The Role Of MTOR Signaling Pathway In Synaptic Plasticity In The Spinal Dorsal Horn With Neuropathic Pain Rats

Objective:The synaptic plasticity in Spinal dorsal horn plays a critical role in the generation and maintenance of neuropathic pain. The maintainance of long-time potentiation(LTP) plasticity in hippocampal neuron is modulat-ed by mammalian target of rapamycin (mTOR) signal pathway, which is dependent on gene transcription and protein synthesis.Up to date,it is unknown whether spinal mTOR signal pathway is responsible for synaptic plasticity in spinal dorsal horn after CCI,which which may be related to neuropathic pain.The research is about the role of spinal mTOR signaling pathway in synaptic structure and transmission plasticity in spinal dorsal horn in CCI rats and its effect on regulating the generation and mainte-nance of neuropathic pain.Method:35 male and healthy SD rats were randomly divided into 7 groups with 5 rats each.Five rats were selected as sham-operation group(sham group).Five rats were selected as control group(Norm group).Ten CCI rats were injected 10ul rapamycin and 10ul 0.9% Sodium Chloride into cerebro spinal fluid on post-operative 4 hours and selected as rapamycin (RAP)group(RAP group).CCI rats were killed on post-operative day of 3 (CCI3D group),7(CCI7D group)and14(CCI14D group);Basic mechanical and thermal Pain threshold were tested before building CCI model.rats in Sham-operation group,RAP7D group,control group and CCI7Dgroup were killed on seventh day. RAP7D group and CCI14D group were killed on fourteenth day.Lumbar spinal cords of rats in all groups were dissected out. The ultrastructure changes of synapses in lamine II of the spinal dorsal horn of neuropathic pain rats were recorded by using stereological morphomei- trictechiniques.The localization of GAP-43 in spinal cords of rats was demonstrated by Fluorescence technology with immunity.The mRNA expression of GAP-43 in is detected by real-time PCR. The .protein expression of GAP-43 in rats checked out by the Western-blot technology.Result:1.there were no differences among 7 groups with basic pain thresho-ld(P>0.05);PWTL and PWMT of left paw on the 7th day and 14th day in Group 7D and 14D were much lower than the respective basic pain threshold(P<0.01);There were statistical differences between RAP groups and the corresponding CCI groups(P<0.05);There were not different from pain threshold in Group sham(P>0.05).2.on the 7th day afteroperation,the rough endoplasmic reticulum(RER) was dilated into cisterna. however, the number of free ribosomes increas-ted and it diffused around cells edge.mitochondrion swelled and carina ruptured,Golgi apparatus vesicle expanded in spinal dorsal horn nerve cells and neuropil edema were observed.on the 7th day after rapamycin, morphous of Golgi complex,RER,mitochondrions and free ribosomes fundamental had been recovery. Comparing the control group and sham group,there were no differences among the examined synapse parameters (P>0.05).Comparing the control groups and CCI7D group,we found the curvature of the synaptic interface,the thickness of the postsynaptic desity (PSD) and width of the synaptic cleft were increased significantly in the neuropathic pain rats(P<0.05);The number of Negative synapses and per- forated synapses in the spinal dorsal horn of neuropathic pain rats also significantly increased (P＜0.05);However,Comparing RAP7D groups and CCI7D group,the parameter value of PSD, the synaptic cleft,spine synapse s and perforated synapses decreased significantly (P＜0.05).3.In Lumbar segment of spinal cords of rats in CCI group,GAP-43 positive particles were widespreadly presented in neuronal cytoplasm and synapse of spinal cord.4.The GAP-43mRNA content was significantly higher in the CCI groups than that of the control group(P<0.01).The mRNA expression of GAP-43 in CCI7D,CCI14D,RAP7D and RAP14D groups were 5.300, 7.428,3.564 and 4.476 folds that of the control group respectively.No significant difference was observed in the GAP-43mRNA content betwe-en the control group and the sham-operation group(P>0.05).5.The protein content of GAP-43 was higher in the 7th and 14thCCI groups than that in the control group significantly(P<0.01).The protein content of GAP-43 was higher in the CCI groups than the corresponding Group RAP(P<0.05).There was no significant difference of GAP-43 protein content between the control group and the sham-operation group(P>0.05). Conclusion:1.The synapse plasticity in lamine II of the spinal dotsal horn of CCI rats may play an important role in maintainance of neuropathic pain.The increase in curvature of the synaptic interface might be respo-nsible for the major morphological change during the maintainance of neuropathic pain.2.The synapse plasticity in the spinal dotsal horn with neuropathic pain is regulated by spinal mTOR signal pathway.Which may be mediat ed by GAP-43.and alleviates pain in rats with CCI.