Cholecystokinin tetrapeptide (CCK-4, also PTK7) is a peptide fragment derived from the larger peptide hormone cholecystokinin. CCK-4 acts primarily in the brain as an anxiogenic, although it does retain some GI effects, but not as much as CCK-8 or the full length polypeptide CCK-58.http://www.creative-peptides.com/product/cck-acetate-item-10-101-74-27.html
