Investigation of nerve plasticity for the better results of nerve repair

臂丛神经根撕脱伤可通过神经移植物将损伤神经末端连接到损伤侧对侧的臂丛神经根来修复。这些患者的感觉恢复表明，对侧初级躯体感觉皮层（S1）被旁路到对侧BP的传入输入激活。为了证实这一假设，本研究通过使用经颅黄素蛋白荧光成像可视化小鼠交叉神经转移后的皮质活动。在幼稚的小鼠，振动刺激施加到前爪引起本地化的荧光反应在S1对侧的刺激侧，几乎没有活动在同侧S1。4周后，交叉神经转移，前爪刺激在受伤和修复侧只在S1同侧刺激侧皮层反应。在交叉神经移植后8周，前爪刺激导致S1 cor ...更多信息 两个半球的反应。通过切断用于修复的神经移植物来消除这些皮质反应。同侧S1暴露于蓝色激光抑制同侧S1以及对侧S1的皮质反应，表明同侧反应通过皮质-皮质通路传播到对侧S1。直接高频刺激同侧S1结合前爪刺激急性诱导S1双侧皮质代表的前爪区在幼稚小鼠。在皮层限制性异型GluN1（NMDAR 1）基因敲除小鼠中，交叉神经转移后对侧S1的皮层反应降低。在两个半球S1之间的皮质-皮质通路受损的遗传操作小鼠中，没有清楚地观察到功能性双侧皮质代表。总之，这些发现强烈表明，皮质-皮质通路的活动依赖性增强对交叉神经转移后患者的感觉恢复具有关键作用。

Avulsion of spinal nerve roots in the brachial plexus(BP) can be repaired by crossing nerve transfer via a nerve graft to connect injured nerve ends to the BP contralateral to the lesioned side. Sensory recovery in these patients suggests that the contralateral primary somatosensory cortex(S1) is activated by afferent inputs that bypassed to the contralateral BP. To confirm this hypothesis, the present study visualized cortical activity after crossing nerve transfer in mice through the use of transcranial flavoprotein fluorescence imaging. In naive mice, vibratory stimuli applied to the forepaw elicited localized fluorescence responses in the S1 contralateral to the stimulated side, with almost no activity in the ipsilateral S1. Four weeks after crossing nerve transfer, forepaw stimulation in the injured and repaired side resulted in cortical responses only in the S1 ipsilateral to the stimulated side. At eight weeks after crossing nerve transfer, forepaw stimulation resulted in S1 cor … More tical responses of both hemispheres. These cortical responses were abolished by cutting the nerve graft used for repair. Exposure of the ipsilateral S1 to blue laser light suppressed cortical responses in the ipsilateral S1, as well as in the contralateral S1, suggesting that ipsilateral responses propagated to the contralateral S1 via cortico-cortical pathways. Direct high-frequency stimulation of the ipsilateral S1 in combination with forepaw stimulation acutely induced S1 bilateral cortical representation of the forepaw area in naive mice. Cortical responses in the contralateral S1 after crossing nerve transfer were reduced in cortex-restricted heterotypic GluN1(NMDAR1) knockout mice. Functional bilateral cortical representation was not clearly observed in genetically manipulated mice with impaired cortico-cortical pathways between S1 of both hemispheres. Taken together, these findings strongly suggest that activity-dependent potentiation of cortico-cortical pathways has a critical role for sensory recovery in patients after crossing nerve transfer Less