Identifying the neural ensembles mediating fear generalization during adolescence

项目总结/摘要 在焦虑症和创伤后应激障碍（PTSD）中观察到的一个核心症状是恐惧增加 泛化，定义为恐惧从条件化的、引起恐惧的刺激过度泛化到 中性刺激恐惧泛化会导致在安全环境中的适应不良反应。本实验室 使用一种称为情境恐惧辨别（CFD）的行为分析来评估小鼠的恐惧泛化。我们 在一个情境中电击一只老鼠（情境A），然后我们可以测量它们是否能区分 这种令人厌恶的，休克配对的背景和类似的，但安全的背景（背景B）超过大约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 小鼠过度概括恐惧; 2）成年雌性，但不是成年雄性小鼠过度概括恐惧;和3） 男女都过度概括恐惧，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概括的影响。然而，调节恐惧的神经系统 在整个生命周期中的泛化还有待确定。在这份拨款申请中，我们将使用CFD 范例，结合活性依赖性标记遗传小鼠系来鉴定和 操纵神经系综介导恐惧泛化。 在目标1中，我们将识别和量化青少年介导恐惧泛化的神经系综 和成年小鼠。这条鼠标线允许不可磨灭的标签， 表达立即早期基因（IEG）Arc/Arg3.1的细胞，并允许比较 在记忆的编码过程中被激活，而在记忆的提取过程中被激活的那些， 对应的记忆，其中两个群体之间的重叠被定义为印迹或记忆 跟踪。因此，使用我们的活动依赖性标记小鼠系，我们可以确定性别和 年龄影响整个大脑的恐惧概括神经系统。 在目标2中，我们将连续操纵青少年和成年小鼠，目的是提高 行为恐惧过度概括和相应的神经回路。在过去的二十年里，（R，S）- 克他命已经成为一种快速起效的抗抑郁药。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小鼠将被给予单次皮下注射。 生理盐水或（R，S）-氯胺酮剂量。将使用CFD和离体全脑成像来识别 潜在的神经系统这项研究的结果将提供直接的证据，改变神经 合奏导致恐惧过度泛化，（R，S）-氯胺酮有可能减少恐惧 过度概括，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.