Otoprotective Effects of Resveratrol and Melatonin in Noise-Exposed Wistar Rats

In consideration of the benefits of antioxidant substances, this study evaluated the effect of resveratrol and melatonin in Wistar rats with or without exposure to high sound pressure levels (HISHLs).

This work is a prospective, comparative, longitudinal, in vivo experimental study involving Wistar rats. On Day 0, the animals underwent general health assessments, otoscopic examination and baseline hearing evaluations based on distortion-product otoacoustic emissions (DPOAEs) and auditory brainstem responses (ABRs). They were divided into groups and treated with or without melatonin or resveratrol (10 mg/kg/day) for 14 consecutive days. From Day 5 onwards, the noise, resveratrol noise and melatonin noise groups were exposed to white noise (4 kHz; 100 ± 3 dB) for 8 hours per day for 10 days. Hearing assessments were repeated on Day 15 (D15) and Day 30 (D30). Data were analysed by using t-tests or Mann-Whitney U tests, depending on distribution and normality.

D15 and D30 evaluations revealed that the groups exposed to noise had statistically significantly worsened amplitude and signal-to-noise ratio of DPOAE compared with the groups that were not subjected to noise exposure. The analysis of the noise-exposed animals showed that DPOAE recovered partially in the melatonin and resveratrol groups at the end of the experiment (D30). The melatonin and resveratrol groups showed a statistically significant difference from the noise group, although their medians were even lower than those of the control group. ABR analysis showed that the electrophysiological auditory thresholds in the melatonin and resveratrol groups recovered at D30.

Melatonin and resveratrol demonstrated otoprotective effects on the hearing of Wistar rats exposed to HISHL.