Santello M, Volterra A
Department of Cell Biology and Morphology, University of Lausanne, Rue du Bugnon 9, 1005 Lausanne, Switzerland.
Neuroscience. 2009 Jan 12;158(1):253-9. doi: 10.1016/j.neuroscience.2008.03.039. Epub 2008 Mar 22.
In the past 15 years the classical view that astrocytes play a relatively passive role in brain function has been overturned and it has become increasingly clear that signaling between neurons and astrocytes may play a crucial role in the information processing that the brain carries out. This new view stems from two seminal observations made in the early 1990s: 1. astrocytes respond to neurotransmitters released during synaptic activity with elevation of their intracellular Ca2+ concentration ([Ca2+]i); 2. astrocytes release chemical transmitters, including glutamate, in response to [Ca2+]i elevations. The simultaneous recognition that astrocytes sense neuronal activity and release neuroactive agents has been instrumental for understanding previously unknown roles of these cells in the control of synapse formation, function and plasticity. These findings open a conceptual revolution, leading to rethink how brain communication works, as they imply that information travels (and is processed) not just in the neuronal circuitry but in an expanded neuron-glia network. In this review we critically discuss the available information concerning: 1. the characteristics of the astrocytic Ca2+ responses to synaptic activity; 2. the basis of Ca2+-dependent glutamate exocytosis from astrocytes; 3. the modes of action of astrocytic glutamate on synaptic function.
在过去15年里，星形胶质细胞在脑功能中发挥相对被动作用的传统观点已被推翻，并且越来越清楚的是，神经元与星形胶质细胞之间的信号传导可能在大脑进行的信息处理中起关键作用。这一新观点源于20世纪90年代初的两项重大发现：1. 星形胶质细胞在突触活动期间释放的神经递质作用下，其细胞内Ca2+浓度（[Ca2+]i）升高；2. 星形胶质细胞响应[Ca2+]i升高而释放化学递质，包括谷氨酸。同时认识到星形胶质细胞能感知神经元活动并释放神经活性物质，有助于理解这些细胞在控制突触形成、功能和可塑性方面以前未知的作用。这些发现引发了一场概念上的革命，促使人们重新思考大脑通信的工作方式，因为它们意味着信息不仅在神经元回路中传播（和处理），还在扩展的神经元-胶质细胞网络中传播。在这篇综述中，我们批判性地讨论了有关以下方面的现有信息：1. 星形胶质细胞对突触活动的Ca2+反应的特征；2. 星形胶质细胞中Ca2+依赖性谷氨酸胞吐作用的基础；3. 星形胶质细胞谷氨酸对突触功能的作用方式。
