title: The possible impact of noise-induced Ca2+-dependent activity in the central auditory pathway: a manganese-enhanced MRI study.
abstract: Noise exposure at high intensities leads to a temporary shift of hearing thresholds (TTS) and is followed by a permanent threshold shift (PTS). Permanent threshold shift is not only associated with cochlear damage as the primary site-of-lesion, but also with subsequent structural and functional changes within the central auditory pathway. The aim of the present study was to monitor neuronal activity within central auditory structures in mice after noise exposure at different time intervals using manganese-enhanced magnetic resonance imaging (MEMRI). The results demonstrate for the first time that calcium-dependent activity patterns are modified in several structures of the central auditory system as the result of a noise-induced hearing loss (NIHL). The MEMRI data demonstrate that temporary threshold shift is correlated with an activity increase in hierarchically lower structures of the auditory pathway. This seems to be indicative of a direct noise impact at the first stage of central auditory processing. However, noise-dependent changes of higher auditory structures were found as well in the phase of PTS. Repeated noise exposure was found to induce an additional elevation of calcium-dependent activity in all investigated auditory structures - without a significant shift in auditory thresholds. Sustained manganese accumulation was present in the auditory brainstem after moderate acoustic stimulation as well without PTS induction. The long-lasting enhancement of MEMRI signals suggests a noise-induced activity increase of various calcium-dependent processes of different origin (such as neuroprotective mechanisms). The present findings could be helpful to better understand the time-course of different symptoms in NIHL and the individual susceptibility to noise.
authors.affiliation: Department of Otolaryngology at UKB, Charité Medical School, Warener Str. 7, 12683 Berlin, Germany; Department of Biology, Humboldt-University of Berlin, Philippstr. 13, 10115 Berlin, Germany.
authors.forename: Moritz
authors.initials: M
authors.lastname: Gröschel
authors.affiliation: Neuroscience Research Center (NWFZ), Charité University Medicine Berlin, Campus Charité Mitte, Charitéplatz 1, 10117 Berlin, Germany.
authors.forename: Susanne
authors.initials: S
authors.lastname: Müller
authors.affiliation: Department of Biology, Humboldt-University of Berlin, Philippstr. 13, 10115 Berlin, Germany.
authors.forename: Romy
authors.initials: R
authors.lastname: Götze
authors.affiliation: Department of Otolaryngology at UKB, Charité Medical School, Warener Str. 7, 12683 Berlin, Germany.
authors.forename: Arne
authors.initials: A
authors.lastname: Ernst
authors.affiliation: Department of Otolaryngology at UKB, Charité Medical School, Warener Str. 7, 12683 Berlin, Germany; Department of Biology, Humboldt-University of Berlin, Philippstr. 13, 10115 Berlin, Germany. Electronic address: dietmar.basta@ukb.de.
authors.forename: Dietmar
authors.initials: D
authors.lastname: Basta
mesh_terms: D000161:Acoustic Stimulation; D000818:Animals; D001303:Auditory Cortex / Q000378:metabolism / Q000503:physiopathology; D001306:Auditory Pathways / Q000378:metabolism / Q000503:physiopathology*; D002118:Calcium / Q000378:metabolism*; D016057:Evoked Potentials, Auditory, Brain Stem / Q000502:physiology; D006317:Hearing Loss, Noise-Induced / Q000378:metabolism / Q000503:physiopathology*; D007089:Image Enhancement / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008345:Manganese; D051379:Mice; D009622:Noise
chemical_list: D008345:Manganese; D002118:Calcium