Effects Of Pulsed Radiofrequency On Dorsal Root Ganglion On The Expression Of Spinal IRF8 And Hippocampal BDNF In A Rat SNI Model

Objective: This study aimed to determine whether downregulated spinal interferon regulatory factor 8(IRF8)could result in the increased expression of brain-derived neurotrophic factor(BDNF)in hippocampus conducive to alleviate depression in a rat spared nerve injury(SNI)model.And this study amied to investigate whether upregulated hippocampal BDNF resulted from the pulsed radiofrequecy(PRF)on dorsal root ganglion to refrain IRF8 expression in the spinal cord contributes to anti-depression effect in a SNI rat model.Methods: 144 healthy pathogen-free adult male Wistar rats were randomly divided into 6 groups(n=24 for each group): Sham,SNI,sham pulsed radiofrequency(SPRF),PRF,nuclease-free water(NCFW),IRF8 si RNA.All rats were received the SNI surgery to induce neuropathic pain(NP)except Sham group.Sham group were exposed the left sciatic nerve without injury.NCFW group and IRF8 si RNA group rats were intrathecally injected equal volumes of nuclease-free water and IRF8 si RNA on 5th and 6th day after SNI.While PRF group rats were received PRF on left L5 dorsal root ganglion,SPRF group rats were only put electrode adjacent to left L5 DRG without PRF on 7th day after SNI.The mechanical paw withdrawal threshold(MWT)was measured before SNI and on 1st,3rd,7th,8th,10 th,14th,21 st,28th,35 th,42nd day after SNI.After accepted sucrose preference test and forced swim test on 21 st and 42 nd day after SNI,12 rats from each group were randomly selected to be determined the expression of spinal IRF8 and hippocampal BDNF by immunohistochemistry,polymerase chain reaction(PCR)and Western blot.Results: Compared with Sham group,MWT was decreased and the expression of spinal IRF8 was upregulated after SNI in other groups(P<0.01),sucrose preference rate and the expression of hippocampal BDNF were decreased but forced swim immobility time was increased on 42 nd day after SNI in other groups(P<0.05).After IRF8 si RNA group were intrathecally injected IRF8 si RNA on 5th and 6th day after SNI,MWT was elevated from 7th day after SNI.After PRF group were received PRF on 7th day after SNI,MWT was elevated from 8th day after SNI.Not significant difference of MWT was found between IRF8 si RNA group and PRF group after treatment(P>0.05).Compared with SNI group,SPRF group and NCFW group,MWT was significantly increased after treatment in PRF groups and IRF8 si RNA group(P<0.01),the expression of spinal IRF8 was downregulated on 21 st and 42 nd day after SNI in PRF groups and IRF8 si RNA group(P<0.01),sucrose preference rate and the expression of hippocampal BDNF were increased but forced swim immobility time was decreased on 42 nd day after SNI in PRF groups and IRF8 si RNA group(P<0.05).There were not significantly differences between IRF8 si RNA group and PRF group(P>0.05),and not significant difference was found among SNI group,SPRF group and NCFW group(P>0.05).Conclusion:Upregulated hippocampal BDNF could alleviate depression by inhibiting the expression of spinal IRF8 in a rat SNI model.The increased expression of hippocampal BDNF resulted from the PRF on dorsal root ganglion to refrain IRF8 expression in the spinal cord contributes to anti-depression effect in a SNI rat model.