Zeumer C, Hanitzsch R, Mättig W U
Carl-Ludwig-Institute of Physiology, Leipzig, Germany.
Vision Res. 1994 Oct;34(20):2673-8. doi: 10.1016/0042-6989(94)90223-2.
ERG and light-induced extracellular potassium ([K+]o) changes have been measured in isolated retinas of both Rana esculenta and Rana temporaria. The conditions of the preparations have been varied. Isolated frog retinas kept receptor side-upward in a moist chamber without perfusion showed the well-known slow PIII in the ERG. Retinas superfused from the receptor side, with O2 enrichment at their vitreal surface, however, exhibit a slow cornea-positive potential in the ERG. The slow ERG-potentials relate to different light-induced potassium changes in the proximal retina. There was a long lasting and larger proximal potassium increase in adequately maintained retinas but a smaller and shorter one in preparations lacking superfusion and oxygen. There was no significant difference between the size of potassium decrease around receptors of retinas superfused from their vitreal side and those superfused from receptor side. A reduction of slow PIII should therefore not be responsible for the slow cornea-positive potential. The long lasting and larger (by 59%) potassium increase in the proximal retina may counteract the potential in the Müller cells caused by the potassium decrease around receptors and thereby cancel slow PIII and generate a third component of the electroretinogram c-wave.
在食用蛙和林蛙的离体视网膜中测量了视网膜电图（ERG）和光诱导的细胞外钾离子（[K⁺]o）变化。制备条件有所不同。在无灌注的湿润小室中使分离的蛙视网膜受体面向上放置，其ERG中显示出众所周知的缓慢的PIII波。然而，从受体侧进行灌注、玻璃体表面富含氧气的视网膜，其ERG中呈现出缓慢的角膜正向电位。这些缓慢的ERG电位与近端视网膜中不同的光诱导钾离子变化有关。在充分维持的视网膜中，近端钾离子有持续时间长且幅度大的增加，但在缺乏灌注和氧气的制备物中，增加幅度较小且持续时间较短。从玻璃体侧灌注的视网膜受体周围的钾离子减少幅度与从受体侧灌注的视网膜相比，没有显著差异。因此，缓慢的PIII波减小不应是缓慢的角膜正向电位的原因。近端视网膜中持续时间长且幅度大（增加59%）的钾离子增加可能抵消了受体周围钾离子减少在米勒细胞中引起的电位，从而消除缓慢的PIII波并产生视网膜电图c波的第三个成分。
