The Role Of GRK2 In The Dorsal Horn Of Spinal Cord In The Pulsed Radiofrequency On Dorsal Root Ganglion To Improve The Comorbidity Of Neuropathic Pain And Depression In SNI Rats

Objective:To explore whether the G protein coupled receptor kinase 2(GRK2)in spinal dorsal horn is involved in the neuropathic pain induced depression of rats subjected to Spared Nerve Injury(SNI).To explore the role of two inflammatory factors(IL-1β and IL-10)in the state of comorbidity of SNI rats.To investigate whether the up-regulated expression of GRK2 took participate in the therapeutic efficacy of pulsed radiofrequency on dorsal root ganglion(DRG)to improve the neuropathic pain-depression comorbidities.To further clarify the role of GRK2 in spinal dorsal horn and the up-stream IL-1β and IL-10 in hippocampus in the pulsed radiofrequency on DRG to treat the neuropathic pain-depression comorbidities in SNI rats.Method:A total of 120 healthy adult male Wistar rats were divided into 6 groups(each group contains 20 rats)by random number table method:Sham operation group(Sham group),Spared nerve injury group(SNI group),Sham pulsed radiofrequency(SPRF group),Pulsed radiofrequency(PRF group),Pulsed radiofrequency plus intrathecal injection GRK2 antisense oligonucleotide(PRF+ AS-ODN group)and Pulsed radiofrequency plus intrathecal injection GRK2 mismatch oligonucleotide(PRF+MM-ODN group).Except for the Sham group,SNI model was established in the other five groups.In the PRF+AS-ODN group and PRF+MM-ODN group,intrathecal tube was inserted during model establishment.The PRF group,PRF+AS-ODN group and PRF+MM-ODN group were treated with the pulsed radiofrequency therapy on the 7th day after modeling.Only radiofrequency electrodes were placed without pulsed radiofrequency therapy in the SPRF group.The PRF+AS-ODN group and the PRF+MM-ODN group received intrathecal injection of 40μg AS-ODN and 40μg MM-ODN on the day after pulsed radiofrequency therapy and for 2 consecutive days,once a day,respectively.All rats received the 50% mechanical pain threshold(Mechanical paw withdrawal threshold,MWT)measurement before the SNI model and on 1,3,7,8,9,14,21,28,35,42 days after SNI.Forced swimming test and sugared water preference test were conducted on the 21 st and 42 nd day after SNI respectively.The expression levels of GRK2 in dorsal horn of spinal cord were detected by immunofluorescence and Western-blot,and the expression levels of IL-1β and IL-10 in hippocampus were assayed by immunofluorescence,Western-blot and ELISA.Results : Except for the Sham group,the MWT at each time point after the SNI was significantly decreased in the other five groups compared to the pre-SNI(P < 0.05).The immobile time of forced swimming and the preference rate of sugar water on the 42 nd day after SNI were significantly prolonged and significantly decreased compared to the Sham(P<0.05).The MWT of PRF group and PRF+MM-ODN group increased at each time point after PRF treatment(the 7th day after SNI)compared to the SNI group and the SPRF group(P < 0.05).On 42 nd day after SNI,except Sham group,the immobile time of forced swimming in the other 5 groups were significantly prolonged,while the preference rates of sugar water were significantly decreased(P<0.05);Compared with SNI group,SPRF group and PRF+AS-ODN group,the immobility time of forced swimming in PRF group and PRF+MM-ODN group were significantly shortened,whereas the preference rates of sugar and water were significantly increased(P<0.05).On day 21 and 42 after SNI,compared with PRF group and PRF+MM-ODN group,the fluorescence detection and protein expression of GRK2 in spinal dorsal horn of SNI group,SPRF group and PRF+AS-ODN group were significantly decreased(P < 0.05).Compared with those in Sham group,PRF group and PRF+MM-ODN group,the expression levels of IL-1β protein and fluorescence detection in the hippocampus of SNI group,SPRF group and PRF+AS-ODN group were significantly increased on the 42 nd day after SNI(P < 0.05).There were no significant differences in the expression levels of IL-10 in hippocampus by protein and fluorescence detection on day 21 and 42 after SNI(P>0.05).Conclusions:The decreased expression levels of GRK2 in spinal dorsal horn could enhance the expressions of IL-1β in hippocampus to develop the neuropathic pain-depression comorbidity in SNI rats.The reduced GRK2 could be reversed by the therapy of pulsed radiofrequency on DRG to partly inhibit the expression of IL-1β in hippocampus to improve the neuropathic pain-depression comorbidity.While the other inflammatory cytokine-IL-10 in the hippocampus of rats was not involved in the comorbidity state in our study.