Protective effects of N-acetylcysteine on noise-induced hearing loss in guinea pigs

摘要

Increasing evidence suggests the involvement of oxidative stress in noise-induced hearing loss. The present study analysed, in an animal ex- perimental model, the time course of the pathogenic mechanisms of noise-induced cochlear damage and the effcacy of the antioxidant drug N-acetylcysteine in reducing noise ototoxicity. animals were divided into two groups, exposed to noise one treated with N-acetylcysteine for 3 days and one (the control group) with saline. acoustic trauma was induced by a continuous pure tone of 6 kHz, at 120 dB SPL for 30 minutes. Electrocochleographic recordings were made from an implanted round window electrode and the compound action potentials were measured daily at 2-16 kHz for 7 days. morphological changes were analysed by scanning electron microscopy. The acoustic thresh- old measured 1 hour after acoustic trauma was elevated in the control group to 70-90 dB in the higher frequencies of the compound action potential audiogram, with a maximum threshold elevation ranging between 12 and 16 kHz. During the frst 24 h, following acoustic trauma, there was a partial recovery of compound action potential thresholds of about 20 dB to reach a fnal threshold elevation of about 50-70 dB; there was no further improvement over the remaining experimental week. animals treated with N-acetylcysteine showed a similar tempo- rary threshold shift but a clear improvement in the recovery of compound action potential thresholds, with signifcantly reduced permanent threshold shift and hair cell loss. These data suggest that N-acetylcysteine is able to attenuate the toxic effect of acoustic trauma and could represent an interesting molecule for preventing inner ear injuries.