In the brain’s gray matter, astrocytes regulate synapse properties, but their role is unclear for the white matter, where myelinated axons rapidly transmit information between gray matter areas. We found that in rodents, neuronal activity raised the intracellular calcium concentration ([Ca²⁺]_i) in astrocyte processes located near action potential–generating sites in the axon initial segment (AIS) and nodes of Ranvier of myelinated axons. This released adenosine triphosphate, which was converted extracellularly to adenosine and thus, through A_2a receptors, activated HCN2-containing cation channels that regulate two aspects of myelinated axon function: excitability of the AIS and speed of action potential propagation. Variations in astrocyte-derived adenosine level between wake and sleep states or during energy deprivation could thus control white matter information flow and neural circuit function.

中文翻译：

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星形胶质细胞 Ca2+ 诱发的 ATP 释放调节有髓轴突兴奋性和传导速度

在大脑的灰质中，星形胶质细胞调节突触特性，但它们对白质的作用尚不清楚，白质有髓轴突在灰质区域之间快速传递信息。我们发现，在啮齿动物中，神经元活动提高了位于轴突初始段 (AIS) 和有髓轴突 Ranvier 节点附近动作电位产生位点的星形胶质细胞突起的细胞内钙浓度 ([Ca ²⁺ ] _{i )。}这释放了三磷酸腺苷，它在细胞外转化为腺苷，因此通过 A _2a受体，活化的含 HCN2 的阳离子通道，调节有髓轴突功能的两个方面：AIS 的兴奋性和动作电位传播的速度。因此，星形胶质细胞衍生的腺苷水平在觉醒和睡眠状态或能量剥夺期间的变化可以控制白质信息流和神经回路功能。