P-glycoprotein(P-gp)is one of the transmembrane protein of ATP-binding cassette (ABC)which be encoded by Mdr1 gene.Until now the therapy for cerebrovascular disease is not efficient.The relationship between the P-gp and cerebrovascular disease is poor.The aim of the research is study the expression of P-gp in the cerebral cortex and striatum following the cerebral ischemia reperfusion.Methods: Adult male SD rats were randomly assigned control group and one of three groups that were submitted to focal cerebral ischemia 90min followed the reperfusion and subsequently either survive 1day,or 3day or 7day.The expression of P-gp in brain were studied by double-labelling immunofluorescence with antibody P-gp,CD31,NeuN and GFAP.The P-gp positive microvessel density(MVD)in cerebral cortex and striatum were counted.Meanwhile the expression of P-gp in microvessel be studied by Western blot technique.Results: 1.P-gp were expressed in microvessel in control group.However it also can express in neurons and the processes of the astrocytes following the ischemia reperfusion.2.The P-gp positive MVD increased in 1day and 3day groups in ischemia cortex compared with the control group(p<0.05).There was no change in 7day group.It also increased in 3day group in the contralateral cortex,but lower than the ischemia cortex.Westem blot showed the P-gp went up in 3 day group(p<0.05)while there were no change in 1 dye and 7 day group compared with the control.3.The P-gp positive MVD increased in 1day and 3day groups in ischemia striatum compared with the control group(p<0.05)and the peak appeared at the 3 day group.It went back to normal lever in 7 day group.For the contralateral striatum,there was no change to be observed.Western blot results showed that P-gp updated in 3 day group(p<0.05) rather than in the 1 day and 7 day group compared with the control group.Conclusion.1.P-gp were expressed in microvessel in control group.But it also can express in neurons and the processes of the astrocytes following the cerebral ischemia reperfusion.2.The expression of the P-gp increased following the cerebral ischemia reperfusion which may refer as to the protect the brain from the poison.