dynorphin- ( 1-17 ) and - ( 1-8 ) , alpha- and beta-neo-endorphin , [ met5 ] -enkephalin-arg6-phe7 and des acetyl salmon endorphin i significantly inhibited the electrically-evoked contractions of rabbit vas deferens which had been shown to contain kappa-receptors exclusively , indicating that endogenous 6- ( arg or lys ) -opioid peptides could act on kappa-receptors as agonists .
C0014298
enkephalin
C0205753
opioid