Auerbach A, Akk G
Department of Physiology and Biophysics, State University of New York at Buffalo, Buffalo, New York 14214, USA.
J Gen Physiol. 1998 Aug;112(2):181-97. doi: 10.1085/jgp.112.2.181.
The rate constants of acetylcholine receptor channels (AChR) desensitization and recovery were estimated from the durations and frequencies of clusters of single-channel currents. Diliganded-open AChR desensitize much faster than either unliganded- or diliganded-closed AChR, which indicates that the desensitization rate constant depends on the status of the activation gate rather than the occupancy of the transmitter binding sites. The desensitization rate constant does not change with the nature of the agonist, the membrane potential, the species of permeant cation, channel block by ACh, the subunit composition (epsilon or gamma), or several mutations that are near the transmitter binding sites. The results are discussed in terms of cyclic models of AChR activation, desensitization, and recovery. In particular, a mechanism by which activation and desensitization are mediated by two distinct, but interrelated, gates in the ion permeation pathway is proposed.
通过单通道电流簇的持续时间和频率来估算乙酰胆碱受体通道（AChR）脱敏和恢复的速率常数。双配体结合开放的AChR脱敏速度比未结合配体或双配体结合关闭的AChR快得多，这表明脱敏速率常数取决于激活门的状态而非递质结合位点的占据情况。脱敏速率常数不会因激动剂的性质、膜电位、通透阳离子的种类、ACh对通道的阻断、亚基组成（ε或γ）或靠近递质结合位点的几个突变而改变。根据AChR激活、脱敏和恢复的循环模型对结果进行了讨论。特别提出了一种机制，即离子通透途径中的两个不同但相互关联的门介导激活和脱敏。
