Okada Yukio, Miyazaki Toshihiro, Fujiyama Rie, Toda Kazuo
Integrative Sensory Physiology, Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki 852-8588, Japan.
Cell Biology, Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki 852-8588, Japan.
Biochem Biophys Rep. 2015 Sep 24;4:175-179. doi: 10.1016/j.bbrep.2015.09.010. eCollection 2015 Dec.
The rod cells in frog taste discs display the outward current and maintain the negative resting potential in the condition where internal K is replaced with Cs. We analyzed the properties of the Cs-permeable conductance in the rod cells. The current-voltage () relationships obtained by a voltage ramp were bell-shaped under Cs internal solution. The steady state relationships elicited by voltage steps also displayed the bell-shaped outward current. The activation of the current accelerated with the depolarization and the inactivation appeared at positive voltage. The gating for the current was maintained even at symmetric condition (Cs external and internal solutions). The wing cells did not show the properties. The permeability for K was a little larger than that for Cs. Internal Na and NMDG could not induce the bell-shaped outward current. Carbenoxolone inhibited the bell-shaped outward Cs current dose dependently ( : 27 μM). Internal arachidonic acid (20 μM) did not induce the linear current-voltage () relationship which is observed in two-pore domain K channel (K). The results suggest that the resting membrane potentials in the rod cells are maintained by the voltage-gated K channels.
在内部钾离子被铯离子取代的情况下，青蛙味觉盘的视杆细胞呈现外向电流并维持负静息电位。我们分析了视杆细胞中铯离子通透电导的特性。在内部溶液为铯离子的情况下，通过电压斜坡获得的电流 - 电压（I-V）关系呈钟形。电压阶跃引发的稳态I-V关系也显示出钟形外向电流。电流的激活随着去极化而加速，并且失活出现在正电压下。即使在对称条件下（外部和内部溶液均为铯离子），电流的门控作用依然存在。翼状细胞不表现出这些特性。钾离子的通透性略大于铯离子。内部的钠离子和N-甲基-D-葡萄糖胺不能诱导出钟形外向电流。羧苄青霉素剂量依赖性地抑制钟形外向铯电流（IC50：27 μM）。内部花生四烯酸（20 μM）不会诱导出在双孔结构域钾通道（K2P）中观察到的线性电流 - 电压（I-V）关系。结果表明，视杆细胞的静息膜电位由电压门控钾通道维持。
