Neher E, Marty A, Fukuda K, Kubo T, Numa S
Max-Planck-Institut für biophysikalische Chemie, Göttingen, FRG.
FEBS Lett. 1988 Nov 21;240(1-2):88-94. doi: 10.1016/0014-5793(88)80345-4.
Four subtypes of muscarinic acetylcholine receptor (mAChR) were stably expressed in neuroblastoma-glioma hybrid cells (NG108-15). By combining fluorescent indicator dye (fura-2) studies with electrophysiological measurements it is shown that stimulation of mAChR I and mAChR III readily leads to release of calcium from intracellular stores and to associated conductance changes, whereas stimulation of mAChR II and mAChR IV exerts no such effect. Dose-response curves describing the amplitude or the delay of the calcium rise induced by acetylcholine suggest that the apparent affinity of mAChR III for its agonist is higher by about one order of magnitude than that of mAChR I. Ionic substitution experiments and current fluctuation analysis indicate that calcium activates a K+-specific conductance of 'small' single-channel amplitude similar to the SK type. Furthermore, an outward current (M current) suppressed by activation of mAChR I and mAChR III has a single-channel amplitude corresponding to a conductance of approximately 3 pS.
毒蕈碱型乙酰胆碱受体（mAChR）的四种亚型在神经母细胞瘤-胶质瘤杂交细胞（NG108-15）中稳定表达。通过将荧光指示剂染料（fura-2）研究与电生理测量相结合，结果表明，刺激mAChR I和mAChR III容易导致细胞内钙库释放钙，并引起相关的电导变化，而刺激mAChR II和mAChR IV则没有这种作用。描述乙酰胆碱诱导的钙升高幅度或延迟的剂量反应曲线表明，mAChR III对其激动剂的表观亲和力比mAChR I高约一个数量级。离子替代实验和电流波动分析表明，钙激活了一种“小”单通道幅度的K+特异性电导，类似于SK型。此外，被mAChR I和mAChR III激活所抑制的外向电流（M电流）具有对应于约3 pS电导的单通道幅度。
