Ketamine, a drug that blocks NMDA receptors in the brain, produces rapid antidepressant effects in people with depression and treatment-resistant depression. This finding has led to new treatments for mood disorders and has advanced understanding of the brain's neurobiology and the synaptic plasticity mechanisms that make ketamine effective. This review covers the clinical aspects of ketamine's rapid antidepressant action, the synaptic and circuit mechanisms behind it, and how these insights can guide future research toward more effective treatments for neuropsychiatric disorders.
Ketamine produces rapid and sustained antidepressant effects in patients with major depressive disorder that has not responded to conventional monoamine-based drugs. Recent preclinical studies have begun to clarify the mechanisms underlying these effects. This review compares clinical and preclinical findings to provide a broad perspective on how ketamine works as an antidepressant.
Ketamine rapidly relieves depression by activating BDNF-TrkB signaling specifically in CA1 neurons of the hippocampus. Deleting BDNF in either CA3 or CA1, or deleting its receptor TrkB only in postsynaptic CA1, blocks ketamine-induced synaptic strengthening. Ketamine triggers dynamin1-dependent TrkB activation and downstream signaling to produce these rapid synaptic effects. The findings pinpoint a precise synaptic location—CA1 neurons—where BDNF-TrkB signaling is required for ketamine's rapid antidepressant action.