Influence of Chronic Treatment with Neomycin and Kanamycin on N1 Suppression Produced by Contralateral Olivo-Cochlear Bundle Stimulation in Cats

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Abstract
Twenty cats received one subcutaneous injection per day of neomycin sulfate (100 mg/kg/day) and 5, kanamycin sulfate (200 mg/kg/day) for 8 days; experiments were performed on the ninth day. Nine of 10 untreated control, 13 of 20 neomycin and 5 of 5 kanamycin animals had normal cochlear responses to acoustic stimulation and were usable for this study. The efficacy of contralateral olivo-cochlear bundle (COCB) stimulation was determined at 400 (optimally effective) and 100 (minimally effective) Hz for 4 different current strengths at each frequency of stimulation. Six of the neomycin animals exhibited a significant block of COCB stimulation effects at all currents and both frequencies of stimulation, while the other 7 neomycin animals and the kanamycin animals showed a significant increase in the effectiveness of COCB stimulation at the lower currents of the higher (optimal) stimulation frequency. Thus, chronic treatment with neomycin and kanamycin produces changes in COCB stimulation effects, indicating that alterations of cochlear efferent function may be playing a role in the genesis of the ototoxicity produced by certain Streptomyces antibiotics.