Glutamate agonist causes irreversible degeneration of inner hair cells.
Glutamate neurotoxicity in cochlear hair cells was investigated by administering the glutamate agonist alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) into the scala tympani of Mongolian gerbils. AMPA administration caused the formation of large number of vacuoles in the inner hair cells (IHCs) and dendritic terminals. The number of degenerated hair cells was counted using rhodamine-phalloidin and Hoechst 33342 staining. The administration of 50 microM AMPA caused reversible elevation of the auditory brainstem response threshold without loss of IHCs. In contrast, 200 microM AMPA induced a substantial elevation of the auditory brainstem response threshold with the characteristic disappearance of IHCs. As cochlear ischemia involves excessive glutamate release, these results suggest that an elevated glutamate level in the cochlea is responsible for the progressive IHC death related to ischemic injury.
Hyodo
Jun
J
Department of Otolaryngology, Ehime University School of Medicine, Ehime 791-0295, Japan.
Hakuba
Nobuhiro
N
Hato
Naohito
N
Takeda
Shoichirou
S
Okada
Masahiro
M
Omotehara
Yoshinori
Y
Gyo
Kiyofumi
K
D000818:Animals; D002452:Cell Count; D016923:Cell Death; D003712:Dendrites / Q000187:drug effects / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D016057:Evoked Potentials, Auditory, Brain Stem / Q000187:drug effects / Q000502:physiology; D018690:Excitatory Amino Acid Agonists / Q000633:toxicity*; D005260:Female; D005849:Gerbillinae; D006199:Hair Cells, Auditory, Inner / Q000166:cytology / Q000187:drug effects* / Q000502:physiology*; D019636:Neurodegenerative Diseases / Q000139:chemically induced*; D012533:Scala Tympani / Q000187:drug effects; D013997:Time Factors; D014617:Vacuoles / Q000187:drug effects; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid / Q000633:toxicity*
D018690:Excitatory Amino Acid Agonists; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid