The porcine mu opioid receptor: molecular cloning and mRNA distribution in lymphoid tissues.

The porcine mu opioid receptor (pMOR), was cloned from cerebral cortex RNA using PCR methodologies. Porcine MOR is 96% identical with human MOR in amino acid sequence. An RT-PCR survey for pMOR mRNA indicated that pMOR is widely distributed in the gut, and is present in thymus and Peyer's patches but absent in other immune tissues and in isolated immune cells. Based on these findings, it appears that opioids do not exert an immunosuppressive effect through direct interaction with the mu-opioid receptor on immune cells. In certain tissues, however, opioids may modulate immune function indirectly through neuronal MOR.