Effects of Hyperthermia on the Auditory-Evoked Brainstem Responses in Mice

Abstract

This study investigated the effects of increased body temperature on the latencies and amplitudes of the auditory-evoked brainstem response (ABR) in mice. Six eleven-week-old male CBA/CaJ mice were anesthetized with pentobarbital and screened for normal hearing. Hyperthermia was induced by placing the animal in a thermostatically controlled chamber; a thermistor connected to a digital thermometer measured the rectal temperature. ABRs were evoked with broad-band clicks presented at repetition rates of 21.1/s and 61.1/s. The latencies and amplitudes of waves I-V were measured at 1-degree and/or 0.5-degree intervals between 37 and 42°C. Temperature elevation between 37 and 41°C shortened the latencies of all the ABR waves, the effect being linear and cumulative across the time window. Change in this trend occurred between 41 and 42°C, whereby the latencies of all the waves stabilized or showed minimal prolongation. Amplitudes of the most robust waves I and II showed a trend similar to the latencies, whereas the later waves showed erratic and un-interpretable changes. These findings in the mouse may be indicative of the physiological limit of thermal tolerance and as such may be regarded as a premonitory signal of permanent damage.

Key Words:

• Auditory-evoked brainstem
• responses
• Mice Thermal sensitivity