Aim To investigate the mechanism of berberine on preventing atherosclerosis(As) in rabbits.Methods New Zealand white rabbits(n=24) were randomly divided into three groups including the normal group,the carotid artery atherosclerosis group and berberine group(n=8).The rabbits of the normal group were fed with normal diet.Carotid atherosclerosis was established by an air-drying operation which was performed on the right common carotids,and in conjunction with a high cholesterol-diet in the second week for 4 weeks.Berberine was administrated intragastricly daily for 5 weeks.The right carotid arteries were assayed by HE staining to investigate the effect of berberine on carotid atherosclerotic lesion,and by immunohistochemistry staining to assay the effects of berberine on the activity of nuclear factor kappa B(NF-кB),and by reverse transcription polymerase chain reaction(RT-PCR) to assay the effects of berberine on the expression of NF-кBp65,vascular cell adhesion molecule-1(VCAM-1) and monocyte chemoattractant protein-1(MCP-1).Results The air-operation in conjunction with a high cholesterol diet increased numberous foam cells compared with the normal group,which were decreased in the berberine group.The density of the positive cells increased from 2.00±0.93(the normal group) to 37.50±2.45(the carotid artery atherosclerosis group),and decreased to 19.58±2.60(berberine group)(P<0.01).The relative copies of NF-кBp65 mRNA on β-actin increased from 0.18±0.04(the normal group) to 0.66±0.16(the carotid artery atherosclerosis group),and decreased to 0.42±0.05(berberine group).The relative copies of VCAM-1 mRNA on β-actin increased from 0.20±0.04(the normal group) to 0.81±0.11(the carotid artery atherosclerosis group),and decreased to 0.61±0.11(berberine group)(P<0.01).The relative