Ketamine and rapid antidepressant action: new treatments and novel synaptic signaling mechanisms

Summary & key facts

This review explains how ketamine, a drug that blocks a specific brain receptor for the chemical glutamate, can lift depression symptoms very quickly in many people, including those who did not get better with standard antidepressants. The authors describe clinical findings, show that the antidepressant effect depends on a careful dosing range, and summarize lab research suggesting ketamine triggers fast changes in how brain cells connect and talk to each other. They say these discoveries opened new treatments like Esketamine and point to many unanswered questions about exactly how ketamine works and how it might be combined with therapy safely.

Key facts:

• Ketamine works by blocking a type of glutamate receptor in the brain called an NMDA receptor; this action is tied to its rapid antidepressant effects reported in patients.
• A single carefully controlled ketamine infusion produced fast and often strong antidepressant effects, including in people whose depression had not responded to other treatments.
• Esketamine (Spravato) was approved by the U.S. Food and Drug Administration and has evidence from controlled studies supporting its safety and long-term effectiveness for some patients with depression.
• The dose of ketamine matters a lot: cutting typical antidepressant doses roughly in half tends to reduce benefit, doubling the dose increases dissociative side effects without clear extra benefit, and anesthetic-level doses do not produce antidepressant effects.
• Research points to several brain changes after ketamine, including a short burst of glutamate, activation of downstream signals such as BDNF-TrkB and AMPA receptors, and rapid increases in synaptic plasticity (how strongly brain cells connect).
• Some studies suggest that keeping Esketamine on board with a new oral antidepressant halved the relapse rate over one year compared with the oral antidepressant alone, meaning maintenance with Esketamine appeared to offer added protection against coming back.
• Early studies in animals and humans indicate ketamine can interfere with memory reconsolidation, which has led researchers to explore combining ketamine with psychotherapy to weaken traumatic or drug-related memories in PTSD and addiction — this is still experimental.
• Scientists are still studying which parts of ketamine’s effects come from different forms of the drug, its breakdown products, inflammation, or non-neuronal brain cells, so the exact antidepressant mechanism is not fully settled.

Abstract

Ketamine is an open channel blocker of ionotropic glutamatergic N-Methyl-D-Aspartate (NMDA) receptors. The discovery of its rapid antidepressant effects in patients with depression and treatment-resistant depression fostered novel effective treatments for mood disorders. This discovery not only provided new insight into the neurobiology of mood disorders but also uncovered fundamental synaptic plasticity mechanisms that underlie its treatment. In this review, we discuss key clinical aspects of ketamine's effect as a rapidly acting antidepressant, synaptic and circuit mechanisms underlying its action, as well as how these novel perspectives in clinical practice and synapse biology form a road map for future studies aimed at more effective treatments for neuropsychiatric disorders.

Topics

Neuroscience and Neuropharmacology Research Treatment of Major Depression Tryptophan and brain disorders

Categories

Health Sciences Medicine Pharmacology

Tags

Antidepressant Anxiety Glutamate receptor Glutamatergic Hippocampus Internal medicine Ionotropic effect Ketamine Medicine Mood disorders Neuroscience NMDA receptor Pharmacology Psychiatry Psychology Receptor Synapse Synaptic plasticity

Substances

Ketamine

Conditions & symptoms

Anxiety Depression Obsessive-Compulsive Disorder PTSD Anxiety or worry Lack of energy or motivation Poor sleep Sadness or low mood