Cloning and pharmacological characterization of a rat [mu] opioid receptor

Abstract

We have isolated a rat cDNA clone that displays 75% amino acid homology with the mouse [delta] and rat [kappa] opioid receptors. The cDNA (designated pRMuR-12) encodes a protein of 398 amino acids comprising, in part, seven hydrophobic domains similar to those described for other G protein-linked receptors. Data from binding assays conducted with COS-1 cells transiently transfected with a CMV mammalian expression vector containing the full coding region of pRMuR-12 demonstrated [mu] receptor selectivity. In situ hybridization mRNA analysis revealed an mRNA distribution in rat brain that corresponds well to the distribution of binding sites labeled with [mu]-selective ligands. Based upon these observations, we conclude that pRMuR-12 encodes a [mu] opioid receptor.