KCNK2 and major depressive disorder: Consistent with a proposed role for TREK1 in depression, TREK1 is inhibited by therapeutic doses of selective serotonin reuptake inhibitors (SSRIs) such as fluoxetine (Prozac; Heurteaux et al., 2006; Sandoz et al., 2011) and spadin, a sortilin-derived peptide that also has antidepressive effects (Mazella et al., 2010).