title: Structural changes in the inner ear over time studied in the experimentally deafened guinea pig.
abstract: Today a cochlear implant (CI) may significantly restore auditory function, even for people with a profound hearing loss. Because the efficacy of a CI is believed to depend mainly on the remaining population of spiral ganglion neurons (SGNs), it is important to understand the timeline of the degenerative process of the auditory neurons following deafness. Guinea pigs were transtympanically deafened with neomycin, verified by recording auditory brainstem responses (ABRs), and then sacrificed at different time points. Loss of SGNs as well as changes in cell body and nuclear volume were estimated. To study the effect of delayed treatment, a group of animals that had been deaf for 12 weeks was implanted with a stimulus electrode mimicking a CI, after which they received a 4-week treatment with glial cell-derived neurotrophic factor (GDNF). The electrical responsiveness of the SGNs was measured by recording electrically evoked ABRs. There was a rapid degeneration during the first 7 weeks, shown as a significant reduction of the SGN population. The degenerative process then slowed, and there was no difference in the amount of remaining neurons between weeks 7 and 18. © 2016 The Authors Journal of Neuroscience Research Published by Wiley Periodicals, Inc.
authors.affiliation: Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Anette
authors.initials: A
authors.lastname: Fransson
authors.affiliation: Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Mats
authors.initials: M
authors.lastname: Ulfendahl
mesh_terms: D000161:Acoustic Stimulation; D000818:Animals; D002467:Cell Nucleus / Q000187:drug effects / Q000473:pathology; D003638:Deafness / Q000139:chemically induced / Q000188:drug therapy / Q000473:pathology* / Q000503:physiopathology; D004195:Disease Models, Animal; D007758:Ear, Inner / Q000473:pathology*; D016057:Evoked Potentials, Auditory, Brain Stem / Q000187:drug effects; D005260:Female; D051100:Glial Cell Line-Derived Neurotrophic Factor / Q000627:therapeutic use; D006168:Guinea Pigs; D008297:Male; D009355:Neomycin / Q000633:toxicity; D011500:Protein Synthesis Inhibitors / Q000633:toxicity; D011984:Sensory Receptor Cells / Q000187:drug effects / Q000473:pathology; D013136:Spiral Ganglion / Q000187:drug effects / Q000473:pathology; D013997:Time Factors
chemical_list: D051100:Glial Cell Line-Derived Neurotrophic Factor; D011500:Protein Synthesis Inhibitors; D009355:Neomycin
keywords: cochlear implant; degeneration; delayed treatment; spiral ganglion