1989 Fiscal Year Final Research Report Summary
An investigation of the mechanism of noise induced hearing loss (C_5dip)
| Project/Area Number |
63570233
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
Hygiene
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| Research Institution | Department of Hygiene, Asahikawa Medical College |
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Principal Investigator |
YAMAMURA K Asahikawa Medical College, Hygiene, Professor, 医学部, 教授 (80109959)
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| Co-Investigator(Kenkyū-buntansha) |
MATSUI T. Asahikawa Medical College, Hygiene, Assistant, 医学部, 助手 (00219370)
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| Project Period (FY) |
1988 – 1989
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| Keywords | CM / AP / EP / Noise exposure / C_5dip |
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| Research Abstract |
Using 112 male albino Hartley guinea pigs aged 4-5 weeks with normal hearing, we used the following experimental setup: 1) Exposure to 250 Hz tone at 115 dB SPL for 20 Hrs and 40 Hrs, and at 120 dB SPL for 64 Hrs were examined. 2) Exposure to 500 Hz tone of 115 dB for 20 Hrs and 40 Hrs were examined.
In order to investigate the effects of the above mentioned exposures on the hearing, electrophysiological study of CM (Cochlear microphonics), whole nerve AP (action potential) and EP (endocochlear potential) were examined. We obtained the following results: 1) With extension of exposure time of 500 Hz a decrease of CM maximum output voltage in test frequencies from 2 kHz to 6 kHz and an increase of threshold of CM (psuedo threshold) was observed. At the same time, 250 Hz noise did not have significant effect on the CM. 2) Intensity function of N_1 potential of AP using a 7 kHz tone burst decreased very significantly and the threshold of N_1 potential also increased by 500 Hz exposure, but no change was observed in cases of 250 Hz exposure. 3) A significant extension of the latency period of EP in 250 Hz and 500 Hz exposure was observed, and a very pronounced decrease of the absolute value of the negative potential of EP were seen in 500 Hz exposure at long duration.
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