Psychedelics such as LSD and psilocin produce fast and lasting antidepressant effects by directly binding to the TrkB receptor, the receptor for brain-derived neurotrophic factor (BDNF). These compounds bind to TrkB with affinities 1,000 times higher than other antidepressants like fluoxetine and ketamine, and they interact with a distinct but partially overlapping site within the transmembrane domain of TrkB dimers. In mice, the neuroplasticity and antidepressant-like effects of psychedelics depend on TrkB binding and endogenous BDNF signaling, not on serotonin 2A receptor activation. However, LSD-induced head twitching requires serotonin 2A activation and is independent of TrkB binding. This suggests that high-affinity TrkB positive allosteric modulators without serotonin 2A activity could retain antidepressant benefits without hallucinogenic effects.
Serotonergic psychedelics like psilocybin and LSD activate serotonin 5-HT2A receptors in cortical brain regions, altering perception, cognition, and emotions. Their ability to promote neuroplasticity—forming new neural connections and rewiring networks—is thought to underlie therapeutic potential for depression, anxiety, and substance use disorders. These compounds also interact with other serotonin receptor subtypes (5-HT1A, 5-HT2C) and neurotrophin receptors, adding complexity to their effects. Research is exploring nonhallucinogenic derivatives that retain therapeutic benefits without intense psychedelic experiences, potentially reducing adverse reactions. The review also discusses psychedelics as substrates for post-translational protein modification as part of their mechanism.