NPFF, AN ANTI-OPIATE PEPTIDE, INHIBITS MORPHINE-INDUCED LOCOMOTOR HYPERACTIVITY IN RAT

The neuropeptide FLFQPQRFamide (NPFF) is a FMRFamide-like peptide with some antiopiate properties. NPFF receptors are present in the mammali an central nervous system and have been clearly identified as differen t from opiate receptors. Autoradiographic approach has revealed NPFF r eceptor localization within the ventral tegmental area (VTA), where op iate receptors are also present. By using selective chemical lesions o f dopaminergic cells (6-hydroxydopamine) and intrinsic perikarya (ibot enic acid) of the VTA coupled with in vitro autoradiographic technique s, we show that, like opiate receptors, the NPFF binding sites present at the VTA level are not localized on dopaminergic neurons, but are d istributed on both soma of non dopaminergic cells and on afferent fibe rs. To evaluate the possibility that NPFF receptors affect the opioid modulation of mesocorticolimbic dopaminergic neuron activity, we have tested the effects of intra-VTA infusion of NPFF (0.25-0.5-1-2.5-5-10 mu g/side) on the behavioral activation induced by intra-VTA morphine infusion (0.5 mu g/side). Intra-VTA administration of NPFF (5 and 10 m u g/side) inhibits morphine-induced locomotor hyperactivity.