Ruff R L
Biophys J. 1982 Mar;37(3):625-31.
The effect of the local anesthetic QX222 on the kinetics of miniature end-plate currents (MEPC)and acetylcholine-induced end-plate current fluctuations was studied in voltage-clamped frog cutaneous pectoris neuromuscular junctions. The rate constants for a kinetic scheme of local anesthetic blockage of end-plate channels were calculated from the MEPC decay parameters. At 18 degrees C the blocking rate constant was 1.1 +/- 0.3 x 10(7) exp (-0.009 +/- 0.003 x V)s -1M-1, and the unblocking rate constant was 5.7 +/- 0.6 exp (0.011 +/- 0.002 x V)s -1. The dissociation constant was close to 10 microM at -80 mV. End-plate fluctuations indicated that the local anesthetic QX222 lowered the effective single-channel conductance, suggesting a finite blocked state conductance that was calculated to be 1.6 pS. The apparent differences between QX222 interaction with end-plate and extrajunctional channels are discussed.
在电压钳制的青蛙胸皮神经肌肉接头处，研究了局部麻醉药QX222对微小终板电流（MEPC）动力学以及乙酰胆碱诱导的终板电流波动的影响。根据MEPC衰减参数计算出终板通道局部麻醉药阻断动力学方案的速率常数。在18℃时，阻断速率常数为1.1±0.3×10⁷ exp（-0.009±0.003×V）s⁻¹M⁻¹，解阻断速率常数为5.7±0.6 exp（0.011±0.002×V）s⁻¹。在-80 mV时，解离常数接近10 μM。终板波动表明局部麻醉药QX222降低了有效单通道电导，提示存在一个计算得出为1.6 pS的有限阻断态电导。文中讨论了QX222与终板通道和接头外通道相互作用的明显差异。
