The charge carried by single‐channel currents of rat cultured muscle cells in the presence of local anaesthetics.

Abstract

Acetylcholine-induced single-channel currents were measured in the presence of the lignocaine derivative QX222 [2-(trimethylamino)-N-2,6-dimethylphenylacetamide]. Unit responses appeared as bursts of short current pulses as a result of the fat blocking action of the drug (QX222). The amplitude of the individual current pulses was not changed by the presence of the drug up to a concentration of 250 .mu.M. The time integral of current during a burst, which for a sequential blocking model should be independent of drug concentration, decreased at concentrations of QX222 higher than 40 .mu.M. The distribution of gap times within a burst could not be fitted by a single exponential for high concentrations of QX222. The simple sequential model of channel blockade evidently does not apply for concentrations of QX222 higher than 40 .mu.M.