High frequency hearing in jaundiced rats

All 8 pups in a homozygous-by-heterozygous rat mating were studied using brainstem auditory-evoked responses to clicks and to tone pips at 10, 15, 20, and 25 kc/s. Rats expressing the jaundice trait (N:4) had normal BSAER for click thresholds and latencies of Waves I-IV; however, to tone pips stimulating predominantly the more basal portions of the cochlea. Although thresholds were unaffected, there were mild prolongations of latencies of Waves II-IV representing central conduction time; the prolongation in one jaundiced rat reached significance re controls. Furthermore, amplitude of Waves II-IV to the louder tone pips were about 20% lower for the jaundiced rats. Jaundiced rats may be adequate models for central conduction delay found in human neonatal hyperbilirubinemia when species differences are controlled.