Role of serotonin brain circuit in the developmental emergence ofinnate fear

恐惧是人类在感觉到或认识到危险或威胁时所产生的情绪。适应不良的恐惧 这种模式在焦虑症中很常见。恐惧反应是通过激活特定刺激来编排的 汇聚在中脑导水管周围灰质(PAG)的神经回路。针对5-羟色胺(5-羟色胺)系统的药物 减少焦虑和增加5-羟色胺水平可以减弱动物的恐惧反应。然而，5-羟色胺是如何发挥其 对恐惧行为的影响还不是很清楚。为了研究老鼠的恐惧样反应，我开发了一种 行为测试，其中捕食者的气味被呈现在一个房间里，允许快速地打开和关闭 刺激。我使用深度学习算法来分析行为。使用特定于投影的光遗传学，我已经 发现投射到PAG的5-羟色胺神经元可以改善类似恐惧的行为。在目标1和目标2中，我现在会 确定内源性5-羟色胺信号在PAG对威胁的正常行为反应中的作用。一种风险 成人焦虑样行为的因素是在生命早期增加的5-羟色胺，导致5-羟色胺的持久变化 功能。然而，具体的电路是如何受到影响的还不清楚。我发现化学遗传学或药理学 在出生后第2天到第11天，5-羟色胺信号的增加会导致成人恐惧反应的加剧。 在这个小鼠模型中的功能成像(FMRI)进一步显示了对 捕食者的气味。这些数据表明，发育过程中升高的5-羟色胺信号会产生长期的变化 在成人中，dlPAG中5-羟色胺的输入导致先天恐惧行为的增加。我将在下面测试这一假设 目标3.目标1使用遗传编码的5-羟色胺和钙离子传感器来同时监测5-羟色胺的输入和 通过纤维光度法检测dlPAG在行为过程中的谷氨酸或GABA能输出。AIM 2使用CRE- 依赖抑制性古紫质以光遗传方式抑制5-羟色胺进入dlPAG。AIM 3使用钙离子和 5-羟色胺传感器监测发育后恐惧行为dlPAG中5-羟色胺的输入和神经元输出 5-羟色胺能活性升高。最后，Aim 3还使用了我建立的DR(5-HT)到dlPAG的特定通路 光遗传学方案，以增强dlPAG中的5-羟色胺信号，试图挽救增加的恐惧样反应。 总之，我的目标将揭示支配5-羟色胺对PAG调制的基本原则，这 将提供对焦虑症的病理生理学和病因的洞察。 在我的培训过程中，我将致力于针对发育障碍的神经进行翻译发现 可以逆转不良适应行为的电路，总体目标是开发新的治疗方法 战略。我的职业发展计划充分利用了我以前在分子和发育方面的经验 神经生理学，并增加了电路和行为神经科学的专业知识。我已经聘请了一位强有力的导师 团队来指导我的科学努力和作为一名独立科学家的成长。我相信这个K01提案 结合关键的技术、智力和职业发展指导，帮助我实现我的科学目标 并推动我向建立独立研究计划的过渡。

Fear is the human emotion that is elicited when danger or threat are perceived or recognized. Maladaptive fear patterns are common in anxiety disorders. Fear responses are orchestrated by the activation of stimulus-specific neural circuits that converge in the periaqueductal gray (PAG). Drugs targeting the serotonin (5-HT) system decrease anxiety and increasing 5-HT levels attenuates fear responses in animals. Yet, how 5-HT exerts its effects on fear behavior is not well understood. To study fear-like responses in mice I have developed a behavioral assay, in which a predator odor is presented in a chamber that allows for fast on- and off-set of the stimulus. I use deep learning algorithms to analyze behavior. Using projection-specific optogenetics, I already found that 5-HT neurons projecting to the PAG ameliorate fear-like behavior. In Aim 1 and Aim 2 I will now determine the role of endogenous 5-HT signaling in the PAG during normal behavioral response to threat. A risk factor for adult anxiety-like behavior is increased 5-HT during early life that causes enduring changes in 5-HT function. Yet, how specific circuits are affected is not understood. I found that chemogenetic or pharmacologic increases in 5-HT signaling during postnatal (P) day 2 to 11 lead to exacerbated fear responses in the adult. Functional imaging (fMRI) in this mouse model furthermore revealed robust PAG hyperactivity in response to predator odor. These data suggest that developmentally elevated 5-HT signaling produces long-lasting changes in adult 5-HT input into the dlPAG resulting in increased innate fear-like behaviors. I will test this hypothesis in Aim 3. Aim 1 uses genetically encoded 5-HT and Ca2+ sensors to simultaneously monitor 5-HT input and glutamatergic or GABAergic output in the dlPAG during behavior via fiber photometry. Aim 2 uses Cre- dependent inhibitory Archaerhodopsin to optogenetically inhibit 5-HT input into the dlPAG. Aim 3 uses Ca2+ and 5-HT sensors to monitor 5-HT input and neuronal output in the dlPAG during fear behavior after developmentally elevated 5-HTergic activity. Lastly, Aim 3 also uses my established DR(5-HT)-to-dlPAG pathway specific optogenetic protocol to enhance 5-HT signaling in dlPAG in an attempt to rescue increased fear-like responses. Together my Aims will uncover fundamental principles that govern the modulation of the PAG by 5-HT, which will provide insight into pathophysiology and etiology of anxiety disorders. Throughout my training I will work towards translational discoveries targeting developmentally disrupted neural circuits such that maladaptive behaviors can be reversed, with the overall goal of developing new therapeutic strategies. My career development plan capitalizes on my prior experience in molecular and developmental neurophysiology and adds expertise in circuit and behavioral neuroscience. I have engaged a strong mentoring team to guide my scientific efforts and my growth as an independent scientist. I believe that this K01 proposal combines pivotal technical, intellectual, and career development guidance to help me address my scientific aims and promote my transition towards establishing an independent research program.