Journal of Affective Disorders
July 15, 2025
Theresa R. Lii, Josephine R. Flohr, Robin L. Okada et al.
1 citation
The endogenous opioid system may influence the placebo antidepressant response. A post hoc analysis of a randomized, placebo-controlled trial of intravenous ketamine in depressed patients undergoing routine surgery tested whether baseline opioid use affected antidepressant responses. The analysis found that baseline opioid use significantly reduced post-treatment depression severity in patients who received placebo, but not in those who received ketamine. This reduction was independent of baseline depression severity, pain intensity, and ethnicity. The findings, based on a small sample, require confirmation by prospective controlled studies. Opioid use at baseline attenuated the placebo antidepressant response independently of pain, while the antidepressant response was preserved in opioid users who received ketamine.
Journal of Pain
April 1, 2025
Nicholas Gregory, Tyler E. Girard, Akila Ram et al.
1 citation
No Summary
bioRxiv : the preprint server for biology
October 22, 2024
Matthew B Pomrenze, Sam Vaillancourt, Juliana S Salgado et al.
1 citation
preprint
MDMA releases both dopamine and serotonin in the brain's reward center, the nucleus accumbens, but its strong serotonin release limits dopamine release and abuse potential. Using conditional knockout mice and direct brain infusions, the authors show that MDMA's serotonin release, acting through the serotonin transporter and 5-HT2C receptors, reduces the drug's reinforcing effects and conditioned place preference, while its prosocial effects are mediated by separate mechanisms. This platform predicts that (R)-MDMA, a novel entactogen, will have prosocial effects and low abuse potential.
bioRxiv : the preprint server for biology
March 6, 2024
Matthew B Pomrenze, Sam Vaillancourt, Pierre Llorach et al.
1 citation
preprint
Ketamine's effects on movement in mice are blocked by the opioid receptor antagonist naltrexone, but its analgesic and antidepressant-like effects are not. Whole-brain imaging identified the central amygdala as the region most affected by naltrexone, where neurons expressing mu-opioid receptors and PKCδ were strongly activated by naltrexone but not by ketamine. Disrupting mu-opioid receptor function in the central amygdala, either with drugs or genetic techniques, blocked ketamine's locomotor effects. These results indicate that mu-opioid receptors in the central amygdala gate certain behavioral effects of ketamine without being direct targets of the drug.
ACS Chemical Neuroscience
May 6, 2026
Maxemiliano V. Vargas, Cassandra J. Hatzipantelis, Lee E. Dunlap et al.
A safer analogue of MDMA, called R-MDDMA, shows promise for treating PTSD and depression without the abuse potential of MDMA. Unlike MDMA, R-MDDMA does not activate 5-HT2B receptors, induce serotonin release, cause head-twitch responses, affect body temperature, or increase locomotion at therapeutic doses. However, it still promotes structural neuroplasticity in cortical neurons, facilitates fear extinction learning, and produces sustained antidepressant-like effects. These results suggest that R-MDDMA might be a safer MDMA analogue with similar therapeutic properties.
Neuro-Oncology
November 1, 2025
Richard Drexler, Belgin Yalçın, Rebecca Mancusi et al.
High-grade gliomas integrate into serotonergic circuits via dorsal and median raphe projections, which drive calcium-mediated proliferation. Psilocybin, a serotonergic psychedelic selective for 5-HT2A with activity at TrkB, significantly increased proliferation in glioblastoma and DMG xenografts after a single dose, with effects persisting for at least two weeks. Calcium transients in glioma cells appeared within 30 minutes and remained detectable for two weeks. Genetic knockout of 5-HT2A nearly abolished psilocybin-induced proliferation, while TrkB knockout partially reduced it. These findings indicate that psilocybin promotes sustained glioma growth primarily through 5-HT2A activation, with a modulatory role for TrkB, suggesting caution for clinical use in brain tumor patients.
medRxiv
August 7, 2025
Ben Deverett, Duan Li, Theresa R. Lii et al.
preprint
Ketamine produces dissociative, analgesic, and antidepressant effects, but it is unclear whether its underlying neurophysiological signatures can be separated. In this observational cohort study, 52 participants (healthy volunteers, elective surgery patients, and patients with depression) received a subanesthetic infusion of ketamine or placebo, with or without general anesthesia. When ketamine was given under general anesthesia, its characteristic low-frequency brain wave augmentation was absent, while high-frequency power modulation was preserved. This selective modulation suggests a method for investigating the distinct roles of high- and low-frequency neural activity in ketamine's behavioral effects.
medRxiv : the preprint server for health sciences
November 2, 2024
Theresa R. Lii, Josephine R. Flohr, Robin L. Okada et al.
preprint
The placebo antidepressant response was weaker in depressed patients who were already taking opioid medications, independent of their pain levels. In a re-analysis of a randomized trial, patients on chronic opioid therapy who received a placebo showed depression scores 10 points higher on the Montgomery-Åsberg Depression Rating Scale (MADRS) across 1 to 14 days after treatment, indicating less improvement. When measured as percent change, opioid users experienced 38.4% less improvement than non-users. For patients who received ketamine, baseline opioid use did not significantly affect depression scores. Pain intensity did not predict depression outcomes, and the link between depression and pain was negligible. These results come from a small, unregistered post hoc analysis and require confirmation.
British Journal of Anaesthesia
August 1, 2026
Pilleriin Sikka, Sherry Hu, Boris D. Heifets
Dreaming during anaesthesia is common and has been documented for over a century, but remains poorly understood. This review of 157 studies from 1921 to 2024 involving 87,866 participants found that dream recall rates vary widely, from 3% to 8% in large clinical trials to 40% to 80% in experimental settings. Ketamine and propofol are most consistently associated with recall. Dreams are predominantly pleasant and feature everyday autobiographical content. Dream recall is not linked to intraoperative awareness, challenging the idea that dreams indicate inadequate anaesthetic depth. Higher home dream recall, preoperative suggestion, and immediate post-emergence assessment increase recall rates. Unpleasant dreams reduce willingness to undergo the same anaesthetic again. The positive nature and suggestibility of anaesthesia dreams suggest potential therapeutic uses.
Nature Neuroscience
September 1, 2025
Isak K Aarrestad, Lindsay P. Cameron, Ethan M Fenton et al.
Nonhallucinogenic psychoplastogens like tabernanthalog (TBG) promote cortical neuroplasticity through the same biochemical pathway as classic psychedelics—involving 5-HT2A, TrkB, mTOR, and AMPA receptor activation—but without inducing an immediate glutamate burst or immediate early gene activation. TBG-induced cortical spinogenesis is required for its sustained antidepressant-like behavioral effect in rodents. These findings clarify how certain psychoplastogens can produce neuroplasticity without hallucinogenic effects, challenging assumptions that glutamate burst and IEG activation are necessary for psychedelic-induced neuroplasticity.