Classification of M/sub 1/ and M/sub 2/ receptor subtypes in vivo by autoradiography using (/sup 125/I) (R,R) 4IQNB: Implications for imaging receptor subtypes

Conference · Wed May 01 04:00:00 EDT 1985 · J. Nucl. Med.; (United States)

OSTI ID:6696555

Gibson, R E; Moody, T; Kzeszotarski, W J; Schneidau, T S; Jagoda, E M; Reba, R C

(/sup 125/I) (R,R) 3-Quinuclidinyl 4-Iodobenzilate (4IQNB) is a high affinity radiotracer for the muscarinic acetylcholine receptor which exhibits differential kinetics of dissociation from the receptor subtypes, M/sub 1/ and M/sub 2/. The authors have determined the relative percentages of M/sub 1/ to M/sub 2/-receptor subtype in six structures of rat brain by equilibrium competition using the selective antagonist, QNX, and by analysis of the off-rate profiles for 4IQNB. The results are comparable and provide: (% M/sub 1/) caudate nucleus - 100%, hippocampus - 92%, cortex - 82%, thalamus - 6%, superior + inferior colliculi - 41%, and pons - 23%. To determine the relative proportions of M/sub 1/ to M/sub 2/ receptors in vivo we examined the distribution of 4IQNB at 2 h and 24 h by autoradiography. At 2 h, both M/sub 1/ and M/sub 2/ receptors will be labeled but at 24 h only the M/sub 1/ receptor will retain radiotracer. At 2 h, all structures of the brain are variably labeled with the cortex, hippocampus, caudate nucleus, olfactory nuclei, nucleus accumbens, pontine nuclei, and anteroventral thalamic nucleus (AV) most heavily labeled. At 24 h, both the pontine and AV, as well as the less heavily labeled hypothalamus, superior colliculus and mesencephalic nuclei, are devoid of radiotracer thus indicating predominantly M/sub 2/ receptor. Quantitation is necessary to determine possible washout of activity from the M/sub 2/ receptors in cortex. Similar time studies in man should provide distinctions between the M/sub 1/ and M/sub 2/ receptor rich structures and the preferential loss of a subtype of receptor due to disease.

• Research Organization: The George Washington Univ. Medical Center, Washington, DC
• OSTI ID: 6696555
• Report Number(s): CONF-850611-
• Conference Information: Journal Name: J. Nucl. Med.; (United States) Journal Volume: 26:5
• Country of Publication: United States
• Language: English

Related Subjects

550201 -- Biochemistry-- Tracer Techniques
550801* -- Morphology-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ACETYLCHOLINE
AMINES
AMMONIUM COMPOUNDS
ANATOMY
ANIMALS
AUTONOMIC NERVOUS SYSTEM AGENTS
AUTORADIOGRAPHY
BETA DECAY RADIOISOTOPES
BIOCHEMICAL REACTION KINETICS
BIOLOGICAL FUNCTIONS
BIOLOGICAL LOCALIZATION
BODY
BRAIN
CENTRAL NERVOUS SYSTEM
CEREBRAL CORTEX
CEREBRUM
CHEMICAL ANALYSIS
DAYS LIVING RADIOISOTOPES
DIAGNOSTIC TECHNIQUES
DRUGS
ELECTRON CAPTURE RADIOISOTOPES
ESTERS
FUNCTIONS
HIPPOCAMPUS
IMAGES
IN VIVO
INTERMEDIATE MASS NUCLEI
IODINE 125
IODINE ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPES
KINETICS
MAMMALS
MEMBRANE PROTEINS
NERVOUS SYSTEM
NEUROREGULATORS
NUCLEI
ODD-EVEN NUCLEI
ORGANIC COMPOUNDS
ORGANS
PARASYMPATHOMIMETICS
PROTEINS
QUANTITATIVE CHEMICAL ANALYSIS
QUATERNARY COMPOUNDS
RADIOISOTOPES
RADIORECEPTOR ASSAY
RATS
REACTION KINETICS
RECEPTORS
REMOVAL
RODENTS
THALAMUS
TIME DEPENDENCE
TRACER TECHNIQUES
VERTEBRATES