Department of Comparative Biosciences, School of Veterinary Medicine, University of Wisconsin, Madison, WI 53706-1102, USA.
Respir Physiol Neurobiol. 2009 Nov 30;169(2):115-22. doi: 10.1016/j.resp.2009.08.004. Epub 2009 Aug 12.
The rodent respiratory system is a relevant model for study of the intrinsic post-lesion mechanisms of neuronal plasticity and resulting recovery after high cervical spinal cord injury. An unilateral cervical injury (hemisection, lateral section or contusion) interrupts unilaterally bulbospinal respiratory pathways to phrenic motor neurons innervating the diaphragm and leads to important respiratory defects on the injured side. However, the ipsilateral phrenic nerve exhibits a spontaneous and progressive recovery with post-lesion time. Shortly after a lateral injury, this partial recovery depends on the activation of contralateral pathways that cross the spinal midline caudal to the injury. Activation of these crossed phrenic pathways after the injury depends on the integrity of phrenic sensory afferents. These pathways are located principally in the lateral part of the spinal cord and involve 30% of the medullary respiratory neurons. By contrast, in chronic post-lesion conditions, the medial part of the spinal cord becomes sufficient to trigger substantial ipsilateral respiratory drive. Thus, after unilateral cervical spinal cord injury, respiratory reactivation is associated with a time-dependent anatomo-functional reorganization of the bulbospinal respiratory descending pathways, which represents an adaptative strategy for functional compensation.
啮齿动物呼吸系统是研究神经元可塑性内在损伤后机制以及高位颈脊髓损伤后恢复的相关模型。单侧颈损伤（半横断、侧部损伤或挫伤）中断了支配膈神经的延髓呼吸运动神经元的单侧延髓呼吸通路上行通路，导致损伤侧出现重要的呼吸缺陷。然而，同侧膈神经在损伤后随时间推移表现出自发和逐渐的恢复。在侧部损伤后不久，这种部分恢复依赖于损伤后脊髓中线尾侧的对侧通路的激活。损伤后这些交叉膈神经通路的激活依赖于膈感觉传入纤维的完整性。这些通路主要位于脊髓的外侧部分，涉及 30%的延髓呼吸神经元。相比之下，在慢性损伤后条件下，脊髓的内侧部分足以引发显著的同侧呼吸驱动。因此，单侧颈脊髓损伤后，呼吸再激活与延髓呼吸下行通路上的时间依赖性解剖-功能重组相关，这代表了一种用于功能代偿的适应性策略。
