Effect of sound conditioning on protection of hearing and plasma antioxidant activity in rabbits

Background: Noise is one of the major physical pollutants in present societies. Sound conditioning is used as means of protecting against noise-induced hearing loss. The status of plasma antioxidant system during sound conditioning is important. Objective: To study possible involvement of plasma total antioxidant ability in noise-induced hearing loss and sound conditioning. Methods: This study was carried out on 24 male white New Zealand rabbits (6 in each group). The rabbits were assigned to the following four groups: (1) Noise exposure (250Hz-20000Hz, 110 dB for 8h/day for 12 days), (2) Conditioning noise exposure (80dB for 10 days and 110 dB for 12 days), (3) Noise exposure (80 dB) and (4) control group. Auditory Brain stem Response (ABR) was measured and compared in all pre- and post-exposures groups. Plasma antioxidant power was also measured post exposure. FRAP was assayed in plasma sample collected from each animal using TPTZ reagent. Findings: The ABR assay using click in different experimental groups showed that the absolute latency of 5th wave generation was statistically significant in first group as compared to other groups (p=0.0001). Likewise ABR assay using tone burst showed a higher absolute latency observed in group 1. FRAP assay indicated that the antioxidant parameters were suppressed in group 1 when compared with data obtained from other groups (p<0.05). Conclusion: The ABR results found in our study, confirmed sound conditioning in rabbits exposed to 80 and 110 dB. Furthermore, changes in FRAP in rabbits studied in our experiment was indicative of involvement of antioxidant system in sound conditioning however, further studies needed.