Voltage fluctuations at the frog sartorius motor endplate produced by a covalently attached activator.

The depolarization that develops after covalent attachment of trimethylammonium benzoyl to the dithiothreitol-reduced frog sartorius acetylcholine receptor is accompanied by a small increase in voltage fluctuations. The amplitude of the elementary voltage event produced by the covalently attached activator is about 0.04 microV, almost an order of magnitude below the acetylcholine shot-effect amplitude in the control preparation, and about one-fourth the acetylcholine shot amplitude after disulfide-bond reduction. Spectral density plots of trimethylammonium-benzoyl noise can be analyzed in terms of two relaxation rates that bracket the single rate observed in response to acetylcholine.