Comparative analysis of mu-opioid receptor expression in immune and neuronal cells

Morphine modulates neuronal and immune cell functions via μ-opioid receptors. In primary and Jurkat T cells, and Raji B cells μ-opioid receptor transcripts were detected only after stimulation of the cells with IL-4 or TNF-α. Moreover, the amount of the induced μ-opioid receptor mRNA in the immune cells was 15 to 200 times less than those in primary cortical and SH SY5Y neuronal cells. Nevertheless, μ-opioid receptor mRNA in immune cells is processed to functional receptors, as demonstrated by morphine-mediated phosphorylation of mitogen activated protein kinase, morphine-mediated up-regulation of IL-4 mRNA and coupling to adenylyl cyclase in Jurkat cells.