Hypoxic changes in the central nervous system of noise-exposed mice.
CONCLUSIONS
After a noise-induced transient threshold shift, hypoxia occurred in the central nervous system, especially in the auditory cortex, the hippocampus, and the inferior colliculus.


OBJECTIVE
Noise-induced inner ear hypoxia was shown by measurement of an increase in hypoxia-inducible factor-1 alpha, which is expressed? in the nucleus under hypoxic conditions. This study uses pimonidazole to localize site-specific hypoxic changes occurring in the mouse central auditory pathway during noise-induced auditory threshold shift.


METHODS
BALB/c hybrid mice with normal hearing were exposed to 122 dB SPL white noise for 3 h. Immediately after exposure to the noise, and 7 d after noise exposure, the brains of mice were collected. Brains were cryosectioned into slices 15 microm thick and examined by immunofluorescence after staining with pimonidazole HCl.


RESULTS
After 3 h of exposure to 120 dB SPL noise, the hearing thresholds of mice decreased to 51.1+/-8.6 dB SPL (n =14), but hearing recovered in 7 d. After noise exposure, pimonidazole signal increased in the auditory cortex, the hippocampus, and the inferior colliculus. The pimonidazole signal remained elevated after 7 d. In control mice, pimonidazole did not stain any brain region.
Kim
Young-Jin
YJ
Department of Otolaryngology, Pundang Jaesang Hospital, DaeJin Medical Center, Seongnam City, Kyunggi Do, Korea.
Kang
Hun Hee
HH
Ahn
Joong Ho
JH
Chung
Jong Woo
JW
D000161:Acoustic Stimulation; D000818:Animals; D001309:Auditory Threshold; D001921:Brain / Q000098:blood supply* / Q000473:pathology*; D015687:Cell Hypoxia; D007758:Ear, Inner / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D006317:Hearing Loss, Noise-Induced / Q000473:pathology; D051379:Mice; D008807:Mice, Inbred BALB C; D009593:Nitroimidazoles / Q000494:pharmacology; D009622:Noise / Q000009:adverse effects*; D011838:Radiation-Sensitizing Agents / Q000494:pharmacology
D009593:Nitroimidazoles; D011838:Radiation-Sensitizing Agents; C033815:pimonidazole