The predominant brain cholecystokinin receptor (CCK-B/gastrin) has been implicated in mediating many of the central effects of cholecystokinin, including anxiety, panic attacks, satiety, and analgesia, suggesting it is an important pharmacologic target. We now report the cloning and characterization of the cDNA encoding the human brain CCK-B/gastrin receptor. The cDNA was isolated from a human brain library by low stringency screening using the canine "gastrin" receptor cDNA as a hybridization probe. Nucleotide sequence analysis revealed an open reading frame encoding a 447-amino-acid protein with seven putative hydrophobic transmembrane domains and significant homology with other known members of the gastrin/cholecystokinin receptor family. Agonist and antagonist affinities of the recombinant human brain receptor expressed in COS-7 cells are consistent with a classical "CCK-B" receptor as defined by the literature. In COS-7 cells expressing the cloned receptor, CCK-8-stimulated phosphatidylinositol hydrolysis and intracellular Ca2+ mobilization suggesting second messenger signaling through phospholipase C. CCK-B/gastrin receptor transcripts were identified in human brain, stomach, and pancreas using high stringency Northern blot analysis. Southern blot hybridization analysis of human genomic DNA indicates that a single gene encodes both the brain and the stomach CCK-B/gastrin receptors. Our data suggest that the CCK-B and gastrin receptors are identical and that the long standing distinction between them may no longer apply.