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Gender-related differences in human hearing have been attributed to genetic, environmental, and/or genetic x environmental interactive factors. These differences tend to increase with age, with males showing greater high frequency threshold elevations. An appropriate animal model could aid in prediction, treatment, and prevention of some of these losses. This paper examines inbred strains of mice that are widely used as models of late- (CBA/J and CBA/CaJ) and early- (C57BL/6J) onset age-related hearing loss. In the former two genotypes, the thresholds to high frequency stimuli of the auditory brainstem response (ABR) are higher in the male than in the female. This gender difference was less pronounced in thresholds to the cochlear nerve envelope response of the CBA/CaJ, although this response was more sensitive to the influence of age than was the ABR. In contrast, the male C57BL/6J had more sensitive thresholds than the female, with both measures showing massive loss of sensitivity with increasing age. The data are discussed in terms of the applicability of these animals as tools for examining factors that degrade cochlear function.

The C57BL/6 mouse has long been considered, in scores of published studies, as a model of early adult-onset, progressive sensorineural hearing loss (presbycusis). The auditory brainstem response (ABR) has most often been used in these studies as a measure of functional loss. Whereas the ABR measures the response to a rapid acoustic onset, the cochlear nerve envelope response (CNER) measures the ability of cochlear nerve axons to respond to the low frequency modulations of the entire acoustic waveform, acoustic changes that are utilized in vocalizations and music. The present study compared the ability of these two measures to assess presbycusis in male and female C57BL/6 mice, at ages ranging from 50 to 400 days. Thresholds to the CNER were almost invariably more sensitive than the ABR, in response to stimulus frequencies ranging from 8 to 56 kHz. By 100 days of age, mice showed elevation of thresholds in response to high frequency stimuli, and this loss was greater in females than in males. These trends persisted for both measures over the next 300 days, involving successively lower frequencies.