Changes in the stereocilia and non-monotonic pattern of threshold shift after exposure to impulse noise.
The recovery pattern of threshold shift (TS) and 'dynamic' changes in the stereocilia after exposure to high-level impulse noise in guinea pigs were investigated. 33 albino guinea pigs were exposed to 10 impulse noises at the rate of 1/min. The noise had peak level of 166 dB SPL and a duration of 0.1 ms. Thirteen of the exposed animals were used to systematically measure threshold shifts at regular intervals from 0.5 h to 30 days post-exposure by click auditory cortex evoked response (AC-ER). Twelve of the animals who had typical TS at the same intervals were killed for scanning electron microscopic examination. The recovery pattern of threshold shifts was non-monotonic, which was different from that seen with continuous noise. There was an increase in TS after the exposure and the maximum level of TS was found at 8 h post-exposure. Morphological analysis also showed delayed changes in the stereocilia after exposure. The severity of changes in the stereocilia reached a peak at 8 h, at which time complete fusion of hair bundles took place. The tectorial material found on the tips of the stereocilia may be responsible for the sequence of the changes.
Gao
W Y
WY
Department of Otolaryngology, Chang Zheng Hospital, Shanghai, Peoples Republic of China.
Ding
D L
DL
Zheng
X Y
XY
Ruan
F M
FM
D000161:Acoustic Stimulation; D000818:Animals; D002923:Cilia / Q000502:physiology / Q000648:ultrastructure*; D004594:Electrophysiology; D006168:Guinea Pigs; D006198:Hair Cells, Auditory / Q000502:physiology / Q000648:ultrastructure*; D006199:Hair Cells, Auditory, Inner / Q000502:physiology / Q000648:ultrastructure; D008297:Male; D008855:Microscopy, Electron, Scanning; D009622:Noise; D012684:Sensory Thresholds