Sustained phosphorylation of mitogen-activated protein kinase is required for basic fibroblast growth factor-mediated axonal branch formation in cultured rat hippocampal neurons

Basic fibroblast growth factor (bFGF) has been reported to promote the form ation of axonal branches in cultured brain neurons. In the present study, w e investigated whether the mitogen-activated protein kinase (MAPK) cascade was involved in this action of bFGF in cultured rat hippocampal neurons. Re combinant human bFGF (0.1-10 ng/ml) induced phosphorylation of p44/42 MAPK in a concentration and time-dependent manner. The phosphorylation of p44/42 MAPK occurred rapidly within 5 min after addition of bFGF, and lasted for 48 h. The bFGF-induced phosphorylation of p44/42 MAPK and axonal branch for mation were both blocked by simultaneous addition of U0126 and PD98059, spe cific inhibitors of MAPK kinases. Furthermore, when U0126 and PD98059 were added 24 h after bFGF, phosphorylation of p44/42 m MAPK was decreased, and axonal branch formation was stopped. These results suggest that sustained a ctivation of the MAPK cascade is required for bFGF-mediated axonal branch f ormation. (C) 2001 Elsevier Science Ltd. All rights reserved.