title: The effects of early bilateral deafening on calretinin expression in the dorsal cochlear nucleus of aged CBA/CaJ mice.
abstract: The aim of this study was to test the hypothesis that calretinin (CR) levels in the aged mouse auditory brainstem depend upon hearing ability. Old animals with good hearing, and thus higher sound-evoked activity levels, were predicted to have higher levels of CR immunoreactivity than old animals with hearing loss. CR immunoreactivity was analyzed in the deep layer (layer III) of the dorsal cochlear nucleus (DCN) in CBA/CaJ mice that were bilaterally deafened at 3 months of age with kanamycin, and then aged until 24 months. This manipulation partially mimics the lack of sound-evoked auditory activity experienced by old C57BL/6J mice, who are deaf at 24 months of age (but show residual hearing at 15 months) and have lower levels of CR immunoreactivity than old CBA mice with normal hearing [Hear. Res. 158 (2001) 131]. Cell counts revealed that the density of CR+ cells in DCN layer III of the deafened CBA mice was statistically different from old intact CBA mice raised under identical conditions. Old deafened CBAs showed a decline of 47% in the mean density of CR+ cells compared to old hearing CBAs, thus supporting the hypothesis. Interestingly, while there tended to be fewer CR+ cells in the old deaf C57s as compared to young C57s and young and old CBAs with normal hearing, the difference was not statistically significant. It is possible that the residual hearing of C57 mice at 15 months may provide sufficient auditory input to maintain CR at levels higher than CBA mice that are deafened completely at 3 months of age, and are profoundly deaf for a much longer time (21 months).
mesh_terms: D000375:Aging / Q000378:metabolism* / Q000473:pathology; D000704:Analysis of Variance; D000818:Animals; D001300:Audiometry, Evoked Response; D001309:Auditory Threshold; D064032:Calbindin 2; D002452:Cell Count; D017626:Cochlear Nucleus / Q000378:metabolism* / Q000473:pathology; D003638:Deafness / Q000378:metabolism* / Q000473:pathology; D016057:Evoked Potentials, Auditory, Brain Stem; D005260:Female; D007150:Immunohistochemistry; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008808:Mice, Inbred CBA; D010784:Photomicrography; D064030:S100 Calcium Binding Protein G / Q000032:analysis / Q000096:biosynthesis*
chemical_list: C576511:Calb2 protein, mouse; D064032:Calbindin 2; D064030:S100 Calcium Binding Protein G