Brew H, Gray P T, Mobbs P, Attwell D
Nature. 1986;324(6096):466-8. doi: 10.1038/324466a0.
A major function of glial cells in the central nervous system is to buffer the extracellular potassium concentration, [K+]o. A local rise in [K+]o causes potassium ions to enter glial cells, which have membranes that are highly permeable to K+; potassium then leaves the glial cells at other locations where [K+]o has not risen. We report here the first study of the individual ion channels mediating potassium buffering by glial cells. The patch-clamp technique was employed to record single channel currents in Müller cells, the radial glia of the vertebrate retina. Those cells have 94% of their potassium conductance in an endfoot apposed to the vitreous humour, causing K+ released from active retinal neurones to be buffered preferentially to the vitreous. Recordings from patches of endfoot and cell body membrane show that a single type of inward-rectifying K+ channel mediates potassium buffering at both cell locations. The non-uniform density of K+ conductance is due to a non-uniform distribution of one type of K+ channel, rather than to the cell expressing high conductance channels at the endfoot and low conductance channels elsewhere on the cell.
中枢神经系统中神经胶质细胞的一个主要功能是缓冲细胞外钾离子浓度，即[K+]o。[K+]o的局部升高会使钾离子进入神经胶质细胞，这些细胞的膜对K+具有高度通透性；然后钾离子会在[K+]o未升高的其他位置离开神经胶质细胞。我们在此报告了第一项关于介导神经胶质细胞钾缓冲作用的单个离子通道的研究。采用膜片钳技术记录了Müller细胞（脊椎动物视网膜的放射状神经胶质细胞）中的单通道电流。这些细胞94%的钾电导位于与玻璃体相邻的终足，使得从活跃的视网膜神经元释放的K+优先被缓冲到玻璃体中。对终足和细胞体膜片的记录表明，一种单一类型的内向整流K+通道在这两个细胞位置介导钾缓冲。K+电导的不均匀密度是由于一种K+通道的分布不均匀，而不是因为细胞在终足表达高电导通道，而在细胞其他位置表达低电导通道。
