ABSTRACT
The skeletal muscle relaxing effects of gentamicin (Gen) and amikacin (Amk) were investigated and compared with tubocu-rarine (Tub) in rat phrenic nerve-muscle preparation, conscious chicken and mouse. The potency of the neuro-muscular blocking action of Gen was two times that of Amk. The blocking effect of Gen was observed as an 'all or none' phenomenon with a bigger S value compared with Tub. The drug concentrations were decreased by pumping drug free perfusate into or-gan baths to simulate an elimination rate constant fixed at 0. 1/min. To plot effects against declined concentrations there was a clockwise hysteresis loop with Tub, but a counter-clockwise hystereksis loop presented by Gen. The mode of the skeletal muscle relaxing effect of Gen and Amk was classified as non-depolarization like Tub.