Altered traveling wave propagation and reduced endocochlear potential associated with cochlear dysplasia in the BETA2/NeuroD1 null mouse.
J Assoc Res Otolaryngol
; 8(4): 447-63, 2007 Dec.
Article
em En
| MEDLINE
| ID: mdl-17701252
ABSTRACT
The BETA2/NeuroD1 null mouse has cochlear dysplasia. Its cochlear duct is shorter than normal, there is a lack of spiral ganglion neurons, and there is hair cell disorganization. We measured vertical movements of the tectorial membrane at acoustic frequencies in excised cochleae in response to mechanical stimulation of the stapes using laser doppler vibrometry. While tuning curve sharpness was similar between wild-type, heterozygotes, and null mice in the base, null mutants had broader tuning in the apex. At both the base and the apex, null mice had less phase lag accumulation with increasing stimulus frequency than wild-type or heterozygote mice. In vivo studies demonstrated that the null mouse lacked distortion product otoacoustic emissions, and the cochlear microphonic and endocochlear potential were found to be severely reduced. Electrically evoked otoacoustic emissions could be elicited, although the amplitudes were lower than those of wild-type mice. Cochlear cross-sections revealed an incomplete partition malformation, with fenestrations within the modiolus that connected the cochlear turns. Outer hair cells from null mice demonstrated the normal pattern of prestin expression within their lateral walls and normal FM 1-43 dye entry. Overall, these data demonstrate that while tonotopicity can exist with cochlear dysplasia, traveling wave propagation is abnormally fast. Additionally, the presence of electrically evoked otoacoustic emissions suggests that outer hair cell reverse transduction is present, although the acoustic response is shaped by the alterations in cochlear mechanics.
Texto completo:
1
Base de dados:
MEDLINE
Assunto principal:
Cóclea
/
Potenciais Microfônicos da Cóclea
/
Fatores de Transcrição Hélice-Alça-Hélice Básicos
Tipo de estudo:
Risk_factors_studies
Limite:
Animals
Idioma:
En
Ano de publicação:
2007
Tipo de documento:
Article