relative to leu-enkephalin , the modified compounds are more potent in the guinea pig ileum assay and more effectively displace [ 3h ] naloxone from rat brain receptors , while they are generally less potent in the mouse vas deferens assay and only weakly able to displace [ 3h ] ( d-ala2 , d-leu5 ) enkephalin .
C0014294
leu-enkephalin
C0014298
enkephalin