NGF induces sustained activation of p38, a member of the MAPK family (Morooka T, Nishida E, 1998). Both p38 and the ERKs appear to be involved in neurite outgrowth and differentiation caused by NGF in PC12 cells. As a matter of fact, PC12 cell differentiation appears to involve activation of both ERK/MAPK and p38. Both ERK/MAPK and p38 pathways contribute to the phosphorylation of the transcription factor CREB and the activation of immediate-early genes (Xing J, 1998). p38 activation by NGF may occur by at least two mechanisms, involving SRC or MEK kinases.