The first reported behavioral action of the endogenous ligand for the “orphan” opioid
receptor was a seemingly paradoxical increased sensitivity to nociception (ie hyperalgesia) …

Anew sequence, which encoded a novel G protein-coupled receptor, was disclosed by two
different groups, using the nucleic acid probes based on the delta opioid receptor, first …

The endogenous ligand for the orphan opioid receptor, orphanin FQ/nociceptin (OFQ), has
recently been characterized. The OFQ peptide sequence contains paired basic amino acids …