWL prolonged significantly since 1 day after surgery in SNI group,and the differences in MWL and TWL were significant between Sh and SNI groups at each time point (P 0.05). There were significant differences in MWT and TWL between Mb and SNI groups,between Ms and SNI groups,and between Mb and Ms groups (P 0.05). Compared with SIN group,the expression of OX-42 decreased in Mb and Ms groups in a dose-dependent manner. Conclusion The minocyline injected intraperitoneally could decrease the expression of OX-42 in a dose-dependent manner,inhibit the activation of microglia,and alleviate mechanical hyperalgesia and thermal hyperalgesia. It suggests that activated microglia participates in the formation of neuropathic pain after SNI.