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# Spotlight: Antidepressants and the endogenous opioid system (Fricker, et al, 2025)
- URL: https://psychedelicmentalhealth.net/antidepressants-and-endogenous-opioid-system-fricker-2025-ketamine-antidepressant/
- Published: 2025-10-11T13:28:53.000Z
- Updated: 2025-10-11T13:33:56.000Z
- Description: "A growing body of evidence links the opioid system w/ major depressive disorder... two different widely used antidepressants, tianeptine & ketamine, both interact with MOR; tianeptine as a full agonist, ketamine as a positive allosteric modulator. Both produce antidepressant effects within days."
- Author: Michael DeMarco, PhD
- Tags: opiod system, opioid system, at home ketamine, ketamine therapy, ketamine, depression research, ketamine depression, ketamine treatment, depression treatment, ketamine research, mechanisms of action, psychedelic research, psychedelics, opioids, ketamine antidepressant, at home ketamine therapy, allostatic modulator, antidepressants

[Antidepressants and the endogenous opioid system - PubMedThe endogenous opioid system consists of three different G protein-coupled receptors, named mu-, delta- and kappa-opioid receptors (MOR, DOR, and KOR, respectively). These receptors are activated by over 20 distinct peptides produced from proenkephalin, prodynorphin, and proopiomelanocortin. The end …![](https://storage.ghost.io/c/61/a8/61a8484e-df24-47fb-903c-d012ff10c983/content/images/icon/favicon-192-124.png)PubMedLloyd D Fricker![](https://storage.ghost.io/c/61/a8/61a8484e-df24-47fb-903c-d012ff10c983/content/images/thumbnail/pubmed-meta-image-v2-123.jpg)](https://pubmed.ncbi.nlm.nih.gov/41072817/)

(2025): "***While the conventional view is that major depressive disorder is caused by an imbalance of biogenic amine neurotransmitters, drugs that affect these neurotransmitter systems typically require weeks of dosing before showing antidepressant effects... Chronic antidepressant treatment of mice causes changes in gene expression**. "