Murine macrophage cell lines contain mu 3-opiate receptors.

Opiate alkaloid-selective, opioid peptide-insensitive mu 3 receptors are present in three murine macrophage cell lines (J774.2; RAW 264.7; BAC1.2F5). The receptor binds morphine, its active metabolite morphine 6-glucuronide and certain other alkaloids, but not morphine 3-glucuronide or any of the opioid peptides tested. The cell lines thus provide valuable model systems for investigation of mu 3-opiate receptors, previously demonstrated to mediate inhibitory effects of morphine on activation of human peripheral blood macrophages (monocytes).