Dissecting the functional organization of the serotonergic system in C. elegans

剖析线虫血清素系统的功能组织

• 批准号: 10334517
• 负责人: Steven Willem Flavell
• 金额: $ 28.97万
• 依托单位: MASSACHUSETTS INSTITUTE OF TECHNOLOGY
• 依托单位国家: 美国
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-02-19 至 2024-01-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/10334517
• 关键词: Action Potentials; Afferent Neurons; Animal Behavior; Animal Feed; Animals; Architecture; Aversive Stimulus; Behavior; Behavior Control; Behavioral; Biological Models; Brain; Brain imaging; CRISPR/Cas technology; Caenorhabditis elegans; Calcium; Cells; Circadian Rhythms; Complex; Cues; Data; Desire for food; Drosophila genus; Enteral; Enzymes; Equilibrium; Food; Genes; Genetic; Goals; Human; Image; Immobilization; Ingestion; Invertebrates; Kinetics; Label; Link; Locomotion; Mammals; Maps; Measures; Mediating; Membrane; Membrane Transport Proteins; Monitor; Mutation; Nervous system structure; Neurons; Neurosciences; Optics; Orthologous Gene; Output; Pattern; Pharmaceutical Preparations; Publishing; Satiation; Sensory; Serotonergic System; Serotonin; Signal Transduction; Site; Source; Stimulus; Synapses; System; Technology; Work; behavioral response; cell type; connectome; egg; feeding; genetic approach; imaging approach; in vivo; mind control; neural circuit; optogenetics; raphe nuclei; receptor; receptor expression; receptor function; relating to nervous system; response; serotonin receptor; squid axon; tool

The serotonergic system impacts a wide range of human behaviors and is a common target of psychiatric drugs. In mammals, neural circuits that receive serotonergic inputs are composed of diverse cell types, each of which expresses a subset of 14 distinct serotonin (5-HT) receptors. The impact of 5-HT release on circuit function involves the coordinated activation of many receptor types in distinct neurons. However, we do not yet understand the fundamental principles by which 5-HT acts at many sites within a circuit to coherently alter circuit function. Here, we propose to resolve this question in C. elegans. The C. elegans nervous system is particularly attractive for whole-circuit questions in neuroscience because it consists of exactly 302 neurons, every neuron can be identified in every animal, the synaptic connections between these neurons (the “connectome”) have been fully defined, and excellent genetic tools can be used to manipulate single cells in this well-defined system. Moreover, this animal’s transparency allows us to use cutting-edge imaging approaches – including whole-brain calcium imaging – to monitor neural activity in freely-behaving animals. Importantly, 5-HT signaling is well- conserved from C. elegans to mammals: C. elegans orthologs of human genes encode for 5-HT synthesis enzymes (TPH), vesicular and membrane transporters (VMAT, SERT), 5-HT receptors (5-HT1, 5-HT2, etc) and more. Thus, studies of this animal should reveal general principles of 5-HT function that can be subsequently applied to more complex animals. The studies in this proposal build off recently published work from my lab and new preliminary data. In a recent study, we found that food ingestion by C. elegans activates a specific 5-HTergic neuron, called NSM, whose release of 5-HT drives slow locomotion while animals feed. We also showed that this neuron’s dynamical response to food ingestion controls locomotion dynamics: different patterns of 5-HT release drive different locomotion changes. In new preliminary data, we have systematically examined how patterned 5-HT release impacts locomotion, begun mapping out the 5-HT receptors that mediate these effects, and developed an approach to monitor 5-HT-induced changes in whole-brain activity. In the current proposal, we will use this well-constrained experimental paradigm and these cutting-edge imaging approaches to probe the functional architecture of the 5-HT system and examine how 5-HT receptors interact to control brain function. Specifically, we will first map out the 5-HT receptors and circuits that mediate behavioral responses to different patterns of 5-HT release (Aim 1). In a second aim, we will use new calcium imaging approaches to determine how different patterns of 5-HT release engage different 5-HT receptor types to alter whole-brain activity (Aim 2). Finally, we will also examine how aversive cues that antagonize 5-HT signaling modulate the function of serotonergic circuits, allowing animals to balance aversive and appetitive inputs (Aim 3). These studies will reveal how patterned 5-HT release engages specific 5-HT receptor types to impact brain function, yielding a new framework for 5-HT circuit organization and function.

多巴胺能系统影响广泛的人类行为，并且是精神病学研究的常见目标。 毒品在哺乳动物中，接受多巴胺能输入的神经回路由不同的细胞类型组成，每种细胞类型都是 其表达14种不同的5-羟色胺（5-HT）受体的子集。5-HT释放对回路功能的影响 涉及不同神经元中多种受体类型的协调激活。然而，我们还没有 了解5-HT在回路中的许多部位起作用以连贯地改变回路的基本原理 功能在这里，我们建议在C中解决这个问题。优美的梭线虫的神经系统 对于神经科学中的整个回路问题很有吸引力，因为它由302个神经元组成，每个神经元 可以在每种动物中识别，这些神经元之间的突触连接（“连接体”） 已经被完全定义，并且优秀的遗传工具可以用于在这个定义良好的系统中操纵单细胞。 此外，这种动物的透明性使我们能够使用尖端的成像方法-包括全脑成像。 钙成像-监测自由行为动物的神经活动。重要的是，5-HT信号传导良好- 从C. elegans到哺乳动物：C.人类基因的直向同源物编码5-HT合成 酶（TPH）、囊泡和膜转运蛋白（VMAT、SERT）、5-HT受体（5-HT 1、5-HT 2等）和 更多.因此，对这种动物的研究应该揭示5-HT功能的一般原理， 适用于更复杂的动物。这项提案中的研究建立在我实验室最近发表的工作基础上， 新的初步数据。在最近的一项研究中，我们发现C。elegans激活了一种特异的5-HTergic 神经元，称为NSM，其释放5-HT驱动动物进食时缓慢运动。我们还证明了 这种神经元对食物摄取的动态反应控制着运动动力学：5-HT的不同模式 释放驱动不同的运动变化。在新的初步数据中，我们系统地研究了 模式化的5-HT释放影响运动，开始绘制介导这些效应的5-HT受体， 并开发了一种监测5-HT诱导的全脑活动变化的方法。在目前的提案中， 我们将使用这种严格限制的实验范例和这些尖端的成像方法来探测 5-HT系统的功能结构，并研究5-HT受体如何相互作用以控制大脑功能。 具体来说，我们将首先绘制出5-HT受体和介导不同行为反应的回路， 5-HT释放模式（目的1）。在第二个目标中，我们将使用新的钙成像方法来确定 不同的5-HT释放模式如何与不同的5-HT受体类型结合以改变全脑活动（目的2）。 最后，我们还将研究拮抗5-HT信号传导的厌恶性线索如何调节 神经元能回路，使动物能够平衡厌恶和食欲输入（目的3）。这些研究将揭示 模式化的5-HT释放如何与特定的5-HT受体类型结合，以影响大脑功能，从而产生一种新的 5-HT电路组织和功能的框架。