scholarly journals Imaging Muscarinic Cholinergic Receptors in Human Brain in vivo with SPECT, [123I]4-Iododexetimide, and [123I]4-Iodolevetimide

1992 ◽  
Vol 12 (4) ◽  
pp. 562-570 ◽  
Author(s):  
Hans W. Müller-Gärtner ◽  
Alan A. Wilson ◽  
Robert F. Dannals ◽  
Henry N. Wagner ◽  
J. James Frost
Keyword(s):  
Human Brain ◽  
Muscarinic Receptor ◽  
Muscarinic Receptors ◽  
Acetylcholine Receptors ◽  
Brain Regions ◽  
Muscarinic Acetylcholine Receptors ◽  
Emission Computed Tomography ◽  
Nonspecific Binding ◽  
Muscarinic Acetylcholine

A method to image muscarinic acetylcholine receptors (muscarinic receptors) noninvasively in human brain in vivo was developed using [123I]4-iododexetimide ([123I]IDex), [123I]4-iodolevetimide ([123I]ILev), and single photon emission computed tomography (SPECT). [123I]IDex is a high-affinity muscarinic receptor antagonist. [123I]ILev is its pharmacologically inactive enantiomer and measures nonspecific binding of [123I]IDex in vitro. Regional brain activity after tracer injection was measured in four young normal volunteers for 24 h. Regional [123I]IDex and [123I]ILev activities were correlated early after injection, but not after 1.5 h. [123I]IDex activity increased over 7–12 h in neocortex, neostriatum, and thalamus, but decreased immediately after the injection peak in cerebellum. [123I]IDex activity was highest in neostriatum, followed in rank order by neocortex, thalamus, and cerebellum. [123I]IDex activity correlated with muscarinic receptor concentrations in matching brain regions. In contrast, [123I]ILev activity decreased immediately after the injection peak in all brain regions and did not correspond to muscarinic receptor concentrations. [123I]IDex activity in neocortex and neostriatum during equilibrium was six to seven times higher than [123I]ILev activity. The data demonstrate that [123I]IDex binds specifically to muscarinic receptors in vivo, whereas [123I]ILev represents the nonspecific part of [123I]IDex binding. Subtraction of [123I]ILev from [123I]IDex images on a pixel-by-pixel basis therefore reflects specific [123I]IDex binding to muscarinic receptors. Owing to its high specific binding, [123I]IDex has the potential to measure small changes in muscarinic receptor characteristics in vivo with SPECT. The use of stereoisomerism directly to measure nonspecific binding of [123I]IDex in vivo may reduce complexity in modeling approaches to muscarinic acetylcholine receptors in human brain.

scholarly journals Role of M1, M3, and M5 muscarinic acetylcholine receptors in cholinergic dilation of small arteries studied with gene-targeted mice

2011 ◽  
Vol 300 (5) ◽  
pp. H1602-H1608 ◽  
Author(s):  
Adrian Gericke ◽  
Jan J. Sniatecki ◽  
Veronique G. A. Mayer ◽  
Evgeny Goloborodko ◽  
Andreas Patzak ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Muscarinic Receptor ◽  
Acetylcholine Receptors ◽  
Muscarinic Acetylcholine Receptors ◽  
Receptor Subtypes ◽  
Wild Type ◽  
Luminal Diameter ◽  
Small Arteries ◽  
Muscarinic Acetylcholine

Acetylcholine regulates perfusion of numerous organs via changes in local blood flow involving muscarinic receptor-induced release of vasorelaxing agents from the endothelium. The purpose of the present study was to determine the role of M1, M3, and M5 muscarinic acetylcholine receptors in vasodilation of small arteries using gene-targeted mice deficient in either of the three receptor subtypes (M1R−/−, M3R−/−, or M5R−/− mice, respectively). Muscarinic receptor gene expression was determined in murine cutaneous, skeletal muscle, and renal interlobar arteries using real-time PCR. Moreover, respective arteries from M1R−/−, M3R−/−, M5R−/−, and wild-type mice were isolated, cannulated with micropipettes, and pressurized. Luminal diameter was measured using video microscopy. mRNA for all five muscarinic receptor subtypes was detected in all three vascular preparations from wild-type mice. However, M3 receptor mRNA was found to be most abundant. Acetylcholine produced dose-dependent dilation in all three vascular preparations from M1R−/−, M5R−/−, and wild-type mice. In contrast, cholinergic dilation was virtually abolished in arteries from M3R−/− mice. Deletion of either M1, M3, or M5 receptor genes did not affect responses to nonmuscarinic vasodilators, such as substance P and nitroprusside. These findings provide the first direct evidence that M3 receptors mediate cholinergic vasodilation in cutaneous, skeletal muscle, and renal interlobar arteries. In contrast, neither M1 nor M5 receptors appear to be involved in cholinergic responses of the three vascular preparations tested.

Synthesis,18F-Labeling, and Biological Evaluation of Piperidyl and Pyrrolidyl Benzilates as in Vivo Ligands for Muscarinic Acetylcholine Receptors

2000 ◽  
Vol 43 (23) ◽  
pp. 4552-4562 ◽  
Author(s):  
Marc B. Skaddan ◽  
Michael R. Kilbourn ◽  
Scott E. Snyder ◽  
Phil S. Sherman ◽  
Tim J. Desmond ◽  
...  
Keyword(s):  
Acetylcholine Receptors ◽  
Biological Evaluation ◽  
Muscarinic Acetylcholine Receptors ◽  
Muscarinic Acetylcholine

scholarly journals Effect of proteolytic cleavage on functional properties of muscarinic acetylcholine receptors in rat pancreatic and parotid acinar cells

1985 ◽  
Vol 231 (3) ◽  
pp. 617-622 ◽  
Author(s):  
S R Hootman ◽  
T M Picado-Leonard
Keyword(s):  
Muscarinic Receptors ◽  
Acetylcholine Receptors ◽  
Digestive Enzyme ◽  
Covalent Binding ◽  
Acinar Cells ◽  
Proteolytic Cleavage ◽  
Muscarinic Acetylcholine Receptors ◽  
Pancreatic Acinar Cells ◽  
Muscarinic Acetylcholine ◽  
Parotid Acinar Cells

Muscarinic acetylcholine receptors in isolated rat pancreatic acinar cells have an apparent Mr of 88 000, which could be decreased to 46 000 by papain, as deduced by covalent binding of the specific alkylating agent [3H]propylbenzilylcholine mustard. Muscarinic receptors on papain-treated acinar cells retained the antagonist-binding site and both high- and low-affinity binding sites for the cholinergic agonist carbachol. Similar results were observed in studies with rat parotid acinar cells, although the receptors in both control and papain-treated cells were each 10 000-15 000 Da smaller than in pancreas. Additionally, muscarinic receptors in papain-treated pancreatic acinar cells retained the ability to mediate carbachol stimulation of digestive-enzyme secretion. These results demonstrate that the characteristic binding properties of muscarinic receptors for both agonists and antagonists as well as their ability to translate agonist occupancy into a physiological response are not altered by proteolytic cleavage.

Effects of Autoantibodies against M2 Muscarinic Acetylcholine Receptors on Rabbit Atria in vivo

Cardiology ◽  
2009 ◽  
Vol 112 (3) ◽  
pp. 180-187 ◽  
Author(s):  
Chang Ming Hong ◽  
Qiang Sun Zheng ◽  
Xiong Tao Liu ◽  
Fu Jun Shang ◽  
Hong Tao Wang ◽  
...  
Keyword(s):  
Acetylcholine Receptors ◽  
Muscarinic Acetylcholine Receptors ◽  
Muscarinic Acetylcholine ◽  
Rabbit Atria

scholarly journals Control of Cardiac Function in vivo with a Light-Regulated Drug

2018 ◽  
Author(s):  
Fabio Riefolo ◽  
Carlo Matera ◽  
Aida Garrido-Charles ◽  
Alexandre M. J. Gomila ◽  
Luca Agnetta ◽  
...  
Keyword(s):  
Cardiac Function ◽  
Mammalian Cells ◽  
Acetylcholine Receptors ◽  
Genetic Manipulation ◽  
Muscarinic Acetylcholine Receptors ◽  
Therapeutic Interventions ◽  
Muscarinic Acetylcholine ◽  
First Time

<p>Remote control of physiological functions with light offers the promise of unveiling their complex spatiotemporal dynamics in vivo, and enabling highly focalized therapeutic interventions with reduced systemic toxicity. Optogenetic methods have been implemented in the heart, but the need of genetic manipulation jeopardizes clinical applicability. This study aims at developing, testing and validating the first light-regulated drug with cardiac effects, in order to avoid the requirement of genetic manipulation offered by optogenetic methods. A M2 muscarinic acetylcholine receptors (mAChRs) light-regulated drug (PAI) was designed, synthesized and pharmacologically characterized. The design was based on the orthosteric mAChRs agonist Iperoxo, an allosteric M2 ligand, and a photoswitchable azobenzene linker. PAI can be reversibly photoisomerized between <i>cis</i> and <i>trans</i> configurations under ultraviolet (UV) and visible light, respectively, and it reversibly photoswitches the activity of M2 muscarinic acetylcholine receptors. We have evaluated <i>in vitro</i> photoresponses using a calcium imaging assay in genetically unmodified receptors overexpressed in mammalian cells. Furthermore, using this new chemical tool, we demonstrate for the first time photoregulation of cardiac function <i>in vivo</i> in wildtype frog tadpoles and in rats with a method that does not require genetic manipulation. Such a new approach may enable enhanced spatial and temporal selectivity for cardiovascular drugs.</p>

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