A COMPARATIVE-STUDY ON THE EFFECT OF PURE-TONE EXPOSURE OF THE GUINEA-PIG COCHLEA

Electrophysiological methods were applied to 160 healthy adult male gu inea pigs in order to investigate the effects of pure-tone exposure fo r 24 h on the inner ear. A reduction in cochlear microphonics (CM), ac tion potential (AP) and endocochlear potential was observed following exposure to 110 dB at 100 Hz, 100 dB at 200 and 600 Hz and 95 dB at 2 kHz. The observed K+ endolymphatic concentration during 40 min anoxia remained unchanged. In contrast K+ decreased in control animals and fo llowing exposure to pure tones varying from 110 dB at 60 Hz to 85 dB a t 2 kHz. These findings indicate that high frequency tones have a grea ter effect on inner ear functions than those of lower frequency, decre asing the maximum output voltage of CM and AP but not changing K+ endo lymphatic concentration.