The Effect Of Pulsed Radiofrequency On Dorsal Root Ganglion Of CCI Rats On The IRF8 Levels In Spinal Microglia

Objective:In this study, we investigated the abirritation effect and the potential mechanism of pulsed radiofrequency(PRF) on dorsal root ganglion(DRG) of rats and intrathecal injection of IRF8 antisense oligodeoxynucleotide(ODN) of rats with chronic constriction injury(CCI). Adult male Sprague-Dawley rats were subjected to CCI and then treated with PRF or IRF8 antisense ODN. The general behavioral, 50%MWT, TWL changes were observed, the expression of spinal cords IRF8 and Iba1 protein were tested by using Western-Blot and immunohistochemistry(IHC).Methods:1、The effect of PRF on DRG of CCI rats on pain therholds and the IRF8 levels in spinal.On the 7th postoperative we administered PRF on DRG of rats with CCI. The general behavioral, 50%MWT, TWL changes were respectively tested before operation, on 1st, 3rd, 5th, 7th day after peripheral nerve injured and 1st,7th,14 th day after PRF therapy. The expression of IRF8 protein were respectively measured in spinal cords by using Western-Blot and IHC in all groups on 7th day after peripheral nerve injured and 7th,14 th day after PRF therapy.2. Effects of intrathecally of IRF8 antisense ODN on pain thersholds and the IRF8,Iba1 levels in spinal cords in a rat model of CCI.All rats were subjected to intrathecal catheter implantation and peripheral nerve injured successfully. The rats were intrathecally treated with antisense ODN of IRF8, mismatch ODN of IRF8 or same volume 0.9% Na Cl once daily, beginning from 1 day after nerve ligation 12 hours later and lasting for 6 days. The general behavioral, 50%MWT, TWL changes were respectively tested before operation, on 1st, 3rd, 5th, 7th, 10 th, 12 th, 14 th day after peripheral nerve injured. The expression of IRF8 and Iba1 protein were respectively measured in spinal cords by using Western-Blot in each group on 7th, 14 th day after peripheral nerve injured.Results:1、The 50%MWT, TWL at all time points were significantly decreased(P<0.01), whereas the expression of IRF8 protein in spinal cords after nerve ligation were significantly increased in CCI group, CCI+PRF group and CCI+NPRF group than those in Sham group(P<0.05). After PRF treatment in CCI+PRF group 50%MWT, TWL were up-regulated than those before PRF treatment, at the same points in CCI group and CCI+NPRF group(P<0.01), but still far below Sham group(P<0.01). And the expression of IRF8 protein in rats spinal cords were significantly down-regulated after PRF treatment in CCI+PRF group than those before PRF treatment, at the same points in CCI group and CCI+NPRF group(P<0.05).2、The 50%MWT, TWL at all time points after nerve ligation were significantly decreased(P<0.01), whereas the level of IRF8 and Iba1 protein in the rats spinal cords were significantly increased in MM group and NS group than those in Sham group(P<0.05). The withdrawal thresholds in AS group were lower than those in Sham group from day 10 after CCI(P<0.01), but still apparently were higher than those in MM and NS group(P<0.01). The IRF8 and Iba1 protein levels on day 7, 14 after CCI in AS group were weakened significantly than those in MM and NS group(P<0.05), but still apparently were enhanced than in Sham group(P<0.05). IRF8 and Iba1 protein levels on day 14 were up-regulated compared with on day 7 in AS group(P<0.05).Conclusions:1、The neuropathic pain induced by CCI was attenuated by PRF procedure on the ipsilateral DRG.The analgesic effect mechanism of PRF may be relate to an attenuation of IRF8 protein expression in spinal cords.2、The IRF8 is the critical transcription factor for pain sensitization induced by peripheral nerve injured. In advance to block IRF8 can relieve NP.