Syntheses of cholecystokin (CCK) fragment analogues (26-33) and comparative effect on decreased feeding in rats by CCK fragment (26-33)

The peptide analogues of cholecystokinin (CCK) fragment 26-33 in which phenylalanine residue at the 33th position are replaced by phenylglycine [Phg], 1-naphthylalanine [1-Nal], 4-fluorophenylalanine [Phe(4F)], cyclohexylalanine [cHex] and O-methyltyrosine [Tyr(Me)]], were synthesized by a solid-phase method and the feeding significance of the aromatic amino acid of this position was comparatively investigated. The in vivo comparative effect on the decreased feeding in rats by peripherally CCK-8 was tested. The observed activities of these peptides were in order [Phe(4F)(33)]CCK-8 > [1-Nal(33)]CCK-8 > CCK-8 > [Tyr(Me)(33)]CCK-8 > [Phg(33)]CCK-8. However, the one analogue, [cHex(33)]CCK-8, had no inhibitory effect on food intake in rats.