NGF and diabetes mellitus: These findings report that regular exercise had effects not only on CREB phosphorylation but also on increase of MAPK/Erk phosphorylationin the hippocampus of rat[30], particularly, in cases of diabetes-induced rat, it activates phosphorylation of Erk and CREB, and increases the level of NGF so as it induces activations of MAPK/Erk1/2 signaling pathway and CREB in the hippocampus even more[10].