Long-term regulation of opioid receptors in neuroblastoma and lymphoma cell lines.

Long-term regulation of opioid binding was studied in the human neuroblastoma NMB and in the murine lymphoma R1.1 and R1.EGO cell lines. Binding was down-regulated following prolonged exposure to opioid agonists and up-regulated following exposure to antagonist. Down-regulation was inhibited by the metabolic blocker sodium-azide and by the protein kinase H-7. Up-regulation was blocked by the protein and mRNA synthesis blockers cycloheximide, alpha-amanitin and actinomycin D. A significant difference was found between the response of neuronal and immune cells to ethanol exposure: while opioid binding in neuroblastoma culture underwent a pronounced (75%) up-regulation, no effect of ethanol on opioid receptors in lymphoma cultures was detected. The described cell lines present an excellent experimental model to study long-term regulation of opioid receptors in the nervous and immune systems and to elucidate the biological effects of chronic use of opiates and alcohol.