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.

5-羟色胺能系统影响广泛的人类行为，是精神病学研究的共同目标。 毒品。在哺乳动物中，接受5-羟色胺能输入的神经回路由不同类型的细胞组成，每种细胞类型 它表达14个不同的5-羟色胺(5-HT)受体的子集。5-羟色胺释放对电路功能的影响 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-羟色胺在电路中的多个位置一致改变电路的基本原理 功能。在这里，我们建议在线虫中解决这个问题。线虫的神经系统特别是 对神经科学中的全电路问题很有吸引力，因为它正好由302个神经元组成，每个神经元 在每种动物中都可以识别，这些神经元之间的突触连接(“连接体”)有 已经被完全定义，在这个定义明确的系统中，可以使用优秀的遗传工具来操纵单个细胞。 此外，这种动物的透明度使我们能够使用尖端的成像方法-包括全脑 钙成像--用于监测行为自由的动物的神经活动。重要的是，5-HT信号是很好的- 从线虫到哺乳动物的保守：线虫人类基因的同源基因编码5-羟色胺合成 酶(TPH)、囊膜转运蛋白(VMAT、SERT)、5-羟色胺受体(5-HT1、5-HT2等)和 更多。因此，对这种动物的研究应该揭示5-羟色胺功能的一般原理，以便后续研究 适用于更复杂的动物。这项建议中的研究建立在我的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，我们发现线虫摄取食物会激活一种特定的5-羟色胺 神经元，被称为NSM，它的5-羟色胺的释放驱动动物进食时的缓慢运动。我们还展示了 这种神经元对食物摄取的动态反应控制着运动动力学：不同的5-羟色胺模式 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-羟色胺释放影响运动，开始绘制出介导这些影响的5-羟色胺受体， 并开发了一种方法来监测5-羟色胺诱导的全脑活动的变化。在目前的提案中， 我们将使用这个受限的实验范例和这些尖端的成像方法来探测 5-羟色胺系统的功能结构，并研究5-羟色胺受体如何相互作用来控制大脑功能。 具体地说，我们将首先绘制出5-羟色胺受体和回路，这些受体和回路调节不同的行为反应 5-羟色胺释放模式(目标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-羟色胺释放模式如何使不同的5-羟色胺受体类型参与改变整个大脑的活动(目标2)。 最后，我们还将研究拮抗5-羟色胺信号的厌恶线索如何调节 5-羟色胺能回路，允许动物平衡厌恶和欲望的输入(目标3)。这些研究将揭示 模式化的5-羟色胺释放如何与特定的5-羟色胺受体类型结合影响大脑功能，产生新的 5-HT电路组织和功能的框架。