SUBCUTANEOUS INJECTION OF AN ANALOG OF NEUROPEPTIDE FF PREVENTS NALOXONE-PRECIPITATED MORPHINE ABSTINENCE SYNDROME

There is evidence that neuropeptide FF (NPFF) has antiopiate activity and may play a role in opiate dependence and subsequent abstinence syndrome. A fragment of NPFF was modified at the C-terminal in an effort to convert it to an NPFF antagonist. It was also dansylated at the N-terminal in an effort to render it more lipophilic and increase its penetration of the blood-brain barrier. Third ventricle administration of the resulting compound, dansyl-PQRamide (0.75 mu g and 1 mu g), dose-dependently antagonized the quasi-morphine abstinence activity of NPFF (10 mu g) in opiate-naive rats. Subcutaneous injection of dansyl-PQRamide (13 mg/kg) in chronically morphine-infused rats attenuated opiate dependence as indicated by prevention of naloxone-precipitated abstinence syndrome. Dansyl-PQRamide displaced radiolabelled ligand from NPFF receptors in a concentration-dependent manner with a K-i of 13 mu M, and had a half-life over 300 times longer than NPFF under aminopeptidase digestion.