Acetylcholine responses on clonal myogenic cells in vitro.

1. Some electrophysiological properties of the acetylcholine response shown by clonal rat myogenic cells were studied in vitro. Some mononucleate myoblasts showed a slow hyperpolarizing response. 2. Multinucleate myotubes showed a fast depolarizing response that was very similar to that of mammalian skeletal muscle in vivo, and differed from the hyperpolarizing response of myoblasts. 3. The depolarizing response involved Na, K and Ca ions, but not Cl ions. The dependence of the reversal potential on external ion concentrations was generally similar to that shown by frog muscle, but some quantitative differences were seen. 4. The reversal potential determined at sites of nerve-muscle interaction did not differ from those at background or non-interacted sites.