抄録
Cochlear changes were studied in three different age groups of Sprague-Dawley rats: 1 month, 6 months, 24 months. Morphological changes in the cochlea were investigated by scanning electron and light microscopy, and auditory brainstem responses (ABR) were recorded.
At 24 months the threshold of ABR was significantly higher than at 1 and 6 months. Hair cell and ganglion cell loss increased with aging.
At 1 and 6 months of age hair cell loss was very slight. At 24 months it had increased, especially in the apex and basal turn. Hair cell loss was most severe in the outer hair cells of the third row, followed by those in the second row and the first row and least severe in the inner hair cells.
At 24 months inner hair cell loss was scattered and averaged 3.3%. Outer hair cell loss was greatest in the third row at 24 months (average, 21.3%).
The population of spiral ganglion cells was decreased at 24 months throughout the ganglia, with the greatest loss in the basal turn.
No significant correlation was found between age and the number of nerve fibers in the habenula perforata.
The pattern of cochlear changes with aging in Sprague-Dawley rats was similar to the human pattern.
