WNK2 and major depressive disorder: Chronic treatment with the SSRI escitalopram as well as increasing 5-HT postsynaptic function via stimulation of the cAMP/mitogen-activated protein kinase (MAPK) signaling cascades restores some cognitive functions such as memory performance and Arc, suggesting a role for the 5-HT/MEK cascade in regulating Arc in depression (Eriksson et al., 2012).