RESUMO
OBJECTIVE: To study the effect of nerve growth factor (NGF) pretreatment on apoptosis of neurons and the expression of Bcl-2 and Bax protein in cerebral cortex and hippocampus CA1 zone following global cerebral ischemia/reperfusion (I/R) injury in gerbils and to explore the mechanism of protection and the best time window of NGF pretreatment. METHODS: Global cerebral I/R injury model was induced by occlusion of bilateral carotid arteries. NGF was injected into the lateral ventricle. Thirty gerbils were randomly divided into five groups, with six animals in each: sham operation group (A group), I/R injury group (B group), NGF pretreatment 12, 24 and 48 hours groups (C, D and E group). Gerbils in all groups were sacrificed after being subjected to 20 minutes of cerebral ischemia followed by 72 hours reperfusion, except A group. Neural apoptosis was identified by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL), and immunohistochemistry was used to detect the expression of Bcl-2 and Bax protein in cerebral cortex and hippocampus CA1 zone. RESULTS: Compared with B group, the number of apoptotic neurons and the expression of Bax positive cells in NGF pretreatment groups were decreased significantly (all P<0.05), while the expression of Bcl-2 positive cells was increased significantly (all P<0.05). The apoptotic rate in cerebral cortex and hippocampus CA1 zone and expression rate of Bax protein positive cells were the lowest, but the expression rate of Bcl-2 protein positive cells was the highest at 48 hours. CONCLUSION: NGF pretreatment can significantly decrease the neuronal apoptosis of the cerebral I/R injury in gerbils, and the best time window of NGF pretreatment is 48 hours. The mechanism of protection may be related to induction of Bcl-2 protein expression and inhibition of Bax protein expression by NGF pretreatment, thereby preventing neuronal apoptosis.
