[Reactivating and cholinolytic action of dipyroxime in the myoneural synapse of warm-blooded animals].

Reactivating (RA) and cholinolytic (Chl) effects of dipyroxime in soleus and diaphragm muscles of the rat were estimated by amplitudes and durations of miniature end-plate potentials (MEPP) and currents (MEPC). After armin-induced inhibition of acetylcholinesterase (AchE), the action of dipyroxime in concentrations of 5.10(-6)-5.10(-4) mol/l on the amplitude and duration of MEPPs and MEPCs represents the combination of RA and Chl effects. Separate study of the RA effect (after washing out of the reactivator) has shown that this effect increased within the whole range of concentrations used. Complete reactivation of phosphorylated AchE was achieved at dipyroxime concentrations of 2-5.10(-4) mol/l. Separate analysis of Chl effect (in voltage-clamp experiments with intact AchE) has shown that dipyroxime suppressed acetylcholine-induced responses due to a block of cholinoreceptors in the open conformation. This block was characterized by prolongation of MEPCs decay without affecting its exponential nature. It is concluded that dipyroxime is a "very fast blocker".