Neuropeptide Y (NPY) is one of the most abundant neuropeptides in the mammalian nervous system and exhibits a diverse range of important physiological activities, including effects on psychomotor activity, food intake, regulation of central endocrine secretion, and potent vasoactive effects on the cardiovascular system. Two major subtypes of NPY receptor (Y1 and Y2) have been defined by pharmacological criteria. We report here the molecular cloning of a cDNA sequence encoding a human NPY receptor and the corrected sequence for a rat homologue. Analysis of this sequence confirms that the receptor is a member of the G protein-coupled receptor superfamily. When expressed in Chinese hamster ovary (CHO) or human embryonic kidney (293) cells, the receptor exhibits the characteristic ligand specificity of a Y1 type of NPY receptor. In the 293 cell line, the receptor is coupled to a pertussis toxin-sensitive G protein that mediates the inhibition of cyclic AMP accumulation. In the CHO cell line, the receptor is coupled not to the inhibition of adenylate cyclase but rather to the elevation of intracellular calcium. These results demonstrate that second messenger coupling of the NPY-Y1 receptor is cell type specific, depending on the specific repertoire of G proteins and effector systems present in any cell type.