The Role of Gamma-Aminobutyric Acid- (GABA-)ergic Long-Range Projections in Fear Inhibition

恐惧和焦虑相关障碍是全球最常见的精神疾病之一，由于俄乌战争和新冠肺炎相关的社会经济和健康相关后果，这种疾病有增加的趋势。大规模神经元网络的协调行动，即通过远程连接连接在一起的局部电路组件，对于正常的大脑功能和行为调节至关重要。然而，虽然杏仁核（一个调节恐惧的关键脑区）中局部抑制回路的作用已被广泛表征，但GABA能长距离投射的参与却被忽视了。为了克服这一知识空白，本项目旨在研究抑制性GABA能长距离投射到中央杏仁核是否直接影响恐惧和焦虑相关的行为。通过利用囊泡GABA转运蛋白（VGAT）-IRES-Cre小鼠和病毒示踪方法的组合，沿着深层组织免疫组织化学和3D全脑组织清除/成像，本课题首先筛选GABA能长距离投射神经元向中央杏仁核的分布（目的1）。为了具体了解GABA能长距离投射神经元如何介导恐惧及其抑制，将通过设计药物专门激活的设计受体和体内钙成像来验证功能相关的GABA能长距离投射及其起源脑区（目标2）。为了进一步阐明这些投射影响恐惧行为的分子和细胞机制，我将应用三维单细胞成像和荧光原位杂交链反应来寻找新的药物干预措施（目标3）.该项目将促进我们对存在，性质，和中央杏仁核中长距离投射GABA能神经元的可能功能，并确定神经元激活模式的因果变化，这反过来又代表了解剖潜在的分子和治疗机制的把手。

Fear and anxiety-related disorders are one of the most prevalent psychiatric disorders worldwide, with an increasing tendency due to the Russo-Ukrainian war and Covid-19-related socio-economic and health-related consequences. The coordinated action of large-scale neuronal networks, that is, local circuit components that are linked together by long-range connections, is essential for proper brain functioning and the modulation of behavior. However, while the role of local inhibitory circuits in the amygdala, a key brain region for the modulation of fear, has been extensively characterized, the involvement of GABAergic long-range projections has been overlooked. To overcome this gap in knowledge, the current project aims to investigate whether inhibitory GABAergic long-range projections to the central amygdala directly influence fear- and anxiety-related behaviors.By utilizing Vesicular GABA Transporter (VGAT)-IRES-Cre mice and a combination of viral tracing methods, along with deep-tissue immunohistochemistry and 3D-whole-brain tissue clearing / imaging, this project will first screen the distribution of GABAergic long-range projection neurons to the central amygdala (Objective 1). To specifically understand how GABAergic long-range projection neurons mediate fear and its inhibition, the functionally relevant GABAergic long-range projections and their originating brain regions will be validated by means of Designer receptors exclusively activated by designer drugs and in vivo calcium imaging (Objective 2). To further characterize the molecular and cellular mechanisms through which the identified projections act to affect fear behavior, I will apply 3-D single cell imaging and fluorescence in situ hybridization chain reaction in order to find new pharmacological interventions (Objective 3).The project will advance our knowledge about the existence, properties, and possible functions of long-range projecting GABAergic neurons in the central amygdala and identify causal changes in neuronal activation patterns, which in turn represent the handle with which to dissect both the underlying molecular and therapeutic mechanisms.