Land B R, Salpeter E E, Salpeter M M
Proc Natl Acad Sci U S A. 1981 Nov;78(11):7200-4. doi: 10.1073/pnas.78.11.7200.
The dependency of miniature endplate current (mepc) rise time upon mepc amplitude and acetylcholine receptor site density was measured in lizard intercostal muscles and used to fit the rate constants in a simple kinetic scheme. The kinetic scheme included diffusion, two-step sequential binding of acetylcholine to receptor, and opening of the ion channel. Numerical simulation of the observed mepc behavior yielded the following kinetic constants; (i) diffusion constant, 4 X 10(-6) cm2 sec-1; (ii) forward binding rates, 4.7 X 10(7) M-1 sec-1; (iii) channel relaxation rate, 25 msec-1. The value above for the forward binding rates assumed both rates to be equal. If they are different, the slower of the two is in the range of 2-5 X 10(7) M-1 sec-1. A radial profile of bound receptor indicated that activation of the receptor was very local, occurring essentially within a radius of about 0.3 micrometers from the point of acetylcholine release.
在蜥蜴肋间肌中测量了微小终板电流（mepc）上升时间对mepc幅度和乙酰胆碱受体位点密度的依赖性，并用于拟合简单动力学方案中的速率常数。该动力学方案包括扩散、乙酰胆碱与受体的两步顺序结合以及离子通道的开放。对观察到的mepc行为进行数值模拟得到了以下动力学常数：（i）扩散常数，4×10^(-6) cm² sec⁻¹；（ii）正向结合速率，4.7×10⁷ M⁻¹ sec⁻¹；（iii）通道松弛速率，25 msec⁻¹。上述正向结合速率的值假定两个速率相等。如果它们不同，则较慢的速率在2 - 5×10⁷ M⁻¹ sec⁻¹范围内。结合受体的径向分布表明，受体的激活非常局部，基本上发生在距乙酰胆碱释放点约0.3微米半径范围内。
