nature neuroscience

评语： 

亮点：该研究用电压荧光成像方法探究神经元活动时星形胶质细胞分支的膜电位变化，提供了检测胶质细胞膜电位和分析其响应特性的新方法，提出了理解胶质-神经元交流机制的新方式——神经元可能通过释放钾离子改变星形胶质细胞的电活动，进而控制神经递质。这些结果有助于重新思考大脑如何维持兴奋抑制平衡，也有利于更新大家对这种平衡失控时（如癫痫）的可能机制的认识。

关键词： 

peripheral astrocyte processes (PAPs); K+ efflux; glutamate clearance

文章链接DOI： 

https://www.nature.com/articles/s41593-022-01049-x?msclkid=930ddd11cfb311ecb20aca7ddf2af723

Abstract

Astrocytes are glial cells that interact with neuronal synapses via their distal processes, where they remove glutamate and potassium (K+) from the extracellular space following neuronal activity. Astrocyte clearance of both glutamate and K+ is voltage dependent, but astrocyte membrane potential (Vm) is thought to be largely invariant. As a result, these voltage dependencies have not been considered relevant to astrocyte function. Using genetically encoded voltage indicators to enable the measurement of Vm at peripheral astrocyte processes (PAPs) in mice, we report large, rapid, focal and pathway-specific depolarizations in PAPs during neuronal activity. These activity-dependent astrocyte depolarizations are driven by action potential-mediated presynaptic K+ efflux and electrogenic glutamate transporters. We find that PAP depolarization inhibits astrocyte glutamate clearance during neuronal activity, enhancing neuronal activation by glutamate. This represents a novel class of subcellular astrocyte membrane dynamics and a new form of astrocyte–neuron interaction.

Neuron

评语： 

亮点：本文利用在体双光子钙成像和膜片钳记录技术，实现了对初级视觉皮层中1至6层的兴奋性和抑制性神经元自发活动的记录，较全面系统地描述了全局麻醉状态与清醒状态下皮层各层不同类型神经元的自发活动时空同步化特征的差异。以往观点认为麻醉状态下皮层活动降低，与大脑其他区域之间是暂时失联的。而本文结果提示，清醒切换到全局麻醉时，皮层可能是从空间非同步化模式（该模式可以编码大量信息，类似于人们在球赛前各自交谈）切换到了高度活跃的空间同步化输出模式（此模式信息含量低，类似于人们在球赛中一起呐喊）。简言之，皮层以增强第5层的锥体神经元同步信号输出的形式编码了麻醉—清醒状态切换的指令。本研究提出了新的脑状态切换编码模式的观点。

局限性：本文观察到的L5兴奋性神经元的同步化活动的输入来源并未明确，与皮层下的联系仍需进一步探究。

关键词： 

Anesthetics; layer 5 pyramidal neurons; synchrony

文章链接 ： 

https://www.cell.com/neuron/fulltext/S0896-6273(22)00303-8?rss=yes

Abstract

General anesthetics induce loss of consciousness, a global change in behavior. However, a corresponding global change in activity in the context of defined cortical cell types has not been identified. Here, we show that spontaneous activity of mouse layer 5 pyramidal neurons, but of no other cortical cell type, becomes consistently synchronized in vivo by different general anesthetics. This heightened neuronal synchrony is aperiodic, present across large distances, and absent in cortical neurons presynaptic to layer 5 pyramidal neurons. During the transition to and from anesthesia, changes in synchrony in layer 5 coincide with the loss and recovery of consciousness. Activity within both apical and basal dendrites is synchronous, but only basal dendrites’ activity is temporally locked to somatic activity. Given that layer 5 is a major cortical output, our results suggest that brain-wide synchrony in layer 5 pyramidal neurons may contribute to the loss of consciousness during general anesthesia.

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