Cholecystokinin (CCK) and gastrin exert their effects through two receptors, the CCK-A and CCK-B receptors. We have cloned the mouse CCK-B receptor gene (Cckbr) and determined its complete genomic structure, nucleotide sequence, and tissue-specific expression pattern. Cckbr is divided into five exons spanning 11 kb. A primer extension assay was used to map the transcription initiation site to 199 bp upstream of the translational start site. Rapid amplification of cDNA ends was used to localize the 3' end downstream of an atypical polyadenylation site (GATAAA). Mouse Cckbr transcripts were most abundant in brain and stomach, but were also detected in colon, kidney, ovary, and pancreas. Prenatal expression of both CCK-A and CCK-B receptors in various tissues was analyzed by RT-PCR. The expression pattern was similar to the adult pattern, suggesting that receptor transcription is an early event in gastrointestinal development. (C) 2000 Academic Press.