Normative auditory brainstem response data for hearing threshold in the rabbit

In an experimental study, we determined the physiological hearing threshold of the rabbit in order to use these data as normative values for further experimental investigations. The aim was to use different acoustic stimuli (click and tone-pip stimuli) with different frequency spectra for air and bone conduction (BC) in order to obtain further information about the optimal form of stimulus when recording auditory evoked potentials in the rabbit. For the investigation, we used 46 female New Zealand rabbits weighing 3.2-4.4 kg and aged 6 months. The equipment used to record brainstem auditory evoked potentials was the Nicolet Viking IV P System (Nicolet Biomedical, Inc.). In accordance with the experimental set-up, the measurements took place under intubation anesthesia, with a total of four repeat measurements performed on each ear at different times. Tone-pip and click stimuli with varying intensities of stimulus, transmitted via air conduction and BC, were applied. The I-IV waves proved the most stable for both stimulus modalities. They were registrable in 98.7% of cases, whereas only 30.2% of the V waves could be recorded. Values averaged from all measurements made throughout the study yielded a potential threshold of 34.8 dB peak equivalent (p.e.) SPL for the click stimulus, 13.8 dB p.e. SPL for the tone-pip stimulus at 8 kHz and 34.2 dB p.e. SPL for the click stimulus transmitted via BC. With regard to latencies, the results indicated a good reproducibility through different stimuli with acceptable standard deviations. The values for physiological hearing threshold obtained here can serve as normative data in subsequent experimental animal studies.