THE EFFECTS OF
BILIRUBIN ON EVOKED POTENTIAL AND LONG TERM POTENTIATION OF RAT HIPPOCAMPAL
CA3 REGION
Zhang Lian, Liu Wanjun
Department of Pediatrics, Tongji Hospital, Tongji Medical College,
Huazhong University of Science and Technology, Wuhan, China
Objective: Hyperbilirubinemia is a common disorder
with severe potential neurotoxicity, especially in the newborns. We want to
detect the mechanism of brain damage induced by bilirubin.
Methods: In this electrophysiological study, we observed
the effects of acute bilirubin injection on the evoked potential
(population spike, PS) and the long-term potentiation (LTP) in hippocampal
CA3 region of Sprague-Dawley rat. The animals were fast injected with
60mg/kg or 30mg/kg of bilirubin, or vihicle control, in 20 ml of buffer via
venous catheters within 5 minutes.
Results: The results showed that both bilirubin treated
groups had longer peak latency of PS after injection at all the time points
measured (1,3,5,10,15,30,45,60,90,120 minutes) in a dose-independent fashion,
while the amplitudes of PS didn’t change significantly. Neither the peak
latency nor the amplitude o PS had changed in the control group.
Furthermore, the LTP could be induced by high-frequency stimulation in the
control animals. This phenomenon was disappeared in both bilirubin treated
groups. The amplitudes of PS of the two treated groups after stimulation
were also smaller than that of the control animal at every moment during
observation. These results confirmed that bilirubin has significant depressive
effects on the nerve system.
Conclusion: LTP is generally proved to be a
neurophysiologic foundation of learning and memory. Our novel finding that
bilirubin can inhibit the induction of LTP in hippocampus by a rapid
uptake, which evolves the possibility that the neonatal hyperbilirubinemai
would decline children’s ability of learning and memory.