Cholecystokinin (CCK) gene-related peptides: distribution and characterization of immunoreactive pro-CCK and an amino-terminal pro-CCK fragment in rat brain.

An antiserum specific for the amino terminus of pro-CCK detects 3 major peptides in rat brain with molecular weights of 13,000, 8000 and 2700 daltons. These peptides are abundant both in CCK terminal-field regions and regions rich in CCK perikarya. The two high molecular weight peptides probably represent CCK precursor molecules. The smaller peptide is probably the amino-terminal fragment of pro-CCK and may be stored and released along with CCK-8, and have a potential role in synaptic transmission.