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In vitro binding properties and autoradiographic imaging of 3-iodobenzamide ((/sup 125/I)-IBZM): a potential imaging ligand for D-2 dopamine receptors in SPECT

Journal Article · · Life Sci.; (United States)
; ; ; ; ; ;

The in vitro binding properties of the (/sup 125/I) labeled benzamide, (S(-)-N-((1-ethyl-2-pyrrolidinyl)-methyl)-2-hydroxy-3-iodo-6-methoxy-benzamide, IBZM) were determined in bovine and mouse caudate membrane homogenates and by autoradiography of mouse brain slices. (/sup 125/I)-IBZM binding is saturable and reversible with B/sub max/ of 373 +/- 51 fmol/mg protein and a K/sub d/ of 3.1 +/- 0.62 nM and 0.56 nM as calculated by association and dissociation time constants. In competition experiments, K/sub i/ values for the D-2 antagonists YM-09151-2 and spiperone are 4 orders of magnitude lower than the K/sub i/ value for the D-1 antagonist SCH-23390 and S(-)-IBZM is ten-fold more potent than R(+)-IBZM. (/sup 125/I)-IBZM has a low affinity for serotonin S-2 and for alpha receptors. Therefore, it is a highly selective ligand for dopamine D-2 receptors. Autoradiographic images of brain sections incubated with (/sup 125/I)-IBZM show the dopamine D-2 receptors of the striatum, nucleus accumbens and olfactory tubercle with a high ratio of specific to nonspecific binding. Thus, S(-)-IBZM, when labeled with (/sup 125/I), may be useful for in vivo imaging of dopamine D-2 receptors by single photon emission computerized tomography (SPECT).

Research Organization:
National Institute of Mental Health, Bethesda, MD (USA)
OSTI ID:
6938663
Journal Information:
Life Sci.; (United States), Journal Name: Life Sci.; (United States) Vol. 42:21; ISSN LIFSA
Country of Publication:
United States
Language:
English

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Related Subjects

550601* -- Medicine-- Unsealed Radionuclides in Diagnostics
62 RADIOLOGY AND NUCLEAR MEDICINE
AMINES
ANIMALS
AROMATICS
AUTONOMIC NERVOUS SYSTEM AGENTS
AUTORADIOGRAPHY
BETA DECAY RADIOISOTOPES
BIOCHEMICAL REACTION KINETICS
CARDIOTONICS
CARDIOVASCULAR AGENTS
CATTLE
CELL CONSTITUENTS
CELL MEMBRANES
COMPUTERIZED TOMOGRAPHY
DAYS LIVING RADIOISOTOPES
DIAGNOSTIC TECHNIQUES
DOMESTIC ANIMALS
DOPAMINE
DRUGS
ELECTRON CAPTURE RADIOISOTOPES
EMISSION COMPUTED TOMOGRAPHY
HYDROXY COMPOUNDS
IMAGES
IN VITRO
INTERMEDIATE MASS NUCLEI
IODINE 125
IODINE ISOTOPES
ISOTOPES
KINETICS
LABELLED COMPOUNDS
LIGANDS
MAMMALS
MEMBRANE PROTEINS
MEMBRANES
MICE
NEUROREGULATORS
NUCLEI
ODD-EVEN NUCLEI
ORGANIC COMPOUNDS
PHENOLS
POLYPHENOLS
PROTEINS
RADIOISOTOPES
RADIOPHARMACEUTICALS
REACTION KINETICS
RECEPTORS
RODENTS
RUMINANTS
SINGLE PHOTON EMISSION COMPUTED TOMOGRAPHY
SYMPATHOMIMETICS
TOMOGRAPHY
VERTEBRATES