Spinal circuitry for ventilatory control and compensation

Crone，S. A. 项目摘要 所提出的研究调查了脊髓V2 a神经元在控制辅助（非- 呼吸肌（ARM）用于吸气。这些肌肉通常用于增加 运动期间的通气，但它们也用于增强受伤或疾病后的横膈膜功能。尽管 ARM对于增强通气或补偿横膈膜功能丧失的重要性， 了解在健康或疾病中驱动其活动的神经回路。ARM活动增加 在ALS模型小鼠的早期疾病阶段，有一个中央赤字，防止激活 手臂呼吸在晚期疾病阶段，尽管事实上，这些肌肉是活跃和功能， 自愿行为。增加（通过Gq信号通路）或减少（通过Gi信号通路 V2 a神经元的兴奋性能够增加健康和ALS模型小鼠中休息时的ARM活性。 因此，这些神经元是增加ALS患者ARM活动和通气的潜在靶点， 神经肌肉疾病或脊髓损伤。然而，V2 a类神经元似乎由以下组成： 在呼吸控制中发挥不同作用的亚型。为了开发改善呼吸的疗法 通过改变活性、防止退化或替换退化的V2 a神经元， 确定影响通气的V2 a神经元的位置和分子亚型， 具体角色。目标1将使用转基因和病毒策略来增加兴奋性，降低兴奋性，或消融 颈、胸或腰脊髓中的V2 a神经元，以确定呼吸肌活动是如何调节的 V2 a神经元在不同节段水平的活动。目的2：研究V2 a神经元的分子多样性。 颈髓通过调查不同的连接和功能内的呼吸回路的内侧 V2 a亚型和外侧V2 a亚型。Aim 2还将评估改变呼吸机的兴奋性对通气的影响。 仅V2 a神经元与呼吸运动神经元具有直接兴奋性连接。目标3将评估长期- V2 a神经元变性通过过早消融颈V2 a神经元对呼吸长期影响 一个ALS的小鼠模型长期增加V2 a兴奋性的潜在获益（和危害） 还将研究ALS模型小鼠中神经元对ARM活性、运动神经元变性和健康状况的影响。 评估。通过实现这些目标，我们将精确定位的位置，分子身份，和连接， 脊髓V2 a神经元模式呼吸肌活动，以及评估潜在的呼吸肌活动， 改变V2 a神经元的兴奋性以改善ALS小鼠模型的呼吸。

Crone, S. A. Project Summary The proposed studies investigate the role of spinal V2a neurons in the control of auxiliary (non- diaphragmatic) respiratory muscles (ARMs) for inspiration. These muscles are normally used to increase ventilation during exercise, but they are also used to augment diaphragm function after injury or disease. Despite the importance of ARMs for enhancing ventilation or compensating for loss of diaphragm function, little is known about the neural circuits that drive their activity in either health or disease. ARM activity increases ventilation in ALS model mice at early disease stages, but there is a central deficit that prevents activation of ARMs for breathing at late disease stages, despite the fact that these muscles are active and functional for voluntary behaviors. Either increasing (through Gq signaling pathways) or decreasing (through Gi signaling pathways) the excitability of V2a neurons is able to increase ARM activity at rest in healthy and ALS model mice. Thus, these neurons are a potential target to increase ARM activity and ventilation in patients with ALS, other neuromuscular diseases, or spinal cord injury. However, the V2a class of neurons appears to be composed of subtypes that play distinct roles in the control of breathing. In order to develop therapies to improve breathing by altering the activity, preventing degeneration, or replacing degenerated V2a neurons, it is necessary to determine the location and molecular subtypes of V2a neurons that impact ventilation and to understand their specific roles. Aim 1 will use transgenic and viral strategies to increase excitability, decrease excitability, or ablate V2a neurons in cervical, thoracic, or lumbar spinal cord to identify how respiratory muscle activity is regulated by V2a neurons at different segmental levels. Aim 2 will investigate the molecular diversity of V2a neurons within the cervical cord by investigating differences in connectivity and function within respiratory circuits of a medial V2a subtype and a lateral V2a subtype. Aim 2 will also asses the effects on ventilation of altering excitability of only V2a neurons with direct excitatory connections to respiratory motor neurons. Aim 3 will assess the long- term impact that degeneration of V2a neurons has on breathing by prematurely ablating cervical V2a neurons in a mouse model of ALS. The potential benefit (and hazards) of chronically increasing the excitability of V2a neurons on ARM activity, motor neuron degeneration, and ventilatory health in ALS model mice will also be assessed. By accomplishing these aims, we will pinpoint the location, molecular identity, and connectivity of spinal V2a neurons that pattern respiratory muscle activity as well as assess the potential of pharmacologically altering the excitability of V2a neurons to improve breathing in a mouse model of ALS.