A potent mu-opioid receptor agonist, dihydroetorphine, fails to produce the conditioned place preference in mice.

Reinforcing effects of dihydroetorphine (DHE) and morphine were evaluated by the conditioned place preference paradigm. Both DHE and morphine produced an antinociceptive effect in a dose-dependent manner. On the other hand, DHE (0.1, 1, 3 and 10 micrograms/kg, i.p.) failed to induce the 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 development as a novel potent analgesic compound that has less dependence liability.