title: Degeneration of axons in the brainstem of the chinchilla after auditory overstimulation.
abstract: The patterns of axonal degeneration following acoustic overstimulation of the cochlea were traced in the brainstem of adult chinchillas. The Nauta-Rasmussen method for axonal degeneration was used following survivals of 1-32 days after a 105 min exposure to an octave-band noise with a center frequency of 4 kHz and a sound pressure level of 108 dB. Hair-cell and myelinated nerve-fiber loss were assessed in the cochlea. The cochleotopic pattern of terminal degeneration in the ventral cochlear nucleus correlated with the sites of myelinated fiber and inner-hair-cell loss: this correlation was less rigorous with outer-hair-cell loss, especially in the dorsal cochlear nucleus. These results are consistent with a dystrophic process with a slow time course depending on hair-cell loss and/or direct cochlear nerve-fiber damage. However, in a number of cases with no damage in the apical cochlea, fine fiber degeneration occurred with a faster course in low-frequency regions in the dorsal cochlear nucleus and, transynaptically, in a non-cochleotopic pattern in the superior olive and inferior colliculus. These findings suggest that neuronal hyperactivity plays a role in the central degeneration following acoustic overstimulation, possibly by an excitotoxic process.
authors.affiliation: Department of Anatomy, School of Medicine, University of Connecticut Health Center, Farmington 06030, USA.
authors.forename: J
authors.initials: J
authors.lastname: Kim
authors.forename: D K
authors.initials: DK
authors.lastname: Morest
authors.forename: B A
authors.initials: BA
authors.lastname: Bohne
mesh_terms: D000161:Acoustic Stimulation / Q000009:adverse effects; D000818:Animals; D001306:Auditory Pathways / Q000293:injuries / Q000473:pathology; D001369:Axons / Q000473:pathology*; D001933:Brain Stem / Q000293:injuries / Q000473:pathology*; D002682:Chinchilla / Q000033:anatomy & histology* / Q000502:physiology; D003051:Cochlea / Q000293:injuries* / Q000473:pathology*; D017626:Cochlear Nucleus / Q000473:pathology; D006199:Hair Cells, Auditory, Inner / Q000473:pathology; D018072:Hair Cells, Auditory, Outer / Q000473:pathology; D007245:Inferior Colliculi / Q000473:pathology; D009410:Nerve Degeneration; D009413:Nerve Fibers, Myelinated / Q000473:pathology; D009622:Noise / Q000009:adverse effects*; D009847:Olivary Nucleus / Q000473:pathology