Selyanko A A, Robbins J, Brown D A
Department of Pharmacology, University College London, UK.
Recept Channels. 1995;3(2):147-59.
Putative M-type K(+)-channels ('M-channels') were recorded in differentiated NG108-15 neuroblastoma x glioma hybrid cells transformed to express m1 muscarinic acetylcholine receptors using cell-attached patch-electrodes. Channels showed multiple conductances, with peaks at 6-9 and 12-15 pS. Averaged currents showed time-dependent activation during 1 s depolarization steps to around -30 mV. Steady-state Po increased in a voltage-dependent manner when the membrane was depolarized between 10 and 60 mV, with a limiting slope of 5.5 mV/e-fold change in Po. Steady-state kinetics were fit by two open and three shut times: depolarization shortened shut times and lengthened open times. Application of muscarine (10 microM) or bradykinin (10 microM) to the membrane outside the patch reversibly reduced steady-state in-patch channel activity to 38.4 +/- 11.7 and 28.8 +/- 6.1% of control values, respectively. Inhibition was accompanied by a lengthening of channel shut times without significant change in open times or distribution of conductance levels. No effect of muscarine or bradykinin on whole-cell or membrane patch delayed rectifier currents was detected. It is concluded that M-channels in NG108-15 cells are qualitatively similar to, but sparser than, those previously reported in rat sympathetic neurones. Their inhibition by extra-patch acetylcholine and bradykinin suggests that a mobile messenger is involved in the transduction process leading from receptor activation to channel closure.
使用细胞贴附式膜片电极，在分化的NG108 - 15神经母细胞瘤x胶质瘤杂交细胞中记录到了假定的M型钾通道（“M通道”），这些细胞经转化后表达m1毒蕈碱型乙酰胆碱受体。通道呈现出多种电导，峰值分别在6 - 9 pS和12 - 15 pS。在向约 - 30 mV进行1秒去极化步骤期间，平均电流显示出时间依赖性激活。当膜在10至60 mV之间去极化时，稳态开放概率（Po）以电压依赖性方式增加，Po每变化e倍的极限斜率为5.5 mV。稳态动力学由两个开放时间和三个关闭时间拟合：去极化缩短了关闭时间并延长了开放时间。向膜片外的膜施加毒蕈碱（10 μM）或缓激肽（10 μM）可分别将膜片内通道的稳态活性可逆地降低至对照值的38.4±11.7%和28.8±6.1%。抑制伴随着通道关闭时间的延长，而开放时间或电导水平分布没有显著变化。未检测到毒蕈碱或缓激肽对全细胞或膜片延迟整流电流有影响。结论是，NG108 - 15细胞中的M通道在性质上与先前在大鼠交感神经元中报道的M通道相似，但数量较少。它们被膜片外乙酰胆碱和缓激肽抑制表明，一种可移动的信使参与了从受体激活到通道关闭的转导过程。
