CGP 71683 is an antagonist of neuropeptide Y (NPY) receptor Y5 (IC50 = 1.4 nM in a radioligand binding assay). It is selective for Y5 over Y1, Y2, and Y4 receptors (IC50s = 2,765, 7,187, and 5,637 nM, respectively). It inhibits NPY-induced increases in BT-549 cell growth and MDA-MB-231 cell migration when used at a concentration of 0.25 μM. CGP 71683 (10 mg/kg, i.p.) inhibits increases in food intake induced by intracerebroventricular administration of NPY in rats.