A new oral otoprotective agent. Part 1: Electrophysiology data from protection against noise-induced hearing loss

Abstract

Background: Data from animal studies show that antioxidants can compensate against noise-induced stress and sensory hair cell death. The aim of this study was to evaluate the otoprotection efficacy of various versions of orally administered Acuval 400 against noise damage in a rat animal model.

Material/methods: Fifty-five Sprague Dawley rats were divided into 4 groups: A) noise-exposed animals; B) animals exposed to noise and treated with the Acuval; C) animals exposed to noise and treated with a combination of Coenzyme Q10 and Acuval; D) animals treated only with Acuval and Coenzyme Q10 and with no exposure to noise. All solutions were administered orally 5 times: 24 and 2 hrs prior to noise exposure, and then daily for 3 days. The auditory function was assessed by measuring auditory brainstem responses (ABR) in the range from 2 to 32 kHz at times =1, 7, 14 and 21 days after noise exposure.

Results: At low frequencies (click and 4 kHz) animals from both A and B groups showed significant threshold shifts in the majority of the tested frequencies and tested times. For the same frequencies, animals from group C presented threshold levels similar to those from group D. At frequencies ≥ 8 kHz the protective performance of the 2 Acuval groups is more clearly distinguished from the noise group A. At 32 kHz the 2 Acuval groups perform equally well in terms of otoprotection. Animals in Group D did not show any significant differences in the hearing threshold during the experiment.

Conclusions: The data of this study suggest that a solution containing Coenzyme Q10 and Acuval 400, administered orally, protects from noise-induced hearing loss.

Figure 1

Data (threshold shifts with 95% confidence interval error bars), from group D. The lack of significant mean differences across the tested frequencies per observation window, is an indication of lack of possible ototoxic side-effects. Negative threshold shifts can interpreted as an improvement over the pre-noise exposure values (t=0), but since these differences are not statistically significant, no final conclusions can be made.

Figure 2

Data from the click and 4 kHz datasets, of all treated groups, in post-treatment observation windows from t=1 to 21d. The Y-axis depicts threshold in dB SPL, the X-axis time in days.

Figure 3

Data from the 8, 16 and 32 kHz datasets, of all treated groups, in post-treatment observation windows from t=1 to 21d. The Y-axis depicts threshold in dB SPL, the X-axis time in days.