Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
4332506 | Brain Research | 2006 | 10 Pages |
Abstract
Intense sound exposure causes permanent hearing loss due to hair cell and cochlear damage. Prior conditioning with sublethal stressors, such as nontraumatic sound, heat stress and restraint protects the ear from acoustic injury. However, the mechanisms underlying conditioning-related cochlear protection remain unknown. In this paper, Young's modulus and the amount of filamentous actin (F-actin) of outer hair cells (OHCs) with/without heat stress were investigated by atomic force microscopy and confocal laser scanning microscopy, respectively. Conditioning with heat stress resulted in a statistically significant increase in Young's modulus of OHCs at 3-6Â h after application, and such modulus then began to decrease by 12Â h and returned to pre-conditioning level at 48Â h after heat stress. The amount of F-actin began to increase by 3Â h after heat stress and peaked at 12Â h. It then began to decrease by 24Â h and returned to the pre-conditioning level by 48-96Â h after heat stress. These time courses are consistent with a previous report in which heat stress was shown to suppress permanent threshold shift (PTS). In addition, distortion product otoacoustic emissions (DPOAEs) were confirmed to be enhanced by heat stress. These results suggest that conditioning with heat stress structurally modifies OHCs so that they become stiffer due to an increase in the amount of F-actin. As a consequence, OHCs possibly experience less strain when they are exposed to loud noise, resulting in protection of mammalian hearing from traumatic noise exposure.
Keywords
AFMOHCPTSDPOAEHspFFTF-actinCLSMfilamentous actinAChHeat stressAcetylcholinedistortion product otoacoustic emissionFast Fourier TransformationPermanent threshold shiftouter hair cellbasilar membraneYoung's modulusatomic force microscopyconfocal laser scanning microscopyreticular laminaCompound Action PotentialHeat shock proteinCaP
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Authors
Michio Murakoshi, Naohiro Yoshida, Yoko Kitsunai, Koji Iida, Shun Kumano, Takashi Suzuki, Toshimitsu Kobayashi, Hiroshi Wada,