ObjectiveTo investigate the effect of acute normovolemic hemodilution (ANH) on the apoptosis in hippocampal cells induced by global cerebral ischemia-reperfusion (I/R) in rats.Methods Thirty-six healthy 50-60 day old male SD rats weighing 280-320 g were randomly divided into 3 groups ( n =12 each):group sham operation (group S); group global cerebral I/R (group I/R) and group ANH.Global cerebral I/R was produced by 4-vessel technique described by Pulsinelli et al.in groups I/R and ANH.ANH was carried out at 24 h after cauterization of bilateral vertebral arteries,before occlusion of bilateral carotid arteries.Blood was withdrawn from femoral artery until Hct was reduced to 30％ and equal volume of hydroxyethyl starch 130/0.4 sodium chloride was infused into femoral vein simultaneously.Bilateral carotid arteries were blocked for 5 min at 10 min after ANH.The rats were sacrificed at 24 h of reperfusion and their hippocampi were isolated.Apoptosis was detected by flow cytometry.The expression of Apaf-1 mRNA and caspase-3 mRNA was determined by RT-PCR.Results Global cerebral I/R significantly increased apoptosis index and up-regulated Apaf-1 mRNA and caspase-3 mRNA expression in group I/R as compared with group S.ANH significantly attenuated apoptosis and down-regulated Apaf-1 mRNA and caspase-3 mRNA expression in group ANH compared with group I/R.ConclusionANH can reduce hippocampal cell apoptosis induced by cerebral I/R through down-regulation of Apaf-1 and caspase-3 expression in hippocampus.