[Effect of vinblastine and colchicine on the postsynaptic membrane of the myoneural junction in the frog].

Postsynaptic effects of vinblastine (VB) and colchicine (CCH) were studied in the frog neuromuscular junction under voltage-clamp conditions. The same concentrations of VB and CCM, which did not affect the amplitude and duration of miniature end plate currents (MEPC), the current-voltage relationship of peak end plate currents (EPC) and voltage sensitivity of the decay phase of EPC, markedly reduced the responses to iontophoretic application of acetylcholine. Both VB and CCH accelerated the EPC decay when acetylcholinesterase was inhibited; they also caused a pronounced depression in the trains of EPC (10 Hz) and trains of responses to acetylcholine application (5-10 Hz). It was concluded that use-dependent effects of VB and CCH are not connected with their influence on the cytoskeleton of the muscle fibre, but can be a result of accelerated desensitization of cholinoreceptors.