Asymmetry of the acetylcholine channel revealed by quaternary anesthetics

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Science  10 Oct 1980:
Vol. 210, Issue 4466, pp. 205-207
DOI: 10.1126/science.6251552


Tissue-cultured rat myoballs were examined electrophysiologically with a suction pipette, which was used for voltage clamping and internal perfusion. The lidocaine derivative QX-314 caused a time- and membrane potentia-dependent block of acetylcholine-induced current only when applied from the extracellular membrane surface. The same compounds caused a use-dependent block of the sodium channel only from the intracellular membrane surface. These experiments demonstrate a fundamental asymmetry of the acetylcholine receptor-channel complex.