title: Neurofilament heavy chain expression and neuroplasticity in rat auditory cortex after unilateral and bilateral deafness.
abstract: Deafness induces many plastic changes in the auditory neural system. For instance, dendritic changes cause synaptic changes in neural cells. SMI-32, a monoclonal antibody reveals auditory areas and recognizes non-phosphorylated epitopes on medium- and high-molecular-weight subunits of neurofilament proteins in cortical pyramidal neuron dendrites. We investigated SMI-32-immunoreactive (-ir) protein levels in the auditory cortices of rats with induced unilateral and bilateral deafness. Adult male Sprague-Dawley rats were divided into unilateral deafness (UD), bilateral deafness (BD), and control groups. Deafness was induced by cochlear ablation. All rats were sacrificed, and the auditory cortices were harvested for real-time quantitative polymerase chain reaction (RT-qPCR) and western blot analyses at 2, 4, 6, and 12 weeks after deafness was induced. Immunohistochemical staining was performed to evaluate the location of SMI-32-ir neurons. Neurofilament heavy chain (NEFH) mRNA expression and SMI-32-ir protein levels were increased in the BD group. In particular, SMI-32-ir protein levels increased significantly 6 and 12 weeks after deafness was induced. In contrast, no significant changes in protein level were detected in the right or left auditory cortices at any time point in the UD group. NEFH mRNA level decreased at 4 weeks after deafness was induced in the UD group, but recovered thereafter. Taken together, BD induced plastic changes in the auditory cortex, whereas UD did not affect the auditory neural system sufficiently to show plastic changes, as measured by neurofilament protein level.
authors.affiliation: Department of Otorhinolaryngology, Seoul Metropolitan Government-Seoul National University Boramae Medical Center, 07061, Boramae Road 5 Gil 20, Dongjak-gu, Seoul, South Korea. Electronic address: drpark@snu.ac.kr.
authors.forename: Min-Hyun
authors.initials: MH
authors.lastname: Park
authors.affiliation: Department of Otorhinolaryngology Head and Neck Surgery, Ajou University Hospital, 16499, World cup-ro 164, Yeongtong-gu, Suwon, Gyeonggi-do, South Korea.
authors.forename: Jeong Hun
authors.initials: JH
authors.lastname: Jang
authors.affiliation: Department of Otorhinolaryngology-Head and Neck Surgery, Seoul National University Bundang Hospital, Seongnam, 13620, Gumi-Ro 173 Beon-Gil 82, Bundang-gu, Gyeonggi-Do, South Korea.
authors.forename: Jae-Jin
authors.initials: JJ
authors.lastname: Song
authors.affiliation: Department of Otorhinolaryngology, Seoul Metropolitan Government-Seoul National University Boramae Medical Center, 07061, Boramae Road 5 Gil 20, Dongjak-gu, Seoul, South Korea.
authors.forename: Ho Sun
authors.initials: HS
authors.lastname: Lee
authors.affiliation: Department of Otorhinolaryngology, College of Medicine, Seoul National University, 03080, Daehangno 101, Jongno-gu, Seoul, South Korea.
authors.forename: Seung Ha
authors.initials: SH
authors.lastname: Oh
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal; D001303:Auditory Cortex / Q000378:metabolism* / Q000473:pathology; D003638:Deafness / Q000378:metabolism; D003712:Dendrites; D034381:Hearing Loss / Q000378:metabolism*; D007382:Intermediate Filaments / Q000502:physiology*; D008297:Male; D016900:Neurofilament Proteins / Q000378:metabolism*; D009473:Neuronal Plasticity / Q000502:physiology*; D009474:Neurons / Q000378:metabolism; D017966:Pyramidal Cells; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors
chemical_list: D000911:Antibodies, Monoclonal; D016900:Neurofilament Proteins; D012333:RNA, Messenger; C051774:neurofilament protein H
keywords: Auditory cortex; Cochlear ablation; Neurofilament protein; SMI-32; Unilateral deafness