Guinea pigs were given daily intramuscular injection of RSM 200 mg/kg, 400 mg/kg, AMK 100mg/kg, 200 mg/kg, AKM 100 mg/kg, 200 mg/kg for 28 days.
They were experimented with Preyer reflex, cochlear microphonics and NBT reducibility, and the results are as follows;
1) Animals receiving AMK 200 mg/kg, AKM 100 & 200 mg/kg caused decrease in formazan production in OHC & IHC in answer to the loss or dull of Preyer reflex in frequency range of 20 kHz to 10 kHz. From these results it was concluded that the changes in Preyer reflex is corresponded to the changes in NBT reducibility.
2) Animals receiving AKM 200 mg/kg caused decrease in NBT reducibility both in OHC & IHC, and the decline of CM was only observed at this dose.
3) The ototoxic effect of aminoglycoside antibiotics has been reported that the loss of OHC progresses from basal turn to the upper, but not in IHC. From this results of NBT reducibility, the disappearance or decline of NBT reducibility was observed in OHC and a matter of degree in IHC. It was presumed that when the first ototoxicity after aminoglycoside antibiotics injection appeared, some organic changes occur not only in OHC but in IHC.
4) Ototoxic effect on cochlea in guinea pigs receiving 10 or 20 times of clinical dose of aminoglycoside antibiotics daily i. m. injection for 28 days was AKM>AMK>RSM in order, and RSM was not toxic. From these results it was presumed that for setting up the doses of ototoxic experiment it is necessary to refer to acute toxicity as well as to maximum recomended clinical dose based on antibiotic activity and to consider wide extent of doses.
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