OPENING RATE OF ACETYLCHOLINE-RECEPTOR CHANNELS
OPENING RATE OF ACETYLCHOLINE-RECEPTOR CHANNELS
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DOI：
10.1016/s0006-3495(91)82068-9
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发表时间：
1991-08-01
影响因子：
3.4
通讯作者：
DILGER, JP
中科院分区：
文献类型：
--
作者：
LIU, Y;DILGER, JP
烟碱乙酰胆碱（ACh）受体负责在神经肌肉接头处将化学信号快速转化为电信号。因为受体和它的离子通道是单一跨膜蛋白的组成部分，所以ACh结合和通道开放之间的时间可以最小化。为了确定通道打开的速度，我们将0.1-10 mM ACh快速（100-400 μ s）应用于BC 3 H-1细胞的外向多通道膜贴片，同时在11 ℃下测量通过通道的电流开始。发作时间是急剧依赖于乙酰胆碱浓度时，通道激活是有限的乙酰胆碱（0.1-1 mM）的结合。在+50 mV时，20-80%的起始时间在高于5 mM ACh时达到接近110 μ s的平台，因为通道开放成为速率限制。因此，我们计算了开放速率，β几乎等于12/ms，而不参考特定的通道激活方案。在-50 mV下，ACh对通道的快速电压依赖性阻断与有限的溶液交换时间的组合扭曲了开始。为了确定在-50 mV下的开放速率，我们从“稳态”电流和噪声分析确定阻断的动力学参数，假设通道激活/阻断的顺序模型，并数值模拟对ACh快速灌注的电流响应。使用这种方法，我们发现β几乎等于15/ms。与通道关闭速率相反，打开速率对电压相对不敏感。
The nicotinic acetylcholine (ACh) receptor is responsible for rapid conversion of chemical signals to electrical signals at the neuromuscular junction. Because the receptor and its ion channel are components of a single transmembrane protein, the time between ACh binding and channel opening can be minimized. To determine just how quickly the channel opens, we made rapid (100-400-mu-s) applications of 0.1-10 mM ACh to outside-out, multichannel membrane patches from BC3H-1 cells, while measuring the onset of current flow through the channels at 11-degrees-C. Onset time is steeply dependent upon ACh concentration when channel activation is limited by binding of ACh (0.1-1 mM). At +50 mV, the 20-80% onset time reaches a plateau near 110-mu-s above 5 mM ACh as channel opening becomes rate limiting. Thus, we calculate the opening rate, beta almost-equal-to 12/ms, without reference to specific channel activation schemes, At -50 mV, the combination of a rapid, voltage-dependent block of channels by ACh with a finite solution exchange time distorts onset. To determine opening rate at -50 mV, we determine the kinetic parameters of block from "steady-state" current and noise analyses, assume a sequential model of channel activation/block, and numerically simulate current responses to rapid perfusion of ACh. Using this approach, we find beta almost-equal-to 15/ms. In contrast to the channel closing rate, the opening rate is relatively insensitive to voltage.