since other endogenous opioid peptides such as [ met5 ] - and [ leu5 ] -enkephalin and beta-endorphin have been shown not to act on kappa-receptors as agonist , data in the present study suggest that endogenous opioid peptides can be classified into two groups in terms of an ability to interact with kappa-receptors as an agonist .
C0014298
enkephalin
C0205753
endogenous opioid peptides