leu-enkephalin , d-ala2-d-leu5-enkephalin or beta h-endorphin potentiate morphine or d-ala2-met-enkephalinamide analgesia whereas met-enkephalin or d-ala2-met-enkephalinamide antagonize opioid-induced analgesia .
C0014294
leu-enkephalin
C0014298
enkephalin