Examining the neural circuit for an instinctive olfactory-induced behavior in lar

描述(申请人提供)：嗅觉--嗅觉--是我们感知周围化学物质的主要手段，因此，它对生活质量有重大影响。嗅觉神经生物学领域的首要目标之一是了解连接嗅觉刺激的神经通路，嗅觉刺激在大脑中的表现，以及驱动下游行为的电路。也许理解这些神经通路的最大障碍是神经系统的复杂性和物理大小。例如，有许多嗅觉引导行为的小鼠，在嗅球中有大约1000个不同的气味感受器，500万到1000万个嗅觉感觉神经元，以及1800个不同的轴突和树突集合，称为肾小球，嗅球是大脑中专门处理嗅觉初始步骤的区域。在这项建议中，我们描述了一种策略，在一个至少比斑马鱼幼虫老鼠简单10倍的系统中研究潜在的嗅觉神经回路。 这一策略的关键创新是我们使用了最近发现的一种天生的嗅觉引导行为来研究嗅觉回路。尽管五天大的斑马鱼表现出几种先天行为，但直到最近，斑马鱼幼体中还没有已知的强大的嗅觉引导行为。在这里，我们证明斑马鱼幼体表现出一种刻板印象的、嗅觉引导的恐惧行为，对斑马鱼皮肤有机溶剂提取物中的成分做出反应。最终，以这种行为为指导，我们将能够将特定分子结构的感觉与它们结合的嗅觉感受器的类型、它们激活的嗅觉感觉神经元的类型以及它们为了产生行为而激发的神经回路联系起来。在具体目标1中，我们描述了识别三种嗅觉神经元类型中哪种类型的嗅觉神经元受到行为活性气味刺激的实验。这些结果将使未来的实验成为可能，使我们能够缩小搜索相关受体和信号通路的范围，这些受体和信号通路是这种嗅觉引导行为的基础。在具体目标2中，我们描述了两种独立但互补的策略来识别大脑中第一个嗅觉处理步骤--嗅球的肾小球--的嗅神经回路的解剖。在特定的目标2.1中，我们通过成像它们的神经活动来识别哪些肾小球是支持嗅觉行为的神经回路的一部分，以响应对纯化的行为活性分子的感觉接收。在具体目标2.2中，我们通过消融相关的肾小球并寻找行为反应减弱来识别它们。这些实验的结果将增加我们对先天嗅觉引导行为背后的神经回路的理解，并将为R01的应用提供坚实的基础，以支持未来对调节固有行为的神经回路的阐明的研究。

DESCRIPTION (provided by applicant): Olfaction-the sense of smell-is the major means though which we sense our chemical surroundings, and as such, it has a significant impact on quality of life. One of the overarching goals in the field of olfactory neurobiology is to understad the neural pathways that connect an olfactory stimulus, its representation in the brain as a percept, and the circuits that drive downstream behaviors. Perhaps the greatest obstacle to understanding these neural pathways is the complexity and physical size of the nervous system. For example, mice, which have numerous olfactory-guided behaviors, have ~1000 different odorant receptors, 5-10 million olfactory sensory neurons, and 1800 distinct collections of axons and dendrites, called glomeruli, in the olfactory bulb, the brain area specialized in processing the initial steps of olfaction. In this proposal, we describe a strategy to study the neural circuiry underlying olfaction in a system that is at least 10 times simpler than mice, the zebrafish larvae. The key innovation of this strategy is our use of a recently identified, innate olfactory-guided behavior to study olfactory circuits. Although five-day-old zebrafish exhibit several innate behaviors, until recently there were no known robust olfactory-guided behaviors in zebrafish larvae. Here we demonstrate that zebrafish larvae exhibit a stereotyped, olfactory-guided fear behavior in response to components in an organic solvent extraction of zebrafish skin. Ultimately, using this behavior as a guide, we will be able to connect the sensation of specific molecular structures with the types of olfactory receptors they bind, the types of olfactory sensory neurons they activate, and the neural circuit they excite in order to generate behavior. In Specific Aim 1, we describe experiments to identify which of the three olfactory sensory neuron types is stimulated by the behaviorally active odorants. These results will enable future experiments that allow us to narrow the search for the relevant receptors and signaling pathways underlying this olfactory-guided behavior. In Specific Aim 2, we describe two separate but complementary strategies to identify the anatomy of the olfactory neural circuit at the first olfactory-processing step in the brain, the glomeruli of the olfactory bulb. In Specific Aim 2.1, w identify which glomeruli are a part of the neural circuit underlying the olfactory behavior by imaging their neural activity in response to sensory reception of purified, behaviorally active molecules. In Specific Aim 2.2, we identify the relevant glomeruli by ablating them and looking for a diminished behavioral response. The results of these experiments will increase our understanding of the neural circuits underlying a innate, olfactory-guided behavior, and will provide a solid foundation for an R01 application to support future studies on the elucidation of neural circuits mediating innate behaviors.