Neuropeptide Y receptor binding sites in human brain. Possible alteration in Alzheimer's disease

Neuropeptide Y (NPY) and peptide YY (PYY) receptor sites were studied in human brain using saturation binding experiments and receptor autoradiography. Additionally, the affinities and densities of [3H]NPY binding sites were compared in the temporal cortex, hippocampus and putamen of patients dying from Alzheimer's disease (AD) and aged matched controls. High densities of [3H]NPY binding sites were found in the putamen (192 +/- 32 fmol/mg protein), followed by the hippocampus (165 +/- 42 fmol/mg protein) and temporal cortex (118 +/- 19 fmol/mg protein). Receptor autoradiography revealed that these sites were especially concentrated in certain layers of the hippocampus, laminae I and IV-V of the temporal cortex and the amygdalo-hippocampal area. No significant changes in [3H]NPY binding affinities were seen between the AD and aged-matched groups (Kd ranges: 2.5-6.8 nM). However, significant decreases in [3H]NPY receptor densities (Bmax) were found in temporal cortex (-43%) and hippocampus (-49%) in AD brains. No significant change in [3H]NPY Bmax values was found in the putamen. It is therefore possible that decreases in [3H]NPY receptor densities may be associated to the degenerative process taking place in certain brain regions in AD, although further work will be necessary to confirm this hypothesis. Part of this work was presented at the 17th Annual Meeting of the Society for Neuroscience.