Role of TLR4/NF-κB signaling pathway in development of postoperative chronic pain in rats: the relationship with expression of Nav 1. 7 in dorsal root ganglion / 中华麻醉学杂志

ABSTRACT

Objective To evaluate the role of Toll-like receptor 4 ( TLR4)/nuclear factor kappa B ( NF-κB) signaling pathway in the development of postoperative chronic pain and the relationship with ex-pression of voltage-gated sodium channel 1. 7 (Nav 1. 7) in the dorsal root ganglion (DRG) of rats. Meth-ods Thirty-six clean-grade healthy male Sprague-Dawley rats, aged 9-11 weeks, weighing 200-250 g, were divided into 3 groups ( n=12 each) using a random number table method: control group ( group C) , normal saline group ( group NS) and TLR4 antagonist LPS-RS group ( group R) . Postoperative chronic pain was produced by skin/muscle incision and retraction (SMIR). From 1 day before SMIR to 10 days after SMIR, NS group received continuous intrathecal injection of normal saline 10μl, while R group received continuous intrathecal injection of LPS-RS 20μg/10μl. Six rats were randomly selected in each group, and the mechanical pain threshold was measured at 1 day before SMIR and 1, 5, 10, 15 and 20 days after SMIR. The 6 rats left in each group were sacrificed at day 10 after SMIR, and the DRGs of the lumbar seg-ment (L4,5) were removed for determination of the expression of phosphorylated NF-κB (p-NF-κB) and Nav 1. 7. Results Compared with group C, the mechanical pain threshold was significantly decreased at 5-20 days after SMIR, and the expression of p-NF-κB and Nav1. 7 was up-regulated at 10 days after SMIR in group NS ( P＜0. 01) . Compared with group NA, the mechanical pain threshold was significantly increased at 5-20 days after SMIR, and the expression of p-NF-κB and Nav 1. 7 was down-regulated at 10 days after SMIR in group R (P＜0. 01). Conclusion Up-regulated expression of Nav1. 7 in DRGs after activating TLR4/NF-κB signaling pathway is involved in the development of postoperative chronic pain in rats.