Binding characteristics of dermorphin, and [dermorphin1–7]-βc-endorphin in rat brain membranes

Dermorphin and a camel beta-endorphin ( β c -EP) analog in which residues 1–7 correspond to the dermorphin sequence ([Dermorphin 1–7 ]- β c -EP) have been investigated with respect to their receptor binding characteristics using human and camel β-EP as reference peptides. Tritiated dihydromorphine, [D-Ala 2 , D-Leu 5 ]-enkephalin, ethylketocyclazocine and human β-endorphin were used as primary ligands in the rat brain membrane preparation for radioreceptor assay. Camel β-endorphin was the most potent peptide in all experiments. [Dermorphin 1–7 ]- β c -EP is significantly less potent towards 3 H-ethylketocyclazocine and 3 H-[D-Ala 2 , D-Leu 5 ]-enkephalin but is as potent towards 3 H-dihydromorphine and 3 H-human β-endorphin. Dermorphin itself weakly displaces tritiated dihydromorphine, [D-Ala 2 , D-Leu 5 ]-enkephalin and ethylketocyclazocine (potency relative to camel β-EP, 1–4%) but it is more potent (9%) in competition with tritiated human β-endorphin. Dermorphin and the [Dermorphin 1–7 ]- β c -EP appear to interact preferentially with μ opiate receptors.