Objective   To evaluated the effect of unilateral intracerebroventricular injection (i.c.v.) of β-amyloid peptide (Aβ) on astrocyte activation and neurogenesis by observing the expression of glial fibrillary acidic protein (GFAP) in the hippocampus around the injecting area.   Methods   Total 40 adult male SD rats were randomly divided into control group (n=10

2 for each time points) and experimental group (n=30

6 for each time points). Aβ1-42 (7 μg) or normal saline (7 μl) was injected into the lateral cerebroventricle of corresponding animals and then sacrificed at 3

7

14 and 30 d after infusion. The expression of GFAP was observed by immunohistochemical staining. The double labeling of BrdU and GFAP was observed by immunofluorescence methods to identify the proliferative cells.   Results   The number of GFAP positive cells in the experimental group was increased significantly after the injection and reached maximum on the 7th day

and then decreased slowly after 14 d after the injection when compared with control (P0.01). Some of BrdU positive cells were GFAP positive in the experimental group

while there were few double positive cells in the control group.   Conclusion   Astrocytes are activated after i.c.v. injection of Aβ

and some of them come from the neural stem cells (NSCs) in the hippocampus. Aβ may be one of the factors promoting NSCs to develop into astrocytes.