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Mukherjee J, Lao PJ, Betthauser TJ, Samra GK, Pan ML, Patel IH, Liang C, Metherate R, Christian BT. Human brain imaging of nicotinic acetylcholine α4β2* receptors using [ 18 F]Nifene: Selectivity, functional activity, toxicity, aging effects, gender effects, and extrathalamic pathways. J Comp Neurol 2017; 526:80-95. [PMID: 28875553 DOI: 10.1002/cne.24320] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2017] [Revised: 08/22/2017] [Accepted: 08/23/2017] [Indexed: 02/06/2023]
Abstract
Nicotinic acetylcholinergic receptors (nAChR's) have been implicated in several brain disorders, including addiction, Parkinson's disease, Alzheimer's disease and schizophrenia. Here we report in vitro selectivity and functional properties, toxicity in rats, in vivo evaluation in humans, and comparison across species of [18 F]Nifene, a fast acting PET imaging agent for α4β2* nAChRs. Nifene had subnanomolar affinities for hα2β2 (0.34 nM), hα3β2 (0.80 nM) and hα4β2 (0.83 nM) nAChR but weaker (27-219 nM) for hβ4 nAChR subtypes and 169 nM for hα7 nAChR. In functional assays, Nifene (100 μM) exhibited 14% agonist and >50% antagonist characteristics. In 14-day acute toxicity in rats, the maximum tolerated dose (MTD) and the no observed adverse effect level (NOAEL) were estimated to exceed 40 μg/kg/day (278 μg/m2 /day). In human PET studies, [18 F]Nifene (185 MBq; <0.10 μg) was well tolerated with no adverse effects. Distribution volume ratios (DVR) of [18 F]Nifene in white matter thalamic radiations were ∼1.6 (anterior) and ∼1.5 (superior longitudinal fasciculus). Habenula known to contain α3β2 nAChR exhibited low levels of [18 F]Nifene binding while the red nucleus with α2β2 nAChR had DVR ∼1.6-1.7. Females had higher [18 F]Nifene binding in all brain regions, with thalamus showing >15% than males. No significant aging effect was observed in [18 F]Nifene binding over 5 decades. In all species (mice, rats, monkeys, and humans) thalamus showed highest [18 F]Nifene binding with reference region ratios >2 compared to extrathalamic regions. Our findings suggest that [18 F]Nifene PET may be used to study α4β2* nAChRs in various CNS disorders and for translational research.
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Affiliation(s)
- Jogeshwar Mukherjee
- Preclinical Imaging, Department of Radiological Sciences, University of California, Irvine, California
| | - Patrick J Lao
- Department of Medical Physics and Waisman Center, University of Wisconsin, Madison, Wisconsin
| | - Tobey J Betthauser
- Department of Medical Physics and Waisman Center, University of Wisconsin, Madison, Wisconsin
| | - Gurleen K Samra
- Preclinical Imaging, Department of Radiological Sciences, University of California, Irvine, California
| | - Min-Liang Pan
- Preclinical Imaging, Department of Radiological Sciences, University of California, Irvine, California
| | - Ishani H Patel
- Preclinical Imaging, Department of Radiological Sciences, University of California, Irvine, California
| | | | - Raju Metherate
- Department of Neurobiology and Behavior, University of California, Irvine, California
| | - Bradley T Christian
- Department of Medical Physics and Waisman Center, University of Wisconsin, Madison, Wisconsin
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Imaging α4β2 Nicotinic Acetylcholine Receptors (nAChRs) in Baboons with [18F]XTRA, a Radioligand with Improved Specific Binding in Extra-Thalamic Regions. Mol Imaging Biol 2016; 19:280-288. [DOI: 10.1007/s11307-016-0999-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Horti AG, Wong DF. Clinical Perspective and Recent Development of PET Radioligands for Imaging Cerebral Nicotinic Acetylcholine Receptors. PET Clin 2016; 4:89-100. [PMID: 20046884 DOI: 10.1016/j.cpet.2009.04.014] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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Divergent functional effects of sazetidine-a and varenicline during nicotine withdrawal. Neuropsychopharmacology 2013; 38:2035-47. [PMID: 23624742 PMCID: PMC3746688 DOI: 10.1038/npp.2013.105] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/17/2012] [Revised: 04/03/2013] [Accepted: 04/20/2013] [Indexed: 01/15/2023]
Abstract
Smoking is the largest preventable cause of death in the United States. Furthermore, a recent study found that <10% of quit attempts resulted in continuous abstinence for 1 year. With the introduction of pharmacotherapies like Chantix (varenicline), a selective α4β2 nicotinic partial agonist, successful quit attempts have significantly increased. Therefore, novel subtype-specific nicotinic drugs, such as sazetidine-A, present a rich area for investigation of therapeutic potential in smoking cessation. The present studies examine the anxiety-related behavioral and functional effects of the nicotinic partial agonists varenicline and sazetidine-A during withdrawal from chronic nicotine in mice. Our studies indicate that ventral hippocampal-specific infusions of sazetidine-A, but not varenicline, are efficacious in reducing nicotine withdrawal-related anxiety-like phenotypes in the novelty-induced hypophagia (NIH) paradigm. To further investigate functional differences between these partial agonists, we utilized voltage-sensitive dye imaging (VSDi) in ventral hippocampal slices to determine the effects of sazetidine-A and varenicline in animals chronically treated with saline, nicotine, or undergoing 24 h withdrawal. These studies demonstrate a functional dissociation of varenicline and sazetidine-A on hippocampal network activity, which is directly related to previous drug exposure. Furthermore, the effects of the nicotinic partial agonists in VSDi assays are significantly correlated with their behavioral effects in the NIH test. These findings highlight the importance of drug history in understanding the mechanisms through which nicotinic compounds may be aiding smoking cessation in individuals experiencing withdrawal-associated anxiety.
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Bartzokis G. Neuroglialpharmacology: myelination as a shared mechanism of action of psychotropic treatments. Neuropharmacology 2012; 62:2137-53. [PMID: 22306524 PMCID: PMC3586811 DOI: 10.1016/j.neuropharm.2012.01.015] [Citation(s) in RCA: 107] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2011] [Revised: 01/18/2012] [Accepted: 01/19/2012] [Indexed: 12/20/2022]
Abstract
Current psychiatric diagnostic schema segregate symptom clusters into discrete entities, however, large proportions of patients suffer from comorbid conditions that fit neither diagnostic nor therapeutic schema. Similarly, psychotropic treatments ranging from lithium and antipsychotics to serotonin reuptake inhibitors (SSRIs) and acetylcholinesterase inhibitors have been shown to be efficacious in a wide spectrum of psychiatric disorders ranging from autism, schizophrenia (SZ), depression, and bipolar disorder (BD) to Alzheimer's disease (AD). This apparent lack of specificity suggests that psychiatric symptoms as well as treatments may share aspects of pathophysiology and mechanisms of action that defy current symptom-based diagnostic and neuron-based therapeutic schema. A myelin-centered model of human brain function can help integrate these incongruities and provide novel insights into disease etiologies and treatment mechanisms. Available data are integrated herein to suggest that widely used psychotropic treatments ranging from antipsychotics and antidepressants to lithium and electroconvulsive therapy share complex signaling pathways such as Akt and glycogen synthase kinase-3 (GSK3) that affect myelination, its plasticity, and repair. These signaling pathways respond to neurotransmitters, neurotrophins, hormones, and nutrition, underlie intricate neuroglial communications, and may substantially contribute to the mechanisms of action and wide spectra of efficacy of current therapeutics by promoting myelination. Imaging and genetic technologies make it possible to safely and non-invasively test these hypotheses directly in humans and can help guide clinical trial efforts designed to correct myelination abnormalities. Such efforts may provide insights into novel avenues for treatment and prevention of some of the most prevalent and devastating human diseases.
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Affiliation(s)
- George Bartzokis
- Department of Psychiatry, The David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA.
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Lotfipour S, Mandelkern M, Brody AL. Quantitative Molecular Imaging of Neuronal Nicotinic Acetylcholine Receptors in the Human Brain with A-85380 Radiotracers. Curr Med Imaging 2011; 7:107-112. [PMID: 22773924 DOI: 10.2174/157340511795445676] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Neuronal nicotinic acetylcholine receptors (nAChRs) have been implicated in a spectrum of cognitive functions as well as psychiatric and neurodegenerative disorders, including tobacco addiction and Alzheimer's Disease. The examination of neuronal nAChRs in living humans is a relatively new field. Researchers have developed brain-imaging radiotracers for nAChRs, with radiolabeled A-85380 compounds having the most widespread use. We provide a brief background on nAChRs, followed by a discussion of the development and application of A-85380 radiotracers in human imaging studies. We describe potential future studies using nicotinic receptor radioligands for the study of tobacco addiction, including the mechanism of action of the smoking-cessation therapy varenicline. Throughout this review, we focus on the significant potential that resides in the identification and quantification of nAChRs in the living human brain.
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Affiliation(s)
- Shahrdad Lotfipour
- Department of Psychiatry, David Geffen School of Medicine, University of California, Los Angeles, California, USA
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Kmecova J, Klimas J. Heart rate correction of the QT duration in rats. Eur J Pharmacol 2010; 641:187-92. [DOI: 10.1016/j.ejphar.2010.05.038] [Citation(s) in RCA: 108] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2010] [Revised: 05/14/2010] [Accepted: 05/28/2010] [Indexed: 11/16/2022]
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Esterlis I, Cosgrove KP, Batis JC, Bois F, Stiklus SM, Perkins E, Seibyl JP, Carson RE, Staley JK. Quantification of smoking-induced occupancy of beta2-nicotinic acetylcholine receptors: estimation of nondisplaceable binding. J Nucl Med 2010; 51:1226-33. [PMID: 20660383 DOI: 10.2967/jnumed.109.072447] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
UNLABELLED 5-(123)I-iodo-85380 ((123)I-5-IA) is used to quantitate high-affinity nicotinic acetylcholine receptors (beta(2)-nAChRs) on human SPECT scans. The primary outcome measure is V(T)/f(P), the ratio at equilibrium between total tissue concentration (free, nonspecifically bound, and specifically bound) and the free plasma concentration. Nondisplaceable uptake (free plus nonspecific) of (123)I-5-IA has not been measured in human subjects. Nicotine has high affinity for beta(2)*-nAChRs (nAChRs containing the beta(2)* subunit, for which * represents other subunits that may also be part of the receptor) and displaces specifically bound (123)I-5-IA. In this study, we measured nicotine occupancy and nondisplaceable binding in healthy smokers after they had smoked to satiety. METHODS Eleven nicotine-dependent smokers (mean age +/- SD, 35.6 +/- 14.4 y) completed the study. One subject was excluded from subsequent analyses because of abnormal blood nicotine levels. Subjects abstained from tobacco smoke for 5.3 +/- 0.9 d and participated in a 15- to 17-h SPECT scanning day. (123)I-5-IA was administered by bolus plus constant infusion, with a total injected dose of 361 +/- 20 MBq. At approximately 6 h after the start of the infusion, three 30-min SPECT scans and a 15-min transmission-emission scan were acquired to obtain baseline beta(2)*-nAChR availability. Subjects then smoked to satiety (2.4 +/- 0.7 cigarettes), and arterial (first 40 min) and venous (until study completion) plasma nicotine and cotinine levels were collected. About 1 h after subjects had smoked to satiety, up to six 30-min SPECT scans were acquired. V(T)/f(P) data, computed from the tissue and plasma radioactivity measurements from the presmoking baseline and postsmoking scans, were analyzed using the Lassen plot method. RESULTS Receptor occupancy after subjects had smoked to satiety was 67% +/- 9% (range, 55%-80%). Nondisplaceable uptake was estimated as 19.4 +/- 5.8 mL x cm(-3) (range, 15-28 mL x cm(-3)). Thus, in the thalamus, where mean V(T)/f(P) is 93 mL x cm(-3), nondisplaceable binding represents approximately 20% of the total binding. CONCLUSION These results are in agreement with previous findings and suggest that when satiating doses of nicotine are administered to smokers, imaging of receptor availability can yield valuable data, such as quantifiable measures of nondisplaceable binding.
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Affiliation(s)
- Irina Esterlis
- Department of Psychiatry, Yale University School of Medicine and the Veteran's Affairs Connecticut Healthcare System, West Haven, Connecticut 06516, USA.
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Brasić JR, Zhou Y, Musachio JL, Hilton J, Fan H, Crabb A, Endres CJ, Reinhardt MJ, Dogan AS, Alexander M, Rousset O, Maris MA, Galecki J, Nandi A, Wong DF. Single photon emission computed tomography experience with (S)-5-[(123)I]iodo-3-(2-azetidinylmethoxy)pyridine in the living human brain of smokers and nonsmokers. Synapse 2009; 63:339-58. [PMID: 19140167 PMCID: PMC2766259 DOI: 10.1002/syn.20611] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
(S)-5-[(123)I]iodo-3-(2-azetidinylmethoxy)pyridine (5-[(123)I]IA), a novel potent radioligand for high-affinity alpha4beta2* neuronal nicotinic acetylcholine receptors (nAChRs), provides a means to evaluate the density and the distribution of nAChRs in the living human brain. We sought in healthy adult smokers and nonsmokers to (1) evaluate the safety, tolerability, and efficacy of 5-[(123)I]IA in an open nonblind trial and (2) to estimate the density and the distribution of alpha(4)beta(2)* nAChRs in the brain. Single photon emission computed tomography (SPECT) was performed for 5 h after the i.v. administration of approximately 0.001 microg/kg ( approximately 10 mCi) 5-[(123)I]IA. Blood pressure, heart rate, and neurobehavioral status were monitored before, during, and after the administration of 5-[(123)I]IA to 12 healthy adults (8 men and 4 women) (6 smokers and 6 nonsmokers) ranging in age from 19 to 46 years (mean = 28.25, standard deviation = 8.20). High plasma-nicotine level was significantly associated with low 5-[(123)I]IA binding in: (1) the caudate head, the cerebellum, the cortex, and the putamen, utilizing both the Sign and Mann-Whitney U-tests; (2) the fusiform gyrus, the hippocampus, the parahippocampus, and the pons utilizing the Mann-Whitney U-test; and (3) the thalamus utilizing the Sign test. We conclude that 5-[(123)I]IA is a safe, well-tolerated, and effective pharmacologic agent for human subjects to estimate high-affinity alpha4/beta2 nAChRs in the living human brain.
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Affiliation(s)
- James Robert Brasić
- Division of Nuclear Medicine, Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, Maryland 21287, USA.
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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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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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Brust P, Patt JT, Deuther-Conrad W, Becker G, Patt M, Schildan A, Sorger D, Kendziorra K, Meyer P, Steinbach J, Sabri O. In vivo measurement of nicotinic acetylcholine receptors with [18F]norchloro-fluoro-homoepibatidine. Synapse 2008; 62:205-18. [PMID: 18088060 DOI: 10.1002/syn.20480] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Functional changes of nicotinic acetylcholine receptors (nAChR) are important during age-related neuronal degeneration. Recent studies demonstrate the applicability of the nAChR ligand 2-[(18)F]F-A-85380 for neuroimaging of patients with dementias. However, its binding kinetics demands a 7-h acquisition time limiting its practicality for clinical PET studies. Thus, the authors developed [(18)F]norchloro-fluoro-homoepibatidine ([(18)F]NCFHEB) for nAChR imaging. The kinetics of the two enantiomers of [(18)F]NCFHEB were compared with 2-[(18)F]F-A85380 in porcine brain to evaluate their potential for human neuroimaging. Twenty-four juvenile female pigs were studied with PET using [(18)F]NCFHEB. Nine animals received an additional i.v. injection (1 mg/kg) of the nAChR agonist A81418 before radiotracer administration followed by infusion (2 mg/kg/7h) thereafter. Several compartment models were applied for quantification. (-)- and (+)-[(18)F]NCFHEB showed a twofold to threefold higher brain uptake than 2-[(18)F]F-A-85380. All three radiotracers displayed spatially heterogeneous binding kinetics in regions with high, moderate, or low specific binding. The equilibrium of specific binding of (-)-[(18)F]NCFHEB was reached earlier than that of (+)-[(18)F]NCFHEB or 2-[(18)F]F-A85380. Continuous administration of the nAChR agonist A81418 inhibited the specific binding of (-)- and (+)-[(18)F]NCFHEB but not of 2-[(18)F]F-A85380. The peripheral metabolism of (+)-[(18)F]NCFHEB proceeded somewhat slower than that of the other radiotracers. Both enantiomers of [(18)F]NCFHEB are appropriate radiotracers for neuroimaging of nAChR in pigs. Their binding profile in vivo appears to be more selective than that of 2-[(18)F]F-A85380. (-)-[(18)F]NCFHEB offers a faster equilibrium of specific binding than 2-[(18)F]F-A85380.
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Affiliation(s)
- Peter Brust
- Department of Radiopharmacy, Institute of Interdisciplinary Isotope Research, Permoserstrasse 15, Leipzig, Germany.
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Gallezot JD, Bottlaender MA, Delforge J, Valette H, Saba W, Dollé F, Coulon CM, Ottaviani MP, Hinnen F, Syrota A, Grégoire MC. Quantification of cerebral nicotinic acetylcholine receptors by PET using 2-[18F]fluoro-A-85380 and the multiinjection approach. J Cereb Blood Flow Metab 2008; 28:172-89. [PMID: 17519978 DOI: 10.1038/sj.jcbfm.9600505] [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] [Indexed: 11/09/2022]
Abstract
The multiinjection approach was used to study in vivo interactions between alpha4beta2(*) nicotinic acetylcholine receptors and 2-[(18)F]fluoro-A-85380 in baboons. The ligand kinetics was modeled by the usual nonlinear compartment model composed of three compartments (arterial plasma, free and specifically bound ligand in tissue). Arterial blood samples were collected to generate a metabolite-corrected plasma input function. The experimental protocol, which consisted of three injections of labeled or unlabeled ligand, was aiming at identifying all parameters in one experiment. Various parameters, including B'(max) (the binding sites density) and K(d)V(R) (the apparent in vivo affinity of 2-[(18)F]fluoro-A-85380) could then be estimated in thalamus and in several receptor-poor regions. B'(max) estimate was 3.0+/-0.3 pmol/mL in thalamus, and ranged from 0.25 to 1.58 pmol/mL in extrathalamic regions. Although K(d)V(R) could be precisely estimated, the association and dissociation rate constants k(on)/V(R) and k(off) could not be identified separately. A second protocol was then used to estimate k(off) more precisely in the thalamus. Having estimated all model parameters, we performed simulations of 2-[(18)F]fluoro-A-85380 kinetics to test equilibrium hypotheses underlying simplified approaches. These showed that a pseudo-equilibrium is quickly reached between the free and bound compartments, a favorable situation to apply Logan graphical analysis. In contrast, the pseudo-equilibrium between the plasma and free compartments is only reached after several hours. The ratio of radioligand concentration in these two compartments then overestimates the true equilibrium value, an unfavorable situation to estimate distribution volumes from late images after a bolus injection.
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15
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Chefer SI, Pavlova OA, Zhang Y, Vaupel DB, Kimes AS, Horti AG, Stein E, Mukhin AG. NIDA522131, a new radioligand for imaging extrathalamic nicotinic acetylcholine receptors: in vitro and in vivo evaluation. J Neurochem 2007; 104:306-15. [PMID: 17986233 DOI: 10.1111/j.1471-4159.2007.05009.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A novel radioligand, 6-chloro-3-((2-(S)-azetidinyl)methoxy)-5-(2-fluoropyridin-4-yl)pyridine (NIDA522131), for imaging extrathalamic nicotinic acetylcholine receptors (nAChRs) was characterized in vitro and in vivo using positron emission tomography. The K(d) and T(1/2) of dissociation of NIDA522131 binding measured at 37 degrees C in vitro were 4.9 +/- 0.4 pmol/L and 81 +/- 5 min, respectively. The patterns of radioactivity distribution in monkey brain in vivo was similar to that of 2-[(18)F]fluoro-3-(2(S)-azetidinylmethoxy)pyridine (2FA), a radioligand that has been successfully used in humans, and matched the alpha(4)beta(2)* nAChRs distribution. Comparison between [(18)F]NIDA522131 and 2FA demonstrated better in vivo binding properties of the new radioligand and substantially greater radioactivity accumulation in brain. Consistent with [(18)F]NIDA522131 elevated affinity for nAChRs and its increased lipophilicity, both, the total and non-displaceable distribution volumes were substantially higher than those of 2FA. Estimated binding potential values in different brain regions, characterizing the specificity of receptor binding, were 3-4 fold higher for [(18)F]NIDA522131 than those of 2FA. Pharmacological evaluation in mice demonstrated a toxicity that was comparable to 2FA and is in agreement with a 2300 fold higher affinity at alpha(4)beta(2)* versus alpha(3)beta(4)* nAChRs. These results suggest that [(18)F]NIDA522131 is a promising positron emission tomography radioligand for studying extrathalamic nAChR in humans.
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Affiliation(s)
- Svetlana I Chefer
- Neuroimaging Research Branch, Intramural Research Program, National Institute on Drug Abuse, National Institute of Health, Department of Health and Human Services, Baltimore, Maryland, USA
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16
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Bartzokis G. Acetylcholinesterase inhibitors may improve myelin integrity. Biol Psychiatry 2007; 62:294-301. [PMID: 17070782 DOI: 10.1016/j.biopsych.2006.08.020] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/17/2006] [Revised: 07/28/2006] [Accepted: 08/21/2006] [Indexed: 12/27/2022]
Abstract
Recent clinical trials have revealed that cholinergic treatments are efficacious in a wide spectrum of neuropsychiatric disorders that span the entire human lifespan and include disorders without cholinergic deficits. Furthermore, some clinical and epidemiological data suggest that cholinergic treatments have disease modifying/preventive effects. It is proposed that these observations can be usefully understood in a myelin-centered model of the human brain. The model proposes that the human brain's extensive myelination is the central evolutionary change that defines our uniqueness as a species and our unique vulnerability to highly prevalent neuropsychiatric disorders. Within the framework of this model the clinical, biochemical, and epidemiologic data can be reinterpreted to suggest that nonsynaptic effects of cholinergic treatments on the process of myelination and myelin repair contributes to their mechanism of action and especially to their disease modifying/preventive effects. The ability to test the model in human populations with safe and noninvasive imaging technologies makes it possible to undertake novel clinical trial efforts directed at primary prevention of some of the most prevalent and devastating of human disorders.
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Affiliation(s)
- George Bartzokis
- Department of Neurology, The Laboratory of Neuroimaging in the Division of Brain Mapping, The David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, CA 90095-1769, USA.
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Vaupel DB, Stein EA, Mukhin AG. Quantification of alpha4beta2* nicotinic receptors in the rat brain with microPET and 2-[18F]F-A-85380. Neuroimage 2007; 34:1352-62. [PMID: 17187994 PMCID: PMC2023973 DOI: 10.1016/j.neuroimage.2006.10.036] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2006] [Revised: 09/27/2006] [Accepted: 10/13/2006] [Indexed: 11/17/2022] Open
Abstract
The radioligand 2-[(18)F]F-A-85380 has been used for PET studies of the alpha4beta2* subtype of nicotinic acetylcholine receptors (nAChRs) in the living brain of humans and nonhuman primates. In order to extend the capacity of microPET to quantify neuroreceptors in rat brain, we carried out studies of 2-[(18)F]F-A-85380 to measure the apparent binding potential BP* in individual rats, which were studied repeatedly over several months. Using a bolus-plus-infusion paradigm, 2-[(18)F]F-A-85380 (specific activity 20-1300 GBq/micromol) was administered intravenously over 8 to 9 h with K(bol) values of 350 to 440 min and a mean infusion rate of 0.03+/-0.01 nmol/kg/h. Studies included a 2-h nicotine infusion initiated 2 h before the end of scanning to displace specifically bound radioactivity. Steady state binding in brain was obtained within 5 h as defined by the occurrence of constant radioactivity concentrations in brain regions and constant, free arterial plasma levels of nonmetabolized radioligand. BP* averages (+/-SEM) for thalamus, forebrain, and cerebellum were 5.9+/-0.7, 2.6+/-0.4, and 1.0+/-0.1, respectively, which are consistent with the alpha4beta2* nAChR distribution in rat brain measured in vitro. Studies of receptor occupancy determined the ED(50) to be 0.29 nmol/kg/h. The demonstration that alpha4beta2* nAChRs are quantifiable in the rat brain using PET measurements, coupled with the ability to conduct longitudinal studies over several months in the same rats, suggests potential applications to studies of chronic nicotine use, its treatment, and abnormal functioning of alpha4beta2* receptors in a rat model.
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Affiliation(s)
- D Bruce Vaupel
- Neuroimaging Research Branch, National Institute on Drug Abuse, Intramural Research Program, National Institutes of Health, Department of Health and Human Services, Baltimore, MD 21224, USA.
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Dollé F. [18F]fluoropyridines: From conventional radiotracers to the labeling of macromolecules such as proteins and oligonucleotides. ERNST SCHERING RESEARCH FOUNDATION WORKSHOP 2007:113-57. [PMID: 17172154 DOI: 10.1007/978-3-540-49527-7_5] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/13/2023]
Abstract
Molecular in vivo imaging with the high-resolution and sensitive positron emission tomography (PET) technique requires the preparation of a positron-emitting radiolabeled probe or radiotracer. For this purpose, fluorine-18 is becoming increasingly the radionuclide of choice due to its adequate physical and nuclear characteristics, and also because of the successful use in clinical oncology of 2-[18F]fluoro-2-deoxy-D-glucose ([18F]FDG), which is currently the most widely used PET-radiopharmaceutical and probably the driving force behind the growing availability and interest for this positron-emitter in radiopharmaceutical chemistry. With a few exceptions, radiofluorinations involving fluorine-18 of high specific radioactivity (e.g. > 185 GBq/micromole) had, until recently, been limited to nucleophilic substitutions in homoaromatic and aliphatic series with [18F]fluoride. Considering chemical structures showing a fluoropyridinyl moiety, nucleophilic heteroaromatic substitution at the ortho-position with no-carrier-added [l8F]fluoride, as its K[18F]F-K222 complex, appears today as a highly efficient method for the radiosynthesis of radiotracers and radiopharmaceuticals. This chapter summarizes the recent applications of this methodology and highlights its potential in the design and preparation of, often drug-based, fluorine-18-labeled probes of high specific radioactivity for PET imaging, including macromolecules of biological interest such as peptides, proteins and oligonucleotides.
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Affiliation(s)
- F Dollé
- Service Hospitalier Frédéric Joliot, Département de Recherche Médicale - CEA, Orsay, France.
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19
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Sorger D, Becker GA, Hauber K, Schildan A, Patt M, Birkenmeier G, Otto A, Meyer P, Kluge M, Schliebs R, Sabri O. Binding properties of the cerebral alpha4beta2 nicotinic acetylcholine receptor ligand 2-[18F]fluoro-A-85380 to plasma proteins. Nucl Med Biol 2007; 33:899-906. [PMID: 17045170 DOI: 10.1016/j.nucmedbio.2006.07.012] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2006] [Revised: 07/26/2006] [Accepted: 07/29/2006] [Indexed: 10/24/2022]
Abstract
INTRODUCTION To determine the availability of nicotinic acetylcholine receptors in different human brain regions using the positron emission tomography (PET) radioligand 2-[18F]fluoro-A-85380 (2-[18F]FA) and invasive approaches for quantification, it is important to correct the arterial input function as well for plasma protein binding (PPB) of the radioligand as for radiolabeled metabolites accumulating in blood. This study deals with some aspects of PPB of 2-[18F]FA. METHODS Patients with different neurological disorders (n=72), such as Parkinson's disease, Alzheimer's disease and multiple sclerosis, and a group of healthy volunteers (n=15) subjected for PET imaging were analyzed for their PPB level of 2-[18F]FA using ultrafiltration. Protein gel electrophoresis of plasma samples was performed to identify the binding protein of 2-[18F]FA. The dependency of PPB on time and on free ligand concentration was analyzed to obtain the binding parameters Bmax and Kd. RESULTS Albumin was identified to be the binding protein of 2-[18F]FA. PPB of 2-[18F]FA was low at 17+/-4% and did not show significant differences between the groups of patients. Corresponding to this, a narrow range of plasma albumin of 0.62+/-0.05 mM was observed. Bmax was determined as twice the albumin concentration, which indicates two binding sites for 2-[18F]FA on the protein. No time dependence of the PPB could be observed. By relating PPB to Bmax, an average Kd value of 6.0+/-1.5 mM was obtained. CONCLUSION This study shows the dependency of PPB of 2-[18F]FA on human albumin plasma concentration. An equation utilizing Bmax and Kd to easily estimate PPB is presented.
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Affiliation(s)
- Dietlind Sorger
- Department of Nuclear Medicine, University of Leipzig, Leipzig, Germany.
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Rueter LE, Donnelly-Roberts DL, Curzon P, Briggs CA, Anderson DJ, Bitner RS. A-85380: a pharmacological probe for the preclinical and clinical investigation of the alphabeta neuronal nicotinic acetylcholine receptor. CNS DRUG REVIEWS 2006; 12:100-12. [PMID: 16958984 PMCID: PMC6494138 DOI: 10.1111/j.1527-3458.2006.00100.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
A-85380 [3-(2(s)-azetidinylmethoxy) pyridine] is a neuronal nicotinic acetylcholine receptor (nAChR) agonist that has been a useful tool in the investigation of the function of nAChRs in both preclinical and clinical studies. Amongst nAChR subtypes, A-85380 shows selectivity for the alpha(4)beta(2) vs. the alpha(7) or alpha(1)beta(1)deltagamma nAChRs. In functional in vitro cation flux assays, A-85380 is a potent and full agonist. A-85380 has a broad-spectrum analgesic profile with efficacy in acute, persistent, and neuropathic pain models. As demonstrated using selective nAChR antagonists or alpha(4) antisense, the alpha(4)beta(2) nAChR mediates the analgesic effects of A-85380. Interestingly, the site of action depends upon the type of pain as antinociception is mediated by descending inhibition into the spinal cord whereas anti-allodynia in neuropathic pain is mediated at both central and peripheral sites. Radiolabelled forms of A-85380 have been developed and shown to be safe for use in vivo in humans. In clinical studies using positron and photon emission tomography, marked decreases in alpha(4)beta(2) nAChRs have been seen in patients with Parkinson's and Alzheimer's disease. Although not developed as a therapeutic agent, A-85380 has proven to be an important component in the development of novel nAChR ligands for the treatment of pain and other disorders.
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Affiliation(s)
- Lynne E Rueter
- Abbott Laboratories, Neuroscience Research, Global Pharmaceutical Research and Development, Abbott Park, IL, USA.
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Roger G, Saba W, Valette H, Hinnen F, Coulon C, Ottaviani M, Bottlaender M, Dollé F. Synthesis and radiosynthesis of [18F]FPhEP, a novel α4β2-selective, epibatidine-based antagonist for PET imaging of nicotinic acetylcholine receptors. Bioorg Med Chem 2006; 14:3848-58. [PMID: 16455259 DOI: 10.1016/j.bmc.2006.01.032] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2005] [Revised: 01/12/2006] [Accepted: 01/17/2006] [Indexed: 11/22/2022]
Abstract
FPhEP (1, (+/-)-2-exo-(2'-fluoro-3'-phenyl-pyridin-5'-yl)-7-azabicyclo[2.2.1]heptane) belongs to a recently described novel series of 3'-phenyl analogues of epibatidine, which not only possess subnanomolar affinity and high selectivity for brain alpha4beta2 neuronal nicotinic acetylcholine receptors (nAChRs), but also were reported as functional antagonists of low toxicity (up to 15 mg/kg in mice). FPhEP (1, K(i) of 0.24 nM against [(3)H]epibatidine) as reference as well as the corresponding N-Boc-protected chloro- and bromo derivatives (3a,b) as precursors for labelling with fluorine-18 were synthesized in eight and nine steps, respectively, from commercially available N-Boc-pyrrole (overall yields=17% for 1, 9% for 3a and 8% for 3b). FPhEP (1) was labelled with fluorine-18 using the following two-step radiochemical process: (1) no-carrier-added nucleophilic heteroaromatic ortho-radiofluorination from the corresponding N-Boc-protected chloro- or bromo derivatives (3 a,b-1mg) and the activated K[(18)F]F-Kryptofix(222) complex in DMSO using microwave activation at 250 W for 1.5 min, followed by (2) quantitative TFA-induced removal of the N-Boc-protective group. Radiochemically pure (>99%) [(18)F]FPhEP ([(18)F]-1, 2.22-3.33 GBq, 66-137 GBq/micromol) was obtained after semi-preparative HPLC (Symmetry C18, eluent aq 0.05 M NaH(2)PO(4)/CH(3)CN, 80:20 (v:v)) in 75-80 min starting from a 18.5 GBq aliquot of a cyclotron-produced [(18)F]fluoride production batch (10-20% nondecay-corrected overall yield). In vitro binding studies on rat whole-brain membranes demonstrated a subnanomolar affinity (K(D) 660 pM) of [(18)F]FPhEP ([(18)F]-1) for nAChRs. In vitro autoradiographic studies also showed a good contrast between nAChR-rich and -poor regions with a low non-specific binding. Comparison of in vivo Positron Emission Tomography (PET) kinetics of [(18)F]FPhEP ([(18)F]-1) and [(18)F]F-A-85380 in baboons demonstrated faster brain kinetics of the former compound (with a peak uptake at 20 min post injection only). Taken together, the preliminary data obtained confirm that [(18)F]FPhEP ([(18)F]-1) has potential for in vivo imaging nAChRs in the brain with PET.
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Affiliation(s)
- Gaëlle Roger
- Service Hospitalier Frédéric Joliot, Département de Recherche Médicale, CEA/DSV, 4 Place du Général Leclerc, F-91401 Orsay, France
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Roger G, Hinnen F, Valette H, Saba W, Bottlaender M, Dollé F. Radiosynthesis of 2-exo-(2′-[18F]Fluoro-3′-(4-fluorophenyl)-pyridin-5′-yl)-7-azabicyclo[2.2.1]heptane ([18F]F2PhEP), a potent epibatidine-based radioligand for nicotinic acetylcholine receptor PET imaging. J Labelled Comp Radiopharm 2006. [DOI: 10.1002/jlcr.1063] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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