The Role And Mechanism Of Adrenorceptor In Neuropathic Pain Induced By Chronic Compression Of Dorsal Root Ganglion

ObjectiveTo investigate the relation between sympathetic nerve,inflammatory cytokines and neuropathic pain.To study the mechanism of the expression of adrenoreceptor and inflammatory cytokines in DRG of rat after chronic compression of dorsal root ganglion(CCD).To investigate the role and mechanism of adrenoreceptor antagonist in the neuropathic pain due to CCD.Methods1.Male SD rats were randomly divided into Sham group and CCD group.The Von Frey filaments were used to quantify mechanical pain behavior.The expression changes and the location of ? 1B,a 2A adrenoreceptor,TNF-?,IL-1? were determined by Western blotting and immunofluorescence double dye method.2.Rats were randomly divided into Sham group,CCD+NS group,CCD+Phentolamine group and Phentolamine group.The Von Frey filaments were used to evaluate the mechanical withdrawal threshold of the rats in each groups before and after intraperitoncal injection of the alpha adrenoreceptor antagonist phentolamine.Moreover,the INF-?,IL-1?,NF-?B,P38 and EDI in DRG were measured and compared in different groups in order to study the mechanism of alpha adrenoreceptor in the neuropathic pain.Results1.We found 50%paw withdrawal threshold of CCD decreased after operation(P<0.01).In addition,the expression of ? 1B and a 2A adrenoreceptor increased significantly in DRG after operation(P<0.01).And the results of the immunofluorescence double dye showed that the a 1B adrenoreceptor expressed around DRG neurons and the ? 2A adrenoreceptor expressed in DRG neurons.Moreover,the expression of TNF-? and IL-1? were also increased significantly in DRG after CCD(P<0.01).And they both located in DRG neurons and satellite glial cells.2.Intraperitoneal injection of alpha adrenoceptor antagonist phentolamine can obviously reduce the mechanical hyperalgesia induced by CCD(P<0.01).The results of western blot show that phentolamine not only can effectively restrain the expression of the inflammatory cytokines and its signaling pathways in DRG,but also can repress the macrophages.Conclusion1.The expression of ? 1B and a 2A adrenoreceptor are much higher in DRG in the CCD group,and they may be involved in the mechanism of mechanical hyperalgesia after chronically compressed DRG.2.CCD can increase the expression of TNF-? and IL-1? in DRG.They are related to the formation and maintain of mechanical hyperalgesia.3.Phentolamine,the alpha adrenoreceptor antagonist,can relieve the mechanical hyperalgesia induced by chronically compressed DRG.It can also inhibit the expression of inflammatory cytokine and the inflammatory signaling pathways in DRG.In addition,it can restrain the chemotaxis of macrophage cell in DRG.In a word,sympathetic nerve may influence the neuropathic pain throuth the regulation of inflammatory cytokine.