Previous studies have demonstrated the protective effect of hypoxic preconditioning on acute cerebral infarction,but the mechanisms underlying this protection remain unclear.To investigate the protective mechanisms of hypoxic preconditioning in relation to its effects on angiogenesis,we induced a photochemical model of cerebral infarction in an inbred line of mice(BALB/c).Mice were then exposed to hypoxic preconditioning 30 minutes prior to model establishment.Results showed significantly increased vascular endothelial growth factor and CD31 expression in the ischemic penumbra at 24 and 72 hours post infarction,mainly in neurons and vascular endothelial cells.Hypoxic preconditioning increased vascular endothelial growth factor and CD31 expression in the ischemic penumbra and the expression of vascular endothelial growth factor was positively related to that of CD31.Moreover,hypoxic preconditioning reduced the infarct volume and improved neurological function in mice.These findings indicate that the protective role of hypoxic preconditioning in acute cerebral infarction may possibly be due to an increase in expression of vascular endothelial growth factor and CD31 in the ischemic penumbra,which promoted angiogenesis. Previous studies have demonstrated the protective effect of hypoxic preconditioning on acute cerebral infarction, but the mechanisms underlying this protection remain unclear. To investigate the protective mechanisms of hypoxic preconditioning in relation to its effects on angiogenesis, we induced a photochemical model of cerebral infarction in an inbred line of mice (BALB / c). Michands then then exposed to hypoxic preconditioning 30 minutes prior to model establishment. Results showed significantly increased vascular endothelial growth factor and CD31 expression in the ischemic penumbra at 24 and 72 hours post infarction, mainly in neurons and vascular endothelial cells. Hypoxic preconditioning of vascular vascular growth factor and CD31 expression in the ischemic penumbra and the expression of vascular endothelial growth factor was positively related to that of CD31. Moreover, hypoxic preconditioning reduced the infarct volume and improved neurological function in mice. These findings indi cate that the protective role of hypoxic preconditioning in acute cerebral infarction may possibly be due to an increase in expression of vascular endothelial growth factor and CD31 in the ischemic penumbra, which promoted angiogenesis.