Fig. 5.

Model of serotonergic regulation of Aβ metabolism. Serotonin receptors are activated on the cell surface, which initiates a signaling cascade that leads to ERK phosphorylation and activation. ERK appears to increase α-secretase cleavage and may reduce γ-secretase cleavage of APP. The particular serotonin receptor subtypes responsible for ERK activation in this paradigm are unknown. Not all receptors or ligands that activate ERK will alter APP processing, however similar to serotonin, NMDA receptors can also modulate APP processing through the ERK pathway.