大鼠健侧颈7移位术后运动皮层兴奋性谷氨酸及其受体变化

目的 探讨大鼠健侧颈7移位术后运动皮层兴奋性谷氨基酸及其受体变化规律.方法 建立颈胸椎后路左侧全臂丛根性撕脱伤和健侧颈7移位正中神经大鼠模型,分别于术后不同时间采用肌电图检测观察正中神经功能的恢复,同时运用运动皮层区微电极刺激法明确大鼠患肢皮层代表区在术后的变化.根据运动皮层区微电极刺激的结果,选择4个皮层重组特异时间点进行取材,行大鼠脑片初级运动皮层区谷氨酸神经元及N-甲基-D-天门冬氨酸受体(NR1、NR2A、NR2B)的免疫组织化学染色.结果 大鼠健侧颈7移位术后,随时间的延长,患侧指深屈肌复合肌肉动作电位潜伏期缩短,波幅升高.术后4个月组,5只大鼠中有3只患爪支配区仅位于同侧运动皮层,同时各手术组双侧运动皮层NR1表达水平均增高,与对照组相比差异有统计学意义(P<0.05).其中右侧运动皮层NR1表达升高显著,与同组对侧相比差异有统计学意义(P<0.05).术后7个月组,4只大鼠患爪支配区位于双侧运动皮层,而且各手术组右侧运动皮层NR2A表达水平升高,与健康大鼠同侧皮层或同组大鼠对侧皮层比较差异均有统计学意义(P<0.05),健侧颈7移位组大鼠右侧皮层NR2A表达水平,较单纯臂丛撕脱或臂丛撕脱健侧颈7切断组同侧皮层升高明显,差异有统计学意义(P<0.05).术后10个月组,3只大鼠患爪支配区位于对侧运动皮层,而在同侧运动皮层却未测到,同时健侧颈7移位组大鼠右侧皮层NR2A表达水平仍维持在升高水平,与其他各组大鼠同侧或同组对侧比较,差异有统计学意义(P<0.05).结论 大鼠全臂丛根性撕脱伤健侧颈7移位正中神经后,大脑发生跨两半球的功能重塑.NR1和NR2A表达的增高可能分别在术后初期和后期功能重组中发挥了一定的作用.

The changes of glutamic acid and NMDA receptors in motor cortex after contralateral C7 transfer

Objective To explore the changes of glutamic acid and NMDA receptor expression in motor cortex following contralateral C7 transfer. Methods Total root avulsion of the left brachial plexus and transfer of the right C7 nerve root to the left median nerve via ulnar nerve graft was established in a rat model. Recovery of median nerve function was monitored with electrophysiologic examination at various postoperative intervals. Representation of the injured forepaw was mapped using intracortical microstimulation (ICMS). According to the ICMS results, brain samples were harvested for determination of glutamic acid and NMDA receptors (NR1、 NR2A、NR2B)in motor cortex by immuno-histochemical assay. Results After the surgery recovery of flexor digitorum profundus was indicated by decrease in compound muscle action potential (CAMP) latency and increase in CMAP amplitude over time. At 4 months, median nerve representation region of the affected forelimb appeared in the ipsilateral motor cortex in 3 rats and upregulation of NR1 was observed in both hemispheres of all rats from the operative groups. The NR1 expression showed significant change in the normal and operative groups. Meanwhile, NR1 expression in the right cortex was significantly higher than that in the left cortex. At 7 months, both hemispheres of cortex activated the injured forepaw in 4 rats. There was a significant increase in NB2A expression in the right motor cortex in the operative groups and NR2A expression in rats following contralateral C7 transfer was significantly higher than that in the rats from the other operative groups. At 10 months, the contralateral motor cortex exclusively controlled the injured forepaw and the expression of NR2A was still up-regulated. NR2A expression in rats following contralateral C7 transfer was still significantly higher than that in the rats from the other operative groups. Conclusion Transhemispheric functional reorganization of the motor cortex is confirmed in rats following contralateral C7 transfer. NR1 plays an important role in the primary cortical plasticity and NR2A is needed to continue this reorganization in later stage.