whereas opiate antagonists , as well as the opioid peptides and some agonists ( etorphine , levorphanol and phenazocine ) display similar affinities in displacing either 3h-opiate or 3h-methionine enkephalin binding , other agonists ( such as morphine and oxymorphone ) are considerably ( 20-50 times ) weaker in displacing 3h-enkephalin than 3h-dihydromorphine binding .
C0205753
opioid peptides
C0014298
enkephalin