The NPY family consists of three 36-amino acid peptides, neuropeptide Y (NPY), peptide YY (PYY) and pancreatic polypeptide (PP), which bind to the NPY receptors. At present five distinct NPY receptors, Y1, Y2, Y4, Y5, and y6, have been established by receptor cloning studies and all of them are Gi-coupled GPCRs. Activation of NPY receptors mediate a variety physiological effects including stimulation of food intake, inhibition of anxiety in the CNS, presynaptic inhibition of neurotransmitter release in the CNS and periphery, modulation of circadian rhythm, release of pituitary hormones, modulation of hippocampal activity, pain transmission, vasoconstriction, inhibition of insulin release and modulation of renal function. Y4 receptor preferentially binds PP, with significant binding to NPY and PYY.