IN-VITRO AUTORADIOGRAPHY OF GTP-GAMMA[S-35] BINDING AT ACTIVATED NPY RECEPTOR SUBTYPES IN ADULT-RAT BRAIN

Guanylyl 5'-[gamma[S-35]thio]-triphosphate (GTP gamma[S-35]) binding t o NPY receptor-activated G-proteins was measured in adult rat brain se ctions in order to determine the neuroanatomical distribution of NPY r eceptor subtypes. Using the pharmacological specificity of the NPY rec eptor subtypes, differential stimulation of GTP gamma[S-35] binding by subtype-specific agonists was used to demonstrate the differential di stribution of these subtypes in rat brain. Treatment of rat brain slic es with selective agonists for the NPY receptor subtypes in the presen ce of 2000 mu M GDP was used to discriminate populations of NPY recept or subtypes. Activation of a NPY Y1 receptor subtype by human [Ley(31) Pro(34)]NPY stimulated GTP gamma[S-35] binding in the rank order: fron tal cortex > dentate gyrus > inferior colliculus greater than or equal to thalamus > hypothalamus. In contrast, NPY Y2/Y5 peptide agonist, h uman PW(3-36), stimulated GTP gamma[S-35] binding in the rank order: h ypothalamus > substantia nigra > hippocampus > frontal cortex greater than or equal to inferior colliculus. Stimulation of NPY Y5 receptor s ubtypes by a NPY Y5 selective agonist, rat/human D-Trp(32)Npy, was sho wn to stimulate GTP gamma[S-35] binding in the hypothalamus and discre te nuclei of the thalamus. Little GTP gamma-[S-35] binding in the dent ate gyrus, frontal cortex, or inferior colliculus was measured followi ng stimulation with D-Trp(32)Npy. Stimulation of GTP gamma[S-35] bindi ng by [Leu(31)Pro(34)]Npy, but not by the other NPY receptor agonists, was blocked by the selective NPY Y1 receptor antagonist, BIBP 3226. I n conclusion, functional coupling at NPY receptor subtypes can be show n in rat brain and populations of NPY receptor subtypes can be anatomi cally discriminated by NPY agonist stimulation of GTP gamma[S-35] bind ing in rat brain. (C) 1998 Elsevier Science B.V. All nights reserved.