Quantitative autoradiography of the binding sites for [125I] iodoglyburide, a novel high-affinity ligand for ATP-sensitive potassium channels in rat brain

• Published in: The Journal of pharmacology and experimental therapeutics Vol. 257; no. 2; pp. 901 - 907
• Main Authors: GEHLERT, D. R, GACKENHEIMER, S. L, MAIS, D. E, ROBERTSON, D. W
• Format: Journal Article
• Language: English
• Published: Bethesda, MD American Society for Pharmacology and Experimental Therapeutics 01.05.1991
• Subjects: 550201 - Biochemistry- Tracer Techniques; Affinity Labels; ALKALI METAL COMPOUNDS; ANIMALS; ATP; AUTORADIOGRAPHY; BASIC BIOLOGICAL SCIENCES; BETA DECAY RADIOISOTOPES; Binding Sites; BIOCHEMICAL REACTION KINETICS; Biochemistry and metabolism; Biological and medical sciences; BODY; BRAIN; Brain - metabolism; CARBONIC ACID DERIVATIVES; CARDIOVASCULAR AGENTS; CENTRAL NERVOUS SYSTEM; DAYS LIVING RADIOISOTOPES; DRUGS; ELECTRON CAPTURE RADIOISOTOPES; Fundamental and applied biological sciences. Psychology; Glipizide - pharmacology; Glyburide - analogs & derivatives; Glyburide - metabolism; Glyburide - pharmacology; GUANIDINES; Guanidines - pharmacology; INTERMEDIATE MASS NUCLEI; INTERNAL CONVERSION RADIOISOTOPES; IODINE 125; IODINE ISOTOPES; Iodine Radioisotopes; ISOTOPES; KINETICS; LIGANDS; Male; MAMMALS; MEMBRANE PROTEINS; MEMBRANE TRANSPORT; NERVOUS SYSTEM; NUCLEI; NUCLEOTIDES; ODD-EVEN NUCLEI; ORGANIC COMPOUNDS; ORGANIC NITROGEN COMPOUNDS; ORGANS; Pinacidil; Potassium Channels - drug effects; Potassium Channels - metabolism; POTASSIUM COMPOUNDS; PROTEINS; RADIOISOTOPES; RATS; Rats, Inbred Strains; REACTION KINETICS; RECEPTORS; RODENTS; Vasodilator Agents - pharmacology; VASODILATORS; VERTEBRATES; Vertebrates: nervous system and sense organs; Brain; Radiolabelling; Rat; Ligand; Rodentia; Central nervous system; Ionic channel; Binding site; Autoradiography; Vertebrata; Mammalia; Cations; Localization; ATP; Potassium
• ISSN: 0022-3565; 1521-0103

We have developed a high specific activity ligand for localization of ATP-sensitive potassium channels in the brain. When brain sections were incubated with [125I]iodoglyburide (N-[2-[[[(cyclohexylamino)carbonyl]amino]sulfonyl]ethyl]-5-125I-2- methoxybenzamide), the ligand bound to a single site with a KD of 495 pM and a maximum binding site density of 176 fmol/mg of tissue. Glyburide was the most potent inhibitor of specific [125I]iodoglyburide binding to rat forebrain sections whereas iodoglyburide and glipizide were slightly less potent. The binding was also sensitive to ATP which completely inhibited binding at concentrations of 10 mM. Autoradiographic localization of [125I]iodoglyburide binding indicated a broad distribution of the ATP-sensitive potassium channel in the brain. The highest levels of binding were seen in the globus pallidus and ventral pallidum followed by the septohippocampal nucleus, anterior pituitary, the CA2 and CA3 region of the hippocampus, ventral pallidum, the molecular layer of the cerebellum and substantia nigra zona reticulata. The hilus and dorsal subiculum of the hippocampus, molecular layer of the dentate gyrus, cerebral cortex, lateral olfactory tract nucleus, olfactory tubercle and the zona incerta contained relatively high levels of binding. A lower level of binding (approximately 3- to 4-fold) was found throughout the remainder of the brain. These results indicate that the ATP-sensitive potassium channel has a broad presence in the rat brain and that a few select brain regions are enriched in this subtype of neuronal potassium channels.