Beech D J, Barnes S
Department of Physiology and Biophysics, University of Washington School of Medicine, Seattle 98195.
Neuron. 1989 Nov;3(5):573-81. doi: 10.1016/0896-6273(89)90267-5.
In this study a K+ current, IKx, in isolated salamander rod photoreceptors was characterized and its role in shaping small photovoltages was examined. IKx is a standing outward current of about 40 pA at -30 mV that deactivates slowly when the cell is hyperpolarized (tau max = 0.25 s). The voltage and time dependence of IKx are similar to that of M-current, but IKx can be distinguished from M-current because it is not suppressed by acetylcholine and is "blocked" by external Ba2+ in a surprising manner: the activation range of IKx is shifted strongly in the positive direction. Using current-clamp recordings and a computer simulation of the photo-response, we show that IKx figures prominently in setting the dark resting potential and accelerates the voltage response to small photocurrents.
在本研究中，对分离出的蝾螈视杆光感受器中的一种钾电流IKx进行了特性描述，并研究了其在形成小光电压方面的作用。IKx是一种在-30 mV时约为40 pA的外向稳态电流，当细胞超极化时，它会缓慢失活（最大时间常数τ = 0.25 s）。IKx的电压和时间依赖性与M电流相似，但IKx可与M电流区分开来，因为它不受乙酰胆碱抑制，并且会以一种令人惊讶的方式被外部Ba2+ “阻断”：IKx的激活范围在正方向上强烈偏移。通过电流钳记录和光反应的计算机模拟，我们表明IKx在设定暗静息电位中起重要作用，并加速了对小光电流的电压反应。
