STATISTICAL-ANALYSIS OF SINGLE SODIUM-CHANNELS - EFFECTS OF N-BROMOACETAMIDE
STATISTICAL-ANALYSIS OF SINGLE SODIUM-CHANNELS - EFFECTS OF N-BROMOACETAMIDE
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DOI：
10.1016/s0006-3495(84)84158-2
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发表时间：
1984-01-01
影响因子：
3.4
通讯作者：
LANGE, K
中科院分区：
文献类型：
--
作者：
HORN, R;VANDENBERG, CA;LANGE, K
电流从细胞系GH 3的膜的由外向外切除的贴片中的单个钠通道获得。在对照贴片和用N-溴乙酰胺（NBA）处理以去除灭活的贴片中检查电流。单通道电流-电压关系在-60 ~+ 10 mV范围内呈线性，不受NBA影响。在9.3 ℃下的斜率电导为12 pS，单通道电流的Q10约为1.35。对照和NBA处理的贴片中的电流都显示出类似于乙酰胆碱受体通道中的脱敏的缓慢过程的证据。这个过程在快速刺激（5 Hz）时尤其明显，其中记录簇中出现开口。运行分析，这表明一个统计上显着的趋势，非随机排序的通道电压脉冲的响应中的记录与不开口的聚类进行了分析。NBA使这种非随机模式更加明显。在激活去极化过程中，单个通道“冬眠”的概率由最大似然法估计。的开放状态的寿命也估计由最大似然法，并作为电压的函数进行了检查。在对照贴片中，开放时间是轻度电压依赖性的，在约-50 mV处显示出最大值。在NBA处理的补丁的开放时间大于在控制情况下，并增加单调的去极化，它渐近接近超极化电位的控制补丁。通过比较对照和NBA处理的贴片中的通道开放时间，我们确定了β A和β I，关闭激活门和快速失活门的速率常数。β I是电压的指数函数，在34 mV时增加e倍。β A具有相反的电压依赖性。开放通道关闭其快速失活门而不是其激活门的概率随着去极化从-60 mV线性增加到-10 mV。这些结果表明，失活是固有的电压依赖性。
Currents were obtained from single sodium channels in outside-out excised patches of membrane from the cell line GH3. The currents were examined in control patches and in patches treated with N- bromoacetamide ( NBA ) to remove inactivation. The single-channel current-voltage relationship was linear over the range -60 to + 10 mV, and was unaffected by NBA . The slope conductance at 9.3 degrees C was 12 pS, and the Q10 for single channel currents was about 1.35. The currents in both control and NBA -treated patches showed evidence of a slow process similar to desensitization in acetylcholine-receptor channels. This process was especially apparent at rapid rates of stimulation (5 Hz), where openings occurred in clusters of records. The clustering of records with and without openings was analyzed by runs analysis, which showed a statistically significant trend toward nonrandom ordering in the responses of channels to voltage pulses. NBA made this nonrandom pattern more apparent. The probability that an individual channel was "hibernating" during an activating depolarization was estimated by a maximum likelihood method. The lifetime of the open state was also estimated by a maximum likelihood method, and was examined as a function of voltage. In control patches the open time was mildly voltage-dependent, showing a maximum at about -50 mV. In NBA -treated patches the open time was greater than in the control case and increased monotonically with depolarization; it asymptotically approached that of the control patches at hyperpolarized potentials. By comparing channel open times in control and NBA -treated patches, we determined beta A and beta I, the rate constants for closing activation gates and fast inactivation gates. Beta I was an exponential function of voltage, increasing e-fold for 34 mV. beta A had the opposite voltage dependence. The probability of an open channel closing its fast inactivation gate, rather than its activation gate, increased linearly with depolarization from -60 to -10 mV. These results indicate that inactivation is inherently voltage dependent.