Two independent research teams have published studies in 2026 identifying separate molecular mechanisms underlying ketamine's antidepressant effects, potentially leading to new treatment strategies for depression. The findings were reported by Weill Cornell Medicine in New York and Yokohama City University in Japan.
Weill Cornell Studies: Receptor-Level Mechanisms
Researchers at Weill Cornell Medicine published two studies detailing how ketamine interacts with specific receptors in the brain to produce both immediate and sustained antidepressant effects.
Study 1: Immediate Effects Through Opioid Receptors
Published in Cell on April 23, 2026, the first study found that ketamine targets a subset of opioid receptors on interneurons in the prefrontal cortex. According to the researchers, stress-induced hyperactivity in these interneurons is reduced by ketamine, which reactivates prefrontal cortex cells for a period of 15 to 20 minutes. This reactivation initiates the antidepressant response.
"The team replicated these antidepressant effects in mice by combining small doses of three existing drugs that target the same pathway."
Co-first authors Dr. Hermany Munguba and Anisul Arefin reported this development.
Study 2: Longer-Term Effects Through TrkB and mGluR5 Interaction
Published in Science Advances on May 1, 2026, the second study identified that ketamine's longer-term antidepressant effects require interaction between two receptor types: TrkB and mGluR5. The researchers found that brain-derived neurotrophic factor (BDNF) stimulates TrkB, promoting interaction with mGluR5. This interaction strengthens synapses and prevents synaptic weakening.
Co-first authors included Anisul Arefin, Dr. Jihye Kim, and Dr. Manas Pratim Chakraborty.
Clinical Translation Plans
Dr. Conor Liston's team stated plans for a clinical trial testing whether combining low doses of existing safe drugs can produce the antidepressant effects described in the first study. Drs. Francis Lee and Joshua Levitz are investigating whether combining low doses of mGluR5-targeting drugs with low-dose ketamine may produce similar effects.
Yokohama City University Study: Enzyme NOX-1 Identified
Researchers from Yokohama City University, led by Professor Takuya Takahashi and Dr. Waki Nakajima, published findings in Molecular Psychiatry identifying the enzyme NADPH oxidase-1 (NOX-1) as a molecular target to extend ketamine's antidepressant benefits.
Research Methodology and Findings
The team focused on α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs), which are involved in neuronal communication. They developed a compound called K-4, a positive allosteric modulator of AMPARs designed to enhance AMPAR-mediated postsynaptic transmission.
Experiments using Wistar Kyoto rats, an animal model for treatment-resistant depression, showed that K-4 produced antidepressant-like effects lasting at least two weeks after discontinuation. This duration exceeded that observed with ketamine or other AMPAR-boosting drugs.
"Gene expression analysis in the medial prefrontal cortex (mPFC) revealed that K-4-treated rats had lower levels of NOX-1." This enzyme contributes to the production of reactive oxygen species, which can impair cell function and brain circuits.
Confirmation of NOX-1 Role
The researchers combined ketamine with a pharmacological NOX-1 inhibitor, which extended ketamine's antidepressant-like effects compared to ketamine alone. Genetically reducing NOX-1 expression in the mPFC achieved similar results.
Circuit-Level Mechanisms
At the circuit level, both K-4 treatment and the combination of ketamine with NOX-1 inhibition reduced abnormal burst firing in the lateral habenula, a brain structure associated with negative mood states. These interventions also restored the balance of excitatory and inhibitory neural circuits in the mPFC.
Background Context
Approximately one-third of depression patients require multiple medications before finding relief, and another third have treatment-resistant depression. Ketamine can provide immediate relief but has side effects including changes in heart rate, dissociation, and addiction risk. The antidepressant effects of ketamine typically diminish within a few weeks.
Future Research Directions
The Weill Cornell team's results suggested two primary approaches for future development: combining ketamine with NOX-1 inhibitors to prolong its clinical efficacy, and advancing K-4 or similar AMPAR modulators as a new category of longer-lasting antidepressants.