| Part1The Expression of Phosphorylated NMDA Receptor Subunit1in Rats with Chronic Central Pain following Spinal Cord InjuryObjective To investigate the expression of pNRl in rats with chronic central pain following spinal cord injury.Methods48male SD rats (3～4weeks, weighing230-250g) were randomly divided into2groups, which received spinal cord injury (SCI group) and sham-operation (sham group) respectively. The pain-related behavior, paw withdrawal threshold (PWPT) and paw withdrawal latency (PWL) changes in preoperation (d0) and postoperation2,4,8,16,24,30days (recorded as d2, d4, d8, d16,d24, d30) were assessed in order to confirm the CCP model success. At the16th days of postoperation,24male SD rats were randomly chosen as control group and the L1segment of spinal cord were removed respectively in3groups. The expression changes of pNR1in spinal cord were analyzed and compared with immunohistology method.Results After14th day of operation, the behavior of autophagia and scratching were observed in SCI group and none in Sham group. Compared with d0, the PWPT and PWL were both significantly decreased (P<0.01) in SCI group and none changes obviously (P> 0.05) in Sham group; Compared with Control group at the16days of postoperation, the expression of pNR1in spinal dorsal horn was significantly increased in SCI group (P<0.01) and there was no obvious changes in Sham group (P>0.05).Conclusions The PWPT and PWL were decreased and the behavior of autophagia and scratching was observed in rats with chronic central pain following spinal cord injury. In addition, the expression of pNRl was increased significantly in spinal dorsal horn in CCP rats. This implicated that pNR1may contributed to the formation of chronic central pain following spinal cord injury. Part2Inhibation Effect andChanges of pNR1Expression in Spinal Dorsal Horn for Chronic Central Pain Rat Treated with Intraperitoneal SODObjective To assess the inhibition effect and the change of pNRl in spinal dorsal horn for chronic central pain rat treated with intraperitoneal SOD.Methods30male SD rats with chronic central pain(CCP) following spinal cord injury (SCI) were randomly divided into3groups (n=10): SOD group (Superoxide dismutase4000U/kg), NS group (normal saline1ml) and Control group (rats were restrained in the holder without any treatment). The paw withdrawal pressure threshold (PWPT) and the paw withdrawal latency (PWL) were observed at8,16,24and48h after the injection of SOD. In addition, To observe whether SOD has a cumulative analgesic effect with multiple treatments,24CCP rats were divided into two groups (n=12):The control group was simply restrained in the holder, and the experimental group was given SOD intraperitoneally once every2days for5sessions. The paw withdrawal threshold was assessed before each session of SOD. After5sessions of injection of SOD, expression of phosphorylated NMDA receptor1subunit (pNR1) was examined in the L1spinal cord of a SOD (5sessions) group, a control group(restraint only) and a naive group, respectively.Results In the control group and the NS group, the paw withdrawal threshold was quite stable over a period of48h. In contrast, in the SOD group, the paw withdrawal threshold increased dramatically from the basal level of15.2±1.8g to30.4±1.6g (P<0.01)16h after injection of SOD and remain high at8h,24h and48h(P<0.05); While the paw withdrawal threshold at the starting points of the two groups were almost identical, they separated from each other gradually (ANOVA, P<0.05), suggesting that the degree of CCP decreased along with the repeated treatments of SOD. pNRl immunoreactivity was enhanced significantly in the superficial laminae of spinal cord dorsal horn in CCP rats (Control group) as compared with the naive rats(P<0.01). No significant difference was found between the SOD group and the naive group.Conclusions SOD inhibited chronic central pain following spinal cord injury in rats and the expression of pNRl was decreased significantly at the same time. |
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