Neural Circuits for Reinstatement of Fear

 描述(由申请者提供)：当前项目的长期目标是揭示电击诱导的消除恐惧恢复的基本神经回路。与恐惧相关的焦虑和创伤障碍(如恐惧症、恐慌症和创伤后应激障碍)非常普遍和普遍；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消除恐惧复发的困扰：在对病理性恐惧进行治疗干预后，威胁和厌恶事件可以重新唤醒恐惧反应。利用大鼠的巴甫洛夫恐惧条件反射和消退程序，该项目将调查导致大鼠暴露在危险(休克相关)环境(即恢复)后恐惧复发的行为和大脑机制。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)在调节情景恐惧和足底电击后消除恐惧的恢复中起作用。其他研究表明，当动物处于厌恶环境中时，BNST损伤也可以防止应激反应(例如皮质酮释放)。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回路。BNST向杏仁中央核(CEA)和下丘脑室旁核(PVN)发出大量投射。CEA对于条件性恐惧的表达是必不可少的，而PVN在调节应激反应中起着重要作用。我们认为，BNST通过作用于这些结构来调节休克相关背景下的冻结和应激反应；这种活动模式可能有助于恢复。我们将在两个主要目标上检验我们的假设。在目标1中，我们将利用逆行(霍乱毒素B亚单位)神经元追踪技术结合神经活动标记物的免疫组织化学(c-Fos)来确定在厌恶环境暴露(Exp.1)。此外，我们将使用顺行病毒示踪方法(1型单纯疱疹病毒H129的荧光重组体)结合c-Fos检测来观察在恢复过程中接受BNST输入的CEA/PVN细胞的活动程度(Exp。2)。目标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背景恐惧做出不可分离的贡献(分别为；Exp。3)，以及BNST：CEA回路是否是BNST促进恐惧恢复的关键途径(实验4)。使用腺相关病毒(AAV)载体携带由设计药物(DREADD)特异性激活的设计受体(DREADD)，我们将在暴露于休克相关环境中和恢复恐惧期间选择性地沉默CEA和PVN的BNST传出。此外，我们将测量皮质酮的释放，以观察这两个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，该项目将为以下方面提供宝贵的科学和临床见解 恐惧调节系统如何与大脑的压力活性核团相互作用。

 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.