[(125)I]EYF: a new high affinity radioligand to neuropeptide FF receptors.
[(125)I]EYF ([(125)I]EYWSLAAPQRFamide), a new radioiodinated probe derived from a peptide present in the rat Neuropeptide FF precursor (EFWSLAAPQRFamide, EFW-NPSF) was synthesized and its binding characteristics investigated on sections of the rat spinal cord and on membranes of mouse olfactory bulb. In both tissues, [(125)I]EYF binding was saturable and revealed a very high affinity interaction with a single class of binding sites in rat and mouse (K(D) = 0.041 and 0.019 nM, respectively). Competition studies showed that [(125)I]EYF bound to one class of binding sites exhibiting a high affinity for all the different peptides the precursor could generate (NPA-NPFF, SPA-NPFF, NPFF, EFW-NPSF, QFW-NPSF) with the exception of NPSF which displayed a low affinity. Autoradiographic studies demonstrated that [(125)I]EYF binding sites were fully inhibited by a synthetic Neuropeptide FF agonist (1DMe) in all areas of the rat brain. The density of [(125)I]EYF binding sites was high in the intralaminar thalamic nuclei, the parafascicular thalamic nucleus and in the superficial layers of the dorsal horn. Non specific binding reached 5-10% of the total binding in all brain areas. Similarly, in mouse brain experiments, the non-specific binding was never superior to 10%. These findings demonstrate that putative neuropeptides generated by the Neuropeptide FF precursor and containing the NPFF or NPSF sequences should bind to the same receptor. Furthermore, these data indicate that [(125)I]EYF is a useful radiolabeled probe to investigate the NPFF receptors; its major advantages being its high affinity and the very low non-specific binding it induces.
Gouardères
C
C
Institut de Pharmacologie et Biologie Structurale, CNRS, 205 route de Narbonne, 31077, Toulouse, France.
Mollereau
C
C
Tafani
J A
JA
Mazarguil
H
H
Zajac
J M
JM
D000818:Animals; D001345:Autoradiography; D007457:Iodine Radioisotopes; D008297:Male; D051379:Mice; D009830:Olfactory Bulb / Q000378:metabolism; D009842:Oligopeptides / Q000378:metabolism*; D011869:Radioligand Assay; D051381:Rats; D017207:Rats, Sprague-Dawley; D018013:Receptors, Neuropeptide / Q000378:metabolism*
C433725:EYWSLAAPQREF amide; D007457:Iodine Radioisotopes; D009842:Oligopeptides; D018013:Receptors, Neuropeptide; C083929:neuropeptide FF receptor