Reuter H, Stevens C F
J Membr Biol. 1980 Dec 15;57(2):103-18. doi: 10.1007/BF01868997.
Delayed potassium channels were studied in internally perfused neurone somata from land snails. Relaxation and fluctuation analysis of this class of ion channels revealed Hodgkin-Huxley type K channels with an average single channel conductance (gamma K) of 2.40 +/- 0.15 pS. The conductance of open channels is independent of voltage and virtually all K channels seem to be open at maximum K conductance (gk) of the membrane. Voltage dependent time constants of activation of gK, calculated from K current relaxation and from cut-off frequencies of power spectra, are very similar indicating dominant first-order kinetics. Ion selectivity of K channels was studied by ion substitution in the external medium and exhibited the following sequence: Tl+ greater than K+ greater than Rb+ greater Cs+ greater than NH4+ greater Li+ greater than Na+. The sequence of the alkali cations does not conform to any of the sequences predicted by Eisenman's theory. However, the data are well accommodated by a new theory assuming a single rate-limiting barrier that governs ion movement through the channel.
对陆地蜗牛体内灌注的神经元胞体中的延迟钾通道进行了研究。对这类离子通道的松弛和波动分析显示，存在霍奇金 - 赫胥黎型钾通道，其平均单通道电导（γK）为2.40±0.15皮西门子。开放通道的电导与电压无关，并且在膜的最大钾电导（gk）时，几乎所有钾通道似乎都是开放的。根据钾电流松弛和功率谱截止频率计算出的gk激活的电压依赖性时间常数非常相似，表明主要是一级动力学。通过在外部介质中进行离子置换研究了钾通道的离子选择性，其表现出以下顺序：Tl +＞K +＞Rb +＞Cs +＞NH4 +＞Li +＞Na +。碱金属阳离子的顺序不符合艾森曼理论预测的任何一种顺序。然而，通过假设一个控制离子通过通道移动的单一限速屏障的新理论，可以很好地解释这些数据。
