Objective:To observe the effect of a Chinese medicine compound,Naoerkang(脑尔康,NEK),on amyloid-beta peptide(1-42;Aβ_(1-42)) and matrix metalloproteinase-9(MMP-9) expressions in the hippocampus of Alzheimer’s disease(AD) model rats.Methods:A total of 48 male Sprague Dawley(SD) rats were randomly divided into normal control,untreated,and piracetam groups,and low-dose,medium-dose,and high-dose NEK groups,with 8 rats in each group.The 5-μL aggregated Aβ_(1-42)(2μg/μL) were injected into both CA1 areas of the hippocampus in the rats to establish an AD model,whereas the normal control was treated with the same dose of normal saline.The rats in the NEK groups were treated with a high,medium,or low dose of NEK[60 g/(kg·d), 30 g/(kg·d),and 15 g/(kg·d)],respectively,intragastrically for 28 days;piracetam(0.375 g/kg,intragastrically) was consecutively administered in the piracetam group;and normal saline was applied in the normal control and untreated groups.A Y-maze test was used for behavioral study to test the learning and memory abilities.Aβ_(1-42) and MMP-9 expressions in the hippocampus was determined immunohistochemically,and the results were analyzed by image acquisition and an analysis system.Results:Aggregated Aβ_(1-42) induced obvious learning and memory dysfunction, as well as up-regulation of Aβ_(1-42) expression in the hippocampus.Compared with those in the normal control group,the learning and memory abilities of rats in the untreated group significantly decreased(P<0.01),and the expression of Aβ_(1-42) was significantly increased(P<0.01).Twenty-eight days after different treatments,compared with those in the untreated group,the learning and memory abilities of AD model rats in the piracetam,low-dose, medium-dose and high-dose NEK groups were significantly improved(P<0.01 or P<0.05),and the expression of Aβ_(1-42) in the hippocampus decreased(P<0.01 or P<0.05),and MMP-9 increased(P<0.01 or P<0.05),especially in the high-dose NEK group.Conclusion:NEK might play a role of anti-dementia by increasing the expression of MMP-9 in the hippocampus of AD model rats,resulting in the reduction of the quantity of Aβ_(1-42) and improvement in learning and memory ability in AD model rats. Objective: To observe the effect of a Chinese medicine compound, Naoerkang, on amyloid-beta peptide (1-42; Aβ 1- (1-42)) and matrix metalloproteinase-9 the hippocampus of Alzheimer’s disease (AD) model rats. Methods: A total of 48 male Sprague Dawley (SD) rats were randomly divided into normal control, untreated, and piracetam groups, and low- dose, medium-dose, and high-dose NEK groups, with 8 rats in each group. 5-μL aggregated Aβ 1-42 (2 μg / μL) were injected into both CA1 areas of the hippocampus in the rats to establish an AD model, the normal control was treated with the same dose of normal saline. The rats in the NEK groups were treated with a high, medium, or low dose of NEK [60 g / (kg · d), 30 g / (kg · d), and 15 g / (kg · d)], respectively, intragastrically for 28 days; piracetam (0.375 g / kg, intragastrically) was consecutively administered in the piracetam group; and normal saline was applied in the normal control and untreated groups. A Y-maze test was used for behavioral study to test the learning and memory abilities. Aβ_ (1-42) and MMP-9 expressions in the hippocampus was determined immunohistochemically, and the results were analyzed by image acquisition and an analysis system. Results: Aggregated Aβ_ (1-42) induced obvious learning and memory dysfunction, as well as up-regulation of Aβ_ (1-42) expression in the hippocampus. Compared with those in the normal control group, the learning and memory abilities of rats in the untreated group significantly decreased (P < 0.01), and the expression of Aβ 1-42) was significantly increased (P <0.01). Twenty-eight days after different treatments, compared with those in the untreated group, the learning and memory abilities of AD model rats in the piracetam , low-dose, medium-dose and high-dose NEK groups were significantly improved (P <0.01 or P <0.05), and the expression of Aβ 1-42 in the hippocampus decreased (P <0.01 or P < , and MMP-9 increased (P <0.01 or P <0.05), especially in the high-dose NEK group. Confluence : NEK might play a role of anti-dementia by increasing the expression of MMP-9 in the hippocampus of AD model rats, resulting in the reduction of the quantity of Αβ_ (1-42) and improvement in learning and memory ability in AD model rats.