Rogawski M A
J Neurophysiol. 1986 Aug;56(2):481-93. doi: 10.1152/jn.1986.56.2.481.
Single-channel recordings using the gigohm seal patch-clamp technique were carried out on the somatic membranes of dissociated embryonic rat hippocampal neurons grown in cell culture. The recording medium contained tetrodotoxin to block the voltage-dependent Na+ conductance and Cd2+ to block Ca2+ and Ca2+-activated conductances. In the cell-attached configuration, depolarizing voltage steps activated outward directed single-channel currents with conductance 15-20 pS. The channel openings exhibited a moderate degree of flickering. The mean burst lifetimes ranged from 5 to 13 ms with a tendency to increase slightly at more depolarized potentials (T = 21-25 degrees C). Reversal potential measurements using excised membrane patches indicated that the channels behaved as expected of a K+-selective membrane pore. Channel opening occurred in Ca2+-free EGTA-containing solutions but was never observed in the presence of tetraethylammonium (TEA; 20 mM). The frequency of channel opening increased as the membrane was depolarized by up to 50 mV from resting potential; the fraction of time spent in the open state during the first 300 ms following a step depolarization increased e-fold for a 8-25 mV change in potential. First-latency histograms and simulations of the macroscopic current based on channel data obtained during repeated depolarizing voltage steps indicated that the probability of the channel being in the open state increases gradually with time after a step depolarization. During repeated depolarizing steps the channels appeared to randomly enter and exit a long-lived inactive state. It is concluded that these channels may underly the slowly activating, very slowly inactivating, TEA-sensitive voltage-dependent K+ current (IK) in cultured hippocampal neurons.
采用千兆欧封接膜片钳技术对细胞培养中生长的离体胚胎大鼠海马神经元的胞体膜进行单通道记录。记录介质中含有河豚毒素以阻断电压依赖性Na⁺电导，以及Cd²⁺以阻断Ca²⁺和Ca²⁺激活的电导。在细胞贴附模式下，去极化电压阶跃激活外向单通道电流，电导为15 - 20 pS。通道开放表现出中等程度的闪烁。平均爆发寿命在5至13毫秒之间，在更去极化的电位下有轻微增加的趋势（温度T = 21 - 25摄氏度）。使用切除的膜片进行的反转电位测量表明，这些通道的行为符合K⁺选择性膜孔的预期。通道开放发生在不含Ca²⁺的含EGTA溶液中，但在存在四乙铵（TEA；20 mM）时从未观察到。通道开放频率随着膜从静息电位去极化高达50 mV而增加；在阶跃去极化后的前300毫秒内，处于开放状态的时间分数对于8 - 25 mV的电位变化呈指数增加。首次潜伏期直方图以及基于重复去极化电压阶跃期间获得的通道数据对宏观电流的模拟表明，在阶跃去极化后，通道处于开放状态的概率随时间逐渐增加。在重复去极化步骤期间，通道似乎随机进入和退出一个长寿命的失活状态。结论是，这些通道可能是培养的海马神经元中缓慢激活、非常缓慢失活、对TEA敏感的电压依赖性K⁺电流（IK）的基础。
