Measurement of dynorphins with ³H-etorphine and canine limbic system receptors

A canine limbic system preparation was used as the source of opioid peptide receptors to screen biologic extracts for the presence of opioid receptoractive peptides following their gradient RP-HPLC separation. Eight synthetic dynorphin peptides were studied for their ability to displace the commonly-used ligand ³H-etorphine from the canine limbic system P₂ preparation. The peptides studied included the dynorphins 1-7, 1-8, 1-9, 1-10, 1-12, 1-13, 1-17, and dynorphin B. Two different types of opioid peptide molecules were utilized for the determination of the level of non-specific binding. In one study, methionine enkephalin, and in the second study each one of the eight corresponding dynorphins, was used for determination of non-specific binding. The experimental data indicated that ³H-etorphine bound to the canine limbic system P₂ receptors, and that those dynorphins displaced effectively the ³H-etorphine from those receptors.