these included the mu agonist , [ d-ala2-n-methyl-phe4-gly5-ol ] enkephalin ( dago ) , the mixed mu-delta agonist , [ d-ala2-d-leu5 ] enkephalin ( dadle ) , and the selective delta agonists , [ d-pen2-d-pen5 ] enkephalin and [ d-pen2-l-pen5 ] enkephalin .
C0525773
dago
C0014298
enkephalin