To explore the effect of Codonopsis pilosula (Franch) Nannf total alkaloids (DSA) on differentiation induced by nerve growth factor (NGF) in PC12 cells. METHODS: After culturing PC12 cells with DSA in the presence or absence of NGF, neurite outgrowth in PC12 cells and correlated protein kinases were assayed. RESULTS: DSA alone did not exhibit neuritogenic activity, but caused a significant enhancement of NGF (2 μg/L)-induced neurite outgrowth in PC12 cells, and increased the phosphorylation of mitogen-activated protein kinase (MAPK). Furthermore, this enhancing effect was completely blocked by a specific MAPK kinase inhibitor, PD98059. CONCLUSION: DSA enhanced the NGF-induced neurite outgrowth in PC12 cells by amplifying an up-stream step of the MAPK-dependent signaling pathway.