Objective   To evaluate the effect of the hyperbaric oxygenation therapy on the apoptosis of the hippocampal neuron and the impairment of cognitive function of the newborn rats suffering from bilirubin encephalopathy.    Methods   One hundred and forty-five five-day-old SD rats of both sex were randomly divided into 3 groups

control group

bilirubin encephalopathy group and hyperbaric oxygenation treated group. Bilirubin (10 mg/ml) was injected into the cerebellomedullary cistern to establish experiment model

and normal sodium was injected for control. The expression of cytochrome C and Caspase-3 in the hippocampus neurons were detected by immunohistochemistry and immunofluorescence

respectively

at the time of 6 h

1

3

5 d and 7 d after intra-cisternal injection. Neuronal apoptosis was checked by TUNEL method. The cognitive function was tested by Morris experiment.    Results   The expressions of the cytochrome C and Caspase-3 in hyperbaric oxygenation treated group were lower than those in bilirubin encephalopathy group

but higher than control group at above-mentioned time points (P0.05). The TUNEL positive cell rate in hyperbaric oxygenation treated group [(27.2±1.8)%] was lower than that in bilirubin encephalopathy group [(37.6±6.6)%] (P0.05). In Morris experiment

the rats of hyperbaric oxygenation treated group were easier to find the safe platform than those of bilirubin encephalopathy group

and the frequency of crossing the safe platform were eight times higher to bilirubin encephalopathy group (P0.05).    Conclusion   By reducing the expressions of cytochrome C and Caspase-3

hyperbaric oxygenation therapy inhibits bilirubin-induced hippocampal neuron apoptosis. Thus

it improves cognitive function of the neonatal rats suffering from bilirubin encephalopathy.