Neurofibrillary tangles are the neuropathological hallmarks of Alzheimer disease (AD). Abnormally hyperphosphorylated tau and neurofilament (NF) are the components of neurofibrillary tangles. Hyperphosphorylation may be the result of an imbalanced regulation between protein kinases and protein phosphatases. Among the many kinases, glycogen synthase kinase-3(GSK-3) might be a key participator in neurodegeneration of AD. To investigate the role of GSK-3 on Alzheimer-like neurofibrillary degeneration, the wild type mouse neuroblastoma cell lines (N2awt) were treated with wortmannin (WT), an inhibitor of phosphatidylinositol 3-kinase (PI3K), and the effect of WT on cell metabolism, cell morphology, cell apoptosis, phosphorylation of NF and tau were detected, as well as the relationship between the alternations of these parameters and GSK-3 activity. It was found (1) that treatment of the cell with 1 μmol/L WT led to a transient (at 1h) activation of GSK-3 with a concurrent increase in phosphorylation of NF and tau. At 3h, the activity of GSK-3 was decreased and the hyperphosphorylation of NF was partially restored. (2) that WT decreased the cell metabolism detected by MTT assay in a dose dependent manner. (3) that treatment of the cell with 1 μmol/L WT for 1h or for 3h induced retraction of cell processes. (4) that no typical apoptotic damage was seen by transient stimulation of GSK-3 activity. It is suggested that transit overactivation of GSK-3 led to Alzheimer-like hyperphosphorylation of cytoskeleton protein and impairment in cell viability.