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Cocolas A, Lane AM, Musiak BS, Chartier EJ, Bedillion DA, Hejnosz SL, Rohde JJ, Lummis PA, Evanseck JD, Montgomery TD. Diastereoselective [3 + 2] Cycloaddition between Tertiary Amine N-Oxides and Substituted Alkenes to Access 7-Azanorbornanes. Org Lett 2024; 26:6546-6550. [PMID: 39038111 PMCID: PMC11320637 DOI: 10.1021/acs.orglett.4c02013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2024] [Revised: 07/11/2024] [Accepted: 07/16/2024] [Indexed: 07/24/2024]
Abstract
We have developed a diastereoselective synthesis of 43 novel 7-azanorbornanes using tertiary amine N-oxides and substituted alkenes. Our method uses an efficient [3 + 2] cycloaddition, starting from either commercially available or easily accessible precursors to generate yields up to 97% and diastereomeric ratios up to >20:1. Density functional theory (DFT) calculations were performed, suggesting that the observed diastereoselectivity is likely due to steric considerations.
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Affiliation(s)
- Alexander
H. Cocolas
- Department
of Chemistry and Biochemistry, Duquesne
University, 600 Forbes Avenue, Pittsburgh, Pennsylvania 15282, United States
| | - Aiden M. Lane
- Department
of Chemistry and Biochemistry, Duquesne
University, 600 Forbes Avenue, Pittsburgh, Pennsylvania 15282, United States
| | - Benjamin S. Musiak
- Department
of Chemistry and Biochemistry, Duquesne
University, 600 Forbes Avenue, Pittsburgh, Pennsylvania 15282, United States
| | - Eric J. Chartier
- Department
of Chemistry and Biochemistry, Duquesne
University, 600 Forbes Avenue, Pittsburgh, Pennsylvania 15282, United States
| | - Derek A. Bedillion
- Department
of Chemistry and Biochemistry, Duquesne
University, 600 Forbes Avenue, Pittsburgh, Pennsylvania 15282, United States
| | - Sarah L. Hejnosz
- Department
of Chemistry and Biochemistry, Duquesne
University, 600 Forbes Avenue, Pittsburgh, Pennsylvania 15282, United States
| | - Jeffrey J. Rohde
- Department
of Mathematics and Physical Sciences, Franciscan
University of Steubenville, 1235 University Boulevard, Steubenville, Ohio 43952, United States
| | - Paul A. Lummis
- Department
of Chemistry and Biochemistry, Duquesne
University, 600 Forbes Avenue, Pittsburgh, Pennsylvania 15282, United States
| | - Jeffrey D. Evanseck
- Department
of Chemistry and Biochemistry, Duquesne
University, 600 Forbes Avenue, Pittsburgh, Pennsylvania 15282, United States
| | - Thomas D. Montgomery
- Department
of Chemistry and Biochemistry, Duquesne
University, 600 Forbes Avenue, Pittsburgh, Pennsylvania 15282, United States
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Xue L, Jie CVML, Desrayaud S, Auberson YP. Developing Low Molecular Weight PET and SPECT Imaging Agents. ChemMedChem 2024; 19:e202400094. [PMID: 38634545 DOI: 10.1002/cmdc.202400094] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2024] [Revised: 04/17/2024] [Accepted: 04/17/2024] [Indexed: 04/19/2024]
Abstract
Imaging agents for positron emission tomography (PET) and single-photon emission computerized tomography (SPECT) have shown their utility in many situations, answering clinical questions related to drug development and medical considerations. The discovery and development of imaging agents follow a well-understood process, with variations related to available starting points and to the envisaged imaging application. This article describes the general development path leading from the expression of an imaging need and project initiation to a clinically usable imaging agent. The definition of the project rationale, the design and optimization of early leads, and the assessment of the imaging potential of an imaging agent candidate are followed by preclinical and clinical development activities that differ from those required for therapeutic agents. These include radiolabeling with a positron emitter and first-in-human clinical studies, to rapidly evaluate the ability of a new imaging agent to address the questions it was designed to answer.
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Affiliation(s)
- Lian Xue
- Monash Institute of Pharmaceutical Sciences, Monash University, 381 Royal Parade Parkville, Victoria 3052, Australia
| | - Caitlin V M L Jie
- ETH Zürich, Department of Chemistry and Applied Biosciences Center for Radiopharmaceutical Sciences, Vladimir-Prelog Weg 1-5/10, 8093, Zürich, Switzerland
| | - Sandrine Desrayaud
- Novartis Biomedical Research, In Vivo preclinical PK/ADME, Novartis campus, WSJ-352/6/73.01, 4056, Basel, Switzerland
| | - Yves P Auberson
- Novartis Biomedical Research, Global Discovery Chemistry, Novartis campus, WSJ-88.10.100, 4056, Basel, Switzerland
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Auberson YP, Lièvre A, Desrayaud S, Briard E. A practical approach to the optimization of positron emission tomography (PET) imaging agents for the central nervous system. J Labelled Comp Radiopharm 2022; 65:343-350. [PMID: 36148533 DOI: 10.1002/jlcr.4004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2022] [Revised: 09/20/2022] [Accepted: 09/21/2022] [Indexed: 11/08/2022]
Abstract
The discovery of novel imaging agents for positron emission tomography (PET) relies on medicinal chemistry best practices, including a good understanding of molecular and pharmacological properties required for the acquisition of relevant, high-quality images. This short note reviews the characteristics of a series of clinically successful imaging agents, providing guidance for the optimization of such molecular tools. PET imaging plays an important role in staging disease and in helping clinical dose selection, which is critical for the efficient development of drug candidates.
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Affiliation(s)
- Yves P Auberson
- Novartis Institutes for BioMedical Research, Basel, Switzerland
| | - Akané Lièvre
- Novartis Institutes for BioMedical Research, Basel, Switzerland
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Wang C, Bai J, Wang C, von Deneen KM, Yuan K, Cheng J. Altered thalamo-cortical resting state functional connectivity in smokers. Neurosci Lett 2017; 653:120-125. [DOI: 10.1016/j.neulet.2017.05.038] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2016] [Revised: 05/19/2017] [Accepted: 10/14/2016] [Indexed: 01/22/2023]
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O'Neill J, Tobias MC, Hudkins M, Oh EY, Hellemann GS, Nurmi EL, London ED. Thalamic glutamate decreases with cigarette smoking. Psychopharmacology (Berl) 2014; 231:2717-24. [PMID: 24535652 PMCID: PMC4182312 DOI: 10.1007/s00213-014-3441-5] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/25/2013] [Accepted: 01/02/2014] [Indexed: 12/23/2022]
Abstract
RATIONALE Findings from animal studies and human PET imaging indicate that nicotine and cigarette smoking affect glutamate (Glu) and related neurochemical markers in the brain and imply that smoking reduces extracellular Glu. As Glu release is mediated by nicotinic acetylcholine receptors (nAChRs), which are present at high concentrations in the thalamus, we examined the effects of smoking on thalamic Glu. OBJECTIVE To determine the effects of tobacco smoking on thalamic glutamate levels. METHODS Thalamic Glu levels were measured in vivo in 18 smokers and 16 nonsmokers using proton magnetic resonance spectroscopic imaging ((1)H MRSI) at 1.5 T. RESULTS Mean Glu levels did not differ significantly between the subject groups. However, within smokers, Glu levels were negatively correlated with self-reports of both cigarettes/day over the last 30 days (r = -0.64, p = 0.006) and pack-years of smoking (r = -0.66, p = 0.005). CONCLUSIONS Consistent with expectations based on preclinical studies, within smokers, cigarettes/day and pack-years are associated with reduced Glu in thalamus, a brain region rich in nAchRs. These results encourage work on candidate glutamatergic therapies for smoking cessation and suggest a noninvasive metric for their action in the brain.
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Affiliation(s)
- Joseph O'Neill
- Division of Child & Adolescent Psychiatry, UCLA Semel Institute for Neuroscience, 760 Westwood Plaza, Box 175919, Los Angeles, CA, 90024-1759, USA,
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6
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Fischer S, Hiller A, Smits R, Hoepping A, Funke U, Wenzel B, Cumming P, Sabri O, Steinbach J, Brust P. Radiosynthesis of racemic and enantiomerically pure (-)-[18F]flubatine--a promising PET radiotracer for neuroimaging of α4β2 nicotinic acetylcholine receptors. Appl Radiat Isot 2013; 74:128-36. [PMID: 23416407 DOI: 10.1016/j.apradiso.2013.01.002] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2012] [Revised: 12/07/2012] [Accepted: 01/01/2013] [Indexed: 10/27/2022]
Abstract
(-)-[(18)F]flubatine is a promising agent for visualization by PET of cerebral α4β2 nicotinic acetylcholine receptors (nAChRs), which are implicated in psychiatric and neurodegenerative disorders. Here, we describe a substantially improved two-step radiosynthesis strategy for (-)-[(18)F]flubatine, based on the nucleophilic radiofluorination of an enantiomerically pure precursor followed by deprotection of the intermediate. An extensive leaving group/protecting group library of precursors was tested. Application of a trimethylammonium-iodide precursor with a Boc-protecting group provided the best results: labeling efficiencies of 80-95%, RCY of 60±5%, radiochemical purity of >98%, and a specific activity of >350GBq/μmol. The radiosynthesis is easily transferable to an automated synthesis module.
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Affiliation(s)
- Steffen Fischer
- Department of Neuroradiopharmaceuticals, Institute of Radiopharmacy, Helmholtz-Zentrum Dresden-Rossendorf, Research Site Leipzig, Permoserstrasse 15, Leipzig, Germany
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Development of radioligands with optimized imaging properties for quantification of nicotinic acetylcholine receptors by positron emission tomography. Life Sci 2009; 86:575-84. [PMID: 19303028 DOI: 10.1016/j.lfs.2009.02.029] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2008] [Revised: 02/05/2009] [Accepted: 02/12/2009] [Indexed: 11/20/2022]
Abstract
AIMS There is an urgent need for positron emission tomography (PET) imaging of the nicotinic acetylcholine receptors (nAChR) to study the role of the nicotinic system in Alzheimer's and Parkinson's diseases, schizophrenia, drug dependence and many other disorders. Greater understanding of the underlying mechanisms of the nicotinic system could direct the development of medications to treat these disorders. Central nAChRs also contribute to a variety of brain functions, including cognition, behavior and memory. MAIN METHODS Currently, only two radiotracers, (S)-3-(azetidin-2-ylmethoxy)-2-[(18)F]fluoropyridine (2-[(18)F]FA) and (S)-5-(azetidin-2-ylmethoxy)-2-[(18)F]fluoropyridine (6-[(18)F]FA), are available for studying nAChRs in human brain using PET. However, the "slow" brain kinetics of these radiotracers hamper mathematical modeling and reliable measurement of kinetic parameters since it takes 4-7 h of PET scanning for the tracers to reach steady state. The imaging drawbacks of the presently available nAChR radioligands have initiated the development of radioligands with faster brain kinetics by several research groups. KEY FINDINGS This minireview attempts to survey the important achievements of several research groups in the discovery of PET nicotinic radioligands reached recently. Specifically, this article reviews papers published from 2006 through 2008 describing the development of fifteen new nAChR (11)C-and (18)F-ligands that show improved imaging properties over 2-[(18)F]FA. SIGNIFICANCE The continuous efforts of radiomedicinal chemists led to the development of several interesting PET radioligands for imaging of nAChR including [(18)F]AZAN, a potentially superior alternative to 2-[(18)F]FA.
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New synthesis and evaluation of enantiomers of 7-methyl-2-exo-(3′-iodo-5′-pyridinyl)-7-azabicyclo[2.2.1]heptane as stereoselective ligands for PET imaging of nicotinic acetylcholine receptors. Bioorg Med Chem Lett 2008; 18:6168-70. [DOI: 10.1016/j.bmcl.2008.10.012] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2008] [Revised: 09/29/2008] [Accepted: 10/02/2008] [Indexed: 11/17/2022]
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Gao Y, Kuwabara H, Spivak CE, Xiao Y, Kellar K, Ravert HT, Kumar A, Alexander M, Hilton J, Wong DF, Dannals RF, Horti AG. Discovery of (−)-7-Methyl-2-exo-[3′-(6-[18F]fluoropyridin-2-yl)-5′-pyridinyl]-7-azabicyclo[2.2.1]heptane, a Radiolabeled Antagonist for Cerebral Nicotinic Acetylcholine Receptor (α4β2-nAChR) with Optimal Positron Emission Tomography Imaging Properties. J Med Chem 2008; 51:4751-64. [DOI: 10.1021/jm800323d] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Yongjun Gao
- Department of Radiology, Division of Nuclear Medicine, The Johns Hopkins University School of Medicine, 600 North Wolfe Street, Baltimore, Maryland 21287-0816, Cellular Neurophysiology Section, Cellular Neurobiology Branch, IRP, National Institute on Drug Abuse, 333 Cassell Drive, Baltimore, Maryland 21224, and Georgetown University, 3900 Reservoir Road, Washington, D.C. 20007
| | - Hiroto Kuwabara
- Department of Radiology, Division of Nuclear Medicine, The Johns Hopkins University School of Medicine, 600 North Wolfe Street, Baltimore, Maryland 21287-0816, Cellular Neurophysiology Section, Cellular Neurobiology Branch, IRP, National Institute on Drug Abuse, 333 Cassell Drive, Baltimore, Maryland 21224, and Georgetown University, 3900 Reservoir Road, Washington, D.C. 20007
| | - Charles E. Spivak
- Department of Radiology, Division of Nuclear Medicine, The Johns Hopkins University School of Medicine, 600 North Wolfe Street, Baltimore, Maryland 21287-0816, Cellular Neurophysiology Section, Cellular Neurobiology Branch, IRP, National Institute on Drug Abuse, 333 Cassell Drive, Baltimore, Maryland 21224, and Georgetown University, 3900 Reservoir Road, Washington, D.C. 20007
| | - Yingxian Xiao
- Department of Radiology, Division of Nuclear Medicine, The Johns Hopkins University School of Medicine, 600 North Wolfe Street, Baltimore, Maryland 21287-0816, Cellular Neurophysiology Section, Cellular Neurobiology Branch, IRP, National Institute on Drug Abuse, 333 Cassell Drive, Baltimore, Maryland 21224, and Georgetown University, 3900 Reservoir Road, Washington, D.C. 20007
| | - Kenneth Kellar
- Department of Radiology, Division of Nuclear Medicine, The Johns Hopkins University School of Medicine, 600 North Wolfe Street, Baltimore, Maryland 21287-0816, Cellular Neurophysiology Section, Cellular Neurobiology Branch, IRP, National Institute on Drug Abuse, 333 Cassell Drive, Baltimore, Maryland 21224, and Georgetown University, 3900 Reservoir Road, Washington, D.C. 20007
| | - Hayden T. Ravert
- Department of Radiology, Division of Nuclear Medicine, The Johns Hopkins University School of Medicine, 600 North Wolfe Street, Baltimore, Maryland 21287-0816, Cellular Neurophysiology Section, Cellular Neurobiology Branch, IRP, National Institute on Drug Abuse, 333 Cassell Drive, Baltimore, Maryland 21224, and Georgetown University, 3900 Reservoir Road, Washington, D.C. 20007
| | - Anil Kumar
- Department of Radiology, Division of Nuclear Medicine, The Johns Hopkins University School of Medicine, 600 North Wolfe Street, Baltimore, Maryland 21287-0816, Cellular Neurophysiology Section, Cellular Neurobiology Branch, IRP, National Institute on Drug Abuse, 333 Cassell Drive, Baltimore, Maryland 21224, and Georgetown University, 3900 Reservoir Road, Washington, D.C. 20007
| | - Mohab Alexander
- Department of Radiology, Division of Nuclear Medicine, The Johns Hopkins University School of Medicine, 600 North Wolfe Street, Baltimore, Maryland 21287-0816, Cellular Neurophysiology Section, Cellular Neurobiology Branch, IRP, National Institute on Drug Abuse, 333 Cassell Drive, Baltimore, Maryland 21224, and Georgetown University, 3900 Reservoir Road, Washington, D.C. 20007
| | - John Hilton
- Department of Radiology, Division of Nuclear Medicine, The Johns Hopkins University School of Medicine, 600 North Wolfe Street, Baltimore, Maryland 21287-0816, Cellular Neurophysiology Section, Cellular Neurobiology Branch, IRP, National Institute on Drug Abuse, 333 Cassell Drive, Baltimore, Maryland 21224, and Georgetown University, 3900 Reservoir Road, Washington, D.C. 20007
| | - Dean F. Wong
- Department of Radiology, Division of Nuclear Medicine, The Johns Hopkins University School of Medicine, 600 North Wolfe Street, Baltimore, Maryland 21287-0816, Cellular Neurophysiology Section, Cellular Neurobiology Branch, IRP, National Institute on Drug Abuse, 333 Cassell Drive, Baltimore, Maryland 21224, and Georgetown University, 3900 Reservoir Road, Washington, D.C. 20007
| | - Robert F. Dannals
- Department of Radiology, Division of Nuclear Medicine, The Johns Hopkins University School of Medicine, 600 North Wolfe Street, Baltimore, Maryland 21287-0816, Cellular Neurophysiology Section, Cellular Neurobiology Branch, IRP, National Institute on Drug Abuse, 333 Cassell Drive, Baltimore, Maryland 21224, and Georgetown University, 3900 Reservoir Road, Washington, D.C. 20007
| | - Andrew G. Horti
- Department of Radiology, Division of Nuclear Medicine, The Johns Hopkins University School of Medicine, 600 North Wolfe Street, Baltimore, Maryland 21287-0816, Cellular Neurophysiology Section, Cellular Neurobiology Branch, IRP, National Institute on Drug Abuse, 333 Cassell Drive, Baltimore, Maryland 21224, and Georgetown University, 3900 Reservoir Road, Washington, D.C. 20007
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Sabri O, Kendziorra K, Wolf H, Gertz HJ, Brust P. Acetylcholine receptors in dementia and mild cognitive impairment. Eur J Nucl Med Mol Imaging 2008; 35 Suppl 1:S30-45. [PMID: 18228017 DOI: 10.1007/s00259-007-0701-1] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
PURPOSE To clarify whether changes in the cholinergic transmission occur early in the course of Alzheimer's disease (AD), we carried out positron emission tomography (PET) with the radioligand 2-[(18)F]F-A-85380, which is supposed to be specific for alpha4beta2 nicotinic acetylcholine receptors (nAChRs). METHOD We included patients with moderate to severe AD and patients with amnestic mild cognitive impairment (MCI), presumed to present preclinical AD. RESULTS Both patients with AD and MCI showed significant reductions in alpha4beta2 nAChRs in brain regions typically affected by AD pathology. These findings indicate that a reduction in alpha4beta2 nAChRs occurs during early symptomatic stages of AD. The alpha4beta2 nAChR availability in these regions correlated with the severity of cognitive impairment, indicating a stage sensitivity of the alpha4beta2 nAChR status. CONCLUSION Together, our results provide evidence for the potential of 2-[(18)]F-A-85380 nAChR PET in the diagnosis of patients at risk for AD. Because of the extraordinary long acquisition time with 2-[(18)F]F-A-85380, we developed the new alpha4beta2 nAChR-specific radioligands (+)- and (-)-[(18)F]norchloro-fluoro-homoepibatidine (NCFHEB) and evaluated them preclinically. (-)-[(18)F]NCFHEB shows twofold higher brain uptake and significantly shorter acquisition times. Therefore, (-)-[(18)F]NCFHEB should be a suitable radioligand for larger clinical investigations.
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Affiliation(s)
- Osama Sabri
- Department of Nuclear Medicine, University of Leipzig, Stephanstrasse 11, Leipzig, Germany.
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11
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Deuther-Conrad W, Patt JT, Lockman PR, Allen DD, Patt M, Schildan A, Ganapathy V, Steinbach J, Sabri O, Brust P. Norchloro-fluoro-homoepibatidine (NCFHEB) - a promising radioligand for neuroimaging nicotinic acetylcholine receptors with PET. Eur Neuropsychopharmacol 2008; 18:222-9. [PMID: 17728108 DOI: 10.1016/j.euroneuro.2007.07.002] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/20/2007] [Revised: 06/27/2007] [Accepted: 07/05/2007] [Indexed: 11/15/2022]
Abstract
Cholinergic neurotransmission depends on the integrity of nicotinic acetylcholine receptors (nAChRs), and impairment of both is characteristic for various neurodegenerative diseases. Visualization of specific receptor subtypes by positron emission tomography (PET) has potential to assist with diagnosis of such neurodegenerative diseases and with design of suitable therapeutic approaches. The goal of our study was to evaluate in vivo the potential of (18)F-labelled (+)- and (-)-norchloro-fluoro-homoepibatidine ([(18)F]NCFHEB) in comparison to 2-[(18)F]F-A-85380 as PET tracers. In the brains of NMRI mice, highest levels of radioactivity were detected at 20 min post-injection of (+)-[(18)F]NCFHEB, (-)-[(18)F]NCFHEB, and 2-F-[(18)F]-A-85380 (7.45, 5.60, and 3.2% ID/g tissue, respectively). No marked pharmacological adverse effects were observed at 25 mug NCFHEB/kg. Uptake studies in RBE4 cells and in situ perfusion studies suggest an interaction of epibatidine and NCFHEB with the carrier-mediated choline transport at the blood-brain barrier. The data indicate that (+)- and (-)-[(18)F]NCFHEB have potential for further development as PET tracers.
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Affiliation(s)
- W Deuther-Conrad
- Institute of Interdisciplinary Isotope Research, Permoserstrasse 15, 04318 Leipzig, Germany.
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Dollé F, Langle S, Roger G, Fulton RR, Lagnel-de Bruin B, Henderson DJ, Hinnen F, Paine T, Coster MJ, Valette H, Bottlaender M, Kassiou M. Synthesis and In-Vivo Evaluation of [11C]p-PVP-MEMA as a PET Radioligand for Imaging Nicotinic Receptors. Aust J Chem 2008. [DOI: 10.1071/ch08083] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Within the class of (4-pyridinyl)vinylpyridines developed by Abbott laboratories as potent neuronal nicotinic acetylcholine receptor ligands, p-PVP-MEMA ({(R)-2-[6-chloro-5-((E)-2-pyridin-4-ylvinyl)pyridin-3-yloxy]-1-methylethyl}methylamine) is the lead compound of a novel series that do not display the traditional nicotinic-like pyrrole-ring but still possessing high subnanomolar affinity (Ki 0.077 nm—displacement of [3H](–)cytisine from whole rat brain synaptic membranes). In the present study, p-PVP-MEMA and its nor-derivative ({(R)-2-[6-chloro-5-((E)-2-pyridin-4-ylvinyl)pyridin-3-yloxy]-1-methylethyl}methylamine) as precursor for labelling with the short-lived positron-emitter carbon-11 (T1/2 20.4 min) were synthesized in 10 chemical steps from 2-hydroxy-5-nitropyridine and Boc-d-alanine. N-Alkylation of nor-p-PVP-MEMA with [11C]methyl iodide afforded [11C]p-PVP-MEMA (>98% radiochemically pure, specific activity of 86.4 GBq μmol–1) in 2% (non-decay corrected and non-optimized) radiochemical yield, in 34 min (including HPLC purification and formulation). Preliminary positron emission tomography (PET) results obtained in a Papio hamadryas baboon showed that [11C]p-PVP-MEMA is not a suitable PET-radioligand.
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Carroll FI, Robinson TP, Brieaddy LE, Atkinson RN, Mascarella SW, Damaj MI, Martin BR, Navarro HA. Synthesis and Nicotinic Acetylcholine Receptor Binding Properties of Bridged and Fused Ring Analogues of Epibatidine. J Med Chem 2007; 50:6383-91. [DOI: 10.1021/jm0704696] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- F. Ivy Carroll
- Organic and Medicinal Chemistry, Research Triangle Institute, Research Triangle Park, North Carolina 27709, and Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, Virginia 23298
| | - T. Philip Robinson
- Organic and Medicinal Chemistry, Research Triangle Institute, Research Triangle Park, North Carolina 27709, and Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, Virginia 23298
| | - Lawrence E. Brieaddy
- Organic and Medicinal Chemistry, Research Triangle Institute, Research Triangle Park, North Carolina 27709, and Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, Virginia 23298
| | - Robert N. Atkinson
- Organic and Medicinal Chemistry, Research Triangle Institute, Research Triangle Park, North Carolina 27709, and Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, Virginia 23298
| | - S. Wayne Mascarella
- Organic and Medicinal Chemistry, Research Triangle Institute, Research Triangle Park, North Carolina 27709, and Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, Virginia 23298
| | - M. Imad Damaj
- Organic and Medicinal Chemistry, Research Triangle Institute, Research Triangle Park, North Carolina 27709, and Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, Virginia 23298
| | - Billy R. Martin
- Organic and Medicinal Chemistry, Research Triangle Institute, Research Triangle Park, North Carolina 27709, and Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, Virginia 23298
| | - Hernán A. Navarro
- Organic and Medicinal Chemistry, Research Triangle Institute, Research Triangle Park, North Carolina 27709, and Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, Virginia 23298
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Romanelli MN, Gratteri P, Guandalini L, Martini E, Bonaccini C, Gualtieri F. Central Nicotinic Receptors: Structure, Function, Ligands, and Therapeutic Potential. ChemMedChem 2007; 2:746-67. [PMID: 17295372 DOI: 10.1002/cmdc.200600207] [Citation(s) in RCA: 145] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The growing interest in nicotinic receptors, because of their wide expression in neuronal and non-neuronal tissues and their involvement in several important CNS pathologies, has stimulated the synthesis of a high number of ligands able to modulate their function. These membrane proteins appear to be highly heterogeneous, and still only incomplete information is available on their structure, subunit composition, and stoichiometry. This is due to the lack of selective ligands to study the role of nAChR under physiological or pathological conditions; so far, only compounds showing selectivity between alpha4beta2 and alpha7 receptors have been obtained. The nicotinic receptor ligands have been designed starting from lead compounds from natural sources such as nicotine, cytisine, or epibatidine, and, more recently, through the high-throughput screening of chemical libraries. This review focuses on the structure of the new agonists, antagonists, and allosteric ligands of nicotinic receptors, it highlights the current knowledge on the binding site models as a molecular modeling approach to design new compounds, and it discusses the nAChR modulators which have entered clinical trials.
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Affiliation(s)
- M Novella Romanelli
- Laboratory of Design, Synthesis, and Study of Biologically Active Heterocycles (HeteroBioLab), Department of Pharmaceutical Sciences, University of Florence, via Ugo Schiff 6, 50019 Sesto Fiorentino, Italy.
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15
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Dallanoce C, Bazza P, Grazioso G, De Amici M, Gotti C, Riganti L, Clementi F, De Micheli C. Synthesis of Epibatidine-Related Δ2-Isoxazoline Derivatives and Evaluation of Their Binding Affinity at Neuronal Nicotinic Acetylcholine Receptors. European J Org Chem 2006. [DOI: 10.1002/ejoc.200600231] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Lee JH, Lim Y, Wiederhold BK, Graham SJ. A Functional Magnetic Resonance Imaging (fMRI) Study of Cue-Induced Smoking Craving in Virtual Environments. Appl Psychophysiol Biofeedback 2005; 30:195-204. [PMID: 16167185 DOI: 10.1007/s10484-005-6377-z] [Citation(s) in RCA: 98] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Smokers who are exposed to smoking-related cues show cardiovascular reactivity and smoking craving compared with their responses to neutral cues, and increased cue reactivity predicts decreased likelihood of successful cessation. Several brain imaging studies suggested four candidate brain regions that might differ in gray matter volumes and densities between smokers and nonsmokers. However, in these studies, smokers were only exposed to smoking-related objects. In our pilot study utilizing a virtual reality (VR) technique, virtual environments (VEs) were more immersive and evoked smoking craving more effectively than traditionally used methods. In this study, we sought to test whether smokers could experience cue-induced smoking craving inside the MRI scanner by using the VR system. The smoking cue reactivity scenario was based in part on our preliminary task and consisted of 2D and 3D (or VE) conditions. The group mean of participants had increased activity in the prefrontal cortex (PFC), left anterior cingulate gyrus (ACC), left supplementary motor area, left uncus, right inferior temporal gyrus, right lingual gyrus, and right precuneus in the 2D condition. Areas of differential activation in the 3D condition were as follows: left superior temporal gyrus, right superior frontal gyrus, and left inferior occipital gyrus in the 3D condition. This finding is consistent with those of previous studies of nicotine craving showing PFC and ACC activation. However, in the 3D condition, the PFC including the superior frontal gyrus as well as the superior temporal gyrus, inferior occipital gyrus, and cerebellum were activated. Therefore, in the 3D condition, participants seemed to have more attention, visual balance, and coordinating movement than in the 2D condition.
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Affiliation(s)
- Jang-Han Lee
- Department of Psychology, Chung-Ang University, Seoul, Korea
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17
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Deuther-Conrad W, Patt JT, Feuerbach D, Wegner F, Brust P, Steinbach J. Norchloro-fluoro-homoepibatidine: specificity to neuronal nicotinic acetylcholine receptor subtypes in vitro. ACTA ACUST UNITED AC 2005; 59:785-92. [PMID: 15474055 DOI: 10.1016/j.farmac.2004.07.004] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2004] [Accepted: 07/03/2004] [Indexed: 10/26/2022]
Abstract
The subtype-specificity of newly synthesised epibatidine-related compounds, norchloro-fluoro-homoepibatidine (NCFHEB) and derivatives, to neuronal nicotinic acetylcholine receptors (nAChR) has been investigated. NCFHEBs were assayed in competitive binding assays to (+/-)-[(3)H]epibatidine-labelled rat thalamic nAChRs and human alpha4beta2, alpha3beta4, and alpha7 nAChRs, expressed in stably transfected HEK-293 and SH-SY5Y cells. The binding affinity of (+)-NCFHEB (K(i): 0.064 nM) and (-)-NCFHEB (K(i): 0.112 nM) to human alpha4beta2 nAChR is in the same order of magnitude as that of epibatidine (K(i): 0.014 nM). However, because the affinity of both NCFHEB-enantiomers to human alpha3beta4 nAChR is up to 65 times lower than that of epibatidine, the alpha4beta2 subtype-specificity of NCFHEB is increased up to 1,400% compared to epibatidine.
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Affiliation(s)
- Winnie Deuther-Conrad
- Institute of Interdisciplinary Isotope Research, Permoserstrasse 15, D-04318, Leipzig, Germany.
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18
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Abstract
Over the last 20 years a number of radiotracers that target various neurotransmitter systems have been developed for use in imaging studies in psychiatry, but there are many more targets still to be investigated. The development of a radiotracer for clinical positron emission tomography (PET) or single photon emission computed tomography (SPECT) neuroimaging studies can be a complex and lengthy process with few imaging agents successfully progressing into clinical human studies. One of the most challenging aspects in the procedure is the development of a rapid and simple radiosynthesis protocol to obtain the potential radiotracer with adequate specific activity, isolated radiochemical yield and radiochemical purity for human imaging. Once a candidate has been radiolabelled, full characterization of the radiotracer is required before it can be used in clinical human studies. Pre-clinical studies include investigation into the binding distribution, pharmacokinetics, metabolism, toxicology and dosimetry of a radiotracer. There are many points during the development procedure where a potential radiotracer can be rejected. Due to interspecies differences the development of a radiotracer can either go too far with an unsuccessful candidate or can potentially lead to rejection of a candidate too soon. It is only when the radiotracer has been used in humans can we be certain that a radiotracer is a useful imaging agent for clinical research studies. The development of new technologies, such as micro-PET or SPECT can only improve our ability to predict the success of a radiotracer.
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Affiliation(s)
- Sally L Pimlott
- West of Scotland Radionuclide Dispensary, North Glasgow University Hospitals NHS Trust, Western Infirmary, Dumbarton Rd, Glasgow, G11 6NT, UK.
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19
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Gurwitz D. The therapeutic potential of nicotine and nicotinic agonists for weight control. Expert Opin Investig Drugs 2005; 8:747-60. [PMID: 15992128 DOI: 10.1517/13543784.8.6.747] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Transdermal nicotine patches have been successfully introduced as a safe and powerful aid to smoking cessation; this has contributed to the rising interest in additional therapeutic applications for nicotine and synthetic nicotinic agonists. Nicotine and nicotinic agonists may have a therapeutic potential for a variety of disorders, including Alzheimer's and Parkinson's diseases, depression, attention deficit disorder, Tourette's syndrome and ulcerative colitis. These interests are partially fuelled by the urgent need of the tobacco industry to find new niches for nicotine in a world bound eventually to retire from cigarette smoking. At the same time, there is an increased interest in developing drugs for fighting obesity, a growing affliction of industrialised nations. This review presents data on the potential of nicotine, and in particular synthetic nicotinic agonists, for controlling body weight. Nicotinic agonists may become relatively safe, effective and inexpensive alternatives for several optional drugs currently being developed for treating human obesity, including beta-3-adrenergic agonists, leptin and its agonists, and neuropeptide Y antagonists.
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Affiliation(s)
- D Gurwitz
- National Laboratory for the Genetics of Israeli Populations, Sackler Faculty of Medicine, Tel-Aviv University, Tel-Aviv 69978, Israel.
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20
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Zhang Y, Pavlova OA, Chefer SI, Hall AW, Kurian V, Brown LL, Kimes AS, Mukhin AG, Horti AG. 5-substituted derivatives of 6-halogeno-3-((2-(S)-azetidinyl)methoxy)pyridine and 6-halogeno-3-((2-(S)-pyrrolidinyl)methoxy)pyridine with low picomolar affinity for alpha4beta2 nicotinic acetylcholine receptor and wide range of lipophilicity: potential probes for imaging with positron emission tomography. J Med Chem 2004; 47:2453-65. [PMID: 15115389 DOI: 10.1021/jm030432v] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Potential positron emission tomography (PET) ligands with low picomolar affinity at the nicotinic acetylcholine receptor (nAChR) and with lipophilicity (log D) ranging from -1.6 to +1.5 have been synthesized. Most members of the series, which are derivatives of 5-substituted-6-halogeno-A-85380, exhibited a higher binding affinity at alpha4beta2-nAChRs than epibatidine. An analysis, by molecular modeling, revealed an important role of the orientation of the additional heterocyclic ring on the binding affinity of the ligands with nAChRs. The existing nicotinic pharmacophore models do not accommodate this finding. Two compounds of the series, 6-[(18)F]fluoro-5-(pyridin-3-yl)-A-85380 ([(18)F]31) and 6-chloro-3-((2-(S)-azetidinyl)methoxy)-5-(2-[(18)F]fluoropyridin-5-yl)pyridine) ([(18)F]35), were radiolabeled with (18)F. Comparison of PET data for [(18)F]31 and 2-[(18)F]FA shows the influence of lipophilicity on the binding potential. Our recent PET studies with [(18)F]35 demonstrated that its binding potential values in Rhesus monkey brain were ca. 2.5 times those of 2-[(18)F]FA. Therefore, [(18)F]35 and several other members of the series, when radiolabeled, will be suitable for quantitative imaging of extrathalamic nAChRs.
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Affiliation(s)
- Yi Zhang
- Neuroimaging Research Branch, Intramural Research Program, National Institute on Drug Abuse, NIH, DHHS, 5500 Nathan Shock Drive, Baltimore, Maryland 21224, USA
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21
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Tsukada H, Nishiyama S, Fukumoto D, Ohba H, Sato K, Kakiuchi T. Effects of acute acetylcholinesterase inhibition on the cerebral cholinergic neuronal system and cognitive function: Functional imaging of the conscious monkey brain using animal PET in combination with microdialysis. Synapse 2004; 52:1-10. [PMID: 14755627 DOI: 10.1002/syn.10310] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
This study demonstrated the effects of acute acetylcholinesterase (AChE) inhibition by donepezil (Aricept) on the cerebral cholinergic neuronal system in the brains of young (5.2 +/- 1.1 years old) and aged (20.3 +/- 2.6 years old) monkeys (Macaca mulatta) in the conscious state. Donepezil at doses of 50 and 250 microg/kg suppressed AChE activity, analyzed by metabolic rate (k(3)) of N-[(11)C]methyl-4-piperidyl acetate ([(11)C]MP4A), in all cortical regions in a dose-dependent manner in both age groups. However, the suppression degree was more marked in young than in aged monkeys. AChE inhibition by donepezil resulted in a dose-dependent increase in acetylcholine levels in the prefrontal cortex of young animals as measured by microdialysis. Binding of (+)N-[(11)C]propyl-3-piperidyl benzilate ([(11)C](+)3-PPB) to cortical muscarinic receptors was reduced by donepezil, probably in a competitive inhibition manner. Aged monkeys showed less reduction of [(11)C](+)3-PPB binding than young animals. As evaluated by an oculomotor delayed response task, aged monkeys showed impaired working memory performance compared to young monkeys, and the impaired performance was partly improved by the administration of donepezil, due to the facilitation of the cholinergic neuronal system by AChE inhibition. These results demonstrate that the PET imaging technique with specific labeled compounds in combination with microdialysis and a behavioral cognition task could be a useful method to clarify the mechanism of drugs in the living brains of experimental animals.
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Affiliation(s)
- Hideo Tsukada
- Central Research Laboratory, Hamamatsu Photonics K. K., Hamakita, Shizuoka 434-8601, Japan.
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22
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Rouden J, Seitz T, Lemoucheux L, Lasne MC. Studies toward Labeling Cytisine with [11C]Phosgene: Rapid Synthesis of a δ-Lactam Involving a New Chemoselective Lithiation−Annulation Method. J Org Chem 2004; 69:3787-93. [PMID: 15153010 DOI: 10.1021/jo0498157] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
With the aim of the radiolabeling of cytisine, a potent agonist of nicotinic receptors, with [(11)C]phosgene, the rapid synthesis of a lactam model of our target has been studied. The key step of the delta-lactam formation is a new chemoselective lithiation-annulation method, under high dilution, of a suitable piperidinylcarbamoyl chloride. This precursor was obtained from (2-hydroxyethyl)piperidine in a linear synthetic sequence involving a Corey-Fuchs olefination of the corresponding aldehyde, followed by a selective reduction, using a diimide equivalent, of an iodoalkyne into a (Z)-iodopropene piperidine. This alkene served as main precursor to study the cyclization according to several procedures using phosgene as the required carbonylating reagent.
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Affiliation(s)
- Jacques Rouden
- Laboratoire de Chimie Moléculaire et Thio-organique, CNRS UMR 6507, ENSICAEN, Université de Caen-Basse Normandie, 6 Boulevard du Maréchal Juin, F14050 Cannes Cedex, France.
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23
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Carroll FI. Epibatidine structure–activity relationships. Bioorg Med Chem Lett 2004; 14:1889-96. [PMID: 15050621 DOI: 10.1016/j.bmcl.2004.02.007] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2003] [Revised: 02/03/2004] [Accepted: 02/03/2004] [Indexed: 10/26/2022]
Abstract
Epibatidine is a potent but nonselective nAChR agonist. Its biological effects appear to be mediated largely by alpha4beta2 nAChRs. Surprisingly, only a limited number of epibatidine analogues have been synthesized and evaluated in in vitro assays. Even fewer analogues have received in vivo pharmacological evaluation. In this paper, SAR studies directed toward epibatidine analogues will be reviewed.
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Affiliation(s)
- F Ivy Carroll
- Organic and Medicinal Chemistry, Research Triangle Institute, Research Triangle Park, NC 27709, USA.
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24
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Wei ZL, Xiao Y, Kellar KJ, Kozikowski AP. Synthesis and pharmacological characterization of bivalent ligands of epibatidine at neuronal nicotinic acetylcholine receptors. Bioorg Med Chem Lett 2004; 14:1855-8. [PMID: 15050615 DOI: 10.1016/j.bmcl.2003.10.071] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/13/2003] [Indexed: 11/23/2022]
Abstract
A series of bivalent ligands 6a-d of epibatidine were synthesized. All four ligands showed nanomolar binding affinities at six neuronal nicotinic acetylcholine receptor (nAChR) subtypes in competition binding assays. In contrast to epibatidine, these bivalent ligands are weak partial agonists at the alpha3beta4 nAChR as shown by functional assays.
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Affiliation(s)
- Zhi-Liang Wei
- Department of Medicinal Chemistry and Pharmacognosy, College of Pharmacy, University of Illinois at Chicago, 833 S. Wood Street, Chicago, IL 60612, USA
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25
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Brody AL, Mandelkern MA, Jarvik ME, Lee GS, Smith EC, Huang JC, Bota RG, Bartzokis G, London ED. Differences between smokers and nonsmokers in regional gray matter volumes and densities. Biol Psychiatry 2004; 55:77-84. [PMID: 14706428 DOI: 10.1016/s0006-3223(03)00610-3] [Citation(s) in RCA: 307] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
BACKGROUND Magnetic resonance imaging (MRI) studies have demonstrated large-scale brain abnormalities in cigarette smokers, such as ventricular enlargement and atrophy. Converging lines of evidence point to functional differences between smokers and nonsmokers in specific brain regions, namely the lateral prefrontal cortex (PFC), anterior cingulate cortex (ACC), ventral striatum, and thalamus. Using MRI, we examined these regions for differences in gray matter between smokers and nonsmokers. METHODS Thirty-six otherwise healthy adults (19 smokers and 17 nonsmoking control subjects) underwent three-dimensional Fourier-transform spoiled-gradient-recalled acquisition MRI of the brain. Both hand-drawn regions of interest and the computer program voxel-based morphometry were used to assess group differences in regional gray matter volumes and densities, respectively. RESULTS Smokers had smaller gray matter volumes and lower gray matter densities than nonsmokers in the PFC bilaterally, along with smaller volumes in the left dorsal ACC and lower gray matter densities in the right cerebellum. Smokers also had negative associations between pack-year smoking history and PFC gray matter densities. CONCLUSIONS Smokers and nonsmokers differed in regional gray matter in brain areas previously linked with nicotine dependence. These findings might reflect effects of chronic smoking, predisposing traits that lead to smoking, or some combination of these factors.
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Affiliation(s)
- Arthur L Brody
- Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, California 90095, USA
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26
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Glennon RA. 2. Medicinal chemistry of alpha4beta2 nicotinic cholinergic receptor ligands. PROGRESS IN MEDICINAL CHEMISTRY 2004; 42:55-123. [PMID: 15003719 DOI: 10.1016/s0079-6468(04)42002-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/29/2023]
Affiliation(s)
- Richard A Glennon
- Department of Medicinal Chemistry, School of Pharmacy, Virginia Commonwealth University, Box 581 MCV Station, Richmond, VA 23298, USA
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27
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Abstract
Epibatidine is a natural product that was isolated and identified by Daly and coworkers in 1992. Since that time, it has had a profound influence on the investigation of alpha4beta2 nicotinic cholinergic (nACh) receptor pharmacophore models, and has inspired the development of novel agents with therapeutic potential in CNS disorders. Apart from acetylcholine and nicotine, probably no other agent has had as much recent impact on nACh research as has epibatidine.
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Affiliation(s)
- Małgorzata Dukat
- Department of Medicinal Chemistry, School of Pharmacy, Virginia Commonwealth University, Richmond, Virginia 23298, USA
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28
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Gohlke H, Schwarz S, Gündisch D, Tilotta MC, Weber A, Wegge T, Seitz G. 3D QSAR analyses-guided rational design of novel ligands for the (alpha4)2(beta2)3 nicotinic acetylcholine receptor. J Med Chem 2003; 46:2031-48. [PMID: 12747776 DOI: 10.1021/jm020859m] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Three-dimensional quantitative structure-activity relationship methods, the comparative molecular field analysis (CoMFA) and the comparative molecular similarity indices analysis (CoMSIA), were applied using a training set of 45 ligands of the (alpha4)2(beta2)3 nicotinic acetylcholine receptor (nAChR). All compounds are related to (-)-epibatidine, (-)-cytisine, (+)-anatoxin-a, and (-)-ferruginine, and additionally, novel diazabicyclo[4.2.1]nonane- and quinuclidin-2-ene-based structures were included. Their biological data have been determined by utilizing the same experimental protocol. Statistically reliable models of good predictive power (CoMFA r2 = 0.928, q2 = 0.692, no. of components = 3; CoMSIA r2 = 0.899, q2 = 0.701, no. of components = 3) were achieved. The results obtained were graphically interpreted in terms of field contribution maps. Hence, physicochemical determinants of binding, such as steric and electrostatic and, for the first time, hydrophobic, hydrogen bond donor, and hydrogen bond acceptor properties, were mapped back onto the molecular structures of a set of nAChR modulators. In particular, changes in the binding affinity of the modulators as a result of modifications in the aromatic ring systems could be rationalized by the steric, electrostatic, hydrophobic, and hydrogen bond acceptor properties. These results were used to guide the rational design of new nAChR ligands such as 48-52 and 54, which were subsequently synthesized for the first time and tested. Key steps of our synthetic approaches were successfully applied Stille and Suzuki cross-coupling reactions. Predictive r2 values of 0.614 and 0.660 for CoMFA and CoMSIA, respectively, obtained for 22 in part previously unknown ligands for the (alpha4)2(beta2)3 subtype, demonstrate the high quality of the 3D QSAR models.
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Affiliation(s)
- Holger Gohlke
- Institut für Pharmazeutische Chemie der Philipps-Universität Marburg, Marbacher Weg 6, D-35032 Marburg, Germany.
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29
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Kassiou M, Loc'h C, Dolle F, Musachio JL, Dolci L, Crouzel C, Dannals RF, Mazière B. Preparation of a bromine-76 labelled analogue of epibatidine: a potent ligand for nicotinic acetylcholine receptor studies. Appl Radiat Isot 2002; 57:713-7. [PMID: 12433046 DOI: 10.1016/s0969-8043(02)00187-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Epibatidine analogues have been labelled with I-123 for single photon emission computed tomography and with short half-life positron emitters (C-11 and F-18) for PET. For easier radiopharmacological studies the bromo analogue of epibatidine (norchlorobromoepibatidine or exo-7-azabicyclo-2-(2-bromo-5-pyridyl)-[2.2.1]heptane) was labelled with Br-76, a longer half-life positron emitter, (T1/2 = 16.2h). [76Br]-norchlorobromoepibatidine was prepared by using a Cu+ assisted bromodeiodination exchange from the iodo analogue in reducing conditions at 190 degrees C. The tracer purified by RP-HPLC was obtained in 70% radiochemical yield with a specific radioactivity of 20 GBq/micromol. Radiochemical and chemical purities measured by radio-TLC and HPLC were >98%.
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Affiliation(s)
- M Kassiou
- Department of PET and Nuclear Medicine, Royal Prince Alfred Hospital, Camperdown, NSW, Australia.
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30
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Avalos M, Parker MJ, Maddox FN, Carroll FI, Luetje CW. Effects of pyridine ring substitutions on affinity, efficacy, and subtype selectivity of neuronal nicotinic receptor agonist epibatidine. J Pharmacol Exp Ther 2002; 302:1246-52. [PMID: 12183686 DOI: 10.1124/jpet.102.035899] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
2'-Pyridine ring substituted analogs of epibatidine were assessed for equilibrium binding affinity, functional potency, and efficacy at rat neuronal nicotinic receptors expressed in Xenopus oocytes. Binding affinities were determined in membrane homogenates from oocytes expressing alpha2beta2, alpha2beta4, alpha3beta2, alpha3beta4, alpha4beta2, or alpha4beta4. Efficacy (relative to acetylcholine) and potency were measured electrophysiologically with oocytes expressing alpha3beta4, alpha4beta2, and alpha4beta4. Hydroxy, dimethylamino, and trifluoromethanesulfonate analogs had affinities too low for accurate measurement. The bromo analog had affinities 4- to 55-fold greater at beta2 than at beta4-containing receptors, modestly greater efficacy at alpha4beta4 than at alpha4beta2, and 5- to 10-fold greater potency at a4beta4 than at alpha3beta4 or alpha4beta2. The fluoro analog displayed affinities 52- to 875-fold greater at beta2- than at beta4-containing receptors, efficacy at alpha4beta4 receptors 3-fold greater than at alpha4beta2 and alpha3beta4, and was equipotent at all receptors tested. The norchloro analog showed affinities 114- to 3500-fold greater at beta2- than at beta4-containing receptors, 2-fold greater efficacy at alpha4beta2 and alpha4beta4 than at alpha3beta4, and 4- to 5-fold greater potency at alpha4beta4 and alpha3beta4 than at alpha4beta2. The amino analog displayed affinities 10- to 115-fold greater at beta2- than at beta4-containing receptors, 3-fold greater efficacy at alpha3beta4 than at alpha4beta2, and 2- to 4-fold greater potency at alpha3beta4 and alpha4beta4 than at alpha4beta2. Although these compounds displayed a variety of differences in affinity, efficacy, and potency, with one exception (binding affinity and functional potency at alpha4beta4 receptors) there were no significant correlations among these properties.
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Affiliation(s)
- Melva Avalos
- Department of Molecular and Cellular Pharmacology, University of Miami School of Medicine, Miami, FL 33101, USA
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31
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Kassiou M, Bottlaender M, Loc'h C, Dolle F, Musachio JL, Coulon C, Ottaviani M, Dannals RF, Maziere B. Pharmacological evaluation of a Br-76 analog of epibatidine: a potent ligand for studying brain nicotinic acetylcholine receptors. Synapse 2002; 45:95-104. [PMID: 12112402 DOI: 10.1002/syn.10087] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
[(76)Br]-Norchlorobromoepibatidine ([(76)Br]BrPH) is a specific and high affinity radioligand for the nicotinic acetylcholine receptors (nAChRs). In vitro, on rat thalamus membranes [(76)Br]BrPH bound to two sites with apparent affinities of 8 pM and 3 nM. The density of binding sites were 1.9 and 70 fmol/mg protein, respectively. In vivo, in biodistribution and autoradiographic studies in rats the regional distribution of [(76)Br]BrPH paralleled the neuroanatomical localization of nAChRs. Two hours postinjection, the highest concentration in the brain was found in thalamus and colliculi (4% ID/g). Competition experiments with specific nicotinic, muscarinic, dopaminergic, and serotoninergic drugs confirmed that the in vivo binding of [(76)Br]BrPH was consistent with neuronal nicotinic receptors. PET imaging of [(76)Br]BrPH in baboon demonstrated a rapid and high uptake in the brain. Peak uptake occurred at 30-40 min for the thalamus. Due to the constant washout in the cerebellum, the thalamus to cerebellum ratio was 5 at 2 h postinjection. Subcutaneous injection of cytisine (1 mg/kg), 3 h postinjection of [(76)Br]BrPH reduced the radioactivity concentration in thalamus and cortex by 58 and 50%, respectively, as observed 1 h later. Cytisine pretreatment (5 mg/kg s.c.) inhibited completely the radioligand accumulation in the thalamus. Chronic MPTP pretreatment resulted in reduction of [(76)Br]BrPH uptake in all brain regions except in cerebellum. These preliminary results suggest that [(76)Br]BrPH has the potential to be a useful radioligand for studying the pharmacology of nicotinic acetylcholine receptors in preclinical experiments.
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MESH Headings
- 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine/metabolism
- 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine/pharmacology
- Alkaloids/pharmacology
- Animals
- Autoradiography
- Azocines
- Brain/diagnostic imaging
- Brain/metabolism
- Bridged Bicyclo Compounds, Heterocyclic/pharmacokinetics
- Dopamine Agents/pharmacology
- Ellipticines/pharmacokinetics
- In Vitro Techniques
- Male
- Nicotine/antagonists & inhibitors
- Nicotinic Agonists/metabolism
- Nicotinic Agonists/pharmacokinetics
- Pyridines/pharmacokinetics
- Quinolizines
- Radioligand Assay
- Rats
- Rats, Wistar
- Receptors, Nicotinic/metabolism
- Time Factors
- Tomography, Emission-Computed
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Affiliation(s)
- Michael Kassiou
- Department of PET and Nuclear Medicine, Royal Prince Alfred Hospital, Camperdown NSW 2050 Australia.
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32
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Brown LL, Kulkarni S, Pavlova OA, Koren AO, Mukhin AG, Newman AH, Horti AG. Synthesis and evaluation of a novel series of 2-chloro-5-((1-methyl-2-(S)-pyrrolidinyl)methoxy)-3-(2-(4-pyridinyl)vinyl)pyridine analogues as potential positron emission tomography imaging agents for nicotinic acetylcholine receptors. J Med Chem 2002; 45:2841-9. [PMID: 12061886 DOI: 10.1021/jm010550n] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Reportedly, 2-[(18)F]fluoro-A-85380, 1, a promising radiotracer for imaging the nicotinic acetylcholine receptor (nAChR) by positron emission tomography (PET) in humans, exhibits slow penetration through the blood-brain barrier (BBB) due to its low lipophilicity. A ligand for nAChRs with greater lipophilicity than that of 1 would be potentially more favorable for PET imaging of nAChR due to its faster penetration through the BBB. Herein, a novel series of compounds has been developed based on the high affinity ligand for nAChRs, 2-chloro-5-((1-methyl-2-(S)-pyrrolidinyl)methoxy)-3-(2-(4-pyridinyl)vinyl)pyridine, 3b. The in vitro binding affinities for the new series were found to be in the range of K(i) = 9-331 pM. A molecular modeling study showed differences in the comformational profiles and the electronic properties of these compounds, which provides further insight into the structure-activity relationships at nAChR. Lipophilicities of the compounds 3b-6b have been found to be substantially higher than that of 1. As a result, compounds 3b-6b might exhibit a faster penetration through the BBB than the less lipophilic 1. The N-methyl derivatives 3b and 6b demonstrated very high affinities at nAChRs (K(i) = 28 and 23 pM, respectively) and will be targets for development of (11)CH(3)-labeled derivatives as radiotracers for PET imaging of nAChRs.
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Affiliation(s)
- LaVerne L Brown
- Neuroimaging Research Branch and Medicinal Chemistry Section, Intramural Research Program, National Institute on Drug Abuse, 5500 Nathan Shock Drive, Baltimore, MD 21224, USA
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Saji H, Ogawa M, Ueda M, Iida Y, Magata Y, Tominaga A, Kawashima H, Kitamura Y, Nakagawa M, Kiyono Y, Mukai T. Evaluation of radioiodinated 5-iodo-3-(2(S)-azetidinylmethoxy)pyridine as a ligand for SPECT investigations of brain nicotinic acetylcholine receptors. Ann Nucl Med 2002; 16:189-200. [PMID: 12126044 DOI: 10.1007/bf02996300] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
5-Iodo-3-(2(S)-azetidinylmethoxy)pyridine (5IA), an A-85380 analog iodinated at the 5-position of the pyridine ring, was evaluated as a radiopharmaceutical for investigating brain nicotinic acethylcholine receptors (nAChRs) by single photon emission computed tomography (SPECT). [123/125I]5IA was synthesized by the iododestannylation reaction under no-carrier-added conditions and purified by high-performance liquid chromatography (HPLC) with high radiochemical yield (50%), high radiochemical purity (> 98%), and high specific radioactivity (> 55 GBq/micromol). The binding affinity of 5IA for brain nAChRs was measured in terms of displacement of [3H]cytisine and [125I]5IA from binding sites in rat cortical membranes. The binding data revealed that the affinity of 5IA was the same as that of A-85380 and more than seven fold higher than that of (-)-nicotine, and that 5IA bound selectively to the alpha4beta2 nAChR subtype. Biodistribution studies in rats indicated that the brain uptake of [125I]51A was rapid and profound. Regional cerebral distribution studies in rats demonstrated that the accumulation of [125I]5IA was consistent with the density of high affinity nAChRs with highest uptake observed in the nAChR-rich thalamus, moderate uptake in the cortex and lowest uptake in the cerebellum. Administration of the nAChR agonists (-)-cytisine and (-)-nicotine reduced the uptake of [125I]5IA in all regions studied with most pronounced reduction in the thalamus, and resulted in similar levels of radioactivity throughout the brain. [125I]5IA binding sites were shown to be saturable with unlabeled 5IA. Behavioral studies in mice demonstrated that 5IA did not show signs of behavioral toxicity. Furthermore, SPECT studies with [123I]5IA in the common marmoset demonstrated appropriate brain uptake and regional localization for a high-affinity nAChR imaging radiopharmaceutical. These results suggested that [123I]5IA is a promising radiopharmaceutical for SPECT studies of central nAChRs in human subjects.
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Affiliation(s)
- Hideo Saji
- Graduate School of Pharmaceutical Sciences, Kyoto University, Japan.
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Brown LL, Pavlova O, Mukhin A, Kimes AS, Horti AG. Radiosynthesis of 5-(2-(4-pyridinyl)vinyl)-6-chloro-3-(1-[(11)C]methyl-2-(S)-pyrrolidinylmethoxy)pyridine, a high affinity ligand for studying nicotinic acetylcholine receptors by positron emission tomography. Bioorg Med Chem 2001; 9:3055-8. [PMID: 11597489 DOI: 10.1016/s0968-0896(01)00224-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
5-(2-(4-pyridinyl)vinyl)-6-chloro-3-(1-methyl-2-(S)-pyrrolidinylmethoxy)pyridine (1b) exhibited high affinity for nicotinic acetylcholine receptors in the in vitro competition binding assays, with a K(d) value in the low picomolar range, performed at room temperature and at physiological temperature. An efficient radiochemical synthesis of 5-(2-(4-pyridinyl)vinyl)-6-chloro-3-(1-[(11)C]methyl-2-(S)-pyrrolidinylmethoxy)pyridine (1c), a potential tracer for the study of nAChR by positron emission tomography, has been developed.
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Affiliation(s)
- L L Brown
- Brain Imaging Center, National Institute on Drug Abuse, National Institutes of Health, 5500 Nathan Shock Drive, Baltimore, MD 21224, USA.
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35
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Patt JT, Spang JE, Buck A, Cristina H, Arras M, Schubiger PA, Westera G. Synthesis and in vivo studies of the stereoisomers of N-[11C]methyl-homoepibatidine. Nucl Med Biol 2001; 28:645-55. [PMID: 11518646 DOI: 10.1016/s0969-8051(01)00225-6] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The carbon-11 labeled enantiomers of nicotinic acetylcholine receptor (nAChR) ligand N-[11C]methyl-homoepibatidine have been synthesized to study the neuronal nicotinic acetylcholine receptors (nAChRs). In vivo evaluations were performed in mice and pig using positron emission tomography (PET). The radioligands displayed a strong enantioselectivity. The (-)-enantiomer showed high uptake in the brain while the (+)-enantiomer was rapidly washed out. In metabolite studies in mice >65% unchanged ligand was found in the blood after 60 minutes. No metabolites were found in the brain. After intravenous application of N-[11C]methyl-(-)-homoepibatidine in the pig specific accumulation in the thalamus was seen. Blocking experiments with cytisine showed specific binding consistent with labeling of the alpha4beta2-nAChR-subtype in the brain. Quantitative kinetic modeling of radiotracers in the pig brain was performed using the arterial input function. The brain uptake of the (-)-isomer was best fitted by a three-compartment model. High distribution volumes were found in the thalamus (DV(TOT) = 66.617, DV(S) = 59.910) versus a low uptake in the cerebellum (DV(TOT) = 8.605m, DV(S) = 1.898). The binding characteristics suggest N-[11C]methyl-(-)-homoepibatidine to be suited for PET imaging studies, but high toxicity prevents routine use in humans.
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Affiliation(s)
- J T Patt
- Center for Radiopharmaceutical Science, Swiss Federal Institute of Technology Zürich, Paul Scherrer Institute Villigen, University Hospital Zürich, CH-8091, Zürich, Switzerland
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Carroll FI, Liang F, Navarro HA, Brieaddy LE, Abraham P, Damaj MI, Martin BR. Synthesis, nicotinic acetylcholine receptor binding, and antinociceptive properties of 2-exo-2-(2'-substituted 5'-pyridinyl)-7-azabicyclo[2.2.1]heptanes. Epibatidine analogues. J Med Chem 2001; 44:2229-37. [PMID: 11405659 DOI: 10.1021/jm0100178] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A convenient, high-yield synthesis of 7-tert-butoxycarbonyl-7-azabicyclo[2.2.1]hept-2-ene (5), which involved the addition of tributyltin hydride to 7-tert-butoxycarbonyl-2-p-toluenesulfonyl-7-azabicyclo[2.2.1]hept-2-ene (4) followed by elimination of the tributyltin and p-tolylsulfonyl groups using tetrabutylammonium fluoride was developed. The addition of 2-amino-5-iodopyridine to 5 under reductive Heck conditions provided 7-tert-butoxycarbonyl-2-exo-(2'-amino-5'-pyridinyl)-7-azabicyclo[2.2.1]heptane (6). Compound 6 was the key intermediate used to prepare epibatidine analogues where the 2'-chloro group on the pyridine ring was replaced with a fluorine (1b), bromine (1c), iodine (1d), hydroxy (1e), amino (1f), dimethylamino (1g), trifluoromethanesulfonate (1h), and hydrogen (1i) group. (+)- and (-)-Epibatidine and compounds 1b-d and 1i all possess similar binding affinities at the alpha(4)beta(2) nAChR receptors labeled by [(3)H]epibatidine. Compound 1f has affinity similar to nicotine, whereas compounds 1e, 1g, and 1h have much lower affinity. The binding affinity appears to be dependent upon the electronic nature of the substituent. However, other factors are also involved. None of the compounds possesses appreciable affinity for the alpha(7) nAChR labeled by [(125)I]iodo-MLA. With the exception of 1f and 1g, all the epibatidine analogues are full agonists (tail flick test) in producing antinociception after intrathecal injection in mice.
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Affiliation(s)
- F I Carroll
- Chemistry and Life Sciences, Research Triangle Institute, P.O. Box 12194, Research Triangle Park, North Carolina 27709, USA.
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Pringle PG, Olsen H, Lemoucheux L, Rouden J, Lasne MC, Rayner CM, Antoni G, Björkman M, Kihlberg T, Ögren M, Långström B, Wiltshire HR, Buss N, Hill AM, Shipley N, Kingston LP, Lockley WJS, Mather AN, Thompson SP, Wilkinson DJ, Booth H, Dedinas RF, Harding JR, White DF. International Isotope Society. Abstracts of the XthI.I.S. (UK Group) Symposium. Current themes in Isotopic chemistry. J Labelled Comp Radiopharm 2001. [DOI: 10.1002/jlcr.459] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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Che D, Wegge T, Stubbs MT, Seitz G, Meier H, Methfessel C. exo-2-(Pyridazin-4-yl)-7-azabicyclo[2.2.1]heptanes: syntheses and nicotinic acetylcholine receptor agonist activity of potent pyridazine analogues of (+/-)-epibatidine. J Med Chem 2001; 44:47-57. [PMID: 11141087 DOI: 10.1021/jm000949w] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A new strategy for the straightforward synthesis of novel racemic epibatidine analogues is presented, in which the 2-chloropyridinyl moiety of epibatidine is bioisosterically replaced by differently substituted pyridazine rings. A key step of the new syntheses is the inverse type Diels-Alder reaction of the electron-rich enol ether 13 with the electron-deficient diazadiene systems of the 1,2,4, 5-tetrazines 14a-d to yield the novel pyridazine analogues of (+/-)-epibatidine 18, 19, 22, and 24. In addition preparation of the N-substituted derivatives, such as 26 and 28, is described. The structures of the novel epibatidine analogues were assigned on the basis of spectral data, that of compound 24 being additionally verified by X-ray crystallography exhibiting two racemic solid-state conformations in the crystal lattice and representing the first X-ray structure of an unprotected 7-azabicyclo[2.2.1]heptane moiety. The nAChR agonist activity of the racemic compounds 18, 19, 22, 24, and 28 was assayed in vitro by whole-cell current recordings from Xenopus oocytes expressing different recombinant nicotinic receptors from the rat. Among the compounds synthesized and tested, the pyridazine analogue 24 of (+/-)-epibatidine and its N-methyl derivative 28 were found to be the most active ones retaining much of the potency of natural epibatidine but with a substantially improved selectivity ratio between the alpha4beta2 and alpha3beta4 subtypes.
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Affiliation(s)
- D Che
- Institut für Pharmazeutische Chemie, Universität Marburg, Marbacher Weg 6, D-35032 Marburg/Lahn, Germany
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39
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Sihver W, Nordberg A, Långström B, Mukhin AG, Koren AO, Kimes AS, London ED. Development of ligands for in vivo imaging of cerebral nicotinic receptors. Behav Brain Res 2000; 113:143-57. [PMID: 10942041 DOI: 10.1016/s0166-4328(00)00209-6] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Nicotinic acetylcholine receptors (nAChRs) mediate a variety of brain functions. Findings from postmortem studies and clinical investigations have implicated them in the pathophysiology and treatment of Alzheimer's and Parkinson's diseases and other CNS disorders (e.g. Tourette's syndrome, epilepsy, nicotine dependence). Therefore, it ultimately might be useful to image nAChRs noninvasively for diagnosis, for studies on how changes in nAChRs might contribute to cerebral disorders, for development of therapies targeted at nAChRs, and to monitor the effects of such treatments. To date, only (S)-(-)-nicotine, radiolabeled with 11C, has been used for external imaging of nAChRs in human subjects. Since this radiotracer presents drawbacks, new ligands, with more favorable properties, have been synthesized and tested. Three general classes of compounds, namely, nicotine and its analogs, epibatidine and related compounds, and 3-pyridyl ether compounds, including A-85380, have been evaluated. Analogs of A-85380 appear to be the most promising candidates because of their low toxicity and high selectivity for the alpha4beta2 subtype of nAChRs.
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Affiliation(s)
- W Sihver
- Department of Medical Pharmacology, Karolinska Institute, Huddinge Hospital, Sweden.
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41
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Spang JE, Bertrand S, Westera G, Patt JT, Schubiger PA, Bertrand D. Chemical modification of epibatidine causes a switch from agonist to antagonist and modifies its selectivity for neuronal nicotinic acetylcholine receptors. CHEMISTRY & BIOLOGY 2000; 7:545-55. [PMID: 10903939 DOI: 10.1016/s1074-5521(00)00138-1] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
BACKGROUND Studies of ligand gated channels strongly rely on the availability of compounds that can activate or inhibit with high selectivity one set or a subset of defined receptors. The alkaloid epibatidine (EPB), originally isolated from the skin of an Ecuadorian poison frog, is a very specific agonist for the neuronal nicotinic acetylcholine receptors (nAChRs). We used EPB derivatives to investigate the pharmacophore of nAChR subtypes. RESULTS Optically pure enantiomers of EPB analogues were synthesised. Analogues were obtained altered in the aromatic part: the chlorine was eliminated and the relative position of the pyridyl nitrogen changed. Voltage clamp electrophysiology was performed with these compounds on neuronal nAChRs reconstituted in Xenopus oocytes. The EPB derivatives show different activities towards the various nAChR subtypes. CONCLUSIONS Small changes in the molecular structure of EPB produce marked changes in its capacity to activate the nAChRs. Subtype specificity can be obtained by changing the position of or by eliminating the pyridyl nitrogen.
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Affiliation(s)
- J E Spang
- Center for Radiopharmaceutical Science, Department of Radiology, Swiss Federal Institute of Technology Zürich, Clinic of Nuclear Medicine, University Hospital Zürich, Switzerland
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Marrière E, Rouden J, Tadino V, Lasne MC. Synthesis of analogues of (-)-cytisine for in vivo studies of nicotinic receptors using positron emission tomography. Org Lett 2000; 2:1121-4. [PMID: 10804569 DOI: 10.1021/ol005685m] [Citation(s) in RCA: 96] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
[formula: see text] 9-Substituted analogues of (-)-cytisine were synthesized in high yields via palladium-mediated couplings of either 9-(-)-bromocytisine and organostannanes or 9-(-)-trimethylstannylcytisine and fluorobromobenzene. The protection of the amine with a nitroso group and the use of PdCl2(PPh3)2 to carry out the Stille reaction allowed the rapid synthesis of 9-(4'-[18F]fluorophenyl)cytisine (18F: t1/2 = 109.7 min), a new promising radioligand (radiochemical yield: 10% from [18F]KF, 150 min, four steps) for positron emission tomography studies of alpha 4 beta 2 nicotinic receptors.
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Affiliation(s)
- E Marrière
- Laboratoire de Chimie Moléculaire et Thio-Organique, UMR CNRS 6507, Institut des Sciences de la Matière et du Rayonnement, Université de Caen-Basse-Normandie, Caen, France
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Spang JE, Patt JT, Westera G, Schubiger PA. Comparison of N-[(11)C]methyl-norchloroepibatidine and N-[(11)C]methyl-2-(2-pyridyl)-7-azabicyclo[2.2.1]heptane with N-[(11)C]methyl-epibatidine in small animal PET studies. Nucl Med Biol 2000; 27:239-47. [PMID: 10832080 DOI: 10.1016/s0969-8051(00)00080-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Structural variations of the nicotinic acetylcholine receptor radioligand N-[(11)C]methyl-epibatidine were made to form (11)C-labeled N-methyl-norchloroepibatidine (N-methyl-NorchloroEPB) and N-methyl-2-(2-pyridyl)-7-azabicyclo[2.2.1]heptane (N-methyl-2PABH). Radiosyntheses were performed by methylation with high radiochemical purities (>98%) and with specific activities between 140 and 500 GBq/micromol at the end of synthesis. The radiochemical yield (decay-corrected, related to [(11)C]CH(3)I) was between 5 and 10%. Positively and negatively radiolabeled enantiomers were prepared in high optical purity (>98%ee) by labeling of the appropriate optically active substrates, which were obtained via chiral high performance liquid chromatography. For in vivo studies radioligands were administered intravenously in rats. Brain uptake curves were acquired and combined with blocking experiments. Brain uptake of N-[(11)C]methyl-NorchloroEPB was similar to that of N-[(11)C]methyl-EPB whereas N-[(11)C]methyl-2PABH with the modified pyridine ring had a significantly lower uptake.
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Affiliation(s)
- J E Spang
- Center for Radiopharmaceutical Science, Swiss Federal Institute of Technology, Paul Scherrer Institute and University Hospital of Zürich, Zurich, Switzerland
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44
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Glennon RA, Dukat M. Central nicotinic receptor ligands and pharmacophores. PHARMACEUTICA ACTA HELVETIAE 2000; 74:103-14. [PMID: 10812946 DOI: 10.1016/s0031-6865(99)00022-9] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Multiple populations of pentameric nicotinic acetylcholinergic (nACh) receptors exist and several may be classified as central or neuronal. Neuronal nACh receptors, however, are primarily of the alpha 4 beta 2 and alpha 7 types, and these have been the focus of most recent investigations aimed at the development of novel agents and identification of pharmacophores. Selectivity data are limited. Furthermore, because several populations of nACh receptors might indirectly influence a given functional effect, it is difficult to discuss structure-activity relationships (SAR) in terms of differential SAR, or to formulate SAR on the basis of functional studies. For the most part, studies are limited to the formulation of structure-affinity relationships (SAFIR) for the binding of agents at nACh receptors, and for these the alpha 4 beta 2 population has been the most extensively investigated. SAFIR and newer agents are reviewed here with reference to earlier studies. Novel agents now have been identified that bind with up to 30 times higher affinity than nicotine and these are providing new insight into the understanding of nACh receptors.
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Affiliation(s)
- R A Glennon
- Department of Medicinal Chemistry, School of Pharmacy, Virginia Commonwealth University, Richmond 23298-0540, USA.
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Mukhin AG, Gündisch D, Horti AG, Koren AO, Tamagnan G, Kimes AS, Chambers J, Vaupel DB, King SL, Picciotto MR, Innis RB, London ED. 5-Iodo-A-85380, an alpha4beta2 subtype-selective ligand for nicotinic acetylcholine receptors. Mol Pharmacol 2000; 57:642-9. [PMID: 10692507 DOI: 10.1124/mol.57.3.642] [Citation(s) in RCA: 153] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
In an effort to develop selective radioligands for in vivo imaging of neuronal nicotinic acetylcholine receptors (nAChRs), we synthesized 5-iodo-3-(2(S)-azetidinylmethoxy)pyridine (5-iodo-A-85380) and labeled it with (125)I and (123)I. Here we present the results of experiments characterizing this radioiodinated ligand in vitro. The affinity of 5-[(125)I]iodo-A-85380 for alpha4beta2 nAChRs in rat and human brain is defined by K(d) values of 10 and 12 pM, respectively, similar to that of epibatidine (8 pM). In contrast to epibatidine, however, 5-iodo-A-85380 is more selective in binding to the alpha4beta2 subtype than to other nAChR subtypes. In rat adrenal glands, 5-iodo-A-85380 binds to nAChRs containing alpha3 and beta4 subunits with 1/1000th the affinity of epibatidine, and exhibits 1/60th and 1/190th the affinity of epibatidine at alpha7 and muscle-type nAChRs, respectively. Moreover, unlike epibatidine and cytisine, 5-[(125)I]iodo-A-85380 shows no binding in any brain regions in mice homozygous for a mutation in the beta2 subunit of nAChRs. Binding of 5-[(125)I]iodo-A-85380 in rat brain is reversible, and is characterized by high specificity and a slow rate of dissociation of the receptor-ligand complex (t(1/2) for dissociation approximately 2 h). These properties, along with other features observed previously in in vivo experiments (low toxicity, rapid penetration of the blood-brain barrier, and a high ratio of specific to nonspecific binding), suggest that this compound, labeled with (125)I or (123)I, is superior to other radioligands available for in vitro and in vivo studies of alpha4beta2 nAChRs, respectively.
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Affiliation(s)
- A G Mukhin
- Brain Imaging Center, Intramural Research Program, National Institute on Drug Abuse, Baltimore, Maryland, USA
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Navarro HA, Zhong D, Abraham P, Xu H, Carroll FI. Synthesis and pharmacological characterization of [(125)I]iodomethyllycaconitine ([(125)I]iodo-MLA). A new ligand for the alpha(7) nicotinic acetylcholine receptor. J Med Chem 2000; 43:142-5. [PMID: 10649969 DOI: 10.1021/jm990544f] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- H A Navarro
- Research Triangle Institute, Post Office Box 12194, Research Triangle Park, North Carolina 27709, USA
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47
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Scheffel U, Horti AG, Koren AO, Ravert HT, Banta JP, Finley PA, London ED, Dannals RF. 6-[18F]Fluoro-A-85380: an in vivo tracer for the nicotinic acetylcholine receptor. Nucl Med Biol 2000; 27:51-6. [PMID: 10755645 DOI: 10.1016/s0969-8051(99)00082-7] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
6-[18F]Fluoro-3-(2(S)-azetidinylmethoxy)pyridine (6-[18F]fluoro-A-85380 or 6-[18F]FA), a new tracer for positron emission tomography, was synthesized by no-carrier-added [18F] fluorination of 6-iodo-3-((1-tert-butoxycarbonyl-2(S)-azetidinyl)methoxy)pyridine followed by acidic deprotection. 6-[18F]FA followed the regional densities of brain nicotinic acetylcholine receptors (nAChRs) reported in the literature. Evidence of binding to nAChRs and high specificity of the binding in vivo was demonstrated by inhibition with nAChR selective ligands as well as with unlabeled 6-FA. A preliminary toxicology study of the 6-FA showed a relatively low biological effect.
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Affiliation(s)
- U Scheffel
- Division of Nuclear Medicine and Radiation Health Sciences, The Johns Hopkins Medical Institutions, Baltimore, Maryland 21205-2179, USA
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Sihver W, Fasth KJ, Horti AG, Koren AO, Bergström M, Lu L, Hagberg G, Lundqvist H, Dannals RF, London ED, Nordberg A, Långström B. Synthesis and characterization of binding of 5-[76Br]bromo-3-[[2(S)-azetidinyl]methoxy]pyridine, a novel nicotinic acetylcholine receptor ligand, in rat brain. J Neurochem 1999; 73:1264-72. [PMID: 10461920 DOI: 10.1046/j.1471-4159.1999.0731264.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
5-[76Br]Bromo-3-[[2(S)-azetidinyl]methoxy]pyridine ([76Br]BAP), a novel nicotinic acetylcholine receptor ligand, was synthesized using [76Br]bromide in an oxidative bromodestannylation of the corresponding trimethylstannyl compound. The radiochemical yield was 25%, and the specific radioactivity was on the order of 1 Ci/micromol. The binding properties of [76Br]BAP were characterized in vitro and in vivo in rat brain, and positron emission tomography (PET) experiments were performed in two rhesus monkeys. In association experiments on membranes of the cortex and thalamus, >90% of maximal specific [76Br]BAP binding was obtained after 60 min. The dissociation half-life of [76Br]BAP was 51 +/- 6 min in cortical membranes and 56 +/- 3 min in thalamic membranes. Saturation experiments with [76Br]BAP revealed one population of binding sites with dissociation constant (K(D)) values of 36 +/- 9 and 30 +/- 9 pM in membranes of cortex and thalamus, respectively. The maximal binding site density (Bmax) values were 90 +/- 17 and 207 +/- 33 fmol/mg in membranes of cortex and thalamus, respectively. Scatchard plots were nonlinear, and the Hill coefficients were <1, suggesting the presence of a lower-affinity binding site. In vitro autoradiography studies showed that binding of [76Br]BAP was high in the thalamus and presubiculum, moderate in the cortex and striatum, and low in the cerebellum and hippocampus. A similar pattern of [76Br]BAP accumulation was observed by ex vivo autoradiography. In vivo, binding of [76Br]BAP in whole rat brain was blocked by preinjection of (S)(-)-nicotine (0.3 mg/kg) by 27, 52, 68, and 91% at survival times of 10, 25, 40, 120, and 300 min, respectively. In a preliminary PET study in rhesus monkeys, the highest [76Br]BAP uptake was found in the thalamus, and radioactivity was displaceable by approximately 60% with cytisine and by 50% with (S)(-)-nicotine. The data of this study indicate that [76Br]BAP is a promising radioligand for the characterization of nicotinic acetylcholine receptors in vivo.
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Affiliation(s)
- W Sihver
- PET Centre Uppsala University, Sweden
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Olivo HF, Colby DA, Hemenway MS. Syntheses of New Open-Ring and homo-Epibatidine Analogues from Tropinone. J Org Chem 1999; 64:4966-4968. [PMID: 11674583 DOI: 10.1021/jo990097b] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Horacio F. Olivo
- Division of Medicinal and Natural Products Chemistry, College of Pharmacy, The University of Iowa, Iowa City, Iowa 52242
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Bertrand S, Patt JT, Spang JE, Westera G, Schubiger PA, Bertrand D. Neuronal nAChR stereoselectivity to non-natural epibatidine derivatives. FEBS Lett 1999; 450:273-9. [PMID: 10359088 DOI: 10.1016/s0014-5793(99)00473-1] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The frog toxin epibatidine is one of the most powerful ligands of the neuronal nicotinic receptors and derivatives show promising possibilities for labeling in positron emission tomography studies. In an attempt to reduce epibatidine toxicity, new methyl derivatives were synthesized, tested in positron emission tomography imaging and in electrophysiology. labeling as well as physiological experiments highlighted the differences in sensitivity of the neuronal nicotinic acetylcholine receptors between two methyl enantiomers and the reduction in sensitivity caused by introducing the methyl group. At present, epibatidine derivatives seem the most promising compounds for in vivo labeling of neuronal nicotinic acetylcholine receptors.
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Affiliation(s)
- S Bertrand
- Département de physiologie, Centre Médical Universitaire (Faculté de Médecine), Geneva, Switzerland
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