| Objective: The abnormal changes of fast components of brainstem auditory evoked potentials (FC-BAEP), slow components of brainstem auditory evoked potentials (SC-BAEP) and middle latency responses (MLR), and the histopathological changes of the brain had been observed in the rat pups with hyperbilirubinemia to find the new experimental proofs for the clinical application of auditory evoked potentials in early detecting the hearing loss and brain damage in neonatal hyperbilirubinemia, and further understand the mechanism of bilirubin-induced injury of nervous tissue.Methods: Fifty-one Sprague-Dewley rat pups were randomly divided into control group(C, n=17) and two test groups (Tl and T2, n1=17, n2=17). Bilirubin solutions were injected into the abdominal cavity of the rat pups in the group T1 and T2 at the postnatal day 7 and 10, and the cumulative amounts of bilirubin were 90mg/kg and 120mg/kg respectively. Meanwhile 0.5ml physiological saline was injected in the rat pups of the group C. Six hours later after the injection, seven rat pups of each group were randomly selected to test serum bilirubin concentration. FC-BAEP, SC-BAEP and MLR were examined in the rest rat pups of each group at postnatal day 12,14,17,and 20. At the postnatal day 20, the endocardial perfusion was performed in these rat pups for the fixation of the brain, and then the brains were taken out and divided into two portions, the left one for observing the changes of morphology and number of the neurons by Nissl stain, the right one for observing the changes of the ultrastructure in the cochlear nucleus via electron microscope.Results:1. Six hours after the injection of bilirubin solution at the postnatal day 10, the serum bilirubin concentrations of the rat pups in group T1 and T2 were increased significantly (P<0.01).2. FC-BAEP could be evoked from 3 rat pups at postnatal day 12 in group C, and could not be recorded from anyone of the rat pups at the same time in group T1 and T2. At the... |
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