| The C57BL/6J mouse is commonly used as a model of human presbycusis. While human males are more susceptible to presbycusis compared to human females, the role of sex in the hearing loss of C57BL/6J mice is controversial. Similarly, subject source---laboratory vs. commercial vendor---has been linked to differentially accelerated patterns of hearing loss. Finally, the interaction between disease and timing of noise exposure has been explored in a variety of studies, with sometimes disparate results. Subjects in the current study included males and females, bred at NMU or obtained from the Jackson Laboratory. Thresholds were measured at 2 and 6.5 months of age. One group of mice was sound exposed (11.2 kHz ½ octave band of noise, 101 dB noise spectrum level, for 76 minutes) at two months of age, while a second group was exposed at 6.5 months. Thresholds in all subjects were re-assessed at 7.5 months of age. Female mice had lower but not significantly different thresholds than males. Data indicated that subject source had no influence on auditory brainstem response thresholds. Age-at-exposure data supported the hypothesis that acoustic over stimulation is more detrimental to the young auditory nervous system that is genetically predisposed to early-onset deafness compared to mature hearing structures. |
