Central and Peripheral Elements of Respiratory Pattern Formation

描述（由申请人提供）：呼吸是一种重要的、多方面的行为，在这种行为中，中枢产生的节奏必须转化为脊神经和脑神经上协调的运动活动模式，从而产生胸壁的泵送作用并调节气道张力。来自气道的机械感觉输入对于这种协调是必不可少的。特别是在胸壁高度柔顺的哺乳动物中——包括人类婴儿——拮抗气道受体组调节吸气末容积（即潮气量）和呼气末容积。然而，这些不同的呼吸运动反应是如何在中枢神经系统内协调的，人们知之甚少。在本应用中，我们将定义（在大鼠中）两种拮抗反射在肺膨胀（缓慢适应受体；SARs）和肺收缩（通货紧缩激活受体；dar）时引发的中枢通路。将讨论三个具体目标。在Aim 1中，不同类型的SAR和DAR NTS中继神经元的轴突投射将通过对一小群NTS细胞进行顺行标记并对其突触靶点进行逆行标记来全面调查。利用同时记录的脉冲序列相互关联的补充研究将评估这些功能相互作用。在Aim 2中，对单个、独特定义的SAR和DAR中间神经元进行细胞旁染料填充，并对其靶标进行逆行标记，将允许对具有多个靶标的NTS中继神经元的突触连接进行光镜和电镜联合分析。在Aim 3中，将使用NTS神经元及其潜在靶点的细胞旁标记来定义突触后SAR和DAR NTS中间神经元的电生理学定义表型。尖峰触发的平均可以表征NTS中继神经元和特定突触后细胞之间的突触连通性及其相对强度。综上所述，这些实验将首次确定SAR和DAR传入中继神经元的突触后靶点，并提供对肺机械感受器的激活产生协调呼吸反射反应的途径的多突触电路图。对这些回路的了解可以阐明以一系列呼吸系统疾病和退行性运动疾病为特征的气道控制受损患者的治疗策略。项目描述：这项研究将检查与中枢反射调节呼吸有关的脑干回路。通过详细跟踪从气道和肺部接收信息的神经元的相互联系，我们将以一种以前不可能的方式描述呼吸的力量和时间模式的控制系统。这种类型的信息对于分析这些回路在从肌萎缩侧索硬化症到婴儿猝死综合症等各种人类疾病中的作用将是重要的。

DESCRIPTION (provided by applicant): Breathing is a vital, multifaceted behavior in which a centrally generated rhythm must be transformed into coordinated patterns of motor activity on spinal and cranial nerves that produce the pumping action of the chestwall and regulate airway tone. Mechanosensory input from the airways is essential for this coordination. Especially in mammals that have highly compliant chest walls - including human infants - antagonistic sets of airway receptors regulate end-inspiratory volume (ie, tidal volume) and end-expiratory volume. However, little is known about how these differential respiratory motor responses are coordinated within the central nervous system. In this application we will define (in rats) the central pathways by which two antagonistic reflexes are elicited in response to lung inflation (slowly adapting receptors; SARs) and lung deflation (deflation activated receptors; DARs). Three Specific Aims will be addressed. In Aim 1 the axonal projections of the different types of SAR and DAR NTS relay neurons will be comprehensively surveyed using anterograde labeling of small groups of NTS cells combined with retrograde labeling of their synaptic targets. Complementary studies using cross-correlation of simultaneously recorded spike trains will assess these functional interactions. In Aim 2, juxtacellular dye filling of single, uniquely defined SAR and DAR interneurons along with retrograde labeling of their targets will permit combined light- and electron-microscopic analysis of the synaptic connections of NTS relay neurons with multiple targets. In Aim 3 the electrophysiologically defined phenotypes of neurons post- synaptic to SAR and DAR NTS interneurons will be defined using juxtacellular labeling of both NTS neurons and their potential targets. Spike-triggered averaging will permit characterization of the synaptic connectivity, and its relative strength, between the NTS relay neurons and specific post-synaptic cells. Taken together, these experiments will identify, for the first time, the post-synaptic targets of SAR and DAR afferent relay neurons and provide a polysynaptic circuit diagram of the pathways producing coordinated respiratory reflex responses to activation of lung mechanoreceptors. Knowledge of these circuits may elucidate treatment strategies for patients with compromised airway control characteristic of a range of respiratory disorders and degenerative motor diseases. PROJECT NARRATIVE: This research will examine the brainstem circuits related to central reflexes modulating breathing. By following in detail the interconnections of neurons receiving information from the airways and lungs we will describe the control system for the force and temporal pattern of breathing in a way that has not previously been possible. This type of information will be important for analyzing the role of these circuits in a variety of human diseases ranging from amyotrophic lateral sclerosis to sudden infant death syndrome.