Acetylcholine noise in cultured chick myoballs: a voltage clamp analysis.

Abstract

Large spherical muscle cells were grown in vitro by allowing dissociated chick embryo myoblasts to fuse in suspension culture. Myoball membranes could be adequately voltage clamped even in the face of large inward currents (100 nA) induced by ACh [acetylcholine]. The single channel conductance, .gamma., estimated from the ratio of the mean to the variance of ACh currents was 25-40 pmho [l/pohm] at temperatures between 25.degree. and 37.degree. C. Spectra of ACh current fluctuations declined with 1/f2. The mean channel open time (.tau.) estimated from the half-power frequency was 2 ms at 37.degree. C and -90 m V holding potential. At lower membrane potentials .tau. was decreased and on hyperpolarization .tau. was prolonged.