Objective To study the role of hypoxia inducible factor-1α (HIF-1α)/stromal cellderived factor-1 (SDF-1) pathway in high altitude  hypoxia preconditioning in rat.  Methods  Seventy-six adult male SD rats, which through fed in low-pressure oxygen chamber (altitude 5000 m) and Xining (altitude 2260 m) to establish the rat model of hypoxia preconditioning. Rats randomly divided into 6 groups: control group (Ctrl), high altitude hypoxic preconditioning 1 day group (HHP-1d), high altitude hypoxic preconditioning 4 days group (HHP-4d), high altitude hypoxic preconditioning 15 days group (HHP-15d), high altitude hypoxic preconditioning 30 days group (HHP-30d), medium altitude hypoxic preconditioning group (MHP). 7.0T small animal MRI was used to observe the intracranial structure, diameter of basilar artery and cerebral blood flow in the hippocampus and brainstem regions by the sequences of T2 weighted images (T2WI) and arterial spin labeling (ASL) in the groups of Ctrl, HHP-4d, HHP-30d and MHP. In each group, blood routine was tested, the concentrations of HIF-1α, SDF-1 in serum, platelet activating factor (PAF）and P-selectin (SELP) in plasma were detected by the method  of ELISA.  Results  In the hypoxia preconditioning groups, intracranial structure and diameter of basilar artery had no significant difference, while cerebral blood flow in the regions of brainstem and hippocampus increased significantly (P<0.05). Meanwhile, red blood cell and white blood cell increased significantly, while platelet decreased significantly in the groups of hypoxia preconditioning (P<0.05). Red blood cell and platelet in MHP group were closer to Ctrl group. The concentrations of HIF-1α and SDF-1 (except HHP-1d group) increased significantly in hypoxia preconditioning groups (P<0.05).The concentrations of PAF and SELP increased significantly in HHP-1d and HHP-15d groups. The concentration of PAF decreased significantly in the HHP-4d and HHP-30d groups, and SELP decreased significantly in HHP-4d group (P<0.05).  Conclusion Hypoxia preconditioning can increase oxygen storage and immune defense capacity, improve brain reserve capacity and play the effect of brain protection through HIF-1α/SDF-1 pathway. The best effect preconditioning was feed at medium altitude (altitude 2260 m) for 30 days.  

 Hypoxia inducible factor-1α, Stromal cell-derived factor-1, Hypoxia preconditioning, Routine blood, 7.0 T small animal magnetic resonance imaging, Rat