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 called the NMDA receptor — can lift symptoms of depression very quickly, even in people who did not get better from standard antidepressants. Clinical studies show single ketamine treatments can produce fast and often strong improvements, and a related form called Esketamine has been approved for clinical use. Scientists are still working out exactly how ketamine works. The review pulls together clinical findings, details about a short window of effective dosing, possible brain mechanisms involving a burst of the chemical glutamate and growth-signaling pathways, and ideas about combining ketamine with therapy. It also notes limits and unanswered questions, like why different doses and delivery methods vary in effect and which specific brain processes are essential.

Key facts:

• Ketamine works by blocking NMDA receptors, a type of brain receptor involved in how nerve cells talk to each other.
• Researchers found ketamine can reduce depression symptoms much faster than standard antidepressants, sometimes after a single treatment.
• Ketamine has shown benefit for people whose depression did not improve on usual treatments, often called treatment-resistant depression.
• A related drug, Esketamine, has been approved for use and studies suggest keeping Esketamine along with an antidepressant can halve relapse risk over one year compared with the antidepressant alone.
• The dose matters a lot: roughly half the usual antidepressant dose often loses benefit, while much higher anesthetic doses do not produce antidepressant effects.
• Common clinical schedules start with twice-weekly doses for the first month, then weekly for the next month, and less often for maintenance, though practices vary.
• Scientists think ketamine’s effects involve a quick rise in glutamate (a brain chemical), activation of growth-related signals like BDNF and TrkB, and engagement of other receptors called AMPA receptors, but no single mechanism is proven to explain everything.
• Ketamine may also change how memories are re-stored after recall, which could help with conditions like PTSD or addiction when combined with re-exposure or therapy, but this work is still early.
• There are still unanswered questions and limits: exact mechanisms are not settled, different delivery routes (intravenous versus intranasal) have not been directly compared in strong trials, and small dose changes can strongly affect results.

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

Addiction Anxiety Depression Obsessive-Compulsive Disorder PTSD Substance abuse disorder Anxiety or worry Lack of energy or motivation Sadness or low mood