Brand S, Hanke W
Institut für Zoophysiologie (230), Universität Hohenheim, Stuttgart, Germany
J Hirnforsch. 1996;37(1):73-9.
The patch-clamp technique was used to investigate the nature of potassium channels localised in the end-feet-membrane of Müller (glial) cells of the chicken retina. Two different preparations were used to examine ion channels in this membrane area. The ion channels were investigated either in eye-cup preparation, leaving the retina intact, or in isolated endfeet. In both preparations the ion channels showed identical characteristics. We found three K+ channels that could be distinguished by their electrical properties. In the inside-out configuration, in a standard bathing solution (6 mM potassium) with the pipette solution containing 100 mM potassium, these channels showed conductances of 15 pS, 29 pS and 68 pS. Whereas the 29 pS-channel was not voltage-dependent, the 15 pS- and 68 pS-channel showed significant voltage-dependence of the open-state probability. By membrane depolarisation the open-state probability of both channels types increased. The resting membrane potential of the glial cells was estimated to be about -80 mV, which is, as result of the high selectivity of the glial membranes for K+, more negative than that of retinal neurons.
采用膜片钳技术研究鸡视网膜Müller（神经胶质）细胞终足膜中钾通道的性质。使用两种不同的标本制备方法来检测该膜区域的离子通道。离子通道的研究要么采用眼杯标本制备，使视网膜保持完整，要么采用分离的终足。在这两种标本制备中，离子通道表现出相同的特性。我们发现了三种钾通道，可根据其电特性加以区分。在反转片模式下，在标准浴液（6 mM钾）中，吸管溶液含100 mM钾，这些通道的电导分别为15 pS、29 pS和68 pS。29 pS通道不依赖电压，而15 pS和68 pS通道的开放态概率表现出显著的电压依赖性。通过膜去极化，两种通道类型的开放态概率均增加。神经胶质细胞的静息膜电位估计约为 -80 mV，由于神经胶质细胞膜对钾具有高选择性，因此比视网膜神经元的静息膜电位更负。
