Neurotrophin-3 (NT-3) is well known to play an important role in facilitating neuronal survival and differentiation during development. However, the mechanisms by which neurotrophin-3 promotes prolonged Akt/MAPK signaling at an early stage are not well understood. Here, we report that NT-3 works at an early stage of neuronal differentiation in mouse neural stem cells (NSCs). After treatment with NT-3 for 12 h, more NSCs differentiated into neurons than did untreated cells. These findings demonstrated that stimulation with NT-3 causes NSCs to differentiate into neurons through a phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway and the phosphorylated extracellular signal-regulated kinase (ERK) pathway. In addition, treatment with NT-3 induced neurite outgrowth by specific phosphorylation of p38 MAPK, which was accompanied by neuronal differentiation. Taken together, these results suggest that NT-3, along with the Trk C receptors in NSCs, might lead to the survival and neuronal differentiation of NSCs via two distinct downstream signaling pathways at an early stage of neuronal differentiation. (c) 2007 Elsevier Inc. All rights reserved.