Abstract:

Objective To observe the effects of ischemic postconditioning(PC) on changes of cerebral water content, cerebral blood flow, infarct area and hippocampal ultrastructural , and to explore the neuroprotective mechanisms of ischemic PC on undergoing thrombotic cerebral ischemic injury. Methods Tree shrews were randomly grouped into control, ischemia 4 hours，ischemia 24 hours，ischemic postconditioning 4 hours and ischemic postconditioning 24 hours (n=8) Eight animals were used for HE staining(n=3)and electron microscopy(n=5). The model of thrombotic cerebral ischemia was induced by photochemistry in tree shrews. Four hours after the model establishment, the common carotid artery on the ischemia side was clamped for 5 minutes, then perfused by removing the clamp for 5 minutes, and repeated the same management 3 times, so that the model of PC was established. The changes of the brain water content of local cortex were measured by Elliott dry-wet weight and the brain infarct area was determind by 2,3,5-triphenyl-tetrazolium chloride staining.In addition, the regional cerebral blood flow of local cortex was measured by laser doppler, and the ultrastructural changes in the CA1 area of hippocampus in different groups were observed under an electron microscope. Results More neuron pycnosis was observed in hippocampal CA1 area. Obvious swelling of mitochondria, partial disrupt and vanish of the mitochondria cristae and more endoplasmic reticulum cisterna appeared in the neuron of hippocampus at the 24th hour after cerebral ischemia.With the time prolonging of ischemic, the brain water content was significantly increased (86.81%±1.08%) in the ischemia group at the 24th hour compared with sham group. Cerebral infarction area was maximum (33.00%±3.03%) and regional cerebral blood flow decreased obviously［(134.27±28.75) ml/min］. The brain water content was significantly decreased (81.04%±1.04%, P<0.01) and the infarct area was significantly shrink in ischemic postconditioning group (16.79%±1.29%, P<0.01) than that in ischemia group.The regional cerebral blood flow in ischemic postconditioning group was in contrast to ischemia group significantly at the 24th hour ［(195.25±21.18) ml/min, P<0.01］. Conclusion Ischemic postconditioning attenuates the edema in ischemic brain and narrow the cerebral infarction area in tree shrews. The mechanism may be related to the improvement of local cerebral blood flow.

Key words: Postconditioning, Cerebral ischemia, Regional erebral blood flow, Brain edema, Neuroprotection, Photochemistry, Tree shrew