title: The effects of acoustic environment after traumatic noise exposure on hearing and outer hair cells.
abstract: Previous studies reported that exposure to non-traumatic level sounds after traumatic noise exposure reduced the degree of noise-induced hearing loss and hair cell stereocilia damage. The current study investigated the effects of a 3-day post-noise acoustic environment on the degree of noise-induced hearing loss and cochlear damage. Female chinchillas were exposed to traumatic continuous noise (4 kHz octave-band noise) at 107 dB SPL for 1h and then placed in either an augmented acoustic environment (AAE) or deprived acoustic environment (DAE) for 3 days. The AAE group was exposed to a broad-band noise (4-20 kHz) at 80 dB SPL and the DAE animals were fit with conventional earplugs to minimize the level of acoustic stimulation. Auditory brainstem responses (ABRs) were recorded before and 3 days after the traumatic noise exposure. The AAE group showed a significantly lower average threshold shift at the frequencies of 4 and 8 kHz (p<0.01). Correspondingly, significantly fewer missing and dying outer hair cells (OHCs) were observed in the AAE group than in the DAE group. Although the cochlear reduced and oxidized glutathione levels (GSH and GSSG, respectively) were essentially the same in two groups at day 3, significant correlations were found between GSSG levels and mean ABR threshold shift (1-16 kHz) in the AAE group; as well as GSSG and percentage of total OHC loss in the DAE group. The results suggest that post-noise acoustic environment influenced the degree of hearing loss and OHC deterioration after traumatic noise exposure.
authors.affiliation: Center for Hearing and Deafness, Department of Communicative Disorders and Sciences, State University of New York at Buffalo, 137 Cary Hall, 3435 Main Street, Buffalo, NY 14214, USA. ctanaka@buffalo.edu
authors.forename: Chiemi
authors.initials: C
authors.lastname: Tanaka
authors.forename: Guang-Di
authors.initials: GD
authors.lastname: Chen
authors.forename: Bo Hua
authors.initials: BH
authors.lastname: Hu
authors.forename: Lai-Har
authors.initials: LH
authors.lastname: Chi
authors.forename: Manna
authors.initials: M
authors.lastname: Li
authors.forename: Guiliang
authors.initials: G
authors.lastname: Zheng
authors.forename: Eric C
authors.initials: EC
authors.lastname: Bielefeld
authors.forename: Samson
authors.initials: S
authors.lastname: Jamesdaniel
authors.forename: Donald
authors.initials: D
authors.lastname: Coling
authors.forename: Donald
authors.initials: D
authors.lastname: Henderson
mesh_terms: D000158:Acoustic Impedance Tests; D000161:Acoustic Stimulation / Q000379:methods; D000162:Acoustics; D000818:Animals; D001309:Auditory Threshold; D002682:Chinchilla; D003051:Cochlea / Q000378:metabolism; D004777:Environment; D016057:Evoked Potentials, Auditory, Brain Stem; D005260:Female; D005978:Glutathione / Q000378:metabolism; D019803:Glutathione Disulfide / Q000378:metabolism; D018072:Hair Cells, Auditory, Outer / Q000473:pathology / Q000502:physiology; D006317:Hearing Loss, Noise-Induced / Q000209:etiology / Q000473:pathology / Q000503:physiopathology / Q000517:prevention & control*; D018613:Microscopy, Confocal
chemical_list: D005978:Glutathione; D019803:Glutathione Disulfide