Ketamine's rapid antidepressant effects depend on mu-opioid receptors (MORs) located on somatostatin-expressing interneurons in the medial prefrontal cortex. Chronic stress causes these interneurons to become hypertrophic, leading to excessive inhibition of pyramidal neurons, a disruption that ketamine reverses. By identifying GPCRs enriched in these interneurons through RNA sequencing, the authors validate several antidepressant targets and show that activating multiple GPCRs synergistically produces potent antidepressant-like effects with fewer side effects. This approach offers a general strategy for discovering GPCR-based treatments for brain disorders.
Ketamine's antidepressant effects depend on the interplay between two types of neuromodulatory receptors: TrkB and mGluR5. mGluR5 amplifies BDNF-driven signaling through TrkB, enabling synaptic potentiation, while BDNF activation of TrkB drives mGluR5 endocytosis, impairing synaptic depression. Ketamine enhances these interactions by increasing surface and postsynaptic levels of TrkB. An mGluR5 positive allosteric modulator can further boost both modes of cross-talk and enhance ketamine's effects, revealing that receptor-receptor interplay can drive therapeutic action.