Department of Neuroscience and Pharmacology, University of Copenhagen, Denmark.
Curr Pharm Des. 2013;19(24):4385-99. doi: 10.2174/13816128113199990384.
For many years, glial cells from the central nervous system have been considered as support cells involved in the homeostasis of the brain. However, a series of key-findings obtained during the past two decades has put light on unexpected roles for glia and it is getting more and more admitted that glia play an active role in several physiological functions. The discovery that a bidirectional communication takes place between astrocytes (the star shaped glial cell of the brain) and neurons, was a major breakthrough in the field of synaptic physiology. Astrocytes express receptors that get activated by neurotransmitters during synaptic transmission. In turn they release other transmitters - called gliotransmitters - that bind to neuronal receptors and modulate synaptic transmission. This feedback, which led to the concept of the tripartite synapse, has been reported with various transmitters including glutamate, ATP, GABA or serine. In the present review we will focus on astrocytes and review the evidence suggesting and demonstrating their role in motor control. Rhythmic motor behaviors such as locomotion, swimming or chewing are generated by networks of neurons termed central pattern generators (CPG). These networks are highly flexible and adjust the frequency of their output to the external environment. In the case of respiration, the CPG reacts when changes in the pH of the blood occur. The chemosensory control of breathing is ensured by astrocytes, which react to variation of the blood pH by releasing ATP on neurons that in turn adapt the frequency of respiration. In the spinal cord, diverse transmitters such as ATP, adenosine or endocannabinoids modulate the CPG responsible for locomotion. A growing body of evidence suggests that glial cells release some of these molecules. These data suggest that astrocytes play an essential role in motor control and we believe that a range of studies will confirm this view in the near future.
多年来，中枢神经系统的神经胶质细胞一直被认为是参与大脑内稳态的支持细胞。然而，在过去的二十年中获得的一系列关键发现揭示了胶质细胞的意想不到的作用，并且越来越多的人承认胶质细胞在几种生理功能中发挥着积极的作用。星形胶质细胞（大脑中的星形胶质细胞）和神经元之间存在双向通讯的发现，是突触生理学领域的一个重大突破。星形胶质细胞表达的受体在突触传递过程中被神经递质激活。反过来，它们释放其他递质-称为神经胶质递质-与神经元受体结合并调节突触传递。这种反馈导致了三突触的概念，已经报道了各种递质，包括谷氨酸、ATP、GABA 或丝氨酸。在本综述中，我们将重点关注星形胶质细胞，并回顾表明和证明其在运动控制中的作用的证据。节律性运动行为，如运动、游泳或咀嚼，是由称为中枢模式发生器（CPG）的神经元网络产生的。这些网络具有高度的灵活性，并根据外部环境调整其输出的频率。在呼吸的情况下，CPG 会对血液 pH 值的变化做出反应。呼吸的化学感觉控制由星形胶质细胞来保证，它们通过向神经元释放 ATP 来对血液 pH 值的变化做出反应，神经元反过来适应呼吸的频率。在脊髓中，多种递质，如 ATP、腺苷或内源性大麻素，调节负责运动的 CPG。越来越多的证据表明，神经胶质细胞释放其中一些分子。这些数据表明，星形胶质细胞在运动控制中起着至关重要的作用，我们相信在不久的将来，一系列的研究将证实这一观点。
