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Late-phase recovery in the cochlear lateral wall following severe degeneration by acute energy failure.
MedLine Citation:
PMID:  21925650     Owner:  NLM     Status:  Publisher    
We previously reported a model of acute cochlear energy failure using a mitochondrial toxin, 3-nitropropionic acid (3-NP), to study mechanisms of inner ear disorders such as inner ear ischemia. In this model, the main cause of hearing loss is apoptosis of fibrocytes in the cochlear lateral wall. Here, we analyzed the time course of structural and hearing level changes in the cochlea from the acute phase to the chronic phase up to 2months after surgery. Hearing levels as determined by auditory brainstem response (ABR) thresholds exceeded the maximum acoustic output (>87 dBSPL) of the system at all frequencies 1day after 3-NP treatment. Histology showed nearly complete loss of fibrocytes 2weeks after 3-NP treatment. However, after 2months, ABR showed significant recovery at low frequency (8kHz) in four of five rats treated with 3-NP. ABR thresholds at 20kHz occasionally showed some recovery. At 40kHz, recovery of ABR thresholds was not observed. Histology of 3-NP-treated rats revealed partial recovery of the lateral wall and the regenerated fibrocytes in the spiral ligament expressed Na/K-ATPase in the cochlear basal turn 2months after 3-NP treatment. These results indicate that ABR recovery is caused by regeneration of the cochlear lateral wall. Our findings demonstrate the recoverable capacity of the cochlear lateral wall that leads to functional recovery after severe damage.
Kunio Mizutari; Susumu Nakagawa; Hideki Mutai; Masato Fujii; Kaoru Ogawa; Tatsuo Matsunaga
Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2011-8-30
Journal Detail:
Title:  Brain research     Volume:  -     ISSN:  1872-6240     ISO Abbreviation:  -     Publication Date:  2011 Aug 
Date Detail:
Created Date:  2011-9-19     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0045503     Medline TA:  Brain Res     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Copyright Information:
Copyright © 2011 Elsevier B.V. All rights reserved.
Laboratory of Auditory Disorders, National Institute of Sensory Organs, National Tokyo Medical Center, Tokyo, Japan; Department of Otolaryngology-Head and Neck Surgery, Keio University School of Medicine, Tokyo, Japan.
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