Artifact Versus Reality-How Astrocytes Contribute to Synaptic Events

一个世纪前发展的神经元学说,认为神经元网络是维持高级大脑功能的唯一细胞类型。胶质细胞生理学的最新进展,促进了另一种假说的提出,它认为大脑信息处理通过神经元-胶质细胞网络利用双重的(神经元动作电位)和同类的(第二信使/代谢物通过缝隙连接或递质在细胞间隙的扩散传播)信号编码来完成。这两种神经细胞间存在前馈和反馈通信,引起信息传递和处理,是通过神经元终端和星形胶质细胞突起的神经递质释放来完成。然而,对这个问题的认识,仍然是不完整的。一些重要的问题和争议有待解决。本文认为,突触旁的胶质细胞突起的主要功能是创建一个"星形胶质细胞摇篮",以保护突触免受大量来自突触外的信号活动的作用,并通过多种机制为突触联系提供多方面的支持和长期的可塑性保护,这些过程并不一定涉及胶质源性神经递质的释放。

The neuronal doctrine, developed a century ago regards neuronal networks as the sole substrate of higher brain function. Recent advances in glial physiology have promoted an alternative hypothesis, which places in- formation processing in the brain into integrated neuronal-glial networks utilizing both binary （neuronal action poten- tials） and analogue （diffusional propagation of second messengers/metabolites through gap junctions or transmitters through the interstitial space） signal encoding. It has been proposed that the feed-forward and feed-back communica tion between these two types of neural cells, which underlies information transfer and processing, is accomplished by the release of neurotransmitters from neuronal terminals as well as from astroglial processes. Understanding of this subject, however, remains incomplete and important questions and controversies require resolution. Here we propose that the primary function of perisynaptic glial processes is to create an ＂astroglial cradle＂ that shields the synapse from a multitude of extrasynaptic signaling events and provides for multifaceted support and long-term plasticity of synaptic contacts through variety of mechanisms, which may not necessarily involve the release of ＂glio＂ transmitters. ^c 2012 Wiley Peroidicals, Inc.