utilizing the mouse tail-flick assay , the rank order of analgesic potency for various opioids ( i.c.v . ) is beta h-endorphin greater than d-ala2-d-leu5-enkephalin greater than morphine greater than d-ala2-met-enkephalinamide much greater than met-enkephalin much greater than leu-enkephalin .
C0014298
enkephalin
C0014294
leu-enkephalin