Lateral Habenula in Stress and Resilience

 描述(由申请人提供)：目前可用的抗抑郁药只对部分患有抑郁症和其他压力相关障碍的人有效。因此，确定治疗抑郁症的新靶点是一项紧迫的健康任务。外侧缰核(LHb)是一个小的、双侧的结构，似乎扮演着重要的中继点角色 连接参与情绪控制的几个关键大脑区域，如中缝背核(DRN)、腹侧被盖区(VTA)和被盖头内侧核(RMTG)。人们对LHb的详细神经化学知之甚少。我们知道，LHb在调节与情绪、奖励和动机有关的负面或厌恶情绪状态方面起着关键作用。在人类和动物模型上的初步研究表明，LHb可能是治疗难治性抑郁症的重要靶点。例如，我们发现，在强迫游泳模型中，GI偶联的抑制性DREADD hM4Di在LHb中的表达和激活产生了抗抑郁作用。该项目的主要技术策略将是使用两种类型的病毒载体在大鼠中交叉表达转基因：AAV-DIO-转基因载体(注射到LHb中)和CAV2-Cre载体(注射到投射靶区之一-DRN、VTA或RMTG)。这些载体加在一起，只在所需途径的神经元中产生转基因表达。这一策略将被用来操纵这些离散通路的活动(使用DREADD)，以及询问每个通路中的mRNA翻译(使用RiboTag)。目标1将测试这些LHb通路中的哪一个负责在强迫游泳测试中调节不动。我们预测，调节LHb到DRN的通路将改变静止，并且用氯氮平-N-氧化物激活Gi偶联的DREADD将减少静止，而激活Gs偶联的DREADD将加剧静止。目的2将利用DREADDS选择性地激活或抑制这些通路，评估这些通路对应激相关情绪状态的不同领域的贡献，如快感缺失(糖精偏好)、焦虑(开放领域)和情绪学习(条件性位置厌恶)。目标3将评估LHb通路如何改变行为脆弱性或韧性的出现，以应对反复的社会失败压力。AIM 4将使用表位标记的核糖体蛋白RiboTag选择性地免疫纯化转导途径中的多聚核糖体，随后进行RNAseq和验证显著不同的mRNAs。这将使我们能够评估每条通路中神经元的基因表达表型，并研究LHb神经元对应激暴露和抗抑郁治疗的反应。这将是识别监管网络和潜在控制节点的有力方法，可以促进对压力的弹性。总之，这些实验将提供大量关于LHb的功能组织及其在应激动物模型中的作用的新信息，并可能有助于确定LHb中可用于治疗应激障碍的新的分子靶点。

 DESCRIPTION (provided by applicant): Currently available antidepressants work well for only a subset of individuals with depression and other stress-related disorders. Therefore, identifying new targets for treating depression is an urgent health imperative. The Lateral Habenula (LHb) is a small, bilateral structure that appears to play a critical role as a relay node connecting several key brain regions that are involved in mood control such as the dorsal raphe nucleus (DRN), ventral tegmental area (VTA), and the rostromedial tegmental nucleus (RMTG). The detailed neurochemistry of the LHb is poorly understood. We know that LHb plays a critical role in mediating negative or aversive emotional states relating to mood, reward, and motivation. Pilot studies in humans and animal models suggest that the LHb may be an important target for treating refractory depression. For example, we found that the expression and activation of hM4Di, a Gi-coupled inhibitory DREADD, in LHb produced an antidepressant effect in the forced swim test model of antidepressant action. The primary technical strategy for this project will be the use of intersectional transgene expression in rats using two types of viral vectors: AAV-DIO-transgene vectors (injected into LHb) and CAV2-Cre vectors (injected into one of the projection target regions-DRN, VTA or RMTG). Together these vectors produce transgene expression only in neurons of the desired pathway. This strategy will be used to manipulate the activity of these discrete pathways (with DREADDs) as well as to interrogate mRNA translation in each (with RiboTag). Aim 1 will test which of these LHb pathways is responsible for modulating immobility in the forced swim test. We predict that modulating the LHb to DRN pathway will alter immobility, and that activating the Gi-coupled DREADD with the ligand clozapine-N-oxide will reduce immobility whereas activating the Gs-coupled DREADD will exacerbate immobility. Aim 2 will assess the contribution of these pathways to different domains of stress-related emotional states such as anhedonia (saccharin preference), anxiety (open field), and emotional learning (conditioned place aversion) using DREADDs that activate or inhibit these pathways selectively. Aim 3 will assess how LHb pathways alter the emergence of behavioral vulnerability or resilience in response to repeated social defeat stress. Aim 4 will use RiboTag, an epitope-tagged ribosomal protein, to selectively immunopurify the polyribosomes from the transduced pathways followed by RNAseq and validation of significantly different mRNAs. This will allow us to evaluate the gene expression phenotypes of neurons in each pathway, and to investigate how LHb neurons respond to stress exposure as well as antidepressant treatment. It will be a powerful method for identifying regulatory networks and potential nodes of control that can promote resilience to stress. Together, these experiments will provide a great deal of new information about the functional organization of LHb, its role in animal models of stress, and may help to identify new molecular targets in LHb that can leveraged in the treatment of stress disorders.