alpha-endopsychosin alpha-endopsychosin α-endopsychosin is an antagonist of the phencyclidine site of the nmda receptor which was discovered in extracts of porcine brain and may also be endogenous in humans. the compound appears to be a peptide, but has yet to be purified and fully characterized. alpha-endopsychosin identifiers cas number 99638-41-2 except where otherwise noted, data are given for materials in their standard state (at 25 °c , 100 kpa). infobox references