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Titolo:
Functional recovery of hearing following AMPA-induced reversible disruption of hair cell afferent synapses in the avian inner ear
Autore:
Reng, D; Muller, M; Smolders, JWT;
Indirizzi:
Univ Frankfurt Klinikum, Inst Physiol 2, D-60590 Frankfurt, Germany Univ Frankfurt Klinikum Frankfurt Germany D-60590 590 Frankfurt, Germany
Titolo Testata:
AUDIOLOGY AND NEURO-OTOLOGY
fascicolo: 2, volume: 6, anno: 2001,
pagine: 66 - 78
SICI:
1420-3030(200103/04)6:2<66:FROHFA>2.0.ZU;2-I
Fonte:
ISI
Lingua:
ENG
Soggetto:
AUDITORY-NERVE FIBERS; GUINEA-PIG COCHLEA; SEVERE ACOUSTIC TRAUMA; KAINIC ACID; GLUTAMATE RECEPTORS; OTOACOUSTIC EMISSIONS; CHICK COCHLEA; ROUND WINDOW; RAT COCHLEA; REGENERATION;
Keywords:
alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA); glutamate; bird; pigeon; inner ear; excitotoxicity; trauma; ototoxicity; transmitter; hair cell; basilar papilla; auditory nerve; cochlear synapses;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Life Sciences
Citazioni:
60
Recensione:
Indirizzi per estratti:
Indirizzo: Smolders, JWT Univ Frankfurt Klinikum, Inst Physiol 2, Theodor Stern Kai 7, D-60590 Frankfurt, Germany Univ Frankfurt Klinikum Theodor Stern Kai 7 Frankfurt Germany D-60590
Citazione:
D. Reng et al., "Functional recovery of hearing following AMPA-induced reversible disruption of hair cell afferent synapses in the avian inner ear", AUDIOL NEUR, 6(2), 2001, pp. 66-78

Abstract

Hair cells in the avian inner ear can regenerate after acoustic trauma or ototoxic insult, and significant functional recovery from hearing loss occurs. However, small residual deficits remain, possibly as a result of incomplete reestablishment of the hair cell neural synaptic contacts. The aim of the present study was to determine if intracochlear application of alpha -amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA), an excitotoxic glutamate agonist, causes reversible disruption of hair cell neural contactsin the bird, and to what extent functional recovery occurs if synaptic contacts are reestablished. Compound action potential (CAP) responses to tone bursts were recorded to determine hearing thresholds during a recovery period of up to 4 months. Subsequently, the response properties of single auditory nerve fibers were analyzed in the same animals. Instillation of AMPA into the perilymph of the scala tympani led to immediate abolition of CAP thresholds. Partial recovery occurred over a period of 2-3 weeks, without further improvement of thresholds thereafter. High-frequency thresholds did notreach control values even after 3-4 months of recovery. Single-ganglion cell response properties, obtained 3-4 months after AMPA treatment, showed elevated thresholds at the fiber's characteristic frequency (CF) for units with CF above 0.3 kHz. Sharpness of tuning (Q(10) (dB)) was reduced in units with CF above 0.4 kHz. The spontaneous firing rate was higher in units withCF above 0.18 kHz. The maximum sound-evoked discharge rate was also increased. Transmission electron micrographs of the basilar papilla showed that, following AMPA treatment, the nerve endings went through a sequence of swelling, degeneration and recovery over a period of 3-7 days. The process of neosynaptogenesis was completed 14 days after exposure. The present findingsare strong evidence for a role of glutamate or a related excitatory amino acid as the afferent transmitter in the avian inner ear. In addition they show that functional recovery after disruption and regeneration of hair cellneural synapses, without apparent damage to the hair cells, is incomplete. Copyright (C) 2001 S. Karger AG, Basel.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 19/02/20 alle ore 14:47:04