How microglia sense and regulate neuronal activity in the adult brain

项目总结/摘要 小胶质细胞是中枢神经系统的先天性免疫细胞，其与成人大脑中的神经元相互作用。 小胶质细胞受体和通路具有改变复杂网络功能的能力。这个过程 开始于小胶质细胞感知特定的神经元信号。然而， 小胶质细胞产生特定反应/结果的机制还不清楚。本研究的目的是 了解小胶质细胞如何在多动症期间感知神经元活动（例如，癫痫发作）和活动减退（例如， 麻醉），然后可能触发独特的功能反应，以改变成人大脑中的神经元回路。ATP 活动过度期间的嘌呤信号传导是小胶质细胞与癫痫发作中的神经元相互作用的有据可查的信号， 降低癫痫发作的严重程度。然而，小胶质细胞内的复杂性（第二信使， Ca 2+信号）对ATP的反应仅部分了解。独特的细胞内信号级联， 小胶质细胞可以不同地影响它们的功能反应。这些通路将使用急性 脑切片和体内双光子成像沿着，以及一套新的遗传和病毒为基础的工具，以揭示 小胶质细胞的钙通道是如何影响癫痫反应的。在活动减退期间， 去甲肾上腺素信号传导允许小胶质细胞在麻醉下更好地与神经元相互作用。施行本 网络功能的相互作用是未知的，但将使用小胶质细胞的体内双光子成像进行解剖， 完整大脑中的神经元动力学，再加上高度详细的三维电子显微镜重建， 结构相互作用先前使用化学遗传学和条件性敲除方法改变 小胶质细胞功能也被用于剖析调节活动减退的神经回路反应的特定途径。 最终，确定小胶质细胞如何调节神经元功能，包括潜在的机制和它们的功能。 对电路的影响，对于充分了解小胶质细胞如何整合到复杂的神经元电路中至关重要 因为它们在脑部疾病中变得失调，如癫痫发作和睡眠障碍。

PROJECT SUMMARY/ABSTRACT Microglia are innate immune cells of the central nervous system, which interact with neurons in the adult brain. Microglial receptors and pathways have a demonstrated ability to alter complex network function. This process begins with microglia sensing specific neuronal signals. However, the downstream mechanisms used by microglia to enact specific responses/outcomes is not well understood. The purpose of this research is to understand how microglia sense neuronal activity during hyperactivity (e.g., seizures) and hypoactivity (e.g., anesthesia), which may then trigger unique functional responses to alter neuronal circuits in the adult brain. ATP purine signaling during hyperactivity is a well-documented signal for microglia to interact with neurons in seizure, reducing seizure severity. However, the complexity of microglial intracellular (secondary messenger such as Ca2+ signaling) responses to ATP is only partially understood. Unique intracellular signaling cascades in microglia may differentially influence their functional responses. These pathways will be interrogated using acute brain slice and in vivo two-photon imaging along with a suite of new genetic and virus-based tools to uncover how the calcium pathway of microglia in particular informs seizure responses. During hypoactivity, a loss of norepinephrine signaling allows microglia to better interact with neurons under anesthesia. The purpose of these interactions for network function is unknown, but will be dissected using in vivo two-photon imaging of microglia- neuron dynamics in the intact brain, coupled with 3D-electron microscope reconstruction of highly detailed structural interactions. Previous experience using chemogenetic and conditional knockout approaches to alter microglia function are also utilized to dissect specific pathways regulating hypoactive neural circuit responses. Ultimately, determining how microglia regulate neuronal function, including underlying mechanisms and their impact on circuitry, is essential to fully understand how microglia are integrated into the complex neuronal circuits as they become dysregulated in brain diseases, such as seizures and sleep disorders.