Auditory brainstem responses (ABR) in guinea pigs to loud tones noise: a preliminary study

It is well known that exposure to intense acoustic stimuli can induce permanent damage to the tissues of the inner ear. In this study the technique of ABR measurement and the experimental animal model of acoustic trauma were presented. In forty 3 months old guinea pigs the hearing threshold was assessed using the ABR technique (Amplaid mk 10 system). The hearing thresholds ranged from 40 to 50 dB-pe-SPL (mean 45.26 dB, sd. 4.73). The mean latencies of the four most prominent peaks in the ABR pattern were also measured. Fourteen of animals were then exposed to a 1 kHz pure tone at different duration and stimulus level. The ABR threshold was measured immediately after exposure and 20 to 30 days later. The exposure at 112 dB for 2h caused the threshold shift in all guinea pigs varying from 25 to 65 dB. After 3-4 weeks of recovery time in all animals hearing threshold improved, in some animals reaching the pre-exposure level. We conclude that the ABR technique allows to measure precisely and with high reproducibility the hearing level in guinea pigs and also allows to estimate the threshold shift after exposure to noise.