ABSTRACT
<p><b>OBJECTIVE</b>To study the role of N-methyl-D-aspartate-receptor (NMDAR) expression in the development of hearing damage in neonatal rats with hyperbilirubinemia.</p><p><b>METHODS</b>Sixty seven-day-old Sprague-Dawley rats were randomly injected with bilirubin of 100 microg/g (low-dose treatment group) or 200 microg/g (high-dose treatment group) or normal saline (control group). Auditory brainstem response (ABR) was examined. The concentrations of bilirubin in blood and brain were measured. NMDAR expression in the cochlear nucleus slices was examined by immunohistochemistry assay.</p><p><b>RESULTS</b>ABR reflecting threshold obviously increased, and I, II and III wave latency as well as I-II, II-III and I-III interval were more prolonged in the two bilirubin treatment groups when compared with the control group. The NMDAR expression in the cochlear nucleuse in the two bilirubin treatment groups was obviously lower than that in the control group. The NMDAR expression in the cochlear nucleuse was negatively correlated with the brain bilirubin content and the ABR reflecting threshold in the two bilirubin treatment groups.</p><p><b>CONCLUSIONS</b>An increased NMDAR activity may play an important role in hearing damage following hyperbilirubinemia.</p>