Effects of impulse noise on cortical response threshold and inner ear activity of succinic dehydrogenase and acetylcholinesterase in guinea pigs

The effects of impulse noise (firecrackers at 170 dB SPL, 1; 10, 20 rounds) on auditory cortical response threshold (CRT) and activity of succinic deh ydrogenase (SDH) and acetylcholinesterase (AchE) in the inner ear were stud ied in 37 guinea pigs. The results showed that extent of damage in the coch lea was related to amount of exposure to the noise. Exposure to 10 rounds r esulted in temporal threshold shift (TTS); to 20 rounds the result was perm anent threshold shift (PTS). For the period when TTS existed, inverse corre lation was noticed between enzyme activity change and CRT shift. The correl ation could not be established when PTS was induced. The results suggest th at the pathomechanism of PTS was more complex than that of TTS. The signifi cance of the results is discussed.