Highly selective heterocyclic opioid ligands with potent δ-antagonist activity have been developed on the basis of the 'message-address' concept. Using this strategy, benzofuran derivatives corresponding to the non- selective opioid antagonist, naloxone, and to the μ-opioid receptor selective agonists, oxymorphone and oxycodone, were synthesized. In vitro opioid receptor binding profiles and agonist/antagonist character of these compounds were determined in rat brain membrane preparations with highly selective radioligands. All three benzofuran derivatives displayed high affinities for the δ-opioid receptor, much less potency toward the μ- binding site, and were the least effective at the κ-site. The results indicated that the addition of the bezofuran moiety to these fused ring opioids confers δ-receptor selectivity. The Na+ indices suggested a partial agonist character for oxymorphone- and oxycodone-benzofuran, and an antagonist character for naloxone-benzofuran. These compounds were capable of irreversible inhibition of opioid binding sites in a dose-dependent.
ASJC Scopus subject areas
- Cellular and Molecular Neuroscience