In vitro autoradiography of GTP γ[ [formula omitted]] binding at activated NPY receptor subtypes in adult rat brain

Guanylyl 5′-[ γ[ 35 S ]thio]-triphosphate (GTP γ[ 35 S ]) binding to NPY receptor-activated G-proteins was measured in adult rat brain sections in order to determine the neuroanatomical distribution of NPY receptor subtypes. Using the pharmacological specificity of the NPY receptor subtypes, differential stimulation of GTP γ[ 35 S ] binding by subtype-specific agonists was used to demonstrate the differential distribution of these subtypes in rat brain. Treatment of rat brain slices with selective agonists for the NPY receptor subtypes in the presence of 2000 μM GDP was used to discriminate populations of NPY receptor subtypes. Activation of a NPY Y1 receptor subtype by human [Leu 31Pro 34]NPY stimulated GTP γ[ 35 S ] binding in the rank order: frontal cortex>dentate gyrus>inferior colliculus≥thalamus>hypothalamus. In contrast, NPY Y2/Y5 peptide agonist, human PYY(3–36), stimulated GTP γ[ 35 S ] binding in the rank order: hypothalamus>substantia nigra>hippocampus>frontal cortex≥inferior colliculus. Stimulation of NPY Y5 receptor subtypes by a NPY Y5 selective agonist, rat/human d-Trp 32 NPY , was shown to stimulate GTP γ[ 35 S ] binding in the hypothalamus and discrete nuclei of the thalamus. Little GTP γ[ 35 S ] binding in the dentate gyrus, frontal cortex, or inferior colliculus was measured following stimulation with d-Trp 32 NPY . Stimulation of GTP γ[ 35 S ] binding by [Leu 31Pro 34]NPY, but not by the other NPY receptor agonists, was blocked by the selective NPY Y1 receptor antagonist, BIBP 3226. In conclusion, functional coupling at NPY receptor subtypes can be shown in rat brain and populations of NPY receptor subtypes can be anatomically discriminated by NPY agonist stimulation of GTP γ[ 35 S ] binding in rat brain.