R (-)-methoxetamine exerts rapid and sustained antidepressant effects and fewer behavioral side effects relative to S (+)-methoxetamine.
Neuropharmacology August 1, 2021 Chrislean Jun Botanas, Raly James Perez Custodio, Hee Jin Kim et al. 13 citations
Both enantiomers of methoxetamine (MXE), a ketamine analog, produce rapid antidepressant effects in mice, but the R-enantiomer causes fewer behavioral side effects. S-MXE and R-MXE both bind to NMDA receptors and inhibit serotonin transporters. At 10 mg/kg, each enantiomer reduced depression-like behavior and increased gamma brain waves, effects blocked by an AMPA receptor antagonist. They also boosted mTOR signaling and AMPA receptor subunit proteins in the hippocampus or prefrontal cortex, and increased serotonin receptor mRNA levels; a serotonin receptor antagonist blocked their antidepressant effects. Unlike S-MXE, R-MXE did not cause prepulse inhibition deficits, hyperactivity, conditioned place preference, or locomotor sensitization, though it briefly impaired motor coordination. R-MXE may be a safer antidepressant candidate.