This invention provides an isolated nucleic acid molecule encoding a human Y4 receptor, an isolated protein which is a human Y4 receptor, vectors comprising an isolated nucleic acid molecule encoding a human Y4 receptors, mammalian cells comprising such vectors, antibodies directed to the human Y4 receptor, nucleic acid probes useful for detecting nucleic acid encoding human Y4 receptors, antisense oligonucleotides complementary to any sequences of a nucleic acid molecule which encodes a human Y4 receptor, pharmaceutical compounds related to human Y4 receptors, and nonhuman transgenic animals which express DNA a normal or a mutant human Y4 receptor. This invention further provides methods for determining ligand binding, detecting expression, drug screening, and treatment involving the human Y4 receptor.