MOLECULAR-CLONING AND TISSUE DISTRIBUTION OF A PUTATIVE MEMBER OF THERAT OPIOID RECEPTOR GENE FAMILY THAT IS NOT A MU-OPIOID, DELTA-OPIOIDOR KAPPA-OPIOID RECEPTOR-TYPE

A novel G protein-coupled receptor was cloned by PCR and homology scre ening. Its deduced amino acid sequence is 47% identical overall to the mu, delta and kappa opioid receptors and 64% identical in the putativ e transmembrane domains. When transiently expressed in COS-7 cells thi s receptor did not bind any of the typical mu, delta or kappa opioid r eceptor ligands with high affinity. In situ hybridization analysis rev ealed that LC132 mRNA is highly expressed in several rat brain areas, including the cerebral cortex, thalamus, subfornical organ, habenula, hypothalamus, central gray, dorsal raphe, locus coeruleus and the dors al horn of the spinal cord. Based on this distribution and its high ho mology with the mu, delta and kappa opioid receptors, it is proposed t hat LC132 is a new member of the opioid receptor family that is involv ed in analgesia and the perception of pain.