the i.c.v . administration of opioid peptides having selectivity for the mu receptor ( d-ala2-nmephe4-gly5 ( ol ) enkephalin and fk 33,824 ) produced effects on the locomotor activity of nondependent and morphine-dependent rats that differed both quantitatively and qualitatively from those effects produced by peptides having selectivity for the delta receptor ( d-ala2-d-leu5enkephalin and metkephamid ) and beta-endorphin , which has similar affinity for both receptors .
C0205753
opioid peptides
C0014298
enkephalin