Worms learning while intoxicated: determining the molecular mechanism and neuronal circuitry required for state dependent learning in Caenorhabditis elegans

摘要 学习的神经生物学和成瘾的神经生物学之间的联系已经被很好地记录下来了。为 例如，如果记忆是在一种环境中获得的，那么在醉酒时，受试者更容易回忆起记忆 醉酒的状态。这就是所谓的状态依赖学习(SDL)。SDL已经在广泛的领域中得到了演示 多种生物体，但对与SDL相关的分子机制和神经回路知之甚少。 在秀丽线虫(C.elegans)中，SDL是通过耦合乙醇的醉酒作用而被证明的 有一种特殊的习得行为，称为嗅觉适应；动物会回忆起自己在醉酒时的暴露 如果他们在喝醉的时候进行测试，对嗅觉刺激的反应会更好。线虫是研究线虫的最佳模型 SDL的分子基础，因为他们有一个简单的302神经元神经系统，具有不变量 从动物到动物的神经回路。神经递质多巴胺是SDL所必需的，而患有 多巴胺合成基因CAT-1和CAT-2的突变并不依赖于状态学习。这些结果 建议醉酒时学习激活不同的SDL神经回路，该回路支配和改变 嗅觉适应神经元。这项工作的最终目标是发现状态所需的电路 依赖性，以及这是如何在分子水平上调节的。初步结果表明，一种信号肽， HEN-1和受体酪氨酸激酶SCD-2是SDL所必需的。表达神经元ASE-R的HEN-1是 也是SDL所必需的。ASE-L神经元，表达几乎所有与ASE-R相同的基因。 除HEN-1外，SDL不需要。在具体目标1中，我将测试HEN-1和SCD-2的充分性 分别在ASE-R和AIA神经元中表达。其他初步结果显示章鱼胺缺乏 蠕虫不显示SDL。唯一能释放章鱼胺的神经元是RIC神经元。我将测试构造 通过基因消融使SDL缺乏RIC神经元。我还演示了SDL从 线虫在嗅觉学习过程中暴露于尼古丁。在特定的目标2中，我将测试 乙醇和尼古丁产生的SDL之间的分子机制和神经电路。我也会 确定暴露于咖啡因的蠕虫中是否出现SDL。此前，进行了正向基因筛查 寻找在酒精中毒期间不能依赖状态学习的动物。一种突变，被称为 通过选择性筛选，得到了一株新的菌株。在特定的目标3中，我将使用遗传图谱和基因组 测序以确定SDL-1的分子同一性并确定包含该突变的基因如何 可能会推广SDL。在这里，我假设酒精中毒诱导的SDL有一个明显的回路 它输入到嗅觉适应神经回路。我的目标是确定分子机制和 这种行为的神经回路，1)研究HEN-1/SCD-2和章鱼能信号，2)使用其他 可能诱发SDL的物质，以及3)利用基因作图来鉴定与SDL相关的新基因。

Abstract Links between the neurobiology of learning and the neurobiology of addiction have been well documented. For instance, human subjects recall memories more readily while intoxicated if the memory was acquired in an intoxicated state. This is known as state dependent learning (SDL). SDL has been demonstrated in a wide variety of organisms, but little is known of the molecular mechanisms and neurocircuitry associated with SDL. In Caenorhabditis elegans (C. elegans), SDL is demonstrated by coupling the intoxicating effects of ethanol with a specific learned behavior known as olfactory adaptation; animals recall their exposure while intoxicated to an olfactory stimulus better if they are tested while intoxicated. C. elegans are an optimal model for studying the molecular underpinnings of SDL, as they have a simple 302-neuron nervous system with invariant neurocircuitry from animal to animal. The neurotransmitter dopamine is required for SDL, and animals with mutations in dopamine synthesizing genes, cat-1 and cat-2, do not learn state-dependently. These results suggest learning while intoxicated activates distinct SDL neurocircuitry that innervate and alter signaling of olfactory adaptation neurons. The ultimate goal of this work is to discover the circuit required for state dependency, and how this is regulated at the molecular level. Preliminary results show that a signaling peptide, hen-1, and a receptor tyrosine kinase, scd-2, are required for SDL. The hen-1 expressing neuron ASE-R is also required for SDL. The ASE-L neuron, which expresses almost all of the same genes as ASE-R with the exception of hen-1, is not required for SDL. In specific aim 1 I will test the sufficiency of hen-1 and scd-2 expression in ASE-R and AIA neurons respectively. Other preliminary results show octopamine deficient worms do not show SDL. The only neurons that release octopamine are RIC neurons. I will test constructs lacking the RIC neuron via genetic ablation for SDL. I have also demonstrated that SDL emerges from exposure to nicotine during olfactory learning in C. elegans. In specific aim 2 I will test for similarities in molecular mechanisms and neurocircuitry between SDL that emerge from ethanol and nicotine. I will also determine if SDL emerges in worms exposed to caffeine. Previously, a forward genetic screen was performed to find animals that are incapable of learning state-dependently during ethanol intoxication. A mutation, dubbed sdl-1, was isolated through selective screens. In specific aim 3 I will use genetic mapping and genomic sequencing to determine the molecular identity of sdl-1 and determine how the gene containing this mutation might promote SDL. Here, I hypothesize that SDL induced by ethanol intoxication has a distinct circuit that inputs onto olfactory adaptation neurocircuitry. My aims identify the molecular mechanism and neurocircuitry of this behavior by, 1) investigating hen-1/scd-2 and octopaminergic signals, 2) using other substances that may induce SDL, and 3) utilizing gene mapping to identify a novel gene associated with SDL.