Lack of protection against gentamicin ototoxicity by auditory conditioning with noise

Abstract

IntroductionAuditory conditioning consists of the pre-exposure to low levels of a potential harmful agent to protect against a subsequent harmful exposure. ObjectiveTo confirm if conditioning with an agent different from that used to cause the trauma can also be effective. MethodsThis was an experimental study with 17 guinea pigs, divided into three groups: an ototoxic control group (Cont) that received intramuscular administration of gentamicin 160mg/kg/day for ten consecutive days, but no sound exposure; a sound control group (Sound) that was exposed to 85dB broadband noise centered at 4kHz, 30min each day for ten consecutive days, but received no ototoxic medications; and an experimental group (Expt) that received sound exposure identical to the Sound group and after each noise presentation, received gentamicin similarly to Cont group. The animals were evaluated by distortion product otoacoustic emissions (DPOAEs), brainstem auditory evoked potentials (BAEPs), and scanning electron microscopy. ResultsThe animals that were conditioned with noise did not show any protective effect compared with the ones that received only the ototoxic gentamicin administration. This lack of protection was observed functionally and morphologically. ConclusionConditioning with 85dB broadband noises, 30min a day for ten consecutive days does not protect against an ototoxic gentamicin administration of 160mg/kg/day for ten consecutive days in the guinea pig.