Intracellular pH Responses of Central Chemoreceptors

描述（由申请人提供）：高碳酸血症（CO2增加）是呼吸的主要刺激，由来自几个脑干区域的称为化学敏感神经元的专门神经元感知。我们一直在研究这些神经元感知二氧化碳的离子通路。基于我们的发现，我们提出了一种新的化学敏感信号模型，即多因素模型。该模型的主要原则是化学敏感神经元对高碳酸血症的反应涉及靶向多个离子通道的多个信号传导途径。本修订申请的工作分为4个目的：1）通过测量来自一个脑干区域的神经元的内在化学敏感性，特别关注在pHi保持恒定的情况下神经元对酸性刺激的反应以及Cai的作用，直接测试化学敏感性信号传导中涉及的多个信号; 2）确定哪些离子通道作为化学敏感性信号传导的靶标并测量它们的性质，使用免疫细胞化学和电压钳技术的组合来描述哪些通道存在于化学敏感性神经元中以及哪些通道受高碳酸血症; 3）比较Aim 1中研究的来自三个不同脑干区域的神经元中的信号通路，蓝斑（低化学敏感性），孤束核（中等化学敏感性）和后斜方核（高化学敏感性），并开发数学模型来描述哺乳动物化学敏感神经元的反应，其组合了针对来自每个区域的神经元描述的多个信号和离子通道靶标;（4）结合逆行标记和细胞内记录，确定CO2化学敏感神经元的传出投射。这些研究将是第一个采用相同的技术在神经元从几个脑干区域有广泛不同的内在chemosensitivitv，并应产生有价值的新见解的细胞特性，确定chemosensitivitv。此外，我们的结果应该定义神经元中化学敏感性的细胞信号通路和离子通道靶点，并用于测试多因素模型。许多疾病，包括睡眠呼吸暂停和婴儿猝死综合征（SIDS）被认为部分涉及中枢呼吸控制紊乱，但目前没有药物治疗可用于改变这种控制途径。我们的研究应该为药物治疗提供新的潜在靶点，并可能很好地表明药物组合在改变中枢呼吸驱动方面最有效。摘要：脑干神经元感知到的二氧化碳增加是驱动呼吸的主要刺激。这种反应的改变被认为部分涉及睡眠呼吸暂停等疾病，但现在没有药物可以影响这种反应。我们正在研究神经元对二氧化碳的反应方式，以确定新的药物靶点，并测试一种新的理论，即这种途径涉及几种不同的信号。

DESCRIPTION (provided by applicant): Hypercapnia (increased CO2) is a major stimulus for breathing and is sensed by specialized neurons, called chemosensitive neurons, from several brainstem regions. We have been studying the ionic pathways by which these neurons sense CO2. Based on our findings, we have proposed a new model of chemosensitive signaling, the multiple factors model. The main tenet of this model is that the response of chemosensitive neurons to hypercapnia involves multiple signaling pathways that target multiple ion channels. The work in this revised application is divided into 4 aims: 1) test directly that there are multiple signals involved in chemosensitive signaling, by measuring the intrinsic chemosensitivity of neurons from one brainstem region, focusing especially on neuronal responses to acidic stimuli with pHi held constant and on the role of Cai; 2) determine which ion channels act as targets of chemosensitive signaling and measure their properties, using a combination of immunocytochemistry and voltage clamp techniques to describe which channels are present in chemosensitive neurons and which are affected by hypercapnia; 3) compare the signaling pathways studied in Aim 1 in neurons from three different brainstem regions, the locus coeruleus (low chemosensitivity), the nucleus tractus solitarius (intermediate chemosensitivity) and the retrotrapezoid nucleus (high chemosensitivity) and develop a mathematical model to describe the response of mammalian chemosensitive neurons which combines the multiple signals and ion channel targets described for the neurons from each region; and 4) determine the efferent projections of CO2-chemosensitive neurons combining retrograde labeling with intracellular recordings. These studies will be the first to employ identical techniques in neurons from several brainstem regions which have widely different intrinsic chemosensitivitv, and should yield valuable new insights into the cellular properties that determine chemosensitivity. Further, our results should define the cellular signaling pathways and ion channel targets of chemosensitivitv in neurons and serve to test the multiple factors model. Many diseases, including sleep apnea and Sudden Infant Death Syndrome (SIDS) are believed to involve, in part, disordered central respiratory control, and yet no current drug treatments are available to modify this control pathway. Our studies should suggest new potential targets for drug treatment and may well indicate that a combination of drugs is most effective in modifying central respiratory drive. Lay Summary: Increased CO2, sensed by brainstem neurons, is a major stimulus that drives breathing. Alterations of this response are thought to be involved, in part, in diseases like sleep apnea, but no drugs are now available to affect this response. We are studying the ways in which neurons respond to CO2 to identify novel drug targets and to test a new theory that this pathway involves several different signals.