A microelectrode study of the effects of atracurium on neuromuscular transmission.

Using standard microelectrode recording techniques, we studied the effects of atracurium on neuromuscular transmission in a concentration range between 10(-13) and 10(-5) M in the rat diaphragm. Both intact and cut diaphragm preparations were used. Atracurium produced no significant alteration of miniature endplate potential (MEPP) frequency (P greater than 0.05). Increasing concentrations of atracurium (10(-6)-10(-5) M) caused a linear decrease in MEPP amplitude from 70.5 +/- 2.3% to 28.0 +/- 2.5% of baseline levels (P less than 0.05). In the cut diaphragm preparation, atracurium increased the degree of rundown and decreased quantum content of the endplate potential (EPP). The above observations suggest that atracurium interferes with neuromuscular transmission by, first of all, producing cholinergic receptor block and secondly, producing frequency-dependent inhibition of release of acetylcholine from the nerve terminal.