Objective To investigate the preventive effect of iptakalim hydrochloride(Ipt) on brain edema in rats after exposure to simulated high altitude and the mechanisms involved.Method Adult Wistar rats were randomly divided into normoxic control group,simulated plateau acute hypoxia group simulated 8 000 m for 8 h and three Ipt taking groups which were pretreated with 2, 4 and 8 mg(kg?d) of Ipt respectively for 7d before exposure to hypoxia.Water content was determined by the wet-dry method;Na~+,K~+,Ca~(2+) and Mg~(2+) content in the cortex was detected with all atomic absorption spectrophotometer;inorganic phosphorus standardization was applied to decide the activities of Na~+/K~+-ATPase,Ca~(2+)-ATPase and Mg~(2+)-ATPase;Occludin and AQP4 gene expression were determined by RT-PCR.Result The water content was increased and the concentration of Na~+ and Ca~(2+),the activities of Na~+/K~+-ATPase,Ca~(2+)-ATPase and Mg~(2+)-ATPase and the gene expression of the Occludin and AQP4 were all down-regulated in acute hypoxia group compared with normoxic control group.And these changes could be significantly relieved by pretreatment with Ipt.Conclusion Ipt can prevent the occurrence of brain edema caused by acute hypobaric hypoxia possibly related to the effect on water content,electrolytes concentration,ATPase activity and gene expressions of aquaporin and tight junction proteins.