GATING OF SINGLE NON-SHAKER A-TYPE POTASSIUM CHANNELS IN LARVAL DROSOPHILA NEURONS
GATING OF SINGLE NON-SHAKER A-TYPE POTASSIUM CHANNELS IN LARVAL DROSOPHILA NEURONS
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DOI：
10.1085/jgp.96.1.135
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发表时间：
1990-07-01
影响因子：
3.8
通讯作者：
ALDRICH, RW
中科院分区：
文献类型：
--
作者：
SOLC, CK;ALDRICH, RW
采用全细胞和单通道电压箝法研究了果蝇中枢神经细胞原代培养的瞬时a2型钾通道的电压依赖性门控。A2通道在基因上不同于果蝇肌肉中观察到的Shaker A1通道，并且在单通道电导、电压依赖性和门控动力学上有所不同。在-30、-10、+10和+30 mV下记录和分析单个A2通道。通道在去极化步骤中以脉冲打开，每个脉冲打开3到4个，每个480毫秒脉冲打开2到3个（2.8毫秒脉冲标准）。平均打开持续时间为2-4毫秒，平均爆发持续时间为9-17毫秒。除了第一潜伏期分布外，所有分布的平均值都与电压的变化趋势不一致。整个细胞A电流和单个A2通道的总体平均电流的宏观失活都可以用两个指数的和很好地拟合。不同细胞的快速时间常数在9 ~ 25 ms之间，慢速时间常数在60 ~ 140 ms之间。通过拟合打开持续时间、突发持续时间、突发关闭持续时间、每个突发打开次数和每个迹线的突发次数的频率直方图，对四种指令电压下的六状态动力学模型（三个关闭、一个打开、两个失活状态）进行了测试。该模型对这些数据以及总体平均值提供了很好的拟合。除了导致初始开闸的速率外，模型中的转换在很大程度上与电压无关。
The voltage-dependent gating of transient A2-type potassium channels from primary cultures of larval Drosophila central nervous system neurons was studied using whole-cell and single-channel voltage clamp. A2 channels are genetically distinct from the Shaker A1 channels observed in Drosophila muscle, and differ in single-channel conductance, voltage dependence, and gating kinetics. Single A2 channels were recorded and analyzed at -30, -10, +10, and +30 mV. The channels opened in bursts in response to depolarizing steps, with three to four openings per burst and two to three bursts per 480-ms pulse (2.8-ms burst criterion). Mean open durations were in a range of 2-4 ms and mean burst durations in a range of 9-17 ms. With the exception of the first latency distributions, none of the means of the distributions measured showed a consistent trend with voltage. Macroscopic inactivation of both whole-cell A currents and ensemble average currents of single A2 channels was well fitted by a sum of two exponentials. The fast time constants in different cells were in a range of 9-25 ms, and the slow time constants in a range of 60-140 ms. A six-state kinetic model (three closed, one open, two inactivated states) was tested at four command voltages by fitting frequency histograms of open durations, burst durations, burst closed durations, number of openings per burst, and number of bursts per trace. The model provided good fits to these data, as well as to the ensemble averages. With the exception of the rates leading to initial opening, the transitions in the model were largely independent of voltage.