Enhancing Respiratory Motor Function after Spinal Cord Injury

摘要 建议的研究集中在BDNF/TrkB信号在促进膈运动神经元(PhMN)中的作用。 颈髓损伤后存活率和突触前后神经可塑性对功能恢复的促进作用 (CSCI)。我们将利用我们丰富的经验，使用两个成熟的不完全CSCI模型，即， C2半横断-C2SH和C4挫伤-C4CI以探讨PhMN的神经可塑性。我们还将带来 多年检查横隔肌(DIAM)运动单位生理学的经验，认识到 PhMN的规模在招募DIAM运动单位。BDNF/TrkB信号对Pre和Pre的影响 不同大小的PhMN的突触后神经可塑性在概念上是创新的，并提供了有价值的 机械的洞察力。“大小原理”是神经运动控制生理学中的一个关键概念，但到目前为止它一直是 很难直接将运动神经元的大小作为一个关键变量。我们假设有大小- 脑源性神经营养因子/TrkB信号对CSCI后突触前和突触后神经可塑性的依赖差异。这个 拟议的研究将提供有关PhMN神经可塑性在脑功能恢复中的新信息 吸气和吸气后直径活动将为开发新的治疗方法提供信息 促进不完全性脊髓损伤患者DIAM功能的恢复。 拟议的研究将利用一系列全面的创新技术，其中许多技术是在我们的 实验室。在所有三个特定的目标中，我们将检查使用增益/损失来调制BDNF/TrkB信号的效果 鞘内应用BDNF或TrkB-Fc治疗的功能途径和带有1NMPP1的新TrkBF616A大鼠 能迅速、选择性地抑制TrkB激酶活性的敏感敲入等位基因。在目标1中，我们将使用HIGH 分辨率共聚焦成像探讨BDNF/TrkB信号在Glu和Gly/GABA恢复中的作用 C2SH后不同大小的逆行标记的PhMN上的突触前终末。在目标2中，我们将使用一个 同时检测NMDA、Gly和GABAA变化的RNAScope原位杂交新技术 不同大小的PhMN中受体mRNA的表达。在目标3中，我们将检查神经保护作用 (PhMN存活率)C4CI后BDNF/TrkB信号转导。此外，我们还将研究BDNF/TrkB的作用 谷氨酸和Gly/GABA突触传入的信号与NMDA、Gly和GABAA受体mRNA的表达(前和 突触后神经可塑性)在C4CI损伤之上(即C3)和之下(即C5)存活的PhMN。

ABSTRACT The proposed studies focus on the role of BDNF/TrkB signaling in promoting phrenic motor neuron (PhMN) survival and pre- and postsynaptic neuroplasticity to enhance functional recovery after cervical spinal cord injury (cSCI). We will leverage our extensive experience using two well-established models of incomplete cSCI, i.e., C2 hemisection - C2SH and C4 contusion injury - C4CI to explore neuroplasticity at PhMNs. We will also bring years of experience examining diaphragm muscle (DIAm) motor unit physiology, recognizing the importance of PhMN size in the recruitment of DIAm motor units. Stratifying the effects of BDNF/TrkB signaling on pre- and postsynaptic neuroplasticity in PhMNs of varying size is conceptually innovative and provides valuable mechanistic insight. The “Size Principle” is a key concept in neuromotor control physiology, but until now it has been difficult to directly include motor neuron size as a critical variable. We hypothesize that there are size- dependent differences in BDNF/TrkB signaling effects on pre- and postsynaptic neuroplasticity after cSCI. The proposed studies will provide novel information about PhMN neuroplasticity underlying functional recovery of inspiratory and post-inspiratory DIAm activity that will inform development of novel therapeutic approaches to enhance recovery of DIAm function in patients with incomplete cSCI. The proposed studies will utilize a comprehensive array of innovative techniques, many developed in our lab. In all 3 specific aims, we will examine the effects of modulating BDNF/TrkB signaling using a gain/loss of function approach utilizing intrathecal BDNF or TrkB-Fc treatment and a novel TrkBF616A rat with a 1NMPP1 sensitive knock-in allele that rapidly and selectively inhibits TrkB kinase activity. In Aim 1, we will use high resolution confocal imaging to explore the role of BDNF/TrkB signaling on the recovery of Glu and Gly/GABA presynaptic terminals on retrogradely labeled PhMNs of varying size following C2SH. In Aim 2, we will employ a novel RNAscope in situ hybridization technique to simultaneously explore changes in NMDA, Gly and GABAA receptor mRNA expression in PhMNs of varying size. In Aim 3, we will examine the neuroprotective effects (PhMN survival) of BDNF/TrkB signaling following C4CI. In addition, we will examine the effect of BDNF/TrkB signaling on Glu and Gly/GABA synaptic input and NMDA, Gly and GABAA receptor mRNA expression (pre- and postsynaptic neuroplasticity) in surviving PhMNs above (i.e., C3) and below (i.e., C5) the C4CI injury.