Characteristics of auditory brainstem responses in miniature pigs and changes after impulse noise exposure

CHEN Zhiting; WANG Fangyuan; JI Fei; YANG Shiming; WU Nan

doi:10.3969/j.issn.1672-2922.2016.06.008

Abstract：Objective To investigate the characteristics of auditory brainstem responses (ABRs) in healthy miniature pigs and their changes after impulse noise exposure. Methods Healthy miniature pigs were exposed to impulse noise at 30, 50, 80 or 100 pulses separately, and auditory brainstem responses were tested before and immediately, at 1, 2, 4 and 8 weeks after exposure. Auditory brainstem response characteristics and changes after noise exposure were recorded. Results ABR waves in healthy miniature pigs showed five typical peaks, consistent with those in other species. The mean threshold of click-ABRs was 25±5 dB SPL. After high intensity impulse noise exposure, the ABR threshold was significantly increased. No identifiable ABR waves could be detected immediately after exposure to more than 50 pulses at the maximum system output. Tone burst ABR thresholds at 4, 8, 16, 20 and 32 kHz also increased to higher than 90 dB SPL immediately after noise exposure. At 1 week after exposure, various degrees of thresholds recovery were observed, constituting most recovery after noise exposure. From the second to the eighth week, threshold recovery was plateaued. Recovery of tone burst ABR thresholds at 4, 8, 16, 20 and 32 kHz were consistent with that of click ABR, with no statistically significant differences among the frequencies. Furthermore, ABR waves showed poor differentiation as the time went on, despite recovery in threshold. Conclusions ABR waves in miniature pigs are similar to those of rodents and humans, but are more sensitive to impulsive noise exposure than in rodents, albeit with shorter recovery period. In addition, because of the high similarities in genetics, anatomy and pathophysiology between miniature pigs and humans, miniature pigs are an ideal large mammal mod-el for auditory research.