Objective To explore the pathological features of Aβ1-42 deposition and its correlation with Apolipoprotein E in brain of streptozotocin (STZ)-induced type Ⅱ diabetic rats.Methods High fat diet combined with small dose of STZ induced diabetic rats were adopted as experiment rats,and randomly divided into 3 months old diabetes mellitus group and 6 months old diabetes mellitus group (n=15).Healthy Wistar rats were adopted as control rats,and divided 3 months old control group and 6 months old control group (n=15).The Aβ1-42 and ApoE location and expressions were detected by immtmohistochemistry.Real-time fluorogenic quantitative-PCR and Westem blotting were used to detect the mRNA and protein levels of ApoE in each group.Results Immunohistochemical results showed that Aβ1-42 in the brain of the diabetic rats gathered around the vessel wall and blood vessel.The number of Aβ1-42 and ApoE positively-stained cells and positively-stained vessels was significantly larger and the ApoE mRNA and protein expressions were significantly increased in the 6 months old diabetes mellitus group as compared with those in the 3 months old diabetes mellitus group (P＜0.05).The number of Aβ1-42 and ApoE positively-stained cells and positively-stained vessels was significantly larger and the ApoE mRNA and protein expressions were significantly increased in the 6 months old control groupas compared with those in the 3 months old control group (P＜0.05).As compared with that in the 6 months old control group,the number of Aβ11-42 and ApoE positively-stained cells and positively-stained vessels was significantly larger and the ApoE mRNA and protein expressions were significantly increased in the 6 months old diabetes mellitus group (P＜0.05).As compared with that in the 3 months old control group,the number of Aβ1-42 and ApoE positively-stained cells and positively-stained vessels was significantly larger and the ApoE mRNA and protein expressions was significantly increased in the 3 months old diabetes mellitus group (P＜0.05).Person correlation coefficient indicated that the number of positively-stained cells of Aβ-42 was positively correlated to ApoE protein expression level (r=0.9755,P=0.000).Conclusions Aβ1-42 in the brain of type Ⅱ diabetic rats expresses both in blood vessel wall and around blood vessel.Age and duration of diabetes can increase the deposition of A3 and ApoE in brain tissues,and there is a positive correlation between them.