Identifying the neural ensembles mediating fear generalization during adolescence

项目摘要/摘要 焦虑症和创伤后应激障碍(PTSD)的核心症状是恐惧增加 泛化，泛化的定义是将恐惧从一种条件性的、引起恐惧的刺激过度泛化为 中性刺激。在安全的环境中，恐惧泛化会导致不适应的反应。我们的实验室 使用一种名为情景恐惧歧视(CFD)的行为分析来评估小鼠的恐惧概括性。我们 在一个上下文(上下文A)中敲击鼠标，然后我们可以衡量它们是否可以区分 这一令人厌恶的、令人震惊的配对情景和类似但安全的情景(情景B)持续了大约10天 辨别学习。在我们最近的出版物中，我们表明：1)青春期男性，而不是青春期女性 小鼠过度泛化恐惧；2)成年雌性小鼠过度泛化恐惧，但成年雄性小鼠不是；3)老年小鼠 男女都过分泛化恐惧，不能区分两种情况。因此，显然有一个 年龄和性别对恐惧过度泛化的影响。然而，调节恐惧的神经集合 对整个寿命的概括还有待确定。在这份拨款提案中，我们将使用此CFD 范例，结合依赖活动的标记遗传小鼠品系来识别和 药理上操纵神经集合，调节恐惧的泛化。 在目标1中，我们将识别和量化调节青少年恐惧泛化的神经集合 和成年小鼠，利用ArcCreERT2 x EYFP小鼠。这一鼠标线允许不可磨灭的标签 表达即刻早期基因(IEG)Arc/Arg3.1的细胞，并允许比较 在对记忆进行编码期间被激活，而在检索期间被激活 相应的记忆，两个群体之间的重叠被定义为印记或记忆 痕迹。因此，使用我们的依赖活动的标记小鼠品系，我们可以确定在哪里以及如何发生性行为 年龄影响恐惧的泛化，整个大脑都有神经集合。 在目标2中，我们将对青春期和成年期的小鼠进行药物操作，目标是改善 行为恐惧过度泛化和相应的神经回路。近二十年来，(右)S-- 氯胺酮已经成为一种快速起作用的抗抑郁药。有趣的是，我们已经报道了(R，S)-氯胺酮 减少恐惧泛化。在这里，雄性和雌性青春期和成年期的小鼠将分别接受一次 生理盐水或(R，S)-氯胺酮。将使用CFD和体外全脑成像来识别 潜在的神经系综群。这项研究的结果将提供改变神经的直接证据 合奏导致恐惧过度泛化，(R，S)-氯胺酮具有减少恐惧的潜力 过度泛化，焦虑症和创伤后应激障碍的核心系统。

PROJECT SUMMARY / ABSTRACT A core symptom observed in anxiety disorders and post-traumatic stress disorder (PTSD) is increased fear generalization, as defined by the overgeneralization of fear from a conditioned, fear-inducing stimulus to neutral stimuli. Fear generalization can lead to maladaptive responses in a safe environment. Our laboratory uses a behavioral assay called contextual fear discrimination (CFD) to assess fear generalization in mice. We shock a mouse in one context (context A), and then we can measure whether they can discriminate between this aversive, shock-paired context and a similar, but safe context (context B) over approximately 10 days of discrimination learning. In our recent publications, we show that 1) adolescent male, but not adolescent female mice overgeneralize fear; 2) adult female, but not adult male mice overgeneralize fear; and 3) aged mice of both sexes overgeneralize fear and cannot discriminate between two contexts. Therefore, there is clearly an age- and sex-dependent influence on fear overgeneralization. However, the neural ensembles mediating fear generalization across the lifespan have yet to be identified. In this grant proposal, we will use this CFD paradigm, in combination with an activity-dependent tagging genetic mouse line to identify and pharmacologically manipulate the neural ensembles mediating fear generalization. In Aim 1, we will identify and quantify the neural ensembles mediating fear generalization in adolescent and adult mice by utilizing the ArcCreERT2 x EYFP mice. This mouse line allows for the indelible labeling of cells expressing the immediate early gene (IEG) Arc/Arg3.1 and allows for a comparison between the cells that are activated during the encoding of a memory and those that are activated during the retrieval of the corresponding memory, with the overlap between the two populations being defined as an engram or memory trace. Therefore, using our activity-dependent tagging mouse line, we can determine where and how sex and age impact fear generalization neural ensembles throughout the brain. In Aim 2, we will pharmacologically manipulate adolescent and adult mice with the goal of improving behavioral fear overgeneralization and the corresponding neural circuits. In the last two decades, (R,S)- ketamine has emerged as a rapid-acting antidepressant. Interestingly, we have reported that (R,S)-ketamine decreases fear generalization. Here, male and female adolescent and adult mice will be administered a single dose of saline or (R,S)-ketamine. CFD and ex vivo whole-brain imaging will be used in order to identify the underlying neural ensembles. The outcome of this study will provide direct evidence that altered neural ensembles result in fear overgeneralization, and that (R,S)-ketamine has the potential to decrease fear overgeneralization, a core system of anxiety disorders and PTSD.