| Background and objectiveDue to involved complex regulation mechanism, the neuropathic pain hadn't effective treatment methods so far. Traditional researchs held that the pain signals was limited to neurons signal transmission, and glial cells only protected and supported, repaired neurons and not participated in pain signaling. In recent years, scholars attented that functions were important of glial cells, especially astrocytes in the neuropathic pain.In this study, we observed the activation of astrocytes in the chronic sciatic nerve ligation model (CCI) and the relationship between areactivated astrocytes and pain increased, to provide experimental data for the the basis study of neuropathic pain.Vimentin protein was mainly expressed in the neural developing astrocytes. Research shows, under the conditions of spinal cord's transection, the vimentin protein expressed in the spinal cord's astrocytes cells in the adult rats. How the expression of vimentin in the rat models of neuropathic pain pathology? We researched expressions of the glial fibrillary acidic protein (GFAP) and the vimentin in the No.4～5 lumbar spinal cord and researched the relationship between their expressions wit4h the pain threshold in neuropathic pain. Both the p38 mitogen-activated protein kinase (p38MAPK) and c- JunN-terminal kinase (JNK) signal pathways were activated in the pathological pain. Which cells'signal transportation of the pain both of the two pathways are involved in in nervous system? If they are related to activated astrocytes? We researched the relationship of expressions of p-p38MAPK,p-JNK whth the expressions of neurons, microglia, astrocytes respectively in the No.4-5 lumbar spinal cord of CCI model which can explore the channel of signal pathway after astrocytes were activated in the neuropathic pain.Methods1. Chronic compression model of the sciatic nerve was established and its variation of paw withdrawal thermal latency (PWTL) and mechnjcal withdaw threshold (MWT) was investigated:120 SD male rats were randomly divided into 2 groups:CCI model group, sham operation group (Sham group). CCI model group were operated with right sciatic nerve ligation; Sham operation group were just exposed right sciatic nerve but no ligation. PWTL and MWT were measured on the left and right limb of hindpaw at the day before operation and the first, third, seven,14st,28st day after operation.10 rats were investeigated at each time point. Statistical analysis was maked with self-control side and sham group.2. Relative expressions of GFAP mRNA and vimentin mRNA were detected by RT-PCR method in the rat's CCI model:Two groups were taked the No.4-5 lumbar spinal cord at each time point. Every group was taked 5 sats at each time point, and detected relative expressions of GFAP mRNA and vimentin mRNA at different time points in each group by RT-PCR method. Statistical analysis was taked with self-countrol side and group countrol.3. Expressions of GFAP and vimentin in the spinal cord of rat's CCI model were measured by immunofluorescence method:Two groups were taked the No.4-5 lumbar spinal cord to make paraffin slices at each time point. Every group was taked 5 sats at each time point, labeled the expression of GFAP and vimentin by immunofluorescence method, and analyze values of PWTL and MWT with expressions of GFAP and vimentin to explore the relationship of them. Choose spinal cord sections of the seven day after operation for which time the expression of immunofluorescence intensity was strongest at CCI group, double immunofluorescent stained by double immunolabeling techinque.4. Expressions of p-p38MAPK and p-JNK in the spinal cord of rat's CCI model were measured by immunofluorescence method:20 SD male rats were randomly divided into 2 groups:CCI model group, sham operation group. Every group was taked the No.4～5 lumbar spinal cord to make paraffin slices at the day before operation and the seven day after operation.labeled the p-p38MAPK and p-JNK by immunofluorescence method, and then double immunofluorescent stained were taked to NeuN, GFAP and OX-42 respectively.Results1. The variation of PWTL and MWT in rat's CCI model:CCI group was appeared ligated side toes closed together, flexion, eversion and other behavioral changes. Both of the PWTL value and the MWT value were significantly lower than the self-control side and the sham group at the operated side in CCI group at the third to 14st day after operation and the difference had statistically significant (P<0.05).2. The relative expressions of GFAP and vimentin mRNA in the spinal cord of rat's CCI model:Both GFAP mRNA and vimentin mRNA's relative expressions were significantly increased than the self-control side and the sham group at the operated side in CCI group at the third to 14st day after operation and the difference had statistically significant (P<0.05).3. Expressions of GFAP and vimentin in the spinal cord of rat's CCI model:Expressions of the GFAP and the vimentin were became stronger and the positive cells were increased in the number, larger in size, longer at the prominent fiber in the CCI group's ipsilateral spinal dorsal horn of operative limb at the third to 14st day after operation. The mean fluorescence intensity was significantly higher and the difference was statistically significant compared with the self-control side and the sham group (P<0.05). The double immunofluorescent stained shows they have a good consistent erea at the seven day after operation. Correlation analysis showed that changes of the PWTL value and the MWT value appeared negative correlation relationship whth mean fluorescence intensity of GFAP and vimentin.4. Expressions of p-p38MAPK and p-JNK in the spinal cord of rat's CCI model:Immunohistochemistry shows that the number of p-p38MAPK and p-JNK were significantly increased compared with the self-control side and the sham group, and the difference was statistically significant (P<0.05). The double immuno fluorescent stained shows that p-p38MAPK/OX-42, p-JNK/GFAP have a good consistent area in operative limb of the spinal dorsal horn in the CCI groups.Conclusions1. In neuropathic pain, spinal dorsal horn astrocytes are activated and show morphological changes, and it has positive correlation between pain increased and activated astrocytes of the spinal cord dorsal horn in rat's CCI model.2. In neuropathic pain, p38MAPK and JNK signal transduction pathways were activated, and the JNK signal transduction is involved in the astrocyte's signal transportation of the pain. |
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