Abstract: Objective: To investigate the role of release of cytochrome c from mitochondria in the protective process of hippocampal neurons against ischemia/reperfusion injury by cerebral ischemic preconditioning (IPC) in rats. Methods: Rats were randomly divided into three groups: an ischemia/reperfusion group (IR), an ischemic preconditioning+ischemia/reperfusion group (IPC+IR), and the control group. Histological changes in the neurons of the hippocampal CA1 region were produced with HE staining. The apoptotic neurons were counted with TUNEL staining and the release of cytochrome c from mitochondria were determined with immunohistochemistry in the same brain area. Results: Compared with IR group, cerebral ischemic preconditioning can increase the number of survival neurons in hippocampal CA1 region（P＜0.001）， markedly reduce the number of apoptotic pyramidal neurons（P＜0.001）, and inhibit the release of cytochrome c from mitochondria. Conclusion: Cerebral ischemic preconditioning (IPC) can protect the hippocampal neurons against ischemia/reperfusion injury by reducing the release of cytochrome c from mitochondria and inhibiting the apoptosis.

Key words: Cytochrome c, Ischemic preconditioning, Hippocampal neurons, Apoptosis, Cerebral ischemia/reperfusion injury