Endocannabinoid regulation of a septohabenular circuit in anxiety and depression

项目摘要 焦虑和抑郁是非常普遍的神经精神疾病，会导致相当大的发病率和 死亡率。NIMH的首要任务是阐明与复合体相关的分子、细胞和神经回路 行为，包括焦虑和抑郁(NIMH战略目标1.1)。内侧缰核(MHB)是 保存完好的上丘脑结构是恐惧和逃避行为的强大调节器 斑马鱼和啮齿动物的焦虑和抑郁行为，核磁共振显示减少 在患有抑郁症的人类中的体积。MHB神经元的输出受到它们的突触输入的影响，例如 来自内侧隔核和斜角带核(MSDB)，它提供了唯一被识别的 对MHB的GABA能输入。我们已经产生的初步数据表明，CB1受体通过 内源性大麻素或由CB1受体激动剂抑制MHB中的GABA能输入。在这些指导下 令人兴奋的发现，我们假设2-AG/CB1信号通过以下途径增加MHB神经元的输出 抑制MSDB的输入和解除MHB神经元的抑制，导致抗焦虑和抗抑郁药样 对行为的影响。这一假设将通过两个具体目标进行检验。在目标I中，我们将确定是否具有功能性 CB1受体在MSDB至MHB轴突终末的表达及其激活对MHB神经元的影响 输出。我们将使用病毒载体在MSDB中表达ChR2，并选择性地激活MSDB轴突终末 通过光发生刺激来支配MHB神经元。然后我们将检查CB1受体是否 激活改变MHB中光诱导的抑制性突触后电流和动作电位放电 神经元。在AIM II中，我们将确定MSDB到MHB中2-AG/CB1信令的功能增减 电路影响CB1介导的对MSDB输入的抑制，并检验这种双向抑制的假设 改变焦虑和抑郁的行为。通过定向删除CB1来实现功能丧失 受体，虽然功能的获得是通过靶向删除降解2-AG的酶来实现的， 单酰甘油脂肪酶。在完成这个项目的过程中，学员将掌握广泛而有力的 实验技术，如体外切片电生理学、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、药理学和动物行为分析。 此外，这项拟议的研究将扩大我们对焦虑和焦虑的神经基础的了解 抑郁障碍，以及它们是如何受到欧洲央行信号调控的。

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.