The psychedelic effects of LSD are attributed to its strong partial agonist effects at 5-HT 2A receptors as specific 5-HT 2A agonists are psychedelics and largely 5-HT 2A specific antagonists block the psychedelic activity of LSD.
The psychedelic effects of LSD are attributed to cross-activation of 5-HT 2A heteroreceptors. PMID 21276828 Many but not all 5-HT 2A agonists are psychedelics and 5-HT 2A antagonists block the psychedelic activity of LSD.