Effects of Aging and Noise Exposure on Auditory Brainstem Responses and Number of Presynaptic Ribbons in Inner Hair Cells of C57BL/6J Mice
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C57BL/6J mice develop age-related hearing loss (HL) early in life. The influence of aging and noise exposure on the number of presynaptic structures in inner hair cells of C57BL/6J mice has not been studied. We monitored auditory brainstem responses, ABRs, in C57BL/6J mice over time and assessed changes in the number of inner hair cell presynaptic ribbons. Multifaceted verification of the effects of aging and noise exposure on hearing in the C57BL/6J strain was performed. The HL was additively increased by noise exposure in 5-week-old mice. The earliest change observed was a decrease in the amplitude of the ABR first wave. Hair cells and spiral ganglion neurons were also lost. Immunohistochemistry and high-resolution confocal microscopy revealed decreased numbers of CtBP2-positive structures in the inner hair cells localized in other than those in the low-frequency region of the cochlea. On the other hand, the influence of acute noise exposure on the inner hair cell ribbons was observed only within the highest-frequency area.
Keywordsauditory brainstem response C57 cochlear synaptopathy CtBP2 hearing loss inner hair cell ribbons
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