Rhythm control and regulation of Lymnaea respiratory central pattern generator neurons

呼吸对生命至关重要。其基本节律由中枢模式发生器（CPG）网络控制，该网络由能够产生内源性节律活动的相互作用神经元组成。CPG中的节律产生依赖于突触相互作用和固有膜特性。呼吸CPG （rCPG）受多种病理生理因素调控，包括低氧水平。慢性缺氧诱导适应性反应，促进呼吸运动活动，也可导致呼吸和神经功能障碍。由于哺乳动物呼吸神经网络的解剖学和功能复杂性，调控rCPG节律性活动的基本机制在很大程度上仍不清楚。突触和内在膜特性的原理在物种间是保守的。因此，使用具有大神经元和良好映射的神经网络的无脊椎动物模型来研究CPG节律特性是有利的。池塘蜗牛（L. stagnation）是一种水生的呼吸空气的肺类动物。它的呼吸节律活动由一个简单的rCPG网络控制，该网络由三个可识别的大神经元组成，包括一个多巴胺能起搏器神经元RPeD1。这些神经元可以进行直接的电生理评估和分子操作，因此停滞乳杆菌是研究rCPG节律产生和调控基本机制的理想模式生物。我们的初步研究表明，慢性缺氧调节了停滞乳杆菌呼吸的节律性活动，同时也改变了突触蛋白水平、细胞信号级联和离子通道特性。这些初步数据表明rCPG神经元的呼吸可塑性是由离子通道调节和多巴胺依赖的突触传递介导的。为了验证这一假设，我们提出了未来5年的以下三个短期目标。1. 确定u型通道在慢性缺氧调节的rCPG神经元节律性放电模式中的作用。2. 确定慢性缺氧对多巴胺介导的呼吸CPG神经元突触活性的调节作用。3. 确定呼吸可塑性所需的关键基因和蛋白质。该研究项目的长期目标是了解在生理和病理生理条件下调节呼吸节律的rCPG神经可塑性的细胞和分子机制。这个项目的新颖之处在于我们能够使用先进的现代技术来揭示新的机制。意义：该研究不仅为呼吸CPG活动的节律控制和调节提供了基础知识，而且为多巴胺依赖性突触调节提供了基础知识。它们将有助于确定新的靶标，用于开发在病理生理条件下操纵节律活动的试剂。

Respiration is vital to life. Its essential rhythm is controlled by central pattern generator (CPG) networks comprising interactive neurons capable of generating an endogenous rhythmic activity. Rhythm generation in CPG relies on synaptic interactions and intrinsic membrane properties. Respiratory CPG (rCPG) is regulated by multiple pathophysiological factors, including low oxygen levels. Chronic hypoxia induces adaptive responses to facilitate respiratory motor activities and can also result in respiratory and neural dysfunction. The fundamental mechanisms by which the rhythmic activities of rCPG are regulated remain largely unclear, primarily because of the anatomical and functional complexities of the respiratory neuronal network in mammals. The principles of synaptic and intrinsic membrane properties are conserved across species. Thus, using invertebrate models that have large neurons and well-mapped neuronal networks to study the CPG rhythmic properties is advantageous. The pond snail, L. stagnalis, is an aquatic air-breathing pulmonate. Its respiratory rhythmic activity is controlled by a simple rCPG network consisting of three large and identifiable neurons, including a dopaminergic pacemaker neuron, RPeD1. These neurons allow for direct electrophysiological assessments and molecular manipulation, and thus L. stagnalis is an ideal model organism for studying fundamental mechanisms of rhythmic generation and regulation of rCPG. Our preliminary studies show that the rhythmic activities of L. stagnalis respiration are regulated chronic hypoxia which also alters levels of synaptic proteins, cell signaling cascade and ion channel properties. These preliminary data lead to the hypothesis that the respiratory plasticity is mediated by ion channel regulation and dopamine-dependent synaptic transmission in rCPG neurons. To test this hypothesis, we propose the following three short-term objectives for the next 5 years. 1. Determine the role of the U-type channel in chronic hypoxia-regulated rhythmic firing pattern of rCPG neurons. 2. Determine the modulatory effect of chronic hypoxia on dopamine-mediated synaptic activity in respiratory CPG neurons. 3. Identify critical genes and proteins that are required for respiratory plasticity. The long-term goal of the research program is to understanding cellular and molecular mechanisms of neural plasticity in rCPG that regulate respiratory rhythms under physiological and pathophysiological conditions.  The novelty of this program lies in our ability to use advanced modern technologies to reveal the new mechanisms. Significance: The studies will provide fundamental knowledge of not only rhythm control and regulation of respiratory CPG activities, but also dopamine-dependent synaptic regulation. They will assist in identifying new targets for developing reagents that manipulate rhythmic activity in pathophysiological conditions.