Further characterization of neuropeptide Y receptor subtypes using centrally truncated analogs of neuropeptide Y: evidence for subtype-differentiating effects on affinity and intrinsic efficacy

Previous attempts to classify neuropeptide Y receptor subtypes suffered from relying only on carboxyl-terminal analogs and fragments of neuropeptide Y. We have tested the potency and affinity of chemically different compounds, i.e., centrally truncated analogs of neuropeptide Y, in three Y1-like (Ca2+ mobilization in HEL cells, blood pressure increases in pithed rats, and 125I-neuropeptide Y binding in SK-N-MC cells) and two Y2-like (125I-neuropeptide Y binding to rabbit kidney membranes and presynaptic inhibition in rat vas deferens) model systems of neuropeptide Y receptors. Our data confirm the concept of two major subclasses of neuropeptide Y receptors, with some centrally truncated neuropeptide Y analogs having high affinity for Y2-like and low affinity for Y1-like neuropeptide Y receptors. Some of the truncated neuropeptide Y analogs are antagonists at Y1-like receptors and (possibly partial) agonists at Y2-like receptors. Our data also indicate that amino acid residues distal from the amino- and carboxyl-terminal ends of the peptide may subtype-selectively affect affinity and intrinsic efficacy of peptide agonists at neuropeptide Y receptors.