Abstract: Objective  To study the effect and mechanism of morroniside(Mor) on the vascular dementia(VD) model rats.　Methods　VD model rats were randomly divided into sham operation group (Sham group), model group (VD group), VD+Mor (25, 50 and 100 mg) groups. Rats were intragastric administration Mor once a day for 28 days. The spatial learning and memory ability were measured by Morris water maze. Histopathological changes of brain issue, apoptosis rate of hippocampus were detected by HE and TUNEL staining respectively. The serum levels of SOD, MDA and LDH were measured by ELISA, the protein expression of Bax/Bcl-2, cytochrome C, caspase-9, caspase-3 and p53 in hippocampus were measured by Western Blot.　Results　Morroniside  improved the learning and memory ability of VD rats in a dose-dependent manner, inhibited the histopathological changes of brain tissue; decreased the apoptosis rate, increased the serum level of SOD, reduced the content of MDA and LDH, and inhibited the protein expression of Bax/Bcl-2 ratio, cytochrome c, caspase-9, caspase-3 and p53.　Conclusions　Morroniside improves the memory ability and pathological changes of VD rats, reduces the apoptotic rate and free radical level of brain tissue, and inhibits the protein expression of mitochondrial apoptotic pathway, thus playing a therapeutic role in VD rats.

Key words: Vascular dementia, 　Morroniside, 　Mitochondrial apoptotic pathway