Abstract: Objective To investigate the effect of CoCl₂ pretreatment on expression of HIF-1α in the hippocampus of hypoxic preconditioned mice.Methods Balb/c mice were randomly divided into group of CoCl₂ and normal saline(NS),respectively injected with CoCl₂ and NS 3 h before exposure to hypoxia for 0 run(H0),1 run(H1) and 4 runs(H4).The tissue of hippocampus was removed immediately after the exposure.Technique of Western blot and electrophoretic mobility shift assay(EMSA) were used to measure the HIF-1α protein level and HIF-1α DNA binding activity,respectively.Results The hypoxic tolerance time in group NS was significantly increased run by run but unchanged in group CoCl₂.In group CoCl₂,the level of HIF-1α protein was unchanged whereas HIF-1α DNA binding activity was increased in H1 and decreased in H4.In group NS,both HIF-1α protein and DNA binding activity were increased.Conclusion Hypoxic-tolerance of mice to hypoxia and HIF-1α in their hippocampus are,respectively,increased and activated by CoCl₂ while its underlying molecular mechanisms are thought to be different from those induced by acute repetitive hypoxic exposure.

Key words: CoCl₂, HIF-1α, hippocampus, mice