This invention provides isolated nucleic acid molecules encoding human 5-HT.sub.1D receptors, isolated proteins which are human 5-HT.sub.1D receptors, vectors comprising isolated nucleic acid molecules encoding human 5-HT.sub.1D receptors, mammalian cells comprising such vectors, antibodies directed to human 5-HT.sub.1D receptors, nucleic acid probes useful for detecting nucleic acid encoding human 5-HT.sub.1D receptors, antisense oligonucleotides complementary to any sequences of a nucleic acid molecule which encodes a human 5-HT.sub.1D receptor, pharmaceutical compounds related to human 5-HT.sub.1D receptors, and nonhuman transgenic animals which express DNA which encodes a normal or a mutant human 5-HT.sub.1D receptor. This invention further provides methods for determining ligand binding, detecting expression, drug screening, and treatment involving the human 5-HT.sub.1D receptor.