Mechanism Of Electroacupuncture Alleviates CFA-induced Inflammatory Pain

OBJECTIVE:1.To investigate the the mechanism of electroacupuncture stimulation inducing the expression of homer1 a in spinal cord and its antinociceptive effect;2.To investigate the mechanism of chronic inflammatory pain induced by CFA in mice and the the role of homer1a?mGluR5-homer and IP3R-homer crosslinking in CFA-induced pain and then further explore the molecular mechanism of electroacupuncture analgesic effect on CFA-induced chronic inflammatory pain.METHODS:1.The first experiment: ? WT mice were randomly divided into two groups: the sham electroacupuncture group(sham group)and the electroacupuncture group(EA group).The sham electroacupuncture and electroacupuncture were applied to the two groups of mice and then detect the expression of homer1 a in spinal cord;? There are two groups: WT group,H1 aKO group.Both two groups of mice were subjected to EA stimulation at right foot Sanli(ST36)and Kunlun(BL60)for 30 minutes with seting of 2/10 hz,1-3 mA(1 mA per 10 min),and then we test the difference of PWT between baseline and EA stimulation in mice.Von Frey filaments were used to measure the right PWT in mice to assess the changes in mechanical pain;Western blot and COIP were used to detect basal levels of mGluR5-homer crosslinking and IP3R-homer crosslinking in both groups of mice;2.The second experiment: Mice were randomly divided into 4 groups: normal saline group(NS group),CFA-induced inflammatory pain group(CFA group),electroacupuncture treatment group(EA group),and sham electroacupuncture treatment group(sham group).The chronic inflammatory pain model was performed by injecting 20 ?l of 80% CFA into the right hind paw;Electroacupuncture and sham electroacupuncture were performed on the ipsilateral hind limbs of CFA injection;Von Frey filaments was used to detect the mechanical pain threshold,and the right PWT was used to evaluate mechanical pain threshold;Hargreaves test was used to detect the withdraw latency of the right hind limb to evaluate the thermal pain sensitivity;The expression of homer1 a in the spinal cord and the changes of mGluR5-homer crosslinking and IP3R-homer crosslinking were detected by western blot and COIP;Electrophysiological was used to further verify that electroacupuncture exerts an analgesic effect on CFA-induced hyperalgesia by overexpressing homer1 a.RESULTS:1.Compared with the sham control group,the expression of spinal homer1 a was significantly increased in the EA group;Compared with the baseline value,WT mice had a higher mechanical pain threshold in the right hind paw after electroacupuncture,but the homer1 a knockout mice was not;Compared with the WT group,linking of the mGluR5/IP3 R and homer in H1 a KO mice was increased;2.The right hind limbs PWT,paw withdrawal latency,%?-threshold and %MPE were significantly reduced after subcutaneous injection of CFA and both of them were resversed by EA,that is,CFA produced a good pain-causing effect and EA produced a good analgesic effect;mGluR5-homer crosslinking and IP3R-homer crosslinking in the spinal cord of the CFA group were increased compared with the saline group.Compared with the CFA group,the expression of the homer1 a in the EA group was significantly increased,and the mGluR5-homer crosslinking and IP3R-homer crosslinking were decreased,which suggested that it is upregulation of homer1 a that depolymerized the linking between mGluR5/IP3 R and homer;Electrophysiological results show that CFA causes central hypersensitivity to produce hyperalgesia,and electroacupuncture can inhibit spinal cord dorsal horn C-fibers caused by TSS in CFA-induced pain model;Whereas in H1 aKO mice,the effect of electroacupuncture blocking LTP was significantly attenuated,indicating that electroacupuncture exerts analgesia by inducing homer1 a expression.CONCLUSIONS:1.Electroacupuncture increase the expression of homer1 a in the spinal cord to produce an anti-nociceptive effect;2.Electroacupuncture alleviates CFA-induced hyperalgesia by increase the level of homer1 a,which depolymerizing mGluR5/IP3R-homer complex.