Protti D A, Uchitel O D
Instituto de Biología Celular y Neurociencias: "Pr. Dr. Eduardo P. de Robertis", Facultad de Medicina, Universidad de Buenos Aires, Paraguay 2155, Buenos Aires (1121), Argentina.
Pflugers Arch. 1997 Aug;434(4):406-12. doi: 10.1007/s004240050414.
The identity of the voltage-dependent calcium channels (VDCC), which trigger the Ca2+-gated K+ currents (IK(Ca)) in mammalian motor nerve terminals, was investigated by means of perineurial recordings. The effects of Ca2+ chelators with different binding kinetics on the activation of IK(Ca) were also examined. The calcium channel blockers of the P/Q family, omega-agatoxin IVA (omega-Aga-IVA) and funnel-web spider toxin (FTX), have been shown to exert a strong blocking effect on IK(Ca). In contrast, nitrendipine and omega-conotoxin GVIA (omega-CgTx) did not affect the Ca2+-activated K+ currents. The intracellular action of the fast Ca2+ buffers BAPTA and DM-BAPTA prevented the activation of the IK(Ca), while the slow Ca2+ buffer EGTA was ineffective at blocking it. These data indicate that P/Q-type VDCC mediate the Ca2+ influx which activates IK(Ca). The spatial association between Ca2+ and Ca2+-gated K+ channels is discussed, on the basis of the differential effects of the fast and slow Ca2+ chelators.
通过神经束膜记录法研究了触发哺乳动物运动神经末梢中Ca2+门控K+电流（IK(Ca)）的电压依赖性钙通道（VDCC）的特性。还研究了具有不同结合动力学的Ca2+螯合剂对IK(Ca)激活的影响。P/Q家族的钙通道阻滞剂ω-芋螺毒素IVA（ω-Aga-IVA）和漏斗网蜘蛛毒素（FTX）已被证明对IK(Ca)有强烈的阻断作用。相比之下，尼群地平和ω-芋螺毒素GVIA（ω-CgTx）不影响Ca2+激活的K+电流。快速Ca2+缓冲剂BAPTA和DM-BAPTA的细胞内作用可阻止IK(Ca)的激活，而慢速Ca2+缓冲剂EGTA对其阻断无效。这些数据表明，P/Q型VDCC介导激活IK(Ca)的Ca2+内流。基于快速和慢速Ca2+螯合剂的不同作用，讨论了Ca2+与Ca2+门控K+通道之间的空间关联。
