Origin, mechanism, and behavioral context of persistent firing in cortical parvalbumin-positive interneurons

项目摘要 神经元是大脑的基本处理和交流单位，通常使用动作电位来传递信息。 信息从细胞体附近的部位通过轴突传递到神经递质释放终端。动作电位 在某些情况下，也可以沿着轴突向细胞体和树突反向传播;我指的是这些 这里是“异位”异位已经记录在癫痫模型中，以及在一小群抑制性癫痫模型中。 正常情况下的神经元。最近，我发现几乎所有的小清蛋白阳性（PV+）细胞， 大脑中约有一半的新皮层抑制细胞可以激发异位。我们还不知道 轴突异位产生的确切位置除了不知道它们来自轴突的哪里， 我们也不知道是什么机制产生的。最后，我们不知道什么条件导致异位 in vivo.在这里，我提出了一系列旨在回答这些问题的实验。在目标1中，我将测试 是否受体，离子通道，以及能够去极化突触前末梢的协同转运蛋白， 参与异位生殖。我还将使用超快速成像技术来跟踪动作电位， 它们穿过PV+细胞的轴突，直接确认异位产生的位置和 它们触发的突触数量在目标2中，我将确定是否星形胶质细胞，它包裹和调节 PV+细胞终末，通过阻断星形胶质细胞特异性转运蛋白和受体，以及 调节细胞内星形胶质细胞钙储存和光遗传去极化星形胶质细胞。最后，在Aim 3，我将进行一系列实验，以检测小鼠麻醉时PV+细胞中的异位， 在不同的清醒状态下这些实验将辨别异位是如何以及在什么样的背景下发生的， 产生的。了解异位动作电位启动的机制将产生新的见解， 抑制性中间神经元的重要群体的功能。它还可能揭示与人类的行为 涉及皮质过度兴奋的大脑疾病，为未来的研究提供了新的靶点， 与这些脑部疾病相关的回路水平变化，以及潜在的新治疗方法。 这个指导奖将支持我需要建立一个独立的职业生涯作为一个学者的培训 物理学家兼科学家我将开发电压敏感染料成像和活体记录方面的技术专长 在我的导师巴里康纳斯博士的指导下，咨询委员会提供意见 成员Judy Liu博士，医学博士，博士和克里斯托弗摩尔博士他们都是各自领域的顶尖专家我 将补充这一培训课程的负责任的行为研究，分子神经科学， 技术和赠款写作，沿着参加当地研讨会和全国会议，以传播 我的发现和促进合作。这次培训将帮助我实现成为一名独立的 研究者使用尖端技术探索神经精神疾病的神经回路。

PROJECT SUMMARY Neurons, the basic processing and communicating units of the brain, typically use action potentials to transmit messages from a site near the cell body to neurotransmitter releasing terminals via axons. Action potentials can, in some cases, also travel backwards along the axon towards the cell body and dendrites; I refer to these here as ‘ectopics.’ Ectopics have been recorded in models of epilepsy, as well as in a small group of inhibitory interneurons under normal conditions. Recently, I discovered that nearly all parvalbumin positive (PV+) cells of the brain, which account for about half of neocortical inhibitory cells, can fire ectopics. We do not yet know exactly where in the axon ectopics are generated. In addition to not knowing where in the axon they come from, we also do not know what mechanism generates them. Finally, we do not know what conditions lead to ectopics in vivo. Here, I propose a series of experiments designed to answer these questions. In Aim 1, I will test whether receptors, ion channels, and cotransporters capable of depolarizing the presynaptic terminal are involved in ectopic generation. I will also use an ultra-rapid imaging technique to track action potentials as they travel through the axons of PV+ cells to directly confirm both where ectopics are generated and the number of synapses they trigger. In Aim 2 I will determine whether astrocytes, which envelop and modulate PV+ cell terminals, help elicit ectopics by blocking astrocyte-specific transporters and receptors, as well as by modulating intracellular astrocytic calcium stores and optogenetically depolarizing astrocytes. Finally, in Aim 3, I will undertake a series of experiments to detect ectopics in PV+ cells while mice are under anesthesia, and in various awake, behaving conditions. These experiments will discern both how, and in what contexts, ectopics are generated. Understanding the mechanisms of ectopic action potential initiation will yield new insights into the function of an important population of inhibitory interneurons. It may also reveal mechanisms that relate to brain disorders involving cortical hyperexcitability, providing novel targets for future investigations of circuit-level changes related to these brain disorders and, potentially, new approaches to treatment. This mentored award will support the training I need to establish an independent career as an academic physician-scientist. I will develop technical expertise in voltage-sensitive dye imaging and in vivo recording techniques under the direction of my mentor, Dr. Barry Connors, Ph.D., with input from advisory committee members Drs. Judy Liu, M.D., Ph.D. and Christopher Moore, Ph.D., who are leading experts in their fields. I will supplement this training with courses in the responsible conduct of research, molecular neuroscience techniques, and grant writing, along with attendance at local seminars and national meetings to disseminate my findings and foster collaborations. This training will help me achieve my goal of becoming an independent investigator exploring the neurocircuitry underlying neuropsychiatric disorders using cutting edge techniques.