A potential ancestral gene Erik Salaneck1, Robert Fredriksson1, Earl T. Larson1, J. Michael Conlon2 and Dan Larhammar1 Unit of Pharmacology, Department of Neuroscience, Uppsala University, Uppsala, Sweden; 2Regulatory Peptide Center, Creighton University School of Medicine, Omaha, Nebraska, USA We report here the isolation and functional expression of a neuropeptide Y (NPY) receptor from the river lamprey, Lampetra fluviatilis. The receptor displays