Abstract: Objective To investigate the effect of sevoflurane on spatitial cognitive function and them RNA expressions of N-ethyl-aspartate (NMDA)receptor and the subunits of NR1 and NR2B in the hippocampus of elderly rats during the cerebral blood flow changes.Methods Thirty Wistar rats were randomly divided into 4 groups: control group(Ⅰ,n=8),2% sevoflurane group(Ⅱ,n=8),3% sevoflurance group (Ⅲ,n=8) and sevoflumne-ischem ia-group(Ⅳ,n=6).All rats received 0%,2%,3% sevoflurane and O₂ in a flow rate of 2 L·min^-1 and N₂ (6 L·min^-1),100 min every day for 5 days,respectively In group Ⅲ,left common cartid artery was ligated before a week of the mixed gas exposure The cognitive function was tested 4 times a day for 5 consecutive days using Morris water maze.The aninals were killed after the Morris watermaze testperfounance NR,NR1 and NR2B mRNA expressions in the hippocampus were deteunined using reverse transcriptase-polymemse chain reaction (RT-PCR).Results The mean of latency period in Ⅰ-Ⅳ groups graduatly shorterned from 88s to 36s on day 1-5,and the swinming distance shortened from 851 cm to 485cm.The swinming distance was significantly shorter on the 5th day than on the 1st day in group Ⅰ,Ⅱ and Ⅲ (P<0.01).The latency period on the 1st day of group Ⅲ and on 1-5th day of group Ⅳ were significantly longer than in control group.The quadrant of hidden-platfoun of group Ⅲ and Ⅳ were obviously shorter than that of group Ⅰ.The NR mRNA expression in group Ⅲ and NR2B mRNA expression in group Ⅳ were markedly higher than group Ⅰ.Conclusion Sevoflumne inhibits cognitive function of elderly rats in dose-dependentmanner Cerebral blood flow deficits influences the effect of sevoflumne on cognitive function in old rats Sevoflurane at high concentration may inhibit the capacity of NMDA receptor.