Transient evoked otoacoustic emissions can be recorded in the rat

Abstract

Transient (click) evoked (TEOAE) and distortion product (DPOAE) otoacoustic emissions can be recorded in most normal human ears. Even though DPOAEs have been recorded in many laboratory animals, there has not been much success in recording TEOAEs in non-primate mammals except for guinea pigs. In this study, TEOAEs were unequivocally recorded in every rat (and guinea pig) ear studied by using short pulses (40 μs) to generate the clicks and a short (1.1 ms) amplifier gain suppression period. The responses were reproducible in the same rat, above the noise floor and disappeared post-mortem. They were shorter in duration in rats than in guinea pigs and were made up of a broadband frequency spectrum between 2 and 4 kHz. Post-mortem, the TEOAEs to 65 dB SPL clicks disappeared at about the same time as DPOAEs to low stimulus intensities and before the DPOAEs to high stimulus intensities. The ability to record TEOAEs in rats and other animals should permit further experimentation into the basic mechanisms of generation of otoacoustic emissions in general and TEOAEs in particular.