The Role Of GABA Transporter 1 In The DRG In The Etiology Ang Development Of Neuropathic Pain

Background&Objective:Neuropathic pain（NP）is a chronic pain caused by a lesion or disease in the somatosensory system,often manifested as persistent and severe pain,because the NP pathogenesis is not fully understood and the clinical lack of drugs that have a definite effect on the NP,the clinical therapeutic effect is not effective.Nervous system sensitization is one of the pathogenesis of neuropathic pain.The imbalance of excitatory and inhibitory signals in the nervous system is considered to be the mechanism of nervous system sensitization,γ-aminobutyric acid（GABA）is the most important inhibitory neurotransmitter in the central nervous system,GABA reuptake mediated by GABA transporter 1（GAT-1）plays an important role in the regulation of GABAergic signals.At present,it has been found that the expression of GAT-1in the spinal dorsal horn,gracile nucleus and trigeminal nucleus is significantly increased after nerve injury,and contributed to the pathogenesis and development of neuropathic pain.Studies have shown that the dorsal root ganglion,as an important hub for the transmission of injury signals from the periphery to the center,also express GAT-1,but its role in the pathogenesis and development of neuropathic pain is still unclear.Therefore,this study focuses on the role of altered GABA transporter GAT-1 in the pathogenesis and development of neuropathic pain to provides a basis for the search for new treatments targeting GAT-1 in the DRG.Methods:Female Sprague Dawley rats weighing 180～200g were randomly divided into five groups:Sham group,CCI group,sham+NS group,CCI+NS group and CCI+NO-711 group.CCI group rats were used to make chronic constriction injury（CCI）model,Sham group only exposed without ligation of sciatic nerve.We recorded the variation trend of mechanical withdrawal threshold（MWT）and thermal withdrawal latency（TWL）in rats of CCI group and Sham group within two weeks to test model construction,CCI group and Sham group were sacrificed and sampled on the 3rd,7th and 14th day after the operation,Immunofluorescence and Western blot were used to determine the changes of the GAT-1 protein expression in the dorsal root ganglion of the two groups of rats;Sham+NS group,CCI+NS group and CCI+NO-711 group were respectively injected normal saline and GAT-1 inhibitor NO-711 locally on the day of operation and the 7 d after operation,and the changes of MWT and TWL at different time points after administration were measured in CCI+NS group and CCI+NO-711 group of rats;the expression of p-ERK in the dorsal root ganglion and c-Fos in the spinal dorsal horn were detected by Immunofluorescence and Western blot.Results:Both TWL and MWT in the CCI group decreased significantly,indicating that CCI model established successfully;Immunofluorescence and Western blot results showed that compared with the Sham group,the expression of GAT-1 protein in L₄and L₅DRG was significantly increased in the CCI group on the 7rd,14rd day after operation,the difference was statistically significant;after local L₅DRG injection on the day of CCI operation,compared with the CCI+NS group,the TWL and MWT in the CCI+NO-711 group were raised and lasted until the 5th day after operation,the difference was statistically significant;after local administration of CCI on the 7^rdday,compared with the CCI+NS group,the levels of TWL and MWT in the CCI+NO-711 group were significantly increased,the effects maintained for 48 hours,and the low expression of p-ERK in DRG and c-Fos in spinal dorsal horn were detected,the difference was statistically significant.Conclusion:1.The expression of GAT-1 in the dorsal root ganglion after nerve injury was significantly increased.2.The local administration of GAT-1 inhibitor by DRG could effectively relieve neuropathic pain,GAT-1 played a significant role in the pathogenesis and development of neuropathic pain.