Spinal cord stimulation exerts analgesia effects in chronic constriction injury rats via suppression of the TLR4/NF-κB pathway

Spinal cord stimulation (SCS) is an established method for treating chronic neuropathic pain. However, the mechanisms underlying the pain relieving effect of SCS on neuropathic pain remain unclear. Evidence shows that the toll-like receptor 4 (TLR4)/nuclear factor (NF)-kappa B signal transduction pathway plays a key role in chronic neuropathic pain. We investigated changes in the TLR4/NF-kappa B pathway and downstream pro-inflammatory cytokine expression in L4-6 spinal cord following SCS. Neuropathic pain was induced through chronic constriction injury (CCI) of the sciatic nerve in rats. Mechanical withdrawal threshold (MWT) was assessed before surgery and on days 1, 4, 7, and 14 after CCI. During days 11-14, the nerve-injured rats were treated with SCS for 30 min per day. Compared with the control group, the CCI rats displayed a significantly decreased MWT. After SCS for 3 days, the expression of TLR4/NF-kappa B and the levels of interleuldn(IL)-1 beta, IL-6, and tumor necrosis factor (TNF)-alpha in the spinal cord were lower in the SCS group compared to those in the CCI and sham spinal cord stimulation (S-SCS) groups. These results indicate that SCS could effectively attenuate neuropathic pain in CCI rats by inhibiting the activation of the TLR4/NF-kappa B signaling pathway and by inhibiting the up-regulation of pro-inflammatory cytokines in the spinal cord. (C) 2014 Elsevier Ireland Ltd. All rights reserved.