It has been more than a century since Pío del Río-Hortega first characterized microglia in histological stains of brain tissue. Since then, significant advances have been made in understanding the role of these resident central nervous system (CNS) macrophages. In particular, it is now known that microglia can sense neural activity and modulate neuronal circuits accordingly. We review the mechanisms by which microglia detect changes in neural activity to then modulate synapse numbers in the developing and mature CNS. This includes responses to both spontaneous and experience-driven neural activity. We further discuss activity-dependent mechanisms by which microglia regulate synaptic function and neural circuit excitability. Together, our discussion provides a comprehensive review of the activity-dependent functions of microglia within neural circuits in the healthy CNS, and highlights exciting new open questions related to understanding more fully microglia as key components and regulators of neural circuits.

中文翻译：

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小胶质细胞：神经回路的活动依赖性调节器

自 Pío del Río-Hortega 首次通过脑组织组织学染色来表征小胶质细胞以来，已经过去一个多世纪了。从那时起，人们在了解这些常驻中枢神经系统（CNS）巨噬细胞的作用方面取得了重大进展。特别是，现在已知小胶质细胞可以感知神经活动并相应地调节神经元回路。我们回顾了小胶质细胞检测神经活动变化，然后调节发育和成熟中枢神经系统突触数量的机制。这包括对自发和经验驱动的神经活动的反应。我们进一步讨论小胶质细胞调节突触功能和神经回路兴奋性的活动依赖性机制。总之，我们的讨论对健康中枢神经系统神经回路内小胶质细胞的活动依赖性功能进行了全面回顾，并强调了与更全面地理解小胶质细胞作为神经回路关键组成部分和调节器相关的令人兴奋的新开放问题。