A Mechanism To Reduce Neuropathic Pain And Depression Symptoms By Applying Pulsed Radiofrequency To Dorsal Root Ganglion

Objective:To investigate the mechanism to reduce neuropathic pain and depression symptoms by applying pulsed radiofrequency to dorsal root ganglion.Methods:PART 1:40 adult male Wistar rats were randomly assigned into four groups as follows(n = 10 for each group): sham group,CCI group,CS group and CP group.Sham group was performed by only exposing left sciatic nerve without nerve ligation,CCI group was performed by left sciatic nerve ligation,CS group was performed by putting RF electrode on L5 dorsal root ganglion without PRF on 7th day after CCI operation,CP group was performed by PRF applied to L5 dorsal root ganglion on 7th day after CCI operation.Basal mechanical withdrawal threshold(MWT)was measured before operation,and pain behavioral changes were tested on 3rd,7th,10 th,14th,21 st,28th,35 th,42nd postoperative day.Sucrose preference test,forced swimming test and the expressions of IRF8 protein in spinal cord and BDNF protein in nucleus accumbens were calculated on 42 nd postoperative day by Western blot.PART 2:40 adult male Wistar rats were randomly assigned into four groups as follows(n = 10 for each group): sham group,SNI group,SS group and SP group.Sham group was performed by only exposing left sciatic nerve without nerve ligation,SNI group was performed by cutting left common peroneal and tibial branches,leaving the sural nerve intact.SS group was performed by putting RF electrode on L5 dorsal root ganglion without PRF on 7th day after SNI operation,SP group was performed by PRF applied to L5 dorsal root ganglion on 7th day after SNI operation.Basal mechanical withdrawal threshold(MWT)was measured before operation,and pain behavioral changes were tested on 3rd,7th,10 th,14th,21 st,28th,35 th,42nd postoperative day.Sucrose preference test,forced swimming test and the expressions of IRF8 protein in spinal dorsal horn and BDNF protein in nucleus accumbens were calculated on 21 st and 42 nd postoperative day by immunohistochemistry.Results:1.Sucrose preference and MWT on the left hindpaw at all points after CCI were significantly decreased(P<0.05),whereas forced swimming immobility time and the expressions of IRF8 protein in spinal cord and BDNF protein in nucleus accumbens were significantly increased in CCI group,CS group and CP group compared with those in sham group(P<0.05).MWT in CP group was significantly less than that in sham group from 10 th day after SNI(P<0.01),but higher than that in CCI or CS group(P<0.01).In CP group,sucrose preference was increased,while forced swimming immobility time were decreased compared with those in CCI or CS group(P<0.05);and the expressions of IRF8 and BDNF protein on day 42 after CCI were decreased compared with those in CCI or CS group(P<0.01).2.MWT on the left hindpaw at all points were significantly decreased in SNI group,SS group and SP group compared with those in sham group(P<0.01),MWT in SP group was significantly less than that in sham group from 7th day after PRF(P<0.01),but higher than that in SNI or SS group(P < 0.01).Sucrose preference and forced swimming immobility time on day 21 after SNI were not altered in SNI group,SS group and SP group compared with those in sham group(P>0.05).In SP group,sucrose preference was increased,while forced swimming immobility time were decreased(P<0.05);and the expressions of IRF8 and BDNF protein on day 42 after SNI were decreased compared with those in SNI or SS group(P<0.01).Conclusions:The neuropathic pain and depression induced by CCI and SNI could be attenuated by PRF applied to dorsal root ganglion is possible through the mechanism of inhibiting the expressions of IRF8 in spinal cord and BDNF in nucleus accumbens.