This invention provides isolated nucleic acid molecules encoding a human dopamine D₁ receptor, isolated proteins which are human dopamine D₁ receptor, vectors comprising isolated nucleic acid molecules encoding a human dopamine D₁ receptor, mammalian cells comprising such vectors, antibodies directed to a human dopamine D₁ receptor, nucleic acid probes useful for detecting nucleic acid encoding human dopamine D₁ receptor, antisense oligonucleotides complementary to any sequences of a nucleic acid molecule which encodes a human dopamine D₁ receptor, pharmaceutical compounds related to human dopamine D₁ receptor, and nonhuman transgenic animals which express DNA a normal or a mutant human dopamine D₁ receptor. This invention further provides methods for determining ligand binding, detecting expression, drug screening, and treatment involving a human dopamine D₁ receptor.