Neuromodulator signaling and activity in the C. elegans egg-laying circuit.

描述（由申请人提供）：神经调节剂（如生物胺或神经肽）改变的信号是人类大脑疾病（包括情绪障碍和帕金森病）的基础，但我们对神经调节剂如何产生神经回路正常功能的确切理解仍然模糊。神经调节剂如何与快速作用的神经递质合作，在复杂行为的基础上创造神经回路的活动模式？我们的目标是第一次精确地理解神经调节剂在模型神经回路中的作用。秀丽隐杆线虫的产卵回路只包含三种类型的神经元和一组突触后肌肉。这个回路只涉及一种快速作用的神经递质乙酰胆碱，加上一组神经调节剂：生物胺- 5 -羟色胺和酪胺，以及几种神经肽。该回路产生两种状态的行为，在约2.5分钟的活跃阶段（其中有节奏的产卵收缩发生）和约20分钟的不活跃阶段之间交替。在过去的16年里，我们已经开发了一组秀丽隐杆线虫突变体，由于电路中特定信号分子的缺陷，这些突变体的产卵量增加或减少。我们还开发了细胞特异性启动子，使我们能够在任何单个细胞类型的产卵系统中表达我们想要的任何蛋白质。我们现在已经开发出新的工具来光遗传学操纵单个细胞类型的活性，并使用遗传编码的Ca2+传感器GCaMP来定量分析自由行为动物中每种细胞类型的活性。这些新工具把我们带到了一个临界点，在这个临界点上，我们准备描绘出回路中的每个细胞和每种神经递质是如何共同产生回路的活动模式的。我们期望对神经调节剂有一个新的有意义的理解，现在我们终于可以在详细研究它们调节的电路的背景下分析它们的功能。我们将通过三个目标来产生这种理解，每个目标都侧重于剖析回路中三种神经元类型之一的功能：目标1。我们将确定5 -羟色胺和神经肽NLP-3（从HSN运动神经元共同释放）如何向回路中的其他细胞发出信号，从而启动产卵的活跃阶段。目标2。当血清素和NLP-3激活该回路时，我们将确定在活动阶段从VC运动神经元释放的乙酰胆碱如何剧烈地触发产蛋收缩。目标3。我们将确定uv1神经内分泌细胞如何释放酪胺以延长产卵的非活动阶段，并在活动阶段间隔产卵事件。

DESCRIPTION (provided by applicant): Altered signaling by neuromodulators, such as biogenic amines or neuropeptides, underlies human brain diseases including mood disorders and Parkinson's disease, yet our understanding of exactly how neuromodulators produce proper functioning of neural circuit's remains vague. How do neuromodulators collaborate with fast-acting neurotransmitters to create patterns of activity in neural circuits that underlie complex behaviors? Our goal is to understand for the first time precisely how neuromodulators function in a model neural circuit. The egg-laying circuit of C. elegans contains just three types of neurons and one set of postsynaptic muscles. This circuit involves just one fast-acting neurotransmitter, acetylcholine, plus a set of neuromodulators: the biogenic amines serotonin and tyramine, and several neuropeptides. The circuit generates a two-state behavior that alternates between a ~2.5 minute active phase in which rhythmic egg-laying contractions occur, and a ~20 minute inactive phase. Over the past 16 years, we have developed a battery of C. elegans mutants that show increased or decreased egg laying due to defects in specific signaling molecules in the circuit. We have also developed cell-specific promoters that allow us to express any protein we want in any individual cell type of the egg-laying system. We have now developed new tools to optogenetically manipulate activity of the individual cell types and to use the genetically-encoded Ca2+ sensor GCaMP to quantitatively analyze activity of each cell type within freely-behaving animals. These new tools have brought us to a tipping point at which we are ready to delineate how each cell and each neurotransmitter in the circuit act to together produce the activity pattern of the circuit. We expect a newly meaningful understanding of neuromodulators will be revealed now that we can finally analyze their function in the context of detailed investigation of a circuit they modulate. We will generate this understanding through three aims, each focused on dissecting the function one of the three neuron types in the circuit: Aim 1. We will determine how serotonin and the neuropeptide NLP-3, co-released from the HSN motor neuron, signal onto other cells in the circuit to initiate the active phase of egg laying. Aim 2. W will determine how acetylcholine, released from the VC motor neurons within the active phase, acutely triggers egg-laying contractions only when serotonin and NLP-3 have activated the circuit. Aim 3. We will determine how the uv1 neuroendocrine cells release tyramine to lengthen the inactive phase of egg laying and to space out egg-laying events during the active phase.