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Central nervous system changes associated with noise‐induced hearing loss: An electron microscopic and freeze‐fracture study of the chick nucleus magnocellularis
Author(s) -
Mattox Douglas E.
Publication year - 1991
Publication title -
the laryngoscope
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.181
H-Index - 148
eISSN - 1531-4995
pISSN - 0023-852X
DOI - 10.1288/00005537-199110000-00007
Subject(s) - cochlear nucleus , synaptic vesicle , nucleus , auditory system , neuroscience , synapse , central nervous system , inner ear , biology , anatomy , vesicle , chemistry , membrane , genetics
This investigation assessed the effects of noise‐induced hearing loss on the avian nucleus magnocellularis, the homologue of the mammalian cochlear nucleus. Fifteen‐day‐old chicks were exposed to high‐intensity broad‐band noise (132 dBA) for 24 to 72 hours. Hearing loss was documented with auditory brainstem response recordings and scanning electron microscopy of the basilar papilla. Nucleus magnocellularis was assessed with thin‐section electron‐microscopy and freeze‐fracture techniques. Freeze‐fracture preparations of noise‐exposed animals showed a decrease in synaptic vesicle fusion sites at the synaptic active zone, a decrease in reuptake of presynaptic membrane by coated vesicles, and a shift of the preferential fracture plane at the synapse from the presynaptic membrane to the postsynaptic membrane. These findings support the hypothesis that the effects of noise are not limited to the auditory periphery, but that transneuronal changes extend into the auditory central nervous system.