The Potential Role of CRF Neurons in Mediating Onset of Stress-induced Susceptibility via PVT-BNST Connectivity

项目摘要 严重抑郁障碍(MDD)是最常见的精神疾病，终生患病率为五分之一， 其治疗目前处于次优状态。应对持续的慢性应激源的能力缺陷是 MDD的主要易感因素。丘脑室旁核(PVT)神经元在情绪中起关键作用 唤醒和协调与压力相关的适应性神经体液反应。此外，一个突触靶点 PVT是终纹床核(BNSTov)的椭圆形核，调节行为反应 通过促肾上腺皮质激素释放因子(CRF)释放神经元应激。PVT在调节 对慢性应激的相关神经体液反应，被认为是通过PVT-BNSTov的CRF神经元发生的 巡回赛。此外，我在大鼠和组织中有初步的电生理学和单细胞qRT-PCR数据 在小鼠中，慢性应激伴随着神经元兴奋性的增加和 选择性增强CRF及其受体1基因在BNSTov中的表达。假设这些细胞是 在PVT突触的直接影响下，这可能代表PVT介导的适应性反应。有趣的是， 与急性应激不同，在慢性应激中，PVT介导的适应性神经反应似乎是暂时的 与压力适应的实际行为表现无关。因此，该PVT-BNSTov电路 可能是慢性压力转化为抑郁样行为的潜伏期。要确定 应激性抑郁样行为出现的时间进程，我采用了慢性社会失败 小鼠应激(CSDS)范式，并在不同的应激条件下进行社会互动/蔗糖偏好测试 持续时间为4-10天。我观察到，在CSDS的7到10天之间，动物经历了一个转变 从社交方式(“弹性”)到社交回避(“易受影响”)的表型。电生理学和 这种快速行为转变背后的分子底物尚不清楚。我假设PVT-BNSTov 连接性可能支配着面对持续的压力易感性的暂时出现 心理社会应激，通过PVT突触对CRF BNSTov神经元的影响。我计划调查这件事 使用电生理、单细胞转录和高级光学技术的功能性PVT-BNSTov电路 电路剖析方法(DREADD)。首先，我将通过关联轨迹来建立功能连接 和c-Fos活性，并在捕捉行为开关的时间段内共同出现(目标1)。然后，我 将在体外全细胞膜片钳中记录固有的神经元特性并获取细胞质 行为转变前后细胞的单细胞qRT-PCR分析(目标2)。最后，我将建立 PVT-BNST回路通过时间和回路特异性调节易感性的暂时性发作的必要性 使用DREADD的操作(目标3)。这一建议的最先进的电路和单元类型特定 手法将为MDD病因学基础上的应激侮辱依赖机制提供新的见解， 这将为MDD提供更有效的治疗策略。

Project Summary Major Depressive Disorder (MDD) is the most common psychiatric disorder with a lifetime prevalence of 1 in 5, treatment for which is currently suboptimal. Deficits in ability to cope with ongoing chronic stressors are one of the chief predisposing factors to MDD. Neurons of the Paraventricular Thalamus (PVT) are critical in emotional arousal and orchestrate adaptive stress-relevant neurohumoral responses. Furthermore, a synaptic target of the PVT, the oval nucleus of the Bed Nucleus of the Stria Terminals (BNSTov), regulates behavioral responses to stress through Corticotropin-Releasing Factor (CRF)-releasing neurons. The PVT is critical in regulating relevant neurohumoral responses to chronic stress, thought to occur via CRF-neurons of a PVT-BNSTov circuit. Additionally, I have preliminary electrophysiological and single-cell qRT-PCR data in the rat and tissue micropunches in the mouse, that chronic stress accompanies increases in neuronal excitability and enhancement of crf and crf receptor 1 gene expression selectively in the BNSTov. Given that these cells are under direct PVT synaptic influence, this could represent a PVT-mediated adaptive response. Interestingly, unlike in acute stress, in chronic stress, PVT mediated adaptive neural responses appear to be temporally independent of the actual behavioral expression of that stress adaptation. Therefore, this PVT-BNSTov circuit may underlie the latency in the conversion of chronic stress into depressive-like behaviors. To determine the time course wherein stress-induced depressive-like behavior emerges, I employed the Chronic Social Defeat Stress (CSDS) paradigm in mice, and conducted social interaction/sucrose preference testing at various stress duration lengths of 4-10 days. I observed that between 7 and 10 days of CSDS, animals underwent a switch from social approach (“resilient”) to socially avoidant (“susceptible”) phenotypes. The electrophysiological and molecular substrates underlying this rapid behavioral shift remains unknown. I hypothesize that PVT-BNSTov connectivity may govern the temporal emergence of stress susceptibility in the face of persistent psychosocial stress, through PVT synaptic influence on CRF BNSTov neurons. I plan to investigate this functional PVT-BNSTov circuit using electrophysiological, single-cell transcriptomics, and advanced optical circuit dissection methods (DREADDs). First, I will establish functional connectivity by correlating tract tracing and c-Fos activity with the co-occurrence over the time period capturing the behavioral switch (aim 1). Then, I will record in ex-vivo whole-cell patch clamp the intrinsic neuronal properties and procure the cytoplasm for single-cell qRT-PCR analysis in cells before or after the behavioral transition (aim 2). Lastly, I will establish the necessity of the PVT-BNST circuit in mediating the temporal onset of susceptibility via time- and circuit-specific manipulations using DREADDs (aim 3). This proposed state-of-the-art circuit- and cell-type specific manipulations will provide novel insight into stress insult-dependent mechanisms that underlie MDD etiology, which will give rise to more effective therapeutic strategies for MDD.