Evidence for Half-of-the-Sites Reactivity in the Binding of Opiate Agonists and Antagonists to the Opiate Receptor

Further evidence for an opioid receptor complex

“…Thus, there is substantial agreement between the KD'S of DALA and DAMA determined by direct binding with 3H-DALA and 3H-DAMA, respectively, and their KI's determined indirectly by competition experiments. Interestingly, the number of high affinity binding sites measured with the 3H-analogs is approximately 1/ 2 that generally observed with 3H-LE, and l/4 that observed with 3H-ME, providing further evidence for "half of the sites reactivity" (Byrne and Codd, 1980;Levitzki et al, 1971).…”

“…The data presented in this section strongly suggest that 3H-ME and 3H-LE label the same receptor. The discrepancy in the number of binding sites measured with each 3H-ligand most probably reflects a different mode of interaction with the receptor, and may be evidence for "half-of-the-sites reactivity" (Byrne and Codd, 1980; Levitzki et al, 1971). Alternatively, it is possible that errors intrinsic to the determination of the B, , , value underlie this discrepancy.…”