The role of Dbx1-derived medullary neurons for rhythm generation in the intact respiratory network

1：项目概要 呼吸是一种复杂的行为，是所有哺乳动物生命的基础。功能紊乱， 呼吸协调在中枢神经系统的许多疾病中是常见的。因此，研究 作为这种行为基础的特定神经群不仅具有重大的基础科学意义， 临床意义使用脑干横切片的损伤实验和体外研究已经定义了 对于呼吸的吸气阶段是必要的和足够的最小回路， 延髓腹外侧区的神经元称为前BötC复合体。兴奋性神经元 来自表达转录因子Dbx1的细胞被认为形成了前BötC的节律“核心”。 然而，每次呼吸后Dbx1刺激的“不应期”限制了这些神经元 在体外驱动高频节律。这种特殊的神经元群体在控制广泛的 体内常见的呼吸频率范围是未知的。在这个项目中，我们将使用新的体内和体外 平行进行的方法来研究Dbx1神经元在吸气产生中的作用， 嵌在更宽的骨髓网络中根据我们的初步数据，我们假设吸气 神经网络用作分布式列，并且不限于定义的“核心”区域。抑制 兴奋性Dbx1神经元通过抑制后反弹有效地驱动吸气节律。并且 分布式吸气网络中Dbx 1的不应期可以缩短，以允许更快的呼吸 通过调节短期突触抑制的机制来调节频率。这些假设将得到检验 使用强大的光遗传学、电生理学、药理学和成像技术， 自由行为小鼠（Aim 1）和一种新的水平脑干切片制备，保留了更广泛的 双侧髓网（Aim 2）。我们希望，这些准备工作的整合将提供一个独特的 的角度来研究在呼吸节律生成领域仍然没有解决的问题。

1: PROJECT SUMMARY Breathing is a complex behavior that is fundamental for life in all mammals. Disturbances in the function and coordination of breathing are common in many disorders of the central nervous system. Thus, the study of specific neural populations that underlie this behavior is not only of great basic science interest, but holds high clinical significance. Lesion experiments and in-vitro studies using transverse brainstem slices have defined the minimal circuitry that is necessary and sufficient for the inspiratory phase of breathing, a small “kernel” of neurons in the ventrolateral medulla termed the preBötzinger Complex (preBötC). Excitatory neurons derived from cells expressing the transcription factor Dbx1 are thought to form the rhythmogenic “core” of the preBötC. However, a “refractory period” for Dbx1 stimulation following each breath limits the ability these neurons to drive a high frequency rhythm in-vitro. The role of this specific population of neurons in controlling the wide range of breathing frequencies common in-vivo is unknown. In this project we will use novel in-vivo and in-vitro approaches conducted in parallel to investigate the role of Dbx1 neurons in the generation of inspiration when embedded in the wider medullary network. Based on our preliminary data, we hypothesize that the inspiratory neural network functions as a distributed column, and is not limited to a defined “core” region. Inhibition of excitatory Dbx1 neurons effectively drives the inspiratory rhythm through post-inhibitory rebound. And, the refractory period for Dbx1 can be reduced in the distributed inspiratory network to allow faster breathing frequencies by modulating mechanisms of short-term synaptic depression. These hypotheses will be tested using powerful optogenetic, electrophysiological, pharmacological and imaging techniques in anesthetized and freely behaving mice (Aim1) and in a novel horizontal brainstem slice preparation that preserves the wider medullary network bilaterally (Aim2). We expect that integration of these preparations will provide a unique perspective to examine issues that remain unresolved in the field of respiratory rhythm generation.