Neomycin: Ototoxicity And The Cochlear Efferents

Abstract

The effects of neomycin on cochlear histology were correlated with its effect on contralateral olivo-cochlear bundle (COCB) stimulation in cats given one subcutaneous injection of neomycin per day (100 mg/kg/day) for 0 (controls), 4, 6, 7, 10 and 12 days. Enhancement of COCB stimulation effects occurs first, the highest incidence being found after 6 and 7 days of neomycin treatment. This is then followed by a block of COCB stimulation effects which is greatest at 10 and 12 days of neomycin treatment. There is minimal damage to the cochleas of these animals, indicating that enhancement and block of COCB stimulation effects may be due to a pharmacological action on the efferent synapse which occurs before extensive ototoxicity develops. This pharmacological synaptic activity of neomycin could be playing a role in the genesis of ototoxicity.