Role of the mTOR signaling pathway in the rapid antidepressant action of ketamine.

Some patients with major depressive disorder remain resistant to antidepressant medication. A randomized, placebo-controlled, double-blind trial demonstrated that a single subanesthetic dose (0.5 mg/kg) of the N-methyl-D-aspartate receptor antagonist ketamine caused a rapid antidepressant effect within hours in treatment-resistant patients with major depressive disorder. However, the precise cellular mechanisms underlying ketamine's rapid antidepressant actions were unclear, although it is proposed that the α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptor might be involved in these mechanisms. Recently, Li et al. reported the role of the mammalian target of rapamycin (mTOR) signaling pathway, a ubiquitous protein kinase involved in protein synthesis and synaptic plasticity, in ketamine's rapid antidepressant effects. Here, these findings are put into context and their significance is discussed.