Disparity in the cytocochleogram and the electrocochleogram in aging LP/J and A/J inbred mice

The auditory systems of aging LP/J and A/J inbred mice were studied using electrocochleography (AP thresholds) and surface preparation cytocochleography. Both strains showed marked age-related auditory threshold elevation, the LP/J demonstrating more pronounced elevation with age than the A/J. Surprisingly, the cytocochleograms showed the opposite relationship: the A/J strain had more loss of hair cells than the LP/J. The elevation of AP thresholds of the LP/J mouse was far out of proportion to the expected auditory deficit on the basis of the cytocochleogram alone. Auditory deficits in the aging LP/J mouse must be due to factors other than anatomical loss of sensory cells.