The Q10 of auditory brain stem responses in rats under hypothermia

Auditory brain stem responses (ABRs) were recorded from normal Sprague-Dawley rats ranging in age from 15 to 120 days. Increased latencies for all four waves of the ABR were noted for animals of all ages as their body temperatures were reduced from 38 to 28 degrees C. The Q10S of the latency changes were highly variable but were still significantly higher for the first three waves of the ABR in animals less than 20 days of age compared with older animals. The Q10S for the fourth wave in both groups were alike. Wave heights tended to decrease during cooling, but this effect was inconsistent. The cochlear microphonic was recorded in some animals and tended to decrease in size with cooling. As seen in this study, the significant changes in wave latencies due to small temperature differences underscore the need to carefully control this variable when taking evoked responses from animal preparations and humans subject to variations in body temperature. The interanimal variability of the Q10 precludes any simple 'correction' of latency differences due to temperature for research or clinical purposes.