Acoustic Trauma in the Guinea Pig: I. Electrophysiology and Histology

Abstract

Guinea pigs were exposed to a 500-cps tone at 128 dB SPL for 20 minutes. The acute animals had electrophysiological recordings by differential cochlear electrodes before and after exposure. The cochlear microphonic from Turn 3 showed (on average) a threshold shift of 51 dB and reduction of maximum voltage of 12 dB, while Turn 1 showed a shift of 20 dB and a reduction of voltage of 6 dB. Hair cell injury was proportional to the threshold shift (range 25–85 dB), but inversely related to a split sometimes seen between the Hensen's and Deiters' cells in Turn 3. Such a split apparently protected the organ of Corti. An inner ear conductive loss is postulated as the protective mechanism. In the recovery animals measurements were made 14 days after exposure and compared with normal values. Appreciable recovery occurs. Losses in Turn 1 are smaller but show less recovery.