We have measured transient evoked and distortion-product otoacoustic emissions (OAEs) in the chinchilla and compared them in the awake and anesthetized animal (using either ketamine or barbiturate agents). We report a significant increase in OAE amplitudes during anesthesia particularly using ketamine. These effects are most evident for transient-evoked otoacoustic emissions of (TFOAEs) as measured in the non-linear mode. Our data support the hypothesis that tonic activity levels in cochlear efferents may be reduced by anesthetic effects, either directly or indirectly (e.g., by general reductions in descending pathway activity), and that reduced cochlear efferent activity will result in the observed increase of OAE amplitudes.
Bibliographical noteFunding Information:
This research was supported by MRC (Canada) and Masonic Foundation of Ontario.
- Auditory system
- Cochlear efferents
- Descending auditory pathway
- Otoacoustic emissions
- Outer hair cells