title: Time course of cochlear injury discharge (excitotoxicity) determined by ABR monitoring of contralateral cochlear events.
abstract: The dynamics of cochlear excitotoxicity can be monitored from effects on the contralateral ear. After unilateral mechanical ablation of the cochlea (in a mouse model) we observed immediate elevations in auditory brainstem evoked response (ABR) thresholds in the contralateral ear. Threshold elevations peaked at 2-3 h post ablation, and returned to baseline levels after 5-6 h. These contralateral effects are initiated by cochlear afferent injury discharges most likely activating the olivocochlear efferent system. Six hours after cochlear injury, ABR thresholds were fully returned to pre-lesion baseline levels and remained normal for up to 10 days of monitoring. We have confirmed that our cochlear ablation procedure increases short-term activity levels in the auditory brainstem and midbrain using c-fos labelling. The study provides insight into the dynamics of glutamate excitotoxicity, a pathological process directly related to acute tinnitus after acoustic trauma, and more generally implicated in many types of brain injury and neuro-degenerative disease.
authors: Auditory Science Laboratory, Neuroscience and Mental Health Program, The Hospital for Sick Children, 555 University Ave., Toronto, M5G 1X8 Canada.
authors: Jaina
authors: J
authors: Negandhi
authors: Auditory Science Laboratory, Neuroscience and Mental Health Program, The Hospital for Sick Children, 555 University Ave., Toronto, M5G 1X8 Canada.
authors: Adrienne L
authors: AL
authors: Harrison
authors: Auditory Science Laboratory, Neuroscience and Mental Health Program, The Hospital for Sick Children, 555 University Ave., Toronto, M5G 1X8 Canada.
authors: Cullen
authors: C
authors: Allemang
authors: Auditory Science Laboratory, Neuroscience and Mental Health Program, The Hospital for Sick Children, 555 University Ave., Toronto, M5G 1X8 Canada; Department of Otolaryngology-Head and Neck Surgery, Hospital for Sick Children and the University of Toronto, 190 Elizabeth St., Rm 3S-438, R. Fraser Elliott Building, Toronto, M5G 2N2 Canada. Electronic address: rvh@sickkids.ca.
authors: Robert V
authors: RV
authors: Harrison
mesh_terms: D000818:Animals; D001309:Auditory Threshold / Q000502:physiology*; D003051:Cochlea / Q000293:injuries* / Q000378:metabolism*; D016057:Evoked Potentials, Auditory, Brain Stem / Q000502:physiology*; D005971:Glutamates / Q000378:metabolism; D008297:Male; D051379:Mice; D008808:Mice, Inbred CBA; D023421:Models, Animal; D009476:Neurons, Efferent / Q000502:physiology; D009498:Neurotoxins / Q000378:metabolism*; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D013997:Time Factors
chemical_list: D005971:Glutamates; D009498:Neurotoxins; D016760:Proto-Oncogene Proteins c-fos