Neurobiology of disease
December 1, 2023
Youge Qu, Akifumi Eguchi, Li Ma et al.
26 citations
Pretreatment with MDMA for 14 days blocked anhedonia-like behavior and reduced synaptic proteins and brain-derived neurotrophic factor in the prefrontal cortex of mice exposed to chronic restraint stress. Cutting the subdiaphragmatic vagus nerve (vagotomy) blocked these beneficial effects. The gut microbiome showed differences in α-diversity between groups, and specific microbes varied between vehicle- and MDMA-treated stressed mice. Vagotomy prevented increases in three plasma compounds seen in MDMA-treated stressed mice, and two of those compounds correlated positively with several microbes. The data suggest that the gut-brain axis via the subdiaphragmatic vagus nerve may contribute to MDMA-induced stress resilience.
Neurobiology of disease
September 1, 2024
Lijia Chang, Yan Wei, Youge Qu et al.
22 citations
In mice susceptible to chronic social defeat stress, removing the spleen reduces arketamine's antidepressant-like effects. RNA sequencing of the prefrontal cortex revealed that the oxidative phosphorylation (OXPHOS) pathway mediates this effect. Inhibiting OXPHOS with oligomycin A reversed the spleen removal's suppressive effect. Specific OXPHOS genes—COX11, UQCR11, and ATP5e—may be involved. Transforming growth factor β1 (TGF-β1) and COX11 appear to modulate the suppression; activating the TGF-β1 receptor with SRI-01138 alleviated it. Cutting the subdiaphragmatic vagus nerve also counteracted the inhibitory effect of splenectomy. These results suggest that arketamine's antidepressant-like effects involve the OXPHOS pathway and TGF-β1 in the prefrontal cortex, communicated through a spleen-brain axis via the vagus nerve.
Journal of affective disorders
December 15, 2024
Dan Xu, Guilin Liu, Mingming Zhao et al.
21 citations
A single dose of arketamine (10 mg/kg) improved both depression-like behaviors and demyelination in the corpus callosum of mice exposed to chronic restraint stress. Correlations linked depression-like behaviors with demyelination in that brain region. Blocking the transforming growth factor β1 (TGF-β1) receptor with RepSox prevented arketamine's beneficial effects, while a single intranasal dose of TGF-β1 alone also ameliorated both depression-like behaviors and demyelination. The precise mechanisms remain unclear, but the findings suggest that stress-induced demyelination in the corpus callosum may contribute to depression-like behaviors, and arketamine may act through a TGF-β1-dependent pathway.
Pharmacology, biochemistry, and behavior
December 1, 2023
Guilin Liu, Li Ma, Youge Qu et al.
16 citations
Arketamine, but not the psychedelic drugs DOI or lisuride, produced long-lasting prophylactic effects in mouse models of depression. Male mice pretreated with arketamine six days before an immune challenge (lipopolysaccharide, LPS) showed reduced body weight loss, less spleen enlargement, less immobility in a forced swim test, and higher levels of the synaptic protein PSD-95 in the prefrontal cortex compared to mice pretreated with DOI or lisuride. Similarly, arketamine given one day before seven days of chronic restraint stress prevented increased immobility, restored sucrose preference, and protected PSD-95 expression. DOI and lisuride did not show these protective effects.
European journal of pharmacology
December 15, 2024
Ming-Ming Zhao, Ting-Ting Zhu, Dan Xu et al.
14 citations
Arketamine, the (R)-enantiomer of ketamine, reduces damage to the myelin sheath and promotes its repair in the brains of mice treated with cuprizone, a chemical that induces demyelination. The beneficial effects occur through a mechanism dependent on transforming growth factor β1 (TGF-β1). Blocking the TGF-β1 receptor with RepSox prevented arketamine's protective effects. Directly administering TGF-β1 intranasally also reduced demyelination and enhanced remyelination in the corpus callosum. These findings suggest that arketamine's effects on myelin repair rely on TGF-β1 signaling, pointing to potential therapeutic targets for demyelinating diseases like multiple sclerosis.
Pharmacology, biochemistry, and behavior
May 1, 2024
Li Ma, Akifumi Eguchi, Guilin Liu et al.
11 citations
Pretreatment with the antidepressant arketamine prevented stress-induced body weight loss, increased behavioral despair, decreased sucrose preference, and reduced synaptic protein expression in the prefrontal cortex of male mice exposed to chronic restraint stress. Gut microbiota analysis indicated that arketamine may restore stress-related changes in microbial abundance. Metabolomics identified four blood metabolites altered between stress-exposed and arketamine-pretreated mice. Network analysis linked synaptic proteins in the prefrontal cortex with specific gut microbes and blood metabolites. These findings suggest that the gut-brain axis, including microbial metabolites, may partly underlie the sustained prophylactic effects of arketamine.
European archives of psychiatry and clinical neuroscience
April 25, 2024
Li-Yuan Zhao, Guang-Fen Zhang, Xue-Jie Lou et al.
11 citations
Over the past two decades, research on the antidepressant effects of ketamine and its enantiomers has grown substantially, culminating in the approval of esketamine nasal spray for treatment-resistant depression. A bibliometric analysis of 4,274 publications from 2000 to 2023, using visualization tools, reveals two main research foci: the efficacy and safety of these compounds in treating depression, and the mechanisms underlying their rapid antidepressant effects. The rapid onset of ketamine's effects has spurred further investigation into its mechanisms and the search for new antidepressants with fewer side effects.
Science (New York, N.Y.)
May 8, 2025
Kenji Hashimoto
9 citations
Ketamine's rapid antidepressant effects are limited in duration. Boosting a specific intracellular signaling pathway, the mammalian target of rapamycin (mTOR) pathway, can preserve the antidepressant response to ketamine in animal models. Activating this pathway extends the duration of ketamine's effects, suggesting a potential strategy for prolonging therapeutic benefits in depression treatment.
Science advances
July 11, 2025
Lujuan He, Xuenan Wang, Shilin Luo et al.
8 citations
Arketamine, the (R)-enantiomer of ketamine, produces faster and longer-lasting antidepressant-like effects than esketamine in mice subjected to chronic social defeat stress. Activating the proteins CREB and MeCP2 drives the production of brain-derived neurotrophic factor (BDNF) in microglia, the brain's immune cells. This microglia-derived BDNF strengthens excitatory synaptic transmission in the infralimbic region of the medial prefrontal cortex (mPFC). It also activates mPFC neurons that project to the nucleus accumbens (NAc) shell, a brain area involved in reward and mood. These mechanisms together underlie arketamine's antidepressant-like effects, highlighting the essential role of microglial BDNF in modulating this neural pathway.
European journal of pharmacology
March 15, 2025
Mingming Zhao, Akifumi Eguchi, Rumi Murayama et al.
6 citations
Intermittent MDMA administration (10 mg/kg, three times weekly for 6 weeks) reduced demyelination in the corpus callosum of mice treated with cuprizone, a chemical that induces myelin loss. The effect appears linked to changes in gut bacteria and metabolites, including β-D-allose, L-sorbose, and carnitine, which correlated negatively with specific microbes such as Romboutsia. These findings suggest MDMA may influence brain demyelination through the gut-brain axis, though further research is needed to clarify the roles of gut microbiota and metabolites.
Clinical psychopharmacology and neuroscience : the official scientific journal of the Korean College of Neuropsychopharmacology
November 30, 2025
Xiayun Wan, Akifumi Eguchi, Rumi Murayama et al.
5 citations
Intermittent doses of MDMA (10 mg/kg three times per week for six weeks) increased whole-body and femoral bone mineral density in ovariectomized mice, compared with vehicle. The treatment shifted bone-remodeling markers toward an antiresorptive profile—lower RANKL and higher osteoprotegerin. Gut microbiota profiling showed reduced Clostridia and enriched Bacilli, and untargeted metabolomics revealed a marked decrease in plasma β-D-allose, a metabolite linked to Lactobacillus johnsonii. These findings suggest that intermittent MDMA may mitigate bone density loss after ovariectomy, potentially through remodeling of a gut microbiota–bone axis. Causal microbial and metabolic mediators remain to be defined.
Progress in neuro-psychopharmacology & biological psychiatry
January 10, 2025
Ting-Ting Zhu, Ming-Ming Zhao, Dan Xu et al.
5 citations
Postoperative cognitive dysfunction (POCD) involves declines in memory, attention, and executive abilities after surgery, with no effective drugs available. In a mouse model of POCD, a single injection of arketamine (10 mg/kg) improved cognitive function and reduced demyelination in the corpus callosum. Blocking TGF-β receptor 1 with RepSox (10 mg/kg) prevented these benefits, while intranasal TGF-β1 (3.0 μg/kg) alone alleviated cognitive impairments and demyelination. The findings indicate arketamine acts through a TGF-β1-dependent mechanism, suggesting it as a potential treatment for POCD.
Translational psychiatry
November 9, 2024
Tianwen Huang, Yangyang He, Ruijuan Cheng et al.
5 citations
In mice with cisplatin-induced acute kidney injury (AKI), a single dose of ketamine reduced kidney damage, pathological changes in other organs, and depression-like behaviors. The beneficial effects were reversed by blocking the TrkB receptor, and analysis implicated the TrkB and ERK-CREB signaling pathways and blood metabolites like C16-ceramide. The findings suggest ketamine may alleviate both kidney injury and associated depressive symptoms, though the role of the kidney-brain axis remains unclear.
Progress in neuro-psychopharmacology & biological psychiatry
March 20, 2025
Yong Yue, Xiayun Wan, Guilin Liu et al.
4 citations
The gut-brain axis, specifically the subdiaphragmatic vagus nerve, is critical for MDMA's effects on the oxytocin system in rats. Cutting this nerve (subdiaphragmatic vagotomy) lowered baseline oxytocin levels in the blood and reduced oxytocin expression in the paraventricular and supraoptic nuclei of the hypothalamus. It also dampened MDMA-induced increases in blood oxytocin and the expression of oxytocin and c-Fos in those brain regions. The findings suggest the vagus nerve mediates brain-body communication that underlies MDMA's pharmacological actions on oxytocin.
Current neuropharmacology
January 16, 2025
Sen Wang, Chaoli Huang, Mengyu Wang et al.
4 citations
Depression affects about 300 million people worldwide, and its underlying mechanisms remain unclear. Changes in oligodendrocytes and myelin are implicated in depression pathology. Conventional antidepressants take weeks to work and fail for about one-third of patients. Ketamine provides rapid, sustained antidepressant effects in treatment-resistant patients. Reduced myelination is linked to depression, so repairing myelin damage may be a key mechanism behind ketamine's prolonged effects. This review summarizes the relationship between demyelination and depression and discusses how ketamine might exert antidepressant effects by repairing myelin, offering new insights into the role of myelination in antidepressant mechanisms.
Progress in neuro-psychopharmacology & biological psychiatry
January 10, 2025
Dan Xu, Akifumi Eguchi, Rumi Murayama et al.
4 citations
Repeated oral administration of MDMA (10 mg/kg/day for 14 days) to male rats significantly altered gut microbiota composition in the small intestine, cecum, and colon, with distinct effects in each region. Analysis of microbial functional capabilities indicated shifts in several metabolic pathways. Untargeted metabolomics showed that MDMA changed levels of two metabolites in the colon—ferulic acid and methylmalonic acid—without affecting levels in blood, small intestine, or cecum. Methylmalonic acid levels in the colon positively correlated with the bacteria Lawsonibacter and Oscillibacter. These results suggest that repeated MDMA treatment can modify gut microbiota across intestinal regions, which may contribute to its pharmacological effects.
Pharmacology, biochemistry, and behavior
December 1, 2024
Guilin Liu, Li Ma, Akemi Sakamoto et al.
4 citations
A single dose of arketamine, the (R)-enantiomer of ketamine, reduced depression-like behavior and inflammation in mice given lipopolysaccharide (LPS), a bacterial toxin that triggers an immune response. Arketamine also prevented these effects when given six days before LPS. LPS lowered the proportion of γδ T cells in the spleen, and arketamine reversed this change and reduced spleen enlargement and interleukin-6 levels. Blocking γδ T cells with an antibody eliminated arketamine's benefits, suggesting these immune cells are essential for its effects. The findings indicate splenic γδ T cells may be a new target for treating inflammation-related depression.
Translational Psychiatry
May 20, 2026
Xin Ding, Rumi Murayama, Yi Cai et al.
1 citation
The drug combination KarXT (xanomeline plus trospium) reverses cognitive deficits caused by phencyclidine (PCP) in adult male mice, and this effect is linked to changes in gut and lung microbiota. PCP disrupted recognition memory and caused region-specific imbalances in microbes, especially in the small intestine and cecum. KarXT restored memory and normalized several bacterial species elevated by PCP, including Bacteroides fragilis and Veillonella ratti. Restoration of certain lung and gut microbes correlated with improved memory. The findings suggest that KarXT's cognitive benefits involve microbial modulation, which may guide efforts to reduce gastrointestinal side effects in muscarinic therapies for schizophrenia.
Advances in experimental medicine and biology
January 1, 2026
Yunfei Tan, Kenji Hashimoto
1 citation
Treatment-resistant depression (TRD) affects about one-third of people with major depression, leading to higher suicide rates and impaired functioning. Originally defined as nonresponse to tricyclic antidepressants, TRD now includes inadequate response to multiple antidepressant classes, psychotherapy, and neuromodulation. Inconsistent criteria complicate prevalence estimates and diagnosis, with many presumed TRD cases actually involving bipolar depression or other disorders. Neurobiological research identifies glutamatergic dysregulation, default-mode network hyperactivity, impaired neuroplasticity, chronic inflammation, and epigenetic changes as markers. Clinically, patients experience persistent anhedonia, cognitive deficits, and sleep disturbances. Subtypes with distinct treatment responses have been identified, and biomarker-driven categories guide personalized care. Future work must standardize definitions and integrate multimodal biomarkers.
Translational psychiatry
November 24, 2025
Xin-Yu Li, Di Qiu, Ni Du et al.
1 citation
Patients with preexisting sleep disorders are at higher risk for postoperative sleep disturbance (PSD). In a randomized trial of 130 patients, intraoperative esketamine (0.3 mg/kg/h) reduced the incidence of PSD on postoperative day 1 (43.1% vs. 64.6%; odds ratio, 0.414) and lowered hydromorphone use. Preoperative oral microbiota profiles differed between patients who later developed PSD and those who did not, with specific bacterial taxa linked to sleep disturbance. The findings suggest esketamine may help prevent postoperative sleep disruption, possibly by modulating the oral microbiota.
Progress in neuro-psychopharmacology & biological psychiatry
June 20, 2026
Xin Ding, Kenji Hashimoto, Jian-Jun Yang
Xanomeline and ketamine, two mechanistically distinct antidepressants, partially converge on common molecular pathways despite acting through different upstream receptors. Network pharmacology and molecular docking identified 368 overlapping targets for xanomeline with major depressive disorder and 714 for ketamine. Three shared signaling pathways emerged: EGFR tyrosine kinase inhibitor resistance, Ras signaling, and Rap1 signaling. Three core proteins—EGFR, IGF1R, and SRC—were common to both drugs. Xanomeline associated more strongly with receptor tyrosine kinase and PI3K/AKT signaling, while ketamine linked more to synaptic transmission, NMDA receptors, and glutamatergic signaling. These hypothesis-generating findings suggest partial convergence on downstream plasticity-related signaling nodes.
Clinical psychopharmacology and neuroscience : the official scientific journal of the Korean College of Neuropsychopharmacology
May 31, 2026
Yong Yue, Yi Cai, Rumi Murayama et al.
Gut bacteria contribute to baseline central oxytocin signaling in rats, but are not necessary for the acute oxytocin release triggered by MDMA. Male rats given broad-spectrum antibiotics for seven days showed enlarged ceca, confirming microbiome disruption, yet maintained stable body weight. Baseline oxytocin expression in the paraventricular and supraoptic nuclei of the hypothalamus was significantly reduced after antibiotic treatment, while peripheral oxytocin levels remained unchanged. MDMA administration increased central oxytocin expression similarly in both antibiotic-treated and control rats, and MDMA-induced peripheral oxytocin levels also did not differ between groups. The findings indicate that gut microbiota help maintain central oxytocin under normal conditions but are not required for MDMA's oxytocin-activating effects.
Molecular psychiatry
April 13, 2026
Xin Zhao, Xinyu Zhang, Shiying Yuan et al.
Ketamine, a drug used for anesthesia and rapid antidepressant effects, also modulates systemic immunity and protects organs through interactions with the gut microbiota, microbial metabolites, and immune-cell trafficking. Along the gut-brain axis, ketamine restores microbial balance, normalizes short-chain fatty acid levels, and reduces migration of gut-derived immune cells to the central nervous system, correlating with reduced neuroinflammation and depressive-like behaviors. Through the gut-lung axis, ketamine limits bacterial translocation and reduces pulmonary infiltration of pro-inflammatory cells, suggesting potential relevance in acute lung injury. Arketamine appears to provide more sustained neuroprotection with fewer adverse effects than esketamine. The findings suggest broad therapeutic potential for neuropsychiatric and inflammatory diseases, but causal studies are needed.
Psychiatry and Clinical Psychopharmacology
March 30, 2026
Kenji Hashimoto, Feyza Arıcıoğlu, Mesut Çetin
Classical serotonergic psychedelics—psilocybin, DMT, 5-methoxy-DMT, and LSD—can produce rapid and sometimes durable improvements in mood under supervised conditions. The review synthesizes clinical evidence for these compounds in depression and related disorders, noting challenges such as small sample sizes, expectancy effects, and limitations in maintaining blinding. Mechanistic frameworks extend beyond 5-HT2A receptor activity, involving multiple serotonergic subtypes, glutamatergic modulation, synaptic plasticity, and brain network reorganization. Preclinical and clinical evidence points to neurotrophic mechanisms, particularly BDNF-TrkB signaling, as contributors to sustained effects. Acute mystical-type experiences may enhance response but are not strictly required, suggesting plasticity-promoting mechanisms can be partially dissociated from hallucinogenic effects. Peripheral contributions, including gut-brain axis interactions, may influence treatment durability.
Psychedelics.
October 14, 2025
Mingming Zhao, Jianjun Yang, Kenji Hashimoto
MDMA (ecstasy) is a unique entactogen that increases serotonin in the brain by reversing the serotonin transporter, and also affects catecholamine and oxytocin pathways. In clinical trials, MDMA-assisted psychotherapy has led to substantial improvements in treatment-resistant PTSD, though regulatory approval has been delayed due to concerns about unblinding and protocol rigor. Early placebo-controlled studies suggest benefits for autism spectrum disorder, eating disorders with comorbid PTSD, and anxiety from life-threatening illness. Large observational studies link MDMA use with lower depression rates, reduced suicidal ideation, and improved posttrauma coping, but causal inference is limited.