Cochlear hair cell damage from intermittent noise exposure in young and adult guinea pigs.

A comparative study of age-dependent damage to cochlea from intermittent noise exposure was carried out on five-week-old and one-year-old pigmented guinea pigs. Hair cell loss in the organ of Corti was studied after five weeks' exposure to a pure tone stimulus (95 dB SPL at 2 kHz, one hour per day for five weeks). The noise-induced damage was sharply limited to the 7- and 11-mm marks from the apex. Damage was more marked in younger guinea pigs and was distinct from natural age-induced cell loss. When the 7- to 11-mm zone was further analyzed, outer hair cell damage appeared highly significant in both age groups but more severe in younger animals. Inner hair cell damage in this area was severe in both groups but statistically insignificant.