OBJECTIVE:To investigate the effect of Ginkgo biloba leaf extract on amino acid levels in the cerebral cortex of cerebral ischemia model rats induced by middle cerebral artery occlusion (MCAO).METHODS:A rat model of cerebral ischemia was established by MCAO.Male rats were divided into a negative control group (Control),a sham-operated group (Sham),an ischemic group (MCAO),and an ischemic group treated with Ginkgo biloba leaf extract (MCAO_D).All groups were divided into two subgroups with occlusion times of 12 and 24 h,respectively.The levels of 18 endogenous amino acids in the cerebral cortex were quantified by triple quadrupole-liquid chromatography-mass spectrometry.RESULTS:Compared with the MCAO group,behavioral performance,neurological deficit score,and cerebral infarct volume were significantly improved in the MCAO_D group (P ＜ 0.05,P ＜ 0.01).Compared with the sham group,the levels of 17 amino acids in the cerebral cortex were markedly changed in the MCAO group.The levels of Alanine (Ala),Isoleucine (lle),Glutamic acid (Glu),Serine (Ser),Valine (Val),Phenylalanine (Phe),Proline (Pro),Threonine (Thr),Lysine (Lys),Tyrosine (Tyr),Hydroxyproline (Hyp),Arginine (Arg),Leucine (Leu),Tryptophan (Trp),and Glycine (Gly) were increased (P ＜ 0.001,P ＜ 0.05),while levels of Gin and Tau were decreased (P ＜ 0.001,P ＜ 0.05).Compared with the MCAO group,Ginkgo biloba extract treatment in the MCAO_D group significantly down-regulated the levels of 11 amino acids,especially those of Arg,Thr,and Ser in 12 or 24 h.CONCLUSION:Injection of Ginkgo biloba leaf extract has a therapeutic effect on model rats with MCAO-induced cerebral ischemia by acting on amino acids in the cerebral cortex.This effect might be associated with the regulation of amino acid metabolism in the cerebral cortex.