Frequency-specific threshold estimation values using auditory brainstem responses in healthy adult male rats

Abstract

Title: Frequency-specific threshold estimation values using auditory brainstem responses in healthy adult male rats

Background and Aims: Auditory brainstem response (ABR) is an objective, electrophysiological test that has been used to assess auditory function for nearly 50 years. Rats are one of the most widely used rodent species for laboratory studies of the auditory system, which requires standardization for ABR recording in each laboratory. The aim of the present study was to estimate hearing thresholds using ABR and tonal stimuli at octave frequencies in healthy adult male Wistar rats.

Methods: In this experimental study, 8 adult male Wistar rats were subjected to auditory brainstem response (ABR) measurements using a threshold estimation approach under ketamine/xylazine anesthesia, in accordance with the principles of working with laboratory animals. Tone burst stimuli were presented at octave frequencies of 2000 to 16000 Hz through an appropriate loudspeaker and the threshold of tonal stimuli was recorded in a descending manner by tracking wave II. Data were analyzed using SPSS software and one-way analysis of variance.

Results: The mean and standard deviation of the thresholds obtained at tonal frequencies of 2, 4, 8 and 16 kHz were 21.25 ± 4.43, 10.27 ± 2.67, 6.87 ± 2.58 and 2.31 ± 3.75 dB SPL, respectively. A statistically significant relationship was observed between the threshold values and the frequency evaluated (p<0.001).

Conclusion: An inverse relationship between the frequency of the tonal stimulus and the estimated values of ABR thresholds was observed in rats, which can serve as a basis for the extent of threshold changes in pathological conditions leading to hearing damage in animal models.