Evidence for an endogenous peptide ligand and antagonist for PCP receptors

alpha-Endopsychosin, an endogenous ligand for the phencyclidine receptor, has been isolated from porcine brain. The endogenous ligand is a peptide and has similar actions to PCP and is selectively distributed in the brain. A PCP analogue, Metaphit, has also been found to be an effective PCP antagonist. This antagonist may be useful for evaluating the role of the brain's alpha-endopsychosin system and may have a number of important clinical uses.