Ameliorative effects of an augmented acoustic environment on age-related hearing loss in middle-aged Fischer 344/NHsd rats.
OBJECTIVE
To investigate the effects of an augmented acoustic environment (AAE) on age-related hearing loss (ARHL) and outer hair cell (OHC) pathology in middle-aged Fischer 344/NHsd (F344/NHsd) rats.


METHODS
Eleven F344/NHsd rats were divided into two groups: 1) the AAE group (n = 5), which was exposed to 4-20 kHz broadband noise at 80 dB SPL for 12 h/d, 5 d/wk for 13 weeks starting from 16 months of age; and 2) the control group (n = 6), which did not receive the AAE during the same time span. Auditory brainstem response thresholds were obtained at different time points, and OHC pathology was examined after 13 weeks of AAE using propidium iodide and antiprestin antibody staining.


RESULTS
The AAE-treated rats showed smaller mean threshold shifts (-1 to -3 dB) at 20-40 kHz than the control group (7.5-16.7 dB) at 13 weeks. No significant group differences were observed in the percentage of missing OHCs or abnormal OHC nuclei. However, examination of prestin in a pair of AAE and control rats revealed more uniform prestin staining intensity among OHCs in the AAE-treated cochlea than in the control cochlea.


CONCLUSIONS
Thirteen-week AAE treatment in the middle-aged F344/NHsd rats slowed progression of ARHL. The AAE did not show a significant effect on OHC degeneration, but it is speculated that the AAE may maintain the integrity of prestin to preserve OHC functionality. However, further study is warranted to understand the protective mechanism of AAE as an intervention against ARHL.
Center for Hearing and Deafness, Department of Communicative Disorders and Sciences, State University of New York at Buffalo, Buffalo, New York 14214, USA. ctanaka@buffalo.edu
Chiemi
C
Tanaka
Eric C
EC
Bielefeld
Guang-Di
GD
Chen
Manna
M
Li
Donald
D
Henderson
D000162:Acoustics; D000375:Aging / Q000502:physiology*; D000704:Analysis of Variance; D000818:Animals; D001309:Auditory Threshold / Q000502:physiology; D003051:Cochlea / Q000473:pathology*; D004777:Environment; D006198:Hair Cells, Auditory / Q000473:pathology*; D006317:Hearing Loss, Noise-Induced / Q000473:pathology* / Q000517:prevention & control*; D008297:Male; D051381:Rats; D011916:Rats, Inbred F344