Structural requirements of ceruletide-like peptides for activity on gut and brain

A series of ceruletide analogues were tested in order to evaluate the structural requirements for activity on gut and brain. The effects studied were: contraction of the guinea pig gallbladder and stimulation of the exocrine pancreatic secretion in the dog after intravenous (IV) administration, for activity on the gut; analgesia (hot plate test) and sedation (reduction of spontaneous rearing activity) in mice by subcutaneous (SC) route, for activity on the brain. The structural requirements were roughly the same for central and peripheral activities. Possible mechanisms for the antinociceptive effects of ceruletide in humans were proposed.