1995 Fiscal Year Final Research Report Summary
Experimental Studies on mechanism underlying noise-induced Rearing disorder.
| Project/Area Number |
06671745
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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 |
Otorhinolaryngology
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| Research Institution | University of Occupational and Environmental Health |
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Principal Investigator |
YOSHIDA Masafumi University of Occupational and Environmental Health Medical School, Otorhinolaryngology, Asociate Professor., 医学部, 助教授 (00182783)
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| Project Period (FY) |
1994 – 1995
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| Keywords | Noise exposure / Salicylate toxicity / Hearing disorder / Cochlear microphonics / Otoacoustic emission / 2f_1-f_2 distortion product |
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| Research Abstract |
In the first year, cochlear microphonics (CM) in response to two tone stimuli as well as compound action potential (CAP) of the acoustic nerve were measured before and after exposure to 4kHz pure tone at 100dB SPL for 10min. The output of 2f1-f2 distortion product in the CM (CM-DP) were markedly reduced immediately after the exposure and then recovered gradually. The reduction and recovery in CM-DPs closely paralleled with those in the CAP.This may indicate that the affection of the outer hair cell (OHC) function plays an important role in developing the noise induced temporary threshold shift. The following study with administration of salicylate, which was known to interfere the electro-mechanical transduction (EMT) of OHCs, reveled the different alterations of the CM-DPs from those with sound exposure. From these results it is postulated that acoustic overstimulation affects the mechano-electrical transduction (MET) of OHC.
In the following year, combined effects of loud sound and salicylate were studied. The effects were altered by changing the order in which the two agents were applied. The existing sound-induced damage attenuated the additional ototoxicity of salicylate, whereas attenuation did not occur when salicylate administration preceded sound exposure. From these results it is postulated that the MET holds dominant position over EMT in the cochlear transduction mechanism.
Spontaneous electrical oscillations (AC potentials) were accidentally recorded from the cochlea of several animals without any exposure to sound or drugs. Close observations in the properties of the AC potentials indicated that the potentials were generated by the active mechanical vibration system at the area on the basilar membrane where the characteristic frequency corresponded to that of the potential.
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