| Background and objective:Neuropathic pain(NP) is a clinical syndrome which is common but lack of effective treatment.The International Association for the Study of Pain(IASP) has published its new definition that is "pain arising as a direct consequence of a lesion or disease affecting the somatosensory system".It is clinically characterized by spontaneous pain,allodynia, hyperalgesia and paresthesia.NP is caused by peripheral or central nervous lesions.It is found that its pathogenesis is complex,and the molecular mechanism is unknown,so that NP has became the hotpoint in research of pain in recent years.Due to the mechanism unknown,the current therapy for NP is not satisfactory although there are lots of drugs used for treatment.Recently it has been discovered that gila cells play an important role in the occurrence and development in NP.Astrocytes are being reconsidered,whose molecular mechanism of activation may provide new ideas for clinical pain management.Pannexins are a kind of protein which can form gap junctions(GJs),including three subtypes.Those are widely expressed in most tissues of the body,especially a large number of expression in the nervous system.It can connect the two adjacent cells, and also can form hemi-channel that exchange a wide range of important molecules including ions and small molecules of intermediate metabolism through cell membrane quickly.It has been found that can the release of ATP and intercellular Ca2+ waves via Pannexin1(PX1) hemi-channels in astrocytes,which may lead to the activation of astrocytes. The purpose to this study is that to observe the changes of PX1 in the spinal cord of rats and analyze its relations with astrocytes by intrathecal injection of gap junctions blocker carbenoxolone(CBX),through neuropathic rats of spared nerve injury(SNI).Main methods and techniques:1.24 Male SD rats were divided into 3 groups at radom: sham group(sham,n=4),blank group(WT,n=4) and surgery group(SNI,n=16). The mechanical withdrawal threshold(MWT) of rats in the right hindpaws was measured one day before the operation. And the changes of MWT were measured at 3,5,7 and 14 days after operation. The WT rats and the sham rats were killed on the 14 th day and 4 rats in SNI group were killed at every time point. After that the L3-L6 spinal cord were taken to test the expression of PX1 by Western blot.2.32 Male SD rats were grouped into 2 groups at random: surgery group(SNI,n=16) and sham group(sham,n=16).The MWT values of rats on the right hindpaws was measured one day before the operation. And the changes of MWT values were measured at 3,5,7and 14 days after operation.Every 4 rats were killed in sham and SNI at every time point.After that the L3-L6 spinal cord were taken to test the expression of glial fibrillary acidic protein(GFAP) by immunohistology.3. 20 Male SD rats were divided into four groups at random,and intrathecal catheterization before operation.Group A:blank control+saline 20μl injection;group B:sham control+saline 20μl injection;group C: SNI + saline 20μl injection;group D:SNI+ CBX 20μl injection,and all rats were injected once a day for 7 days.The MWT values of four groups rats were detected at pre-operated 1 day and post-operated 3, 5, 7 days.And the L3-L6 sections of spinal cords of four group rats were obtained for immunohistochemical observation of the expression of GFAP on 7th day after the injection.Results:1.No obvious changes of MWT values were found in WT group and sham group at each time point.The MWT values of SNI group, reduced on the 3rd day after the operation, and reached the lowest on the 7th day.The values of the 14 th day were still lower than that of the pre-operated 1 day(P<0.05).Compared with WT group and sham group,there was significant decrease of MWT values of SNI group at each time point(P<0.05). Compared with WT group and sham group, the expression of PX1 protein of SNI group increased gradually with time(P<0.05). The GFAP of SNI group at each time point was expressed more strongly,than those of WT group and sham group(P<0.05).No significant differences in the expression of PX1 and GFAP were found in WT group and sham group(P>0.05).2.The changes of MWT values of group A and group B were not significant.The MWT values of group C and group D at each time point were obviously lower than that of group A and group B after injection(P<0.05).There was no difference of MWT values between group C and group D on the 3rd day after injection, but the MWT values of group D are higher than that of group C on the 5th day or 7th day.It was showed by immunohistology that the number of GFAP positive cells of group C and D were higher than those of group A and group B, but the number of positive cells of group D at each time point was significantly lower, compared with group C and it has statistical significance(P<0.05). Conclusion: GFAP as a specific trademark protein of astrocytes,the up-regulation of its expression in SNI group and the changes of rats’ MWT values on right hindpaws, indicated that the NP animals were set up successfully.The high expression of PX1 in SNI group suggested it may participate in the activation of NP.And after intrathecal injection of the GJs blocker CBX,it can increase the MWT values on the right hindpaws of rats, and reduce the number of GFAP positive cells in the dorsal horn of spinal cord,which prompted that PX1 hemi-channels may play an important role in NP. |
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