Neuropeptide Y (NPY) is one of the most abundant neuropeptides in the mammalian nervous system and exhibits a diverse range of important physiologic activities, including effects on psychomotor activity, food intake, regulation of central endocrine secretion, and potent vasoactive effects on the cardiovascular system. There are two major subtypes of NPY (Y1 and Y2). The NPY Y1 receptors have been identified in a variety of tissues, including brain, spleen, small intestine, kidney, testis, placenta, breast, colon, ganglion, heart, and aortic smooth muscle. The Y2 receptor is found mainly in the central nervous system. NPY receptors are a member of the G protein-coupled receptor superfamily.