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P>Objective To observe the influences of βamyloid peptide(Aβ) on the proliferation and apoptosis of neural stem cells(NSCs) and to investigate the protective mechanism of insulinlike growth factor1(IGF-1) from toxicity of Aβ. Methods NSCs were isolated from E14 SD rats brains and then treated with IGF-1, Aβ and IGF-1 plus Aβ respectively. The cells were dyed with trypanblue for the count of dead cells and the death rate. BrdU was used to label cells and to evaluate cell proliferation. NSCs and newborn cells were identified by immunocytochemistry and apoptosis was detected by TUNEL technique. Results Cell death rate was low and there were many BrdUpositive cells, but no TUNELpositive cells in the medium containing IGF-1. Cell death rate increased strikingly 6-48 hours after Aβ was added, and a great many TUNELpositive cells were observed in the group treated with Aβ. Death rate of cells and TUNELpositive cell