NEURONAL EXCITABILITY IN THE REGULATION OF CIRCADIAN RHYTHMS

昼夜节律调节中的神经元兴奋性

• 批准号: 8446866
• 负责人: Erik Herzog
• 金额: $ 28.88万
• 依托单位: WASHINGTON UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-01-01 至 2016-12-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8446866
• 关键词: Address; Arrhythmia; Automobile Driving; Behavior; Behavioral; Behavioral Assay; Brain; Cells; Circadian Rhythms; Cognitive; Development; Feedback; Fire - disasters; Gene Expression; Gene Expression Regulation; Generations; Genetic; Genetic Transcription; Goals; Health; In Vitro; Individual; Investigation; Link; Mediating; Membrane; Membrane Potentials; Mental Depression; Methods; Microelectrodes; Molecular; Molecular Profiling; Motor Activity; Mus; Neurons; Obesity; Pattern; Performance; Physiological; Physiology; Play; Potassium; Potassium Channel; Property; Regulation; Research; Resistance; Reverse Transcriptase Polymerase Chain Reaction; Role; Running; System; Testing; Time; Translating; Translations; Wild Type Mouse; base; cell type; circadian pacemaker; design; extracellular; in vivo; insight; neuronal excitability; novel; novel therapeutics; programs; public health relevance; research study; suprachiasmatic nucleus; voltage

DESCRIPTION (provided by applicant): The suprachiasmatic nucleus (SCN) is the master circadian pacemaker driving daily rhythms in mammalian physiology and behavior. SCN neurons utilize a transcription/translation feedback loop to generate circadian changes in electrical activity. Although we have known that SCN neurons fire during the day and are silent at night since 1982 and considerable evidence implicates subthreshold K+ conductance(s), the critical K+ conductance(s) have not been identified. In recent studies focused on testing the hypothesis that subthreshold, A-type (IA) voltage-gated K+ (Kv) channels are involved, we found that mice lacking Kv4.2 (Kv4.2-/-) or Kv1.4 (Kv1.4-/-) pore-forming (¿) subunits have markedly shorter circadian periods of locomotor (wheel running) activity than wild-type (WT) mice. Using in vitro extracellular microelectrode recordings, we found that the periods of circadian rhythms in firing are similarly shortened in SCN neurons lacking either Kv4.2 or Kv1.4. Initial experiments here (aim 1) will determine if Kv4.2 and Kv1.4 are the only Kv ¿ subunits contributing to the IA channels that modulate SCN excitability and reveal the effects the combined loss Kv4.2 and Kv1.4 on rhythms in SCN firing and locomotor activity. The goal of aim 2 is to determine if the shorter period of circadian firing in SCN neurons lacking Kv4.2 or Kv1.4 reflects the functioning of IA channels in the synchronization (i.e., network properties) or the cell-autonomous regulation of SCN neuron excitability. This aim will, for the first time, establish whether the critical K+ conductance(s) in different SCN cell types are distinct. A long-standing debate in the field is whether daily changes in membrane potential are required for the generation of circadian rhythms in gene expression. Aim 3 will test directly the hypothesis that Kv4.2- and Kv1.4-encoded IA channel mediated changes in excitability also modulate the period and amplitude of circadian changes in gene expression. Finally, the observation that the cyclic changes in SCN neuron firing and locomotor activity persist (albeit with a shorter period) in the absence of Kv1.4 or Kv4.2 indicates that other K+ conductances regulate the daily oscillations in SCN neuron membrane potentials. In aim 4, we will exploit a novel, high-throughput quantitative Taqman-based RT-PCR based method to quantify the expression levels of multiple K+ channel subunits simultaneously, as a function of circadian time, and to identify the subthreshold K+ conductance(s) that mediates the daily depolarizations and hyperpolarizations in the membrane potentials of SCN neurons. These studies will provide fundamentally important new insights into the roles of specific K+ conductances in regulating/modulating daily rhythms in the excitability of SCN neurons. In addition to guiding further investigations into the molecular, cellular and systemic mechanisms linking daily rhythms in neuronal excitability, gene expression and behavior, these insights will translate to advances in understanding the regulation and dysregulation of circadian rhythms and to the development of novel therapeutic strategies to benefit individuals suffering genetic and environmentally-induced disruptions in circadian rhythms.

描述（由适用提供）：上型核核（SCN）是昼夜节奏起搏器，驱动哺乳动物生理和行为的每日节奏。 SCN神经元利用转录/翻译反馈回路来产生电活动的昼夜节律变化。尽管我们知道SCN神经元在白天发射，并且自1982年以来一直保持沉默，有大量证据暗示子阈值K+电导量，但尚未确定关键的K+电导。在最近的研究中，重点是测试以下假说：阈值，A型（IA）电压门控k+（KV）涉及的渠道涉及到缺乏Kv4.2（KV4.2 - / - ）或KV1.4（KV1.4 - / - - 孔形成（KV1.4-）的小鼠相比，毛孔形成（KV1.4-/ - ）比较野外的shorter（where shorty cirds of tery cirds） （wt）小鼠。使用体外细胞外微电极记录，我们发现在缺乏KV4.2或KV1.4的SCN神经元中类似地缩短了昼夜节律节奏的时期。此处的初始实验（AIM 1）将确定KV4.2和KV1.4是否是唯一有助于调节SCN令人兴奋性的IA通道的kV“亚基，并揭示了组合损失KV4.2和KV1.4对SCN发射和大型运动活性中节律的效果。 AIM 2的目的是确定缺乏KV4.2或KV1.4的SCN神经元中昼夜节律发射的时间较短，反映了IA通道在同步（即网络属性）中的功能或SCN神经元令人兴奋的细胞自主调节。这个目标将首次建立 不同SCN细胞类型中的临界K+电导是否不同。该领域的一个长期辩论是，在基因表达中产生昼夜节律的每日变化是否需要膜电位变化。 AIM 3将直接检验以下假设：KV4.2-和KV1.4编码的IA通道介导的令人兴奋的变化也调节了基因表达中昼夜节律变化的时期和放大器。最后，在没有KV1.4或KV4.2的情况下，SCN神经输入和运动活性的环状变化的观察持续（尽管时间较短）表明其他K+电导率调节SCN神经元膜电位的每日振荡。在AIM 4中，我们将探索一种基于TAQMAN的新型，高通量定量的基于TAQMAN的方法，以量化多个K+通道亚基的表达水平，这是昼夜节律时间的函数，并确定介导SCNNEurress embrane Entirons中的每日去极化和超极性的亚阈值K+电导。这些研究将对特定的K+电导在调节/调节SCN神经元的刺激性中的调节/调节节奏中的作用提供根本重要的新见解。 In addition to guiding further investigations into the molecular, cellular and systemic mechanisms linking daily rhythms in neuronal exciting, gene expression and behavior, these insights will tr​​anslate to advances in understanding the regulation and dysregulation of circadian rhythms and to the development of novel therapeutic strategies to benefit individuals suffering genetic and environmentally-induced disruptions in circadian rhythms.