Linsdell P, Stanfield P R
Department of Physiology, University of Leicester, UK.
Pflugers Arch. 1993 Oct;425(1-2):41-53. doi: 10.1007/BF00374502.
Patch-clamp recording was used to characterise a delayed rectifier potassium channel and the effects of external tetraethylammonium (TEA) in neurons isolated from the CA1 region of cultured neonatal rat hippocampus. A preliminary kinetic analysis is presented. Very low concentrations of TEA included in the patch pipette solution had two effects on unitary currents: first unitary currents were reduced in amplitude, with an associated increase in open channel noise, and second channel mean open time was reduced. The reduction in unitary amplitude was consistent with a single TEA molecule blocking the channel with a voltage-independent Kd of 53.4 microM. The blocking and unblocking rate constants, estimated using two independent methods, were approximately 350 mM-1 ms-1 and 20 ms-1, both rate constants being independent of voltage. Channels blocked in this way appeared able to close normally without first having to become unblocked. The reduction in mean channel open time was probably due to a second, kinetically slower blocking reaction with a much lower Kd, probably between 300 and 800 microM. The voltage-independent blocking rate constant of the slower block was at least 25 times slower than that of the faster block.
采用膜片钳记录技术对培养的新生大鼠海马CA1区分离出的神经元中的延迟整流钾通道及细胞外四乙铵（TEA）的作用进行了表征。本文给出了初步的动力学分析。膜片钳微管溶液中极低浓度的TEA对单通道电流有两种作用：其一，单通道电流幅度减小，同时开放通道噪声增加；其二，通道平均开放时间缩短。单通道幅度的减小与单个TEA分子以53.4微摩尔的电压非依赖性解离常数阻断通道一致。使用两种独立方法估算的阻断和解阻断速率常数分别约为350毫摩尔-1毫秒-1和20毫秒-1，两个速率常数均与电压无关。以这种方式被阻断的通道似乎能够正常关闭，而无需先解除阻断。平均通道开放时间的缩短可能是由于第二种动力学较慢的阻断反应，其解离常数低得多，可能在300至800微摩尔之间。较慢阻断的电压非依赖性阻断速率常数至少比快速阻断的慢25倍。
