Hoger J H, Rudy B, Lester H A, Davidson N
Division of Chemistry, California Institute of Technology, Pasadena 91125.
Brain Res Mol Brain Res. 1991 Apr;10(1):1-11. doi: 10.1016/0169-328x(91)90050-8.
The voltage-dependent K+ currents encoded by rat brain mRNA were studied in Xenopus oocytes after the voltage-dependent Na+ currents and the Ca(2+)-activated Cl- currents were eliminated pharmacologically. This paper describes the maintained K+ currents (IK), defined primarily by resistance to inactivation for 1 s at a holding potential of -40 mV. IK activates at potentials more positive than -60 to -70 mV and consists of both low-threshold and high-threshold components. IK is partially blocked by both tetraethyl ammonium (TEA) and 4-aminopyridine (4-AP), which appear to be blocking the same component. Long depolarizing pulses result in incomplete inactivation of IK; the inactivating component is inhibited by TEA. Sucrose density gradient fractionation partially resolves the RNA encoding the several components of IK; most IK arises from size classes between 3.8 and 9.5 kb. The study gives further evidence for the existence of numerous distinct RNA populations that encode brain K+ channels different from previously reported cloned K+ channels that have been expressed in Xenopus oocytes.
在通过药理学方法消除电压依赖性Na⁺电流和Ca(2⁺)激活的Cl⁻电流后，对非洲爪蟾卵母细胞中由大鼠脑mRNA编码的电压依赖性K⁺电流进行了研究。本文描述了持续的K⁺电流（IK），其主要定义为在-40 mV的保持电位下1 s内对失活的抗性。IK在比-60至-70 mV更正的电位下激活，由低阈值和高阈值成分组成。IK被四乙铵（TEA）和4-氨基吡啶（4-AP）部分阻断，它们似乎阻断的是同一成分。长时间的去极化脉冲导致IK不完全失活；失活成分被TEA抑制。蔗糖密度梯度分级分离部分解析了编码IK几个成分的RNA；大多数IK来自3.8至9.5 kb之间的大小类别。该研究进一步证明了存在许多不同的RNA群体，它们编码的脑K⁺通道不同于先前报道的已在非洲爪蟾卵母细胞中表达的克隆K⁺通道。
