Ma Yu-Ping, Cui Jinjuan, Hu Hui-Juan, Pan Zhuo-Hua
Department of Anatomy and Cell Biology, Wayne State University School of Medicine, Detroit, Michigan 48201, USA.
J Neurophysiol. 2003 Nov;90(5):3479-89. doi: 10.1152/jn.00426.2003.
Retinal bipolar cells comprise multiple subtypes that are well known for the diversity of their physiological properties. We investigated the properties and functional roles of the hyperpolarization-activated currents in mammalian retinal bipolar cells using whole cell patch-clamp recording techniques. We report that bipolar cells express inwardly rectifying K+ currents (IKir) in addition to the hyperpolarization-activated cationic currents (Ih) previously reported. Furthermore, these two currents are differentially expressed among different subtypes of bipolar cells. One group of cone bipolar cells in particular displayed mainly IKir. A second group of cone bipolar cells displayed both currents but with a much larger Ih. Rod bipolar cells, on the other hand, showed primarily Ih. Moreover, we showed that IKir and Ih differentially influence the voltage responses of bipolar cells: Ih facilitates and/or accelerates the membrane potential rebound, whereas IKir counteracts or prevents such rebound. The findings of the expression of IKir and the differential expression of Ih and IKir in bipolar cells may provide new insights into an understanding of the physiological properties of bipolar cells.
视网膜双极细胞包含多种亚型，其生理特性的多样性广为人知。我们使用全细胞膜片钳记录技术研究了哺乳动物视网膜双极细胞中超极化激活电流的特性和功能作用。我们报告称，除了先前报道的超极化激活阳离子电流（Ih）外，双极细胞还表达内向整流钾电流（IKir）。此外，这两种电流在不同亚型的双极细胞中差异表达。特别是一组视锥双极细胞主要表现为IKir。另一组视锥双极细胞同时表现出这两种电流，但Ih要大得多。另一方面，视杆双极细胞主要表现为Ih。此外，我们表明IKir和Ih对视双极细胞的电压反应有不同影响：Ih促进和/或加速膜电位反弹，而IKir则抵消或阻止这种反弹。IKir的表达以及Ih和IKir在双极细胞中的差异表达的研究结果可能为理解双极细胞的生理特性提供新的见解。
