Effects of noise on inferior colliculus evoked potentials and cochlear anatomy in young and aged chinchillas.
Like many aging humans, the aging chinchilla tends to lose high-frequency sensitivity at a faster rate than low-frequency sensitivity. This feature, combined with its excellent low-frequency hearing, makes the chinchilla attractive as an animal model for studying the relationship between noise-induced hearing loss (NIHL) and age-related hearing loss (AHL). In the present study, we examined susceptibility to noise in 15 aged (10-15 years old) and 15 young chinchillas. Two levels of noise were used, with the aim of determining whether age-related differences exist in the magnitude and rate of recovery from temporary threshold shifts produced by a moderate-level (95 dB) noise exposure, or in susceptibility to permanent threshold shifts and cochlear damage caused by a high-level (106 dB) noise exposure. Thresholds and response amplitudes at 0.5, 1, 2, 4, 8 and 16 kHz were determined from evoked potentials recorded from the inferior colliculus. Cochlear histology was performed on animals exposed to high-level noise. The results suggest that older animals are equally vulnerable to moderate-level noise, but may be slightly more vulnerable to high-level noise. For moderate-level exposures, there appears to be a simple additive relationship (in dB) between AHL and NIHL. For high-level exposures, the relationship may be more complex.
McFadden
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Center for Hearing and Deafness, Department of Communicative Disorders, University at Buffalo, NY 14214-3007, USA. mcfadden@acsu.buffalo.edu
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Ding
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D000161:Acoustic Stimulation; D000375:Aging / Q000502:physiology*; D000704:Analysis of Variance; D000818:Animals; D001309:Auditory Threshold / Q000502:physiology; D002682:Chinchilla; D003051:Cochlea / Q000473:pathology*; D004195:Disease Models, Animal; D016057:Evoked Potentials, Auditory, Brain Stem / Q000502:physiology*; D006199:Hair Cells, Auditory, Inner / Q000473:pathology / Q000648:ultrastructure; D018072:Hair Cells, Auditory, Outer / Q000473:pathology / Q000648:ultrastructure; D006317:Hearing Loss, Noise-Induced / Q000175:diagnosis / Q000209:etiology* / Q000473:pathology / Q000503:physiopathology; D007245:Inferior Colliculi / Q000473:pathology / Q000503:physiopathology*; D008855:Microscopy, Electron, Scanning; D009622:Noise / Q000009:adverse effects*; D009925:Organ of Corti / Q000473:pathology; D011304:Presbycusis / Q000209:etiology*; D013316:Stria Vascularis / Q000473:pathology