Channel open time of acetylcholine receptors on Xenopus muscle cells in dissociated cell culture

The kinetics of acetylcholine (ACh) receptor channels on cultured myotomal muscle cells from Xenopus embryos were studied by analyzing focally recorded membrane currents. The mean open time for receptor channels on embryonic muscle cells grown in dissociated cell cultures showed a time-dependent decrease similar to that seen in vivo. The changes in power density spectra are consistent with the hypothesis that the decrease results from the appearance of a class of ACh receptor with a short mean channel open time (0.7 msec) and a decrease in the proportion of receptors with a long mean channel open time (3 msec). The addition of dissociated neural tube cells to muscle cell cultures resulted in an unexpected increase in mean channel open time for ACh receptors in both synaptic and nonsynaptic regions. These studies demonstrate that ACh receptor function may be altered in cultured muscle cells.