Synaptic and neuronal mechanisms of fear control: the role of hippocampal-amygdalar interactions

从腹侧海马体（vHPC）到杏仁核（其基底外侧核（BLA））的投射，特别是， 在杏仁核的恐惧记忆消退编码过程中的背景表征中起着至关重要的作用。 然而，突触和网络水平的机制，其中vHPC-杏仁核投射可能控制的功能， 杏仁核和杏仁核依赖的恐惧相关行为在很大程度上是未知的。结合使用 离体和体内电生理学的化学遗传学和光遗传学技术，用病毒示踪的道 载体和行为训练和测试，我们将探讨vHPC-杏仁核投射的功能作用， 条件性恐惧和恐惧消退在突触和电路具体水平。在目标1中，我们将研究 vHPC投射到杏仁核亚核中的突触可塑性机制影响了杏仁核中的信号流。 恐惧制约和消退的神经回路光遗传学激活vHPC-杏仁核投射，我们将 记录来自杏仁核不同分区的神经元的切片，这些切片来自控制组、恐惧条件组和恐惧条件组， 并分析行为训练对记录的兴奋性和抑制性驱动的影响。 神经元及其突触驱动的尖峰放电输出。然后我们将探讨vHPC-杏仁核的作用， 控制恐惧相关行为的途径（目的2）。具体来说，我们将研究的贡献， 行为诱导的杏仁核vHPC输入的突触可塑性，特别关注长距离 GABA能vHPC-BLA投射（由我们鉴定），对恐惧消退的背景依赖性编码 使用化学遗传学工具记忆。我们还将系统地探讨是否与预防相关 增强vHPC-BLA投射的GABA能突触传递可能满足突触传递的标准。 可塑性和记忆（SPM）假说，因此可能将这些塑料突触修饰与 恐惧消退的情境依赖性编码。最后（目标3），我们将研究突触和神经 vHPC-杏仁核投射中的回路水平机制与反复应激引发的恐惧更新有关 在恐惧中消灭了老鼠。我们假设反复的压力可能会影响灭绝的机制- 触发vHPC-BLA投射中的突触可塑性，损害上下文表征，因此，可能 导致恐惧的重生我们的研究可以确定特定的突触机制和神经投射， 有可能成为治疗涉及恐惧系统功能障碍的疾病的靶点 大脑。

Projections from the ventral hippocampus (vHPC) to the amygdala, its basolateral nucleus (BLA), specifically, play an essential role in context representation in the amygdala during encoding of fear memory extinction. However, synaptic and network-level mechanisms by which vHPC-amygdala projections may control the function of the amygdala and amygdala-dependent fear-related behaviors are largely unknown. Combining the use of chemogenetic and optogenetic techniques with ex vivo and in vivo electrophysiology, tract tracing with viral vectors and behavioral training and testing, we will explore the functional roles of vHPC-amygdala projections in conditioned fear and fear extinction at synaptic and circuitry-specific levels. In Aim 1 we will investigate how the mechanisms of synaptic plasticity in vHPC projections to subnuclei of the amygdala affect the signal flow in neural circuits of fear conditioning and extinction. Optogeneticaly activating vHPC-amygdala projections, we will record from neurons in different subdivisions of the amygdala in slices from control, fear-conditioned and fear- extinguished mice and assay the effects of behavioral training on both excitatory and inhibitory drive in recorded neurons and their synaptically-driven spike firing output. We will then explore the role of the vHPC-amygdala pathway in control of fear-related behaviors (Aim 2). Specifically, we will examine the contributions of behaviorally-induced synaptic plasticity at vHPC inputs to the amygdala, specifically focusing on long-range GABAergic vHPC-BLA projections (identified by us), to the encoding of context-dependency of fear extinction memory using chemogenetic tools. We will also systematically explore whether extinction-associated potentiation of GABAergic synaptic transmission at vHPC-BLA projections may satisfy criteria of synaptic plasticity and memory (SPM) hypothesis, thus possibly linking these plastic synaptic modifications to the encoding of context-dependency of fear extinction. Finally (Aim 3), we will investigate the synaptic and neural circuit-level mechanisms in vHPC-amygdala projections implicated in fear renewal triggered by repeated stress in fear extinguished mice. We hypothesize that repeated stress may affect the mechanisms of extinction- triggered synaptic plasticity in vHPC-BLA projections, impairing context representation, and, therefore, possibly resulting in fear renewal. Our studies could identify specific synaptic mechanisms and neural projections which could potentially be targeted for therapeutic treatments of disorders implicating dysfunctions of the fear system of the brain.