Objective To establish mild cognitive dysfunction (MCI) models in elderly rats,and to investigate the pathophysiological features.Methods Totally 40 SD rats (14 to 18-month-old) were randomly divided into 2 groups:the model group (n=20) and the sham operation group (n=20).Bilateral carotid artery stenosis was prepared in the model group while bilateral carotid artery was seperated with no bilateral narrowing in the sham operation group.30 days after the operation,Morris water maze test was performed,pathomorphological and electron microscopic observations of the cerebral tissue were examined and the expression of G protein-coupled receptor kinase 2(GRK2) in hippocampus tissue w detected by reverse transcription polymerase chain reaction (RT-PCR) and Western blottin.Results The mortality in model group was only 10％.Pathological morphology and ultrastructure showed that hippocampal tissue structure was almost normal in sham operated group,but in model group group,hippocampal CA1 pyramidal cells were in ischemic demyelination,arranged loose,and part of the cells showed nucleus pyknosis,deeply stained; there was no obvious infarct in white matter,part of the white matter fiher hecame thinner and disorder,nucleolus became smaller and steped aside,cytoplasmic electron density increased,lipofuscin appeared occasionally.Rough endoplasmic reticulum and Golgi were expanded,cytosolic free ribosomes increased,part of mitochondria became swelled,vacuolated.Morris water maze test results showed that the average escape latency in model group was longer than in sham group (P＜0.05).In spatial probe test,the average time of crossing the first original platform in model rats was significantly longer than the sham operated group [(36.80±7.68) s vs.(20.87±6.16)s,P＜0.05].The average number of crossing the original platform in 60 seconds in model group was significantly less than in sham group(1.43±0.51 vs.3.10±1.45,P＜0.05).The expressiones of GRK2 mRNA and protein in the hippocampus were significantly increased in model group rats than in sham group (P＜0.05).Conclusions The model of severe CCA stenosis in elderly rats can be applied for MCI animal models with good stability and repeatability.Compared with sham group,the cells morphology and ultrastructure in model group appeare more obvious pathological changes and mild impairments in cognitive function.GRK2 may play an important role in the development of MCI.