Objective To investigate the expression of inflammatory factors and brain-derived neurotro-phic factor(BDNF)in the brain hippocampus of Alzheimer's disease(AD)-like mice caused by amyloid β-protein 25-35(Aβ25-35).Methods A total of 40 six-week-old male Kunming mice were taken to construct an AD-like mouse model using bilateral ventricular injection of Aβ25-35,and were divided into the 0 d,7 d,14 d,and 28 d groups for observation,with 10 mice in each group.The Y-maze and new object recognition assay were used to test the learning and memory functions of the mice.The hematoxylin-eosin(HE)staining was used to observe the neuronal damage in the hippocampal region.Immunohistochemical staining was used to detect the expression levels of phosphorylated-tau(p-tau),CD11b and BDNF in hippocampus.ELISA was used to detect the expression levels of inflammatory factors in hippocampus,including interleukin-1β(IL-1β)and tumor necrosis factor-α(TNF)-α,and real-time quantitative reverse transcription PCR(RT-qPCR)and Western blot were used to detect the mRNA and protein expression levels of BDNF.Results Aβ25-35 could impair memory and cognitive function in the mice.Compared with the 0 d group,the neuron number in the hippocampal tissue of mice in the 14 d and 28 d groups was significantly reduced(P<0.05),and the optical density values of p-Tau and CD11b,and expression levels of IL-1β and TNF-α in the hippocampal region of mice in the 14 d and 28 d groups were significantly increased(P<0.05).In addition,compared with the 0 d group,the relative expression levels of BDNF mRNA and protein in the hippocampal tissue of mice were sig-nificantly increased in the 7 d group(P<0.05),while the relative expression levels of BDNF mRNA and pro-tein were significantly decreased in the 14 d and 28 d groups(P<0.05).Conclusion Aβ25-35 may increase the expression of TNF-α,IL-1β and p-tau in hippocampal tissue by activating microglia,which in turn impaired the memory and cognitive functions of mice,and the expression level of BDNF in hippocampal tissue showed a first increase and then a decrease in the injury period.