Distortion product otoacoustic emissions in the CBA/J mouse model of presbycusis

CBA mice do not exhibit age-related loss of auditory sensitivity or cochlea r pathology until relatively late in life. Therefore, this strain is believ ed to be an excellent animal model for the examination of the effects of ag e on the cochlea. To evaluate the effects of age on outer hair cell functio n, 2f(1)-f(2) distortion product otoacoustic emissions (DPOAEs) were measur ed for f(2) between 8 and 16 kHz in CBA/J mice between 1 and 25 months of a ge. CBA mice exhibited mild age-related changes in DPOAE level and detectio n threshold at 17 months of age, and changes of 20-40 dB by 25 months of ag e. The DPOAE level decreased and detection threshold increased with age in a frequency-dependent manner, starting at high frequencies and eventually e xtending to low frequencies. The range of frequencies in which notches were observed in the DPOAE input/output (I/O) functions extended toward lower f requencies by 17 months of age. Notches were absent in the I/O functions of 25-month-old mice. The present results for a frequency range of 8-16 kHz s uggest that age has modest effects on outer hair cell function in CBA mice. (C) 1999 Elsevier Science B.V. All rights reserved.