Modulation of Phrenic Motoneuron Plasticity after Cervical Spinal Cord Injury

描述（由申请人提供）：现在认识到损伤的脊髓具有强大的神经可塑性能力，并且期望以增强颈脊髓损伤（SCI）后的呼吸结果的方式治疗性地利用该能力。康复和修复方法的基础是对脊髓呼吸回路的基本了解， 慢性脊髓损伤后脊髓呼吸神经元的调控。原则上，损伤的脊髓本质上是一个“新的脊髓”，其中影响几乎每个功能域的神经网络和控制机制都发生了显着改变。我们的研究小组最近在解剖学上描述了颈椎脊髓损伤后脊髓呼吸回路的特征，但功能解剖学相关性仍有待确定。我们提出了一系列的实验，将神经生理学定义脊髓呼吸回路后，颈脊髓损伤，检查的影响，一个关键的神经调节剂-5-羟色胺（5-HT）-电路，并确定脊髓移植方法脊髓呼吸神经元和恢复颈脊髓损伤后的通气的影响。指导这一建议的总体假设是，膈运动神经元（PMN）活动的调节慢性颈脊髓损伤后的脊髓前膈中间神经元的影响和脊髓5-HT是一个至关重要的调制器的脊髓呼吸回路慢性SCI。高颈脊髓损伤（侧C2半切）的大鼠模型将用于解决三个具体的目标。目的1将检验以下假设： SCI后，PMNs保持了强大的可塑性，其爆发模式部分受到调节 由颈部中间神经元组成。将使用多电极阵列测量PMN和颈部中间神经元活性;将使用解剖学和免疫组织化学方法评价脊髓呼吸回路。目的2将使用神经生理学，药理学，免疫化学和分子技术来验证脊髓5-HT受体激活是慢性颈脊髓损伤后膈运动恢复的一个组成部分的假设。最后，目标3将测试这一假设，即移植肾上腺素能细胞可以增强或恢复脊髓呼吸神经元的肾上腺素能调节，从而改善SCI后的呼吸恢复。在C2半切损伤后一周，成年大鼠将接受来自胎鼠脊髓神经元的脊髓能细胞的脊髓内移植。移植物对膈运动系统的影响将使用行为学、神经生理学、药理学、免疫组织化学和分子技术进行评估。该提案汇集了呼吸神经生理学，多单位记录方法，神经移植和颈椎SCI建模方面的专业知识的独特和协同组合。创新方面包括：1）慢性颈脊髓损伤后中性粒细胞爆发模式的首次描述性和机制研究; 2）颈SC后与脊髓相关的颈中间神经元的首次神经生理学研究; 3）使用多阵列电极描述脊髓呼吸回路，以及4）首次使用移植策略增强脊髓呼吸回路的肾上腺素能神经支配。

DESCRIPTION (provided by applicant): The injured spinal cord is now recognized to have a robust capacity for neuroplasticity, and it is desirable to therapeutically harness that in ways tht will enhance respiratory outcomes after cervical spinal cord injury (SCI). Fundamental to rehabilitation and repair approaches is a basic understanding of the spinal respiratory circuit and the control of spinal respiratory neurons after chronic SCI. In principle, the injured spinal cord s essentially a "new spinal cord" in which neural networks and control mechanisms affecting virtually every functional domain are significantly altered. Our group recently characterized the spinal respiratory circuit anatomically after cervical SCI, but functional-anatomical correlates remain to be determined. We propose a series of experiments which will neurophysiologically define the spinal respiratory circuit after cervical SCI, examine the influence of a key neuromodulator - serotonin (5-HT) - on the circuit, and determine the impact of a promising spinal cord transplantation approach on spinal respiratory neurons and recovery of ventilation after cervical SCI. The overall hypothesis guiding this proposal is that the regulation of phrenic motoneuron (PMN) activity following chronic cervical SCI is influenced by spinal pre-phrenic interneurons and that spinal 5-HT is a critically important modulator of the spinal respiratory circuitry following chronic SCI. A rat model of high cervical SCI (lateral C2 hemisection) will be used to address three specific aims. Aim 1 will test the hypothesis that following chronic cervical SCI, PMNs retain a robust capacity for plasticity, and their bursting patterns are partly regulated by cervical interneurons. PMN and cervical interneuron activity will be measured using a multi- electrode array; anatomical and immunohistochemical methods will be used to evaluate the spinal respiratory circuit. Aim 2 will use neurophysiological, pharmacological, immunochemical, and molecular techniques to test the hypothesis that spinal 5-HT receptor activation is an integral part of phrenic motor recovery after chronic cervical SCI. Lastly, Aim 3 will test the hypothesis that transplantation of serotonergic cells can enhance or restore serotonergic modulation of spinal respiratory neurons thereby improving respiratory recovery after SCI. One week following C2 hemisection injury, adult rats will receive an intraspinal transplant of serotonergic cells derived from fetal rat raph¿ neurons. The impact of the grafts on the phrenic motor system will be assessed using behavioral, neurophysiological, pharmacological, immunohistochemical, and molecular techniques. This proposal brings together a unique and synergistic combination of expertise in respiratory neurophysiology, multi-unit recording approaches, neural transplantation, and cervical SCI modeling. Innovative aspects include: 1) the first descriptive and mechanistic studies of PMN burst patterns after chronic cervical SCI; 2) the first neurophysiological studies of respiratory-related cervical interneurons after cervical SC; 3) the use of multi- array electrodes to describe the spinal respiratory circuitry, and 4) the firs use of transplant strategies to enhance serotonergic innervation of the spinal respiratory circuit.