Objective To investigate the effects of rocuronium on the
neuromuscular junction of rat diaphragm. Methods One hundred
and sixty rats were used in the study which was approved by the Animal Care Committee of the General Hospital of PLA. In isolated non-uniformly stretched muscle preparation (INSMP) of rat diaphragm, micro-
endplate potentials (MEPP) and endplate potentials (EPP) were recorded simultaneously with one microelectrode of one endplate. The effects of rocuronium in dosages of 2.5, 5, 10, 20μg/ml on the amplitude and frequency of MEPP and the amplitude of EPP were observed. Results Rocuronium could decrease both the amplitude and frequency of MEPP obviously and the onset time was 1min after drug administration. The amplitude of EPP was depressed by rocuronium in a dose of 5μg/ml at 3min. Neither 2.5μg/ml nor 0.5μg/ml of rocuronium produced any effect on the amplitude of EPP. Conclusion The results indicated that rocuronium might produce a rapid and early presynaptic effect on
neuromuscular junction in INSMP in rats.