A POTENT MU-OPIOID RECEPTOR AGONIST, DIHYDROETORPHINE, FAILS TO PRODUCE THE CONDITIONED PLACE PREFERENCE IN MICE

Reinforcing effects of dihydroetorphine (DHE) and morphine were evalua ted by the conditioned place preference paradigm. Both DHE and morphin e produced an antinociceptive effect in a dose-dependent manner. On th e other hand, DHE (0.1, 1, 3 and 10 mu g/kg, i.p.) failed to induce th e conditioned preference, while morphine (0.1, 1, 3 and 10 mg/kg, i.p. ) caused a dose-dependent preference for the drug-paired place. Thus, these characteristic properties of DHE make it attractive for developm ent as a novel potent analgesic compound that has less dependence liab ility.