Objective To investigate the effects of rocuronium and vecuronium on the adult-type (?-nAChR) and fetal-type (?-nAChR) muscle nicotinic acetylcholine receptors. Methods HEK293 cells were obtained from Institute of Cytology, Chinese Academy of Sciences.?- and ?-nAChRs were expressed heterologously in HEK293 cells using transfection technique. Whole cell patch clamp technique was used to determine the potencies of the two muscle relaxants alone or in combination in blocking the function of the two types of nAChRs. Results Both rocuronium and vecuronium could competitively inhibit the activation of ?- nAChR and ?-nAChR by Ach. The IC50 of rocuronium and vecuronium for ?-nAChR was 169.2 ? 12.5 and (8.3 ? 2.7) ?mol?L-1 and for ?-nAChR was 8.6 ? 2.7 and (55.0?10.4) ?mol?L-1 respectively. The IC50 of rocuronium in combination with vecuronium was (0.7 ? 0.3) ?mol ? L-1 for ?-nAChR and (36.3 ? 14.2) ?mol ? L-1 for ?-nAChR.Conclusion The two muscle relaxants have different blocking action on the two types of nAChRs. Rocuronium has stronger inhibitory effect on ?-nAChR than on ?-nAChR while vecuronium has stronger inhibitory effect on ?-nAChR than on ?-nAChR. The inhibitory effects of the two muscle relaxants in combination was synergistic on ?-nAChR and additive on ?-nAChR.