Fujimoto M, Yanase H
Department of Biological Science, Faculty of Science, Hiroshima University, Japan.
Neurosci Res. 1994 Mar;19(2):195-200. doi: 10.1016/0168-0102(94)90143-0.
Retinal spreading depression was evoked using low Cl- Ringer's solution and the concomitant field potentials (spreading depression potential; SDP) were recorded. The polarity of the transretinally recorded SDPs was not consistent among animal species. The SDPs recorded from carp and frog were receptor side negative, while chick and cat induced receptor side positive SDPs. According to the K+ hypothesis, the retinal SDP is generated by Müller cells responding to an increase in the extracellular K+ concentration in the inner plexiform layer. In order to clarify the relationship between the K+ increase and the polarity of the SDP, a high-K+ solution was injected at various retinal depths and the evoked potential was recorded transretinally. The neutral zone within the retina, where a change in the extracellular K+ concentration produces no net potential difference, was revealed to be near the proximal end of the retina in carp and frog, while it was located distal to the inner plexiform layer in the chick and cat. These results support the Müller cell K+ hypothesis and explain the polarity of SDPs. We conclude that the concept of the neutral zone is valuable for the investigation of the mechanism and polarity of transretinal field potentials.
使用低氯林格氏液诱发视网膜扩散性抑制，并记录伴随的场电位（扩散性抑制电位；SDP）。经视网膜记录的SDP的极性在不同动物物种之间并不一致。从鲤鱼和青蛙记录到的SDP在感受器侧为负，而鸡和猫则诱发感受器侧为正的SDP。根据钾离子假说，视网膜SDP是由米勒细胞对内网状层细胞外钾离子浓度升高做出反应而产生的。为了阐明钾离子升高与SDP极性之间的关系，在视网膜的不同深度注射高钾溶液，并经视网膜记录诱发的电位。结果显示，在鲤鱼和青蛙中，视网膜内细胞外钾离子浓度变化不会产生净电位差的中性区位于视网膜近端附近，而在鸡和猫中，该中性区位于内网状层的远端。这些结果支持了米勒细胞钾离子假说，并解释了SDP的极性。我们得出结论，中性区的概念对于研究经视网膜场电位的机制和极性具有重要价值。
