title: Age-related hearing impairment in senescence-accelerated mouse (SAM).
abstract: The auditory brainstem response and histopathology of the cochlea were investigated in an accelerated senescence-prone strain, SAM-P/1 mice and a senescence-resistant strain, SAM-R/1 mice. Each strain displayed an age-related auditory loss expressed as elevated thresholds similar to human hearing loss in that high-frequency losses occurred earlier than middle- or low-frequency losses. SAM-P/1 showed a more rapid decline of hearing with age than did SAM-R/1. Interpeak intervals I-III and I-IV were prolonged with age in both strains, especially at high frequency. The prolongation was more marked in SAM-P/1 than in SAM-R/1. The decrease in amplitude of wave I observed in both strains was greater in SAM-P/1 than in SAM-R/1. The auditory function assessed by thresholds, interpeak intervals and amplitudes of wave I in SAM-P/1 at 12 months of age corresponded roughly to that in SAM-R/1 at 20 months of age. In morphological studies, there was an age-related decrease in the cell density as well as in the size of spiral ganglion neurons in both strains, but these changes were more pronounced in SAM-P/1 than in SAM-R/1. These results reveal that age-related hearing impairment associated with morphological changes in the cochlea is manifested earlier and progresses more rapidly in SAM-P/1 than in SAM-R/1. Thus, the SAM-P/1 strain should prove useful as a model of presbycusis.
authors.affiliation: Department of Otolaryngology, Kyoto Prefectural University of Medicine, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Saitoh
authors.forename: M
authors.initials: M
authors.lastname: Hosokawa
authors.forename: A
authors.initials: A
authors.lastname: Shimada
authors.forename: Y
authors.initials: Y
authors.lastname: Watanabe
authors.forename: N
authors.initials: N
authors.lastname: Yasuda
authors.forename: T
authors.initials: T
authors.lastname: Takeda
authors.forename: Y
authors.initials: Y
authors.lastname: Murakami
mesh_terms: D000375:Aging / Q000473:pathology; D000704:Analysis of Variance; D000818:Animals; D001303:Auditory Cortex; D001309:Auditory Threshold / Q000502:physiology*; D002452:Cell Count; D003051:Cochlea / Q000473:pathology*; D004195:Disease Models, Animal; D016057:Evoked Potentials, Auditory, Brain Stem; D005260:Female; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D009474:Neurons / Q000473:pathology; D011304:Presbycusis / Q000473:pathology / Q000503:physiopathology*; D013136:Spiral Ganglion / Q000473:pathology