Hypothermia postconditioning protects hippocampal CA1 neurons from focal cerebral ischemia in tree shrew

AIM: To observe the changes in vascular endothelial growth factor (VEGF) expression and the cell numbers of cellular necrosis in hippocampus CA1 area after cerebral ischemia and hypothermia postconditioning (HPC). METHODS: The focal thrombotic cerebral ischemia was induced by photochemical reaction in tree shrews. 6 h after ischemia, HPC was executed by a focal homoeothermic equipment, which reduced the brain temperature and maintained at 31-32 ℃ for 1 h. VEGF expression in hippocampus CA1 area was detected by immunohistochemistry. The numbers of death cells were counted and the ultrastructure was observed under the electron microscope. RESULTS: Compared to control group, VEGF expressions increased in neuron of hippocampus CA1 area at 24 h, and decreased at 72 h in HPC group (P<0.01). Meanwhile the numbers of necrotic cells reduced at 24 h, and increased at 72 h. In accordance with this, ultrastructure of mitochondrion and endoplasmic reticulum became deterioration at 72 h. CONCLUSION: During the early stage, VEGF expression maybe directly protects neurons from cerebral ischemia. HPC has a remarkable significance to neuroprotective function in this time, but it may aggravate neuron injury in the last stage of cerebral ischemia. The HPC may prolong the treatment time-windows in the acute phase of cerebral ischemia.