Background

Transcranial direct current stimulation [(t)DCS], modulates cortical excitability and promotes neuroplasticity. Microglia has been identified to respond to electrical currents as well as neuronal activity, but its response to DCS is mostly unknown.

Objective

This study addresses effects of DCS applied in vivo to the sensorimotor cortex on physiological microglia properties and neuron-microglia communication.

Methods

Time lapse in vivo 2-photon microscopy in anaesthetized mice was timely coupled with DCS of the sensorimotor cortex to observe microglia dynamics on a population-based and single cell level. Neuron-microglia communication during DCS was investigated in mice with a functional knock out of the fractalkine receptor CX3CR1. Moreover, the role of voltage gated microglial channels and DCS effects on phagocytosis were studied.

Results

DCS promoted several physiological microglia properties, depending on the glial activation state and stimulation intensity. On a single cell level, process motility was predominantly enhanced in ramified cells whereas horizontal soma movement and galvanotaxis was pronounced in reactive microglia. Blockage of voltage sensitive microglial channels suppressed DCS effects in vivo and in vitro. Microglial motility changes were partially driven by the fractalkine signaling pathway. Moreover, phagocytosis increased after DCS in vitro.

Conclusion

Microglia dynamics are rapidly influenced by DCS. This is the first in vivo demonstration of a direct effect of electrical currents on microglia and indirect effects potentially driven by neuronal activity via the fractalkine pathway.

中文翻译：

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带电小胶质细胞：直流电刺激对最通用的脑细胞不同特性的影响

背景

经颅直流电刺激 [(t)DCS]，调节皮质兴奋性并促进神经可塑性。已确定小胶质细胞对电流和神经元活动有反应，但它对 DCS 的反应大多未知。

客观的

这项研究解决了 DCS 在体内应用于感觉运动皮层对生理小胶质细胞特性和神经元-小胶质细胞通讯的影响。

方法

麻醉小鼠体内 2 光子显微镜的延时时间与感觉运动皮层的 DCS 及时结合，以观察基于群体和单细胞水平的小胶质细胞动力学。在具有 fractalkine 受体 CX3CR1 功能性敲除的小鼠中研究了 DCS 期间的神经元-小胶质细胞通讯。此外，还研究了电压门控小胶质细胞通道的作用和 DCS 对吞噬作用的影响。

结果

DCS 促进了几种生理小胶质细胞特性，这取决于神经胶质激活状态和刺激强度。在单细胞水平上，分枝细胞的过程运动性主要增强，而反应性小胶质细胞中的水平体细胞运动和电流趋向性明显。电压敏感小胶质细胞通道的阻塞抑制了体内和体外的 DCS 效应。小胶质细胞运动的变化部分是由 fractalkine 信号通路驱动的。此外，体外 DCS 后吞噬作用增加。

结论

小胶质细胞动力学受到 DCS 的迅速影响。这是首次在体内证明电流对小胶质细胞的直接影响和可能由神经元活动通过 fractalkine 通路驱动的间接影响。