Diisopropylfluorophosphate: suppression of ionic conductance of the cholinergic receptor.

When frog sartorius muscles were exposed to diisopropylfluorophosphate, the amplitude and half-decay time of the end-plate current decreased; the half-decay time became almost potential-independent and the equilibrium potential for the end-plate current was more negative than during control conditions. When the excess reagent was removed by washing so that only the phosphorylated acetylcholinesterase remained, the amplitude of the end-plate current was restored, while its half-decay time was markedly increased. These findings reveal that this organophosphate significantly affects the receptor-ionic conductance modulator complex in addition to its well-known anticholinesterase activity.