Abstract
In this study, we investigated the effects of varying intensity levels of repeated moderate noise exposures on hearing. The aim was to define an appropriate intensity level that could be repeated several times without giving rise to a permanent hearing loss, and thus establish a model for early adulthood moderate noise exposure in rats. Female Sprague-Dawley rats were exposed to broadband noise for 90 min, with a 50 % duty cycle at levels of 101, 104, 107, or 110 dB sound pressure level (SPL), and compared to a control group of non-exposed animals. Exposure was repeated every 6 weeks for a maximum of six repetitions or until a permanent hearing loss was observed. Hearing was assessed by the auditory brainstem response (ABR). Rats exposed to the higher intensities of 107 and 110 dB SPL showed permanent threshold shifts following the first exposure, while rats exposed to 101 and 104 dB SPL could be exposed at least six times without a sustained change in hearing thresholds. ABR amplitudes decreased over time for all groups, including the non-exposed control group, while the latencies were unaffected. A possible change in noise susceptibility following the repeated moderate noise exposures was tested by subjecting the animals to high-intensity noise exposure of 110 dB for 4 h. Rats previously exposed repeatedly to 104 dB SPL were slightly more resistant to high-intensity noise exposure than non-exposed rats or rats exposed to 101 dB SPL. Repeated moderate exposure to 104 dB SPL broadband noise is a viable model for early adulthood noise exposure in rats and may be useful for the study of noise exposure on age-related hearing loss.
Highlights
Hearing impairment is one of the most common disabilities in modern society, according to National Institute on Deafness and Other Communication Disorders (NIDCD, 2010)
At 7 kHz; F(3)=12.6, PG0.001 for 107 dB sound pressure level (SPL) compared to 101 and 104 dB SPL, P=0.001 for 110 dB SPL compared to 101 dB SPL and P=0.004 for 110 dB SPL compared to 104 dB SPL
We investigated the functional effects of moderate noise exposures at different intensity levels in early adulthood of the female Sprague-Dawley rat in order to determine the levels that could be repeated several times without causing permanent threshold shifts
Summary
We are living in an increasingly noisy world where individuals are exposed to moderate everyday noise from their leisure activities, e.g., loud music from earphones and high volume at the cinemas, gyms, rock concerts, etc. While these repeated noise exposures, sometimes of quite high intensities, usually do not elicit a detectable loss of hearing, their longterm effects on auditory function are not well explored. Been suggested that these exposures will adversely affect the progression of agerelated hearing loss (Stockwel et al 1969; Johnsson and Hawkins 1972; Mostafapour et al 1998; Dalton et al 2001)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
