The Expression Of Nav1.8 Ion Channel In DRG And Peripheral Nerve Of SNI Rats

Objective: To investigated the changes of the sodium channel Nav1.8that expressed in dorsal root ganglion(DRG),peripheral axons,and the epidermis nerve fibers in a rat model of spared nerve injury(SNI),and to explore the possible mechanism of Nav1.8 protein in neuropathic pain induced by nerve injury.Methods: Clean SD rats(n=12)were randomly divided into two groups,SNI group and sham operation group(Sham group).Fluorescent gold were injected into the sheath of sural nerve of rats in both SNI and Sham group.The mechanical withdrawal threshold(MWT)of the rats in the two groups was measured on preoperative,7 and 14 days postoperative,respectively.The rats in SNI and Sham group were sacrificed on the 14 th day after operation and L5 DRG,sural nerve,tibial nerve,peroneal nerve tissue,as well as sural nerve and tibial nerve innervation skin tissue were reserved.The expression of Nav1.8 in DRG fluorogold positive(FG+)and fluorogold negative(FG-)region,sural nerve,tibial and peroneal nerves,and the epidermal nerve fibers innervated by sural nerve and tibial were examined by immunofluorescence technique.Results: FG positive region(FG+)and FG negative(FG-)region were distributed in L5 DRG.The MWT in SNI group were significantly lower than that in Sham group on 7 and 14 days after operation(P <0.01).The expression of Nav1.8 in DRG FG+ and FG-area,tibial nerve,sural nerve,peroneal nerve and the epidermal region innervated by sural nerve in SNI group were significantly higher than that inSham group(P <0.05),but theexpression of Nav1.8 was significantly down-regulation in tibial innervated epidermal area(P <0.05).Compared with FG-area,the expression of Nav1.8in DRG was significantly up-regulation in FG+ areain SNI group(P<0.05).The expression of Nav1.8 in tibial innervation epidermal areas in SNI group was significantly lower than in Sham group(P <0.05).Conclusions: The region in DRG projected by common peroneal nerve and tibial nerve were Separated to sural nerve projection area.The up-regulation of Nav1.8 in DRG,intact sural nerve and its dominant skin area maybe one of the pathogenic factors of chronic neuropathic pain induced by partial nerve injury.