Neural Circuits for Reinstatement of Fear

 描述（由申请人提供）：目前项目的长期目标是揭示基本的神经回路的基础上休克诱导恢复熄灭的恐惧。恐惧相关的焦虑和创伤障碍（例如，恐惧症、恐慌症和创伤后应激障碍）是普遍存在的;它们给我们的社会带来了巨大的经济和社会负担。令人遗憾的是，这些疾病的治疗受到已消除的恐惧复发的困扰：在对病理性恐惧进行治疗干预后，威胁性和令人厌恶的事件可能重新唤醒恐惧。利用巴甫洛夫恐惧条件反射和大鼠的灭绝程序，该项目将研究大鼠暴露于危险（休克相关）环境后导致恐惧复发的行为和大脑机制（即，复职）。特别是，我们的实验室已经证明了床核的选择性作用， 终纹（BNST）介导的背景恐惧和恢复后的足电击熄灭的恐惧。其他人已经揭示，BNST病变也阻止应激反应（例如，皮质酮释放）时，动物是在厌恶的情况下。然而，还没有人使用现代工具来确定BNST促成这些效应的精确电路。BNST向杏仁核中央核（CeA）和下丘脑室旁核（PVN）发送重投射。CeA对于条件性恐惧的表达是必不可少的，而PVN在介导应激反应中具有重要作用。我们建议，BNST调制冻结和压力反应在冲击相关的上下文中，通过作用于这些结构，这种模式的活动可能有助于恢复。我们将在两个主要目标中检验我们的假设。在目的1中，我们将利用逆行（霍乱毒素亚单位B）神经元示踪技术结合免疫组织化学的神经活动的标志物（c-Fos），以确定活动模式的CeA和PVN投射细胞的BNST在厌恶的背景暴露（实验）。1）。此外，我们将使用顺行病毒追踪方法（单纯疱疹病毒1型，H129的荧光重组体）结合c-Fos检测来观察在恢复期间接受BNST输入的CeA/PVN细胞中的活性程度（Exp. 2）。目的2将询问BNST：CeA或BNST：PVN回路的失活是否以冻结和应激反应的形式对情境恐惧做出可分离的贡献（分别为; Exp. 3），以及BNST：CeA电路是否是BNST促进恐惧恢复的关键途径（实验3）。4）。使用腺相关病毒（AAV）载体的设计师受体专门激活的设计师药物（DREADDs），我们将选择性沉默BNST传出的CeA和PVN在暴露于休克相关的背景下，并在恢复恐惧。此外，我们将测量皮质酮的释放，以观察这些途径中的任何一个的失活是否能够在危险的环境中调节应激水平。反过来，该项目将提供有价值的科学和临床见解， 恐惧调节系统如何与大脑的压力活跃核团相互作用。

 DESCRIPTION (provided by applicant): The long-term goal of the current project is to reveal the essential neural circuits underlying the shock-induced reinstatement of extinguished fear. Fear-related anxiety and trauma disorders (e.g., phobias, panic disorder, and post-traumatic stress disorder) are prevalent and pervasive; they represent a tremendous economic and social burden on our society. Regrettably, treatments for these illnesses are plagued by the relapse of extinguished fear: threatening and aversive events can reawaken fear responding after therapeutic interventions for pathological fear. Utilizing Pavlovian fear conditioning and extinction procedures in rats, this project will investigate the behavioral and brain mechanisms contributing to fear relapse after the exposure of rats to a dangerous (shock-associated) context (i.e., reinstatement). In particular, our lab has demonstrated a selective role for the bed nucleus of the stria terminalis (BNST) in mediating contextual fear and the reinstatement of extinguished fear after footshock. Others have revealed that BNST lesions also prevent stress responding (e.g., corticosterone release) when animals are in aversive contexts. However, no one has yet used modern tools to identify the precise circuits through which the BNST contributes to these effects. The BNST sends heavy projections to the central nucleus of the amygdala (CeA) and the paraventricular nucleus of the hypothalamus (PVN). The CeA is essential for the expression of conditioned fear, whereas the PVN has an important role in mediating stress responses. We propose that the BNST modulates freezing and stress responses in a shock-associated context by acting on these structures; this pattern of activity may contribute to reinstatement. We will test our hypothesis in two primary aims. In Aim 1, we will utilize retrograde (cholera toxin subuni B) neuronal tracing techniques combined with immunohistochemistry for markers of neural activity (c-Fos) to identify patterns of activity in CeA- and PVN-projecting cells of the BNST during aversive context exposure (Exp. 1). Additionally, we will use anterograde viral tracing methods (fluorescent recombinants of herpes simplex virus type 1, H129) combined with c-Fos detection to observe the degree of activity in CeA/PVN cells receiving BNST input during reinstatement (Exp. 2). Aim 2 will ask whether inactivation of BNST:CeA or BNST:PVN circuits make dissociable contributions to context fear, in the form of freezing and stress responding (respectively; Exp. 3), and whether BNST:CeA circuits are the critical pathway by which BNST promotes reinstatement of fear (Exp. 4). Using adeno-associated viral (AAV) vectors for designer receptors exclusively activated by designer drugs (DREADDs), we will selectively silence BNST efferents to the CeA and PVN during exposure to a shock-associated context and during reinstatement of fear. Additionally, we will measure corticosterone release to observe whether inactivation of either of these pathways is capable of modulating stress levels during in a dangerous context. In turn, this project will provide valuable scientific and clinical insight on how fear-regulating systems interact with stress-active nuclei of the brain.