Deorphanization of ORL-1/LC132 by reverse pharmacology in two landmark studies

Deorphanization of ORL-1/LC132 in 1995 by reverse pharmacology in two simultaneously published landmark studies added a new member to the opioid family of G-protein coupled receptors. Meunier and Reinscheid used cells expressing recombinant ORL-1 (human) or LC132 (rat) and the presumed intracellular inhibition of cyclic AMP formation to ‘fish’ for endogenous peptide ligands in rat whole-brain and pig hypothalamic extracts. Both studies reported the isolation of a 17-amino-acid peptide, which was named nociceptin and orphanin FQ by the two authors, respectively. The behaviour of the isolated peptide was a complete surprise, as a general hyperalgesia was observed when the peptide was administered at supraspinal sites. We now know that this peptide has, in fact, anti-opioid action, particularly in the medulla. The endogenous peptide exerts a multitude of effects both in the nervous system and, unlike classical opioids, has efficacy in neuropathic pain.