Danielson PB, Hoversten MT, Fitzpatrick M, Schreck C, Akil H, Dores RM. Sturgeon Orphanin, a Molecular “Fossil” That Bridges the Gap between the Opioids and Orphanin FQ/Nociceptin. Journal of Biological Chemistry. 2001 Jun;276(25):22114–9. doi: 10.1074/jbc.m011741200.