Endocannabinoid regulation of a septohabenular circuit in anxiety and depression

项目摘要 焦虑和抑郁是高度流行的神经精神障碍，其导致大量的发病率和死亡率。 mortality. NIMH的一个首要任务是阐明与复杂的神经系统相关的分子、细胞和神经回路。 焦虑和抑郁（NIMH战略目标1.1）。内侧缰核（MHb）是一个 一个保存良好的上丘脑结构，已知是一个强大的恐惧和逃避行为的调制器， 斑马鱼和焦虑和抑郁样行为的啮齿类动物，并已显示由MRI减少 在抑郁症患者中的数量。MHb神经元的输出受到其突触输入的影响，例如 从内侧隔和斜角带核（MSDB），这提供了唯一的识别 GABA能输入MHb。我们已经产生了初步的数据，表明CB 1受体的激活， 内源性大麻素或CB 1受体激动剂抑制MHb中的GABA能输入。时遵循这些 令人兴奋的发现，我们假设2-AG/CB 1信号通过以下途径增加MHb神经元的输出： MSDB输入的抑制和MHb神经元的去抑制，导致抗焦虑和抗抑郁样 行为效应这一假设将通过两个具体目标进行检验。在目标I中，我们将确定功能性 CB 1受体在MSDB至MHb轴突终末上表达及其活化如何影响MHb神经元 输出.我们将使用病毒载体在MSDB中表达ChR 2并选择性激活MSDB轴突末端 通过光遗传学刺激支配MHb神经元。然后我们将研究CB 1受体是否 激活改变MHb中光诱导的抑制性突触后电流（IPSC）和动作电位放电 神经元在目标II中，我们将确定MSDB中2-AG/CB 1信号传导功能的获得或丧失如何影响MHb 电路影响CB 1介导的MSDB输入抑制，并测试这一假设，双向 改变类似焦虑和抑郁的行为。通过CB 1的靶向缺失实现功能丧失 受体，而通过靶向缺失降解2-AG的酶来实现功能获得， 单酰基甘油脂肪酶在完成这个项目，学员将掌握广泛的强大的 实验技术，例如离体切片电生理学、光遗传学、共聚焦成像、原位 杂交和免疫组织化学、病毒显微注射、药理学和动物行为测定。 此外，拟议的研究将扩大我们对焦虑背后的神经基质的了解， 抑郁症，以及它们如何通过eCB信号调节。

Project Summary Anxiety and depression are highly prevalent neuropsychiatric disorders which cause substantial morbidity and mortality. A top priority of NIMH is to elucidate the molecules, cells, and neural circuits associated with complex behaviors, including anxiety and depression (NIMH Strategic Objective 1.1). The medial habenula (MHb) is a well-conserved epithalamic structure known to be a powerful modulator of fear and escape behavior in zebrafish and anxiety- and depressive-like behaviors in rodents, and has been shown by MRI to be decreased in volume in humans with depression. The output of MHb neurons is impacted by their synaptic inputs, such as from the medial septum and nucleus of the diagonal band (MSDB), which provides the sole identified GABAergic input to the MHb. We have generated preliminary data showing that CB1 receptor activation by endocannabinoids or by a CB1 receptor agonist suppresses GABAergic inputs in the MHb. Guided by these exciting findings, we hypothesized that 2-AG/CB1 signaling increases the output of MHb neurons via suppression of the MSDB input and disinhibition of MHb neurons, resulting in anxiolytic and antidepressant-like behavioral effects. This hypothesis will be tested via two Specific Aims. In Aim I, we will determine if functional CB1 receptors are expressed on MSDB to MHb axon terminals and how their activation affects MHb neuronal output. We will use viral vectors to express ChR2 in the MSDB and selectively activate MSDB axonal terminals that innervate MHb neurons through optogenetic stimulation. We will then examine whether CB1 receptor activation alters light-induced inhibitory postsynaptic currents (IPSCs) and action potential firing in MHb neurons. In Aim II, we will determine how gain- or loss-of-function in 2-AG/CB1 signaling in the MSDB to MHb circuit affects CB1-mediated suppression of MSDB inputs, and test the hypothesis that this bi-directionally alters anxiety- and depression-like behaviors. Loss-of-function is achieved via targeted deletion of CB1 receptors, while gain-of-function is achieved by targeted deletion of the enzyme that degrades 2-AG, monoacylglycerol lipase. In completing this project, the trainee will master a wide range of powerful experimental techniques, such as ex vivo slice electrophysiology, optogenetics, confocal imaging, in situ hybridization and immunohistochemistry, viral microinjection, pharmacology, and animal behavior assays. Further, the proposed research will expand our knowledge of the neural substrates underlying anxiety and depressive disorders, and how they are regulated by eCB signaling.