NEUROPEPTIDE FF RECEPTORS IN RAT-BRAIN - A QUANTITATIVE LIGHT-MICROSCOPIC AUTORADIOGRAPHIC STUDY USING [I-125] [D.TYR(1),(NME)PHE(3)]NPFF

The anatomical localization of neuropeptide FF receptors was examined by in vitro autoradiography techniques in rat brain sections by using [I-125][D.Tyr(1), (NMe)Phe(3)]NPFF. The specific binding of [I-125][D. Tyr(1), (NMe)Phe(3)]NPFF reached 90% of the total binding at 0.05 nM i n rat spinal cord sections. Up to 40% of the specific binding of [I-12 5][D.Tyr(1), (NMe)Phe(3)]NPFF to rat spinal cord sections was still de tectable following fixation with glutaraldehyde. Afterwards, the distr ibution of NPFF receptors was studied by light microscopy and their de nsities by microdensitometry with an image analysis system. In the lig ht microscope, [I-125][D.Tyr(1), (NMe)Phe(3)]NPFF labelling appeared m ore or less uniformly distributed over nerve-cell bodies and surroundi ng neuropil. High concentrations of binding sites were detected in the presubiculum, parafascicular thalamic nucleus, gracile nucleus, spina l trigeminal tract nucleus, and a number of brainstem nuclei, with vir tually no labelling in the cerebellum. In several areas a rostrocaudal gradient of sites concentration was observed. Neuropeptide FF recepto rs are well-placed to control incoming sensory and autonomic informati on processing. In contrast, the more recently developed areas of the f orebrain possessed low density of sites. The distribution of [I-125][D .Tyr(1), (NMe)Phe(3)]NPFF binding sites should suggest anatomical subs trates for the actions of neuropeptide FF. (C) 1996 Wiley-Liss, Inc.