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Addressing animal model issues in auditory research.

OBJECTIVE
To better understand the differences in auditory systems across species.


METHODS
Auditory brainstem response (ABR) click thresholds were obtained from normal 3- to 6-week-old animals including 15 guinea pigs, 62 mice, and 6 rats. Pure-tone ABR thresholds were obtained in 7 guinea pigs, 6 mice, and 13 rats. Threshold variability was then considered a function of basilar membrane length, mean body weight, basal metabolic rate, and longevity as identified in the literature.


RESULTS
Interspecies variability of auditory thresholds for normal-hearing animals is not explained by differences in mean body weight, metabolic rate, or longevity. Simple linear models appear to adequately describe threshold variability across the parameters studied. Click thresholds, with significant low-frequency content, suggest that mice have better hearing than rats or guinea pigs.


CONCLUSION
In spite of wide variations in cochlear anatomy and metabolic factors, different species have evolved similar auditory thresholds across species in normal, young animals.