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Zhang JJ, Fu H, Lin R, Zhou J, Haider A, Fang W, Elghazawy NH, Rong J, Chen J, Li Y, Ran C, Collier TL, Chen Z, Liang SH. Imaging Cholinergic Receptors in the Brain by Positron Emission Tomography. J Med Chem 2023; 66:10889-10916. [PMID: 37583063 PMCID: PMC10461233 DOI: 10.1021/acs.jmedchem.3c00573] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2023] [Indexed: 08/17/2023]
Abstract
Cholinergic receptors represent a promising class of diagnostic and therapeutic targets due to their significant involvement in cognitive decline associated with neurological disorders and neurodegenerative diseases as well as cardiovascular impairment. Positron emission tomography (PET) is a noninvasive molecular imaging tool that has helped to shed light on the roles these receptors play in disease development and their diverse functions throughout the central nervous system (CNS). In recent years, there has been a notable advancement in the development of PET probes targeting cholinergic receptors. The purpose of this review is to provide a comprehensive overview of the recent progress in the development of these PET probes for cholinergic receptors with a specific focus on ligand structure, radiochemistry, and pharmacology as well as in vivo performance and applications in neuroimaging. The review covers the structural design, pharmacological properties, radiosynthesis approaches, and preclinical and clinical evaluations of current state-of-the-art PET probes for cholinergic receptors.
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Affiliation(s)
- Jing-Jing Zhang
- Jiangsu
Co-Innovation Center of Efficient Processing and Utilization of Forest
Resources, Jiangsu Provincial Key Lab for the Chemistry and Utilization
of Agro-Forest Biomass, Jiangsu Key Lab of Biomass-Based Green Fuels
and Chemicals, International Innovation Center for Forest Chemicals
and Materials, College of Chemical Engineering, Nanjing Forestry University, Nanjing, Jiangsu 210037, China
| | - Hualong Fu
- Division
of Nuclear Medicine and Molecular Imaging, Massachusetts General Hospital
& Department of Radiology, Harvard Medical
School, Boston, Massachusetts 02114, United States
- Key
Laboratory of Radiopharmaceuticals, Ministry of Education, College
of Chemistry, Beijing Normal University, Beijing 100875, China
| | - Ruofan Lin
- Jiangsu
Co-Innovation Center of Efficient Processing and Utilization of Forest
Resources, Jiangsu Provincial Key Lab for the Chemistry and Utilization
of Agro-Forest Biomass, Jiangsu Key Lab of Biomass-Based Green Fuels
and Chemicals, International Innovation Center for Forest Chemicals
and Materials, College of Chemical Engineering, Nanjing Forestry University, Nanjing, Jiangsu 210037, China
| | - Jingyin Zhou
- Key
Laboratory of Radiopharmaceuticals, Ministry of Education, College
of Chemistry, Beijing Normal University, Beijing 100875, China
| | - Ahmed Haider
- Division
of Nuclear Medicine and Molecular Imaging, Massachusetts General Hospital
& Department of Radiology, Harvard Medical
School, Boston, Massachusetts 02114, United States
- Department
of Radiology and Imaging Sciences, Emory
University, 1364 Clifton Road, Atlanta, Georgia 30322, United States
| | - Weiwei Fang
- Jiangsu
Co-Innovation Center of Efficient Processing and Utilization of Forest
Resources, Jiangsu Provincial Key Lab for the Chemistry and Utilization
of Agro-Forest Biomass, Jiangsu Key Lab of Biomass-Based Green Fuels
and Chemicals, International Innovation Center for Forest Chemicals
and Materials, College of Chemical Engineering, Nanjing Forestry University, Nanjing, Jiangsu 210037, China
| | - Nehal H. Elghazawy
- Department
of Pharmaceutical, Chemistry, Faculty of Pharmacy & Biotechnology, German University in Cairo, 11835 Cairo, Egypt
| | - Jian Rong
- Division
of Nuclear Medicine and Molecular Imaging, Massachusetts General Hospital
& Department of Radiology, Harvard Medical
School, Boston, Massachusetts 02114, United States
- Department
of Radiology and Imaging Sciences, Emory
University, 1364 Clifton Road, Atlanta, Georgia 30322, United States
| | - Jiahui Chen
- Division
of Nuclear Medicine and Molecular Imaging, Massachusetts General Hospital
& Department of Radiology, Harvard Medical
School, Boston, Massachusetts 02114, United States
- Department
of Radiology and Imaging Sciences, Emory
University, 1364 Clifton Road, Atlanta, Georgia 30322, United States
| | - Yinlong Li
- Division
of Nuclear Medicine and Molecular Imaging, Massachusetts General Hospital
& Department of Radiology, Harvard Medical
School, Boston, Massachusetts 02114, United States
- Department
of Radiology and Imaging Sciences, Emory
University, 1364 Clifton Road, Atlanta, Georgia 30322, United States
| | - Chongzhao Ran
- Athinoula
A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Charlestown, Massachusetts 02114, United States
| | - Thomas L. Collier
- Division
of Nuclear Medicine and Molecular Imaging, Massachusetts General Hospital
& Department of Radiology, Harvard Medical
School, Boston, Massachusetts 02114, United States
- Department
of Radiology and Imaging Sciences, Emory
University, 1364 Clifton Road, Atlanta, Georgia 30322, United States
| | - Zhen Chen
- Jiangsu
Co-Innovation Center of Efficient Processing and Utilization of Forest
Resources, Jiangsu Provincial Key Lab for the Chemistry and Utilization
of Agro-Forest Biomass, Jiangsu Key Lab of Biomass-Based Green Fuels
and Chemicals, International Innovation Center for Forest Chemicals
and Materials, College of Chemical Engineering, Nanjing Forestry University, Nanjing, Jiangsu 210037, China
- Division
of Nuclear Medicine and Molecular Imaging, Massachusetts General Hospital
& Department of Radiology, Harvard Medical
School, Boston, Massachusetts 02114, United States
| | - Steven H. Liang
- Division
of Nuclear Medicine and Molecular Imaging, Massachusetts General Hospital
& Department of Radiology, Harvard Medical
School, Boston, Massachusetts 02114, United States
- Department
of Radiology and Imaging Sciences, Emory
University, 1364 Clifton Road, Atlanta, Georgia 30322, United States
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2
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Szczurowska E, Szánti-Pintér E, Chetverikov N, Randáková A, Kudová E, Jakubík J. Modulation of Muscarinic Signalling in the Central Nervous System by Steroid Hormones and Neurosteroids. Int J Mol Sci 2022; 24:ijms24010507. [PMID: 36613951 PMCID: PMC9820491 DOI: 10.3390/ijms24010507] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2022] [Revised: 12/16/2022] [Accepted: 12/19/2022] [Indexed: 12/29/2022] Open
Abstract
Muscarinic acetylcholine receptors expressed in the central nervous system mediate various functions, including cognition, memory, or reward. Therefore, muscarinic receptors represent potential pharmacological targets for various diseases and conditions, such as Alzheimer's disease, schizophrenia, addiction, epilepsy, or depression. Muscarinic receptors are allosterically modulated by neurosteroids and steroid hormones at physiologically relevant concentrations. In this review, we focus on the modulation of muscarinic receptors by neurosteroids and steroid hormones in the context of diseases and disorders of the central nervous system. Further, we propose the potential use of neuroactive steroids in the development of pharmacotherapeutics for these diseases and conditions.
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Affiliation(s)
- Ewa Szczurowska
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Flemingovo Náměstí 2, Prague 6, 166 10 Prague, Czech Republic
| | - Eszter Szánti-Pintér
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Flemingovo Náměstí 2, Prague 6, 166 10 Prague, Czech Republic
| | - Nikolai Chetverikov
- Institute of Physiology, Czech Academy of Sciences, Vídeňská 1083, 142 20 Prague, Czech Republic
| | - Alena Randáková
- Institute of Physiology, Czech Academy of Sciences, Vídeňská 1083, 142 20 Prague, Czech Republic
| | - Eva Kudová
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Flemingovo Náměstí 2, Prague 6, 166 10 Prague, Czech Republic
- Correspondence: (E.K.); (J.J.)
| | - Jan Jakubík
- Institute of Physiology, Czech Academy of Sciences, Vídeňská 1083, 142 20 Prague, Czech Republic
- Correspondence: (E.K.); (J.J.)
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3
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Ozenil M, Aronow J, Millard M, Langer T, Wadsak W, Hacker M, Pichler V. Update on PET Tracer Development for Muscarinic Acetylcholine Receptors. Pharmaceuticals (Basel) 2021; 14:530. [PMID: 34199622 PMCID: PMC8229778 DOI: 10.3390/ph14060530] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2021] [Revised: 05/29/2021] [Accepted: 05/31/2021] [Indexed: 02/07/2023] Open
Abstract
The muscarinic cholinergic system regulates peripheral and central nervous system functions, and, thus, their potential as a therapeutic target for several neurodegenerative diseases is undoubted. A clinically applicable positron emission tomography (PET) tracer would facilitate the monitoring of disease progression, elucidate the role of muscarinic acetylcholine receptors (mAChR) in disease development and would aid to clarify the diverse natural functions of mAChR regulation throughout the nervous system, which still are largely unresolved. Still, no mAChR PET tracer has yet found broad clinical application, which demands mAChR tracers with improved imaging properties. This paper reviews strategies of mAChR PET tracer design and summarizes the binding properties and preclinical evaluation of recent mAChR tracer candidates. Furthermore, this work identifies the current major challenges in mAChR PET tracer development and provides a perspective on future developments in this area of research.
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Affiliation(s)
- Marius Ozenil
- Department of Biomedical Imaging and Image-Guided Therapy, Medical University of Vienna, 1090 Wien, Austria; (M.O.); (J.A.); (W.W.); (M.H.)
| | - Jonas Aronow
- Department of Biomedical Imaging and Image-Guided Therapy, Medical University of Vienna, 1090 Wien, Austria; (M.O.); (J.A.); (W.W.); (M.H.)
| | - Marlon Millard
- Department of Pharmaceutical Sciences, Division of Pharmaceutical Chemistry, University of Vienna, 1090 Wien, Austria; (M.M.); (T.L.)
| | - Thierry Langer
- Department of Pharmaceutical Sciences, Division of Pharmaceutical Chemistry, University of Vienna, 1090 Wien, Austria; (M.M.); (T.L.)
| | - Wolfgang Wadsak
- Department of Biomedical Imaging and Image-Guided Therapy, Medical University of Vienna, 1090 Wien, Austria; (M.O.); (J.A.); (W.W.); (M.H.)
| | - Marcus Hacker
- Department of Biomedical Imaging and Image-Guided Therapy, Medical University of Vienna, 1090 Wien, Austria; (M.O.); (J.A.); (W.W.); (M.H.)
| | - Verena Pichler
- Department of Pharmaceutical Sciences, Division of Pharmaceutical Chemistry, University of Vienna, 1090 Wien, Austria; (M.M.); (T.L.)
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Cumming P, Gründer G, Brinson Z, Wong DF. Applications, Advances, and Limitations of Molecular Imaging of Brain Receptors. Mol Imaging 2021. [DOI: 10.1016/b978-0-12-816386-3.00063-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
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5
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Eckelman WC, Kuwert T, Ciarmiello A, Riondato M, Mansi L. Changes over the years in radiopharmaceutical design. THE QUARTERLY JOURNAL OF NUCLEAR MEDICINE AND MOLECULAR IMAGING : OFFICIAL PUBLICATION OF THE ITALIAN ASSOCIATION OF NUCLEAR MEDICINE (AIMN) [AND] THE INTERNATIONAL ASSOCIATION OF RADIOPHARMACOLOGY (IAR), [AND] SECTION OF THE SOCIETY OF... 2019; 66:261-271. [PMID: 31833739 DOI: 10.23736/s1824-4785.19.03216-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Of the many uses of radiopharmaceuticals, developing radiotracers that contribute significantly to diagnosis and therapy of patients has been a major focus. This requires a broad spectrum of expertise including that of the attending physician who lends insight to an unmet clinical need neither addressed by other imaging techniques nor by analysis of tissue, blood, and urine for diagnostics and addressed by pharmaceuticals for therapeutic applications. The design criteria have depended on radiochemistry, on matching the radiopharmaceutical with the imaging devices, and basing the design on current pharmaceuticals. The chelates of technetium-99m were based on radiochemistry rather than clinical need yet are still used today in >70% of the clinical studies. Targeted radiotracers in neurologic and psychiatric disorders, inflammation, cardiovascular disease, and oncology have all been studied with the goal of determining the change in the density of a target protein as a function of disease or treatment or, especially in oncology, detection of the total extent of disease. In latter approach PET in university settings leads the way; however, the use of SPECT/CT has increased the specificity of SPECT imaging to complement the cost- effective generator and instant kits already available. Remarkable advances has been achieved in radionuclide therapy using theragnostic agents, with the exclusive domain of oncology For this application the design of radionuclide therapy follows that used for diagnostics. The increased impact of the discipline depends on the opportunity to continue the search for the most appropriate radiopharmaceutical for each individual patient.
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Affiliation(s)
| | - Torsten Kuwert
- Clinic of Nuclear Medicine, University Hospital Erlangen, Erlangen, Germany
| | | | - Mattia Riondato
- Nuclear Medicine Unit, S. Andrea Hospital, La Spezia, Italy -
| | - Luigi Mansi
- Section Health and Development, Interuniversity Research Center for Sustainability (CIRPS), Napoli, Italy
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Colom M, Vidal B, Zimmer L. Is There a Role for GPCR Agonist Radiotracers in PET Neuroimaging? Front Mol Neurosci 2019; 12:255. [PMID: 31680859 PMCID: PMC6813225 DOI: 10.3389/fnmol.2019.00255] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2019] [Accepted: 10/02/2019] [Indexed: 12/30/2022] Open
Abstract
Positron emission tomography (PET) is a molecular imaging modality that enables in vivo exploration of metabolic processes and especially the pharmacology of neuroreceptors. G protein-coupled receptors (GPCRs) play an important role in numerous pathophysiologic disorders of the central nervous system. Thus, they are targets of choice in PET imaging to bring proof concept of change in density in pathological conditions or in pharmacological challenge. At present, most radiotracers are antagonist ligands. In vitro data suggest that properties differ between GPCR agonists and antagonists: antagonists bind to receptors with a single affinity, whereas agonists are characterized by two different affinities: high affinity for receptors that undergo functional coupling to G-proteins, and low affinity for those that are not coupled. In this context, agonist radiotracers may be useful tools to give functional images of GPCRs in the brain, with high sensitivity to neurotransmitter release. Here, we review all existing PET radiotracers used from animals to humans and their role for understanding the ligand-receptor paradigm of GPCR in comparison with corresponding antagonist radiotracers.
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Affiliation(s)
- Matthieu Colom
- Lyon Neuroscience Research Center, INSERM, CNRS, Université de Lyon, Lyon, France.,CERMEP, Hospices Civils de Lyon, Bron, France
| | - Benjamin Vidal
- Lyon Neuroscience Research Center, INSERM, CNRS, Université de Lyon, Lyon, France
| | - Luc Zimmer
- Lyon Neuroscience Research Center, INSERM, CNRS, Université de Lyon, Lyon, France.,CERMEP, Hospices Civils de Lyon, Bron, France.,Institut National des Sciences et Techniques Nucléaires, CEA Saclay, Gif-sur-Yvette, France
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7
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Shalgunov V, van Waarde A, Booij J, Michel MC, Dierckx RAJO, Elsinga PH. Hunting for the high-affinity state of G-protein-coupled receptors with agonist tracers: Theoretical and practical considerations for positron emission tomography imaging. Med Res Rev 2018; 39:1014-1052. [PMID: 30450619 PMCID: PMC6587759 DOI: 10.1002/med.21552] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2018] [Revised: 10/02/2018] [Accepted: 10/19/2018] [Indexed: 12/15/2022]
Abstract
The concept of the high‐affinity state postulates that a certain subset of G‐protein‐coupled receptors is primarily responsible for receptor signaling in the living brain. Assessing the abundance of this subset is thus potentially highly relevant for studies concerning the responses of neurotransmission to pharmacological or physiological stimuli and the dysregulation of neurotransmission in neurological or psychiatric disorders. The high‐affinity state is preferentially recognized by agonists in vitro. For this reason, agonist tracers have been developed as tools for the noninvasive imaging of the high‐affinity state with positron emission tomography (PET). This review provides an overview of agonist tracers that have been developed for PET imaging of the brain, and the experimental paradigms that have been developed for the estimation of the relative abundance of receptors configured in the high‐affinity state. Agonist tracers appear to be more sensitive to endogenous neurotransmitter challenge than antagonists, as was originally expected. However, other expectations regarding agonist tracers have not been fulfilled. Potential reasons for difficulties in detecting the high‐affinity state in vivo are discussed.
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Affiliation(s)
- Vladimir Shalgunov
- Department of Nuclear Medicine and Molecular Imaging, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Aren van Waarde
- Department of Nuclear Medicine and Molecular Imaging, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Jan Booij
- Department of Radiology and Nuclear Medicine, Amsterdam University Medical Centers, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | - Martin C Michel
- Department of Pharmacology, Johannes Gutenberg University, Mainz, Germany
| | - Rudi A J O Dierckx
- Department of Nuclear Medicine and Molecular Imaging, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands.,Department of Nuclear Medicine, Ghent University, University Hospital, Ghent, Belgium
| | - Philip H Elsinga
- Department of Nuclear Medicine and Molecular Imaging, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
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8
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Parent M, Bedard MA, Aliaga A, Soucy JP, Landry St-Pierre E, Cyr M, Kostikov A, Schirrmacher E, Massarweh G, Rosa-Neto P. PET imaging of cholinergic deficits in rats using [18F]fluoroethoxybenzovesamicol ([18F]FEOBV). Neuroimage 2012; 62:555-61. [DOI: 10.1016/j.neuroimage.2012.04.032] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2012] [Revised: 04/04/2012] [Accepted: 04/12/2012] [Indexed: 11/28/2022] Open
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9
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Synthesis and in vitro evaluation of novel nortropane derivatives as potential radiotracers for muscarinic m(2) receptors. INTERNATIONAL JOURNAL OF MOLECULAR IMAGING 2011; 2011:709416. [PMID: 21755053 PMCID: PMC3132655 DOI: 10.1155/2011/709416] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/24/2010] [Revised: 03/03/2011] [Accepted: 03/25/2011] [Indexed: 11/18/2022]
Abstract
Disturbances of the cerebral cholinergic neurotransmitter system are present in neurodegenerative disorders. SPECT or PET imaging, using radiotracers that selectively target muscarinic receptor subtypes, may be of value for in vivo evaluation of such conditions. 6β-acetoxynortropane, a potent muscarinic M(2) receptor agonist, has previously demonstrated nanomolar affinity and high selectivity for this receptor. Based on this compound we synthesized four nortropane derivatives that are potentially suitable for SPECT imaging of the M(2) receptor. 6β-acetoxynortropane and the novel derivatives were tested in vitro for affinity to the muscarinic M(1-3) receptors. The original 6β-acetoxynortropane displayed high affinity (K(i) = 70-90 nM) to M(2) receptors and showed good selectivity ratios to the M(1) (65-fold ratio) and the M(3) (70-fold ratio) receptors. All new derivatives showed reduced affinity to the M(2) subtype and loss of subtype selectivity. It is therefore concluded that the newly synthesized derivatives are not suitable for human SPECT imaging of M(2) receptors.
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10
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Yamamoto S, Nishiyama S, Kawamata M, Ohba H, Wakuda T, Takei N, Tsukada H, Domino EF. Muscarinic receptor occupancy and cognitive impairment: a PET study with [11C](+)3-MPB and scopolamine in conscious monkeys. Neuropsychopharmacology 2011; 36:1455-65. [PMID: 21430646 PMCID: PMC3096814 DOI: 10.1038/npp.2011.31] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The muscarinic cholinergic receptor (mAChR) antagonist scopolamine was used to induce transient cognitive impairment in monkeys trained in a delayed matching to sample task. The temporal relationship between the occupancy level of central mAChRs and cognitive impairment was determined. Three conscious monkeys (Macaca mulatta) were subjected to positron emission tomography (PET) scans with the mAChR radioligand N-[(11)C]methyl-3-piperidyl benzilate ([(11)C](+)3-MPB). The scan sequence was pre-, 2, 6, 24, and 48 h post-intramuscular administration of scopolamine in doses of 0.01 and 0.03 mg/kg. Occupancy levels of mAChR were maximal 2 h post-scopolamine in cortical regions innervated primarily by the basal forebrain, thalamus, and brainstem, showing that mAChR occupancy levels were 43-59 and 65-89% in doses of 0.01 and 0.03 mg/kg, respectively. In addition, dose-dependent impairment of working memory performance was measured 2 h after scopolamine. A positive correlation between the mAChR occupancy and cognitive impairment 2 and 6 h post-scopolamine was the greatest in the brainstem (P<0.00001). Although cognitive impairment was not observed 24 h post-scopolamine, sustained mAChR occupancy (11-24%) was found with both doses in the basal forebrain and thalamus, but not in the brainstem. These results indicate that a significant degree of mAChRs occupancy is needed to produce cognitive impairment by scopolamine. Furthermore, the importance of the brainstem cholinergic system in working memory in monkey is described.
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Affiliation(s)
- Shigeyuki Yamamoto
- Osaka-Hamamatsu Joint Research Center for Child Mental Development, Hamamatsu University School of Medicine, Hamamatsu, Shizuoka, Japan
| | - Shingo Nishiyama
- Central Research Laboratory, Hamamatsu Photonics KK, Hirakuchi, Hamakita, Hamamatsu, Shizuoka, Japan
| | - Masahiro Kawamata
- Central Research Laboratory, Hamamatsu Photonics KK, Hirakuchi, Hamakita, Hamamatsu, Shizuoka, Japan
| | - Hiroyuki Ohba
- Central Research Laboratory, Hamamatsu Photonics KK, Hirakuchi, Hamakita, Hamamatsu, Shizuoka, Japan
| | - Tomoyasu Wakuda
- Department of Psychiatry and Neurology, Hamamatsu University School of Medicine, Hamamatsu, Shizuoka, Japan
| | - Nori Takei
- Osaka-Hamamatsu Joint Research Center for Child Mental Development, Hamamatsu University School of Medicine, Hamamatsu, Shizuoka, Japan
| | - Hideo Tsukada
- Central Research Laboratory, Hamamatsu Photonics KK, Hirakuchi, Hamakita, Hamamatsu, Shizuoka, Japan
| | - Edward F Domino
- Department of Pharmacology, University of Michigan, Ann Arbor, MI, USA,Department of Pharmacology, University of Michigan, Ann Arbor, MI 48109-05632, USA, Tel: +1 734 764 9115, Fax: +1 734 763 4450, E-mail:
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11
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van Oosten EM, Wilson AA, Mamo DC, Pollock BG, Mulsant BH, Houle S, Vasdev N. Towards the development of new subtype-specific muscarinic receptor radiopharmaceuticals — Radiosynthesis and ex vivo biodistribution of [18F]3-(4-(2-(2-(2-fluoroethoxy)ethoxy)ethylthio)-1,2,5-thiadiazol-3-yl)-1-methyl-1,2,5,6-tetrahydropyridine. CAN J CHEM 2010. [DOI: 10.1139/v10-149] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Muscarinic receptors have been implicated in neurological disorders including Alzheimer’s disease, Parkinson’s disease, and schizophrenia. Nineteen derivatives of thiadiazolyltetrahydropyridine (TZTP), a core that has previously shown high affinities towards muscarinic receptor subtypes, were synthesized and evaluated via in vitro binding assays. The title compound, a fluoro-polyethyleneglycol analog of TZTP (4c), was subsequently labelled with fluorine-18. Fluorine-18-labelled 4c was produced, via an automated synthesis, in an average radiochemical yield of 36% (uncorrected for decay), with high radiochemical purity (>99%) and high specific activity (326 GBq/µmol; end-of-bombardment), within 40 min (n = 3). Ex vivo biodistribution studies following tail-vein injection of [18F]4c in conscious rats displayed sufficient brain uptake (0.4%–0.7% injected dose / gram of wet tissue in all brain regions at 5 min post injection); however, there were substantial polar metabolites present in the brain, thereby precluding future use of [18F]4c for imaging in the central nervous system.
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Affiliation(s)
- Erik M. van Oosten
- PET Centre, Centre for Addiction and Mental Health, Toronto, ON M5T 1R8, Canada
- Department of Chemistry, University of Toronto, Toronto, ON M5S 3H6, Canada
- Department of Psychiatry, University of Toronto, Toronto, ON M5T 1R8, Canada
- Geriatric Mental Health Program, Centre for Addiction and Mental Health, Toronto, ON M6J 1H4, Canada
| | - Alan A. Wilson
- PET Centre, Centre for Addiction and Mental Health, Toronto, ON M5T 1R8, Canada
- Department of Chemistry, University of Toronto, Toronto, ON M5S 3H6, Canada
- Department of Psychiatry, University of Toronto, Toronto, ON M5T 1R8, Canada
- Geriatric Mental Health Program, Centre for Addiction and Mental Health, Toronto, ON M6J 1H4, Canada
| | - David C. Mamo
- PET Centre, Centre for Addiction and Mental Health, Toronto, ON M5T 1R8, Canada
- Department of Chemistry, University of Toronto, Toronto, ON M5S 3H6, Canada
- Department of Psychiatry, University of Toronto, Toronto, ON M5T 1R8, Canada
- Geriatric Mental Health Program, Centre for Addiction and Mental Health, Toronto, ON M6J 1H4, Canada
| | - Bruce G. Pollock
- PET Centre, Centre for Addiction and Mental Health, Toronto, ON M5T 1R8, Canada
- Department of Chemistry, University of Toronto, Toronto, ON M5S 3H6, Canada
- Department of Psychiatry, University of Toronto, Toronto, ON M5T 1R8, Canada
- Geriatric Mental Health Program, Centre for Addiction and Mental Health, Toronto, ON M6J 1H4, Canada
| | - Benoit H. Mulsant
- PET Centre, Centre for Addiction and Mental Health, Toronto, ON M5T 1R8, Canada
- Department of Chemistry, University of Toronto, Toronto, ON M5S 3H6, Canada
- Department of Psychiatry, University of Toronto, Toronto, ON M5T 1R8, Canada
- Geriatric Mental Health Program, Centre for Addiction and Mental Health, Toronto, ON M6J 1H4, Canada
| | - Sylvain Houle
- PET Centre, Centre for Addiction and Mental Health, Toronto, ON M5T 1R8, Canada
- Department of Chemistry, University of Toronto, Toronto, ON M5S 3H6, Canada
- Department of Psychiatry, University of Toronto, Toronto, ON M5T 1R8, Canada
- Geriatric Mental Health Program, Centre for Addiction and Mental Health, Toronto, ON M6J 1H4, Canada
| | - Neil Vasdev
- PET Centre, Centre for Addiction and Mental Health, Toronto, ON M5T 1R8, Canada
- Department of Chemistry, University of Toronto, Toronto, ON M5S 3H6, Canada
- Department of Psychiatry, University of Toronto, Toronto, ON M5T 1R8, Canada
- Geriatric Mental Health Program, Centre for Addiction and Mental Health, Toronto, ON M6J 1H4, Canada
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12
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Chung KA, Lobb BM, Nutt JG, Horak FB. Effects of a central cholinesterase inhibitor on reducing falls in Parkinson disease. Neurology 2010; 75:1263-9. [PMID: 20810998 DOI: 10.1212/wnl.0b013e3181f6128c] [Citation(s) in RCA: 170] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
OBJECTIVE To investigate if a central cholinesterase inhibitor will reduce falling frequency in subjects with Parkinson disease (PD) with advanced postural instability. BACKGROUND Falling due to postural instability is a significant problem in advancing PD, and is minimally impacted by dopaminergic therapy. Anticholinergic medications increase falling in the elderly. Further, CNS cholinergic neuron loss occurs in PD. We hypothesized that acetylcholine augmentation may reduce frequent falling in subjects with PD. METHODS We enrolled 23 subjects with PD who reported falling or nearly falling more than 2 times per week. In a randomized, placebo-controlled, crossover design, subjects were given 6 weeks of donepezil or placebo with a 3-week washout between phases. The primary outcomes were daily falls and near falls reported on postcards. Secondary outcomes included scores on the Activities of Balance Confidence Scale, Berg Balance Scale, Clinical Global Impression of Change, Folstein Mini-Mental State Examination, and the motor section of the Unified Parkinson's Disease Rating Scale. RESULTS Fall frequency per day on placebo was 0.25 ± 0.08 (SEM) compared with 0.13 ± 0.03 on donepezil (p < 0.05). The frequency of near falls was not significantly different between phases. The secondary outcomes did not differ; however, there was a trend to improvement on the subject-completed Global Impression of Change scale. CONCLUSIONS Subjects with PD fell approximately half as often during the 6 weeks on donepezil than on placebo. Larger trials of cholinergic augmentation are warranted in subjects with PD with frequent falls. CLASSIFICATION OF EVIDENCE This study provides Class II evidence that donepezil (maximum 10 mg per day) significantly reduced the number of falls in patients with PD (0.13 falls/day, SEM = 0.03) than when taking placebo (0.25 falls/day, SEM = 0.08, p = 0.049).
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Affiliation(s)
- Kathryn A Chung
- Department of Neurology, Oregon Health & Science University, Portland, OR, USA.
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Localisation of pre- and postsynaptic cholinergic markers in the human brain. Behav Brain Res 2010; 221:341-55. [PMID: 20170687 DOI: 10.1016/j.bbr.2010.02.025] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2010] [Accepted: 02/10/2010] [Indexed: 12/20/2022]
Abstract
The cholinergic neurotransmission in the central nervous system plays an important role in modulating cognitive processes such as learning, memory, arousal and sleep as well as in modulating locomotor activity. Dysfunction of the central cholinergic system is involved in numerous neuropsychiatric diseases. This review will provide a synopsis on the regional localisation of cholinergic and cholinoceptive structures within the adult human brain. On the cholinergic site data based on the distribution of choline acetyltransferase-immunoreactive structures are in the focus, complemented by data from acetylcholinesterase and vesicular acetylcholine transporter studies. On the cholinoceptive site, the distribution and localisation of receptors that transduce the acetylcholine message, i.e. the muscarinic and the nicotinic acetylcholine receptors is summarized. In addition to these data obtained on post mortem brain an overview of markers which allow for the in vivo monitoring of the cholinergic system in the brain is given. The detailed knowledge on the distribution and localisation of cholinergic markers in human brain will provide further information on the cholinergic circuits of neurotransmission - a prerequisite for the interpretation of in vivo imaging data and the development of selective diagnostic and therapeutic compounds.
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Radiopharmaceuticals for positron emission tomography investigations of Alzheimer’s disease. Eur J Nucl Med Mol Imaging 2009; 37:1575-93. [DOI: 10.1007/s00259-009-1301-z] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2009] [Accepted: 10/09/2009] [Indexed: 12/11/2022]
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van Oosten EM, Wilson AA, Stephenson KA, Mamo DC, Pollock BG, Mulsant BH, Yudin AK, Houle S, Vasdev N. An improved radiosynthesis of the muscarinic M2 radiopharmaceutical, [18F]FP-TZTP. Appl Radiat Isot 2009; 67:611-6. [DOI: 10.1016/j.apradiso.2008.12.015] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2008] [Revised: 12/01/2008] [Accepted: 12/19/2008] [Indexed: 11/16/2022]
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16
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Molecular Imaging in Neurology and Psychiatry. Mol Imaging 2009. [DOI: 10.1007/978-3-540-76735-0_16] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
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Reid AE, Ding YS, Eckelman WC, Logan J, Alexoff D, Shea C, Xu Y, Fowler JS. Comparison of the pharmacokinetics of different analogs of 11C-labeled TZTP for imaging muscarinic M2 receptors with PET. Nucl Med Biol 2008; 35:287-98. [PMID: 18355684 DOI: 10.1016/j.nucmedbio.2008.01.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2007] [Revised: 01/03/2008] [Accepted: 01/06/2008] [Indexed: 11/28/2022]
Abstract
INTRODUCTION The only radiotracer available for the selective imaging of muscarinic M2 receptors in vivo is 3-(3-(3-[18F]fluoropropyl)thio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine) ([18F]FP-TZTP). We have prepared and labeled 3-(3-(3-fluoropropylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridne (FP-TZTP, 3) and two other TZTP derivatives with 11C at the methylpyridine moiety to explore the potential of using 11C-labeled FP-TZTP for positron emission tomography imaging of M2 receptors and to compare the effect of small structural changes on tracer pharmacokinetics (PK) in brain and peripheral organs. METHODS 11C-radiolabeled FP-TZTP, 3-(3-propylthio)-TZTP (6) and 3,3,3-(3-(3-trifluoropropyl)-TZTP (10) were prepared, and log D, plasma protein binding (PPB), affinity constants, time-activity curves (TACs), area under the curve (AUC) for arterial plasma, distribution volumes (DV) and pharmacological blockade in baboons were compared. RESULTS Values for log D, PPB and affinity constants were similar for 3, 6 and 10. The fraction of parent radiotracer in the plasma was higher and the AUC lower for 10 than for 3 and 6. TACs for brain regions were similar for 3 and 6, which showed PK similar to the 18F tracer, while 10 showed slower uptake and little clearance over 90 min. DVs for 3 and 6 were similar to the 18F tracer but higher for 10. Uptake of the three tracers was significantly reduced by coinjection of unlabeled 3 and 6. CONCLUSION Small structural variations on the TZTP structure greatly altered the PK in brain and behavior in blood with little change in the log D, PPB or affinity. The study suggests that 11C-radiolabeled 3 will be a suitable alternative to [18F]FP-TZTP for translational studies in humans.
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Affiliation(s)
- Alicia E Reid
- Medical Department, Brookhaven National Laboratory, Upton, NY 11973, USA.
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Gender-dependent increases with healthy aging of the human cerebral cannabinoid-type 1 receptor binding using [18F]MK-9470 PET. Neuroimage 2008; 39:1533-41. [DOI: 10.1016/j.neuroimage.2007.10.053] [Citation(s) in RCA: 97] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2007] [Revised: 10/30/2007] [Accepted: 10/31/2007] [Indexed: 12/21/2022] Open
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Melzer P, Mineo L, Ebner FF. Optic nerve transection affects development and use-dependent plasticity in neocortex of the rat: Quantitative acetylcholinesterase imaging. Brain Res 2007; 1139:68-84. [PMID: 17280650 DOI: 10.1016/j.brainres.2006.12.080] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2006] [Revised: 12/04/2006] [Accepted: 12/14/2006] [Indexed: 11/15/2022]
Abstract
We investigated the effects of neonatal optic nerve transection on cortical acetylcholinesterase (AChE) activity in hooded rats during postnatal development and following behavioral manipulation after weaning. AChE reaction product was quantified on digitized images of histochemically stained sections in layer IV of primary somatic sensory, primary visual and visual association cortex. Rats with optic nerve transection were compared to sham-operated littermates. In all cortical regions of both types of animal, AChE reaction product was increased to peak 2 weeks after birth and decreased thereafter, reaching adult levels at the end of the third postnatal week. During postnatal development, reaction product in primary visual cortex was lower in rats deprived of retinal input than in sham-operated littermates and the area delineated by reaction product was smaller. However, optic nerve transection did not modify the time course of postnatal development or statistically significantly diminish adult levels of AChE activity. Behavioral manipulations after weaning statistically significantly increased enzyme activity in sham-operated rats in all cortical areas examined. Compared with cage rearing, training in a discrimination task with food reward had a greater impact than environmental enrichment. By contrast, in the rats with optic nerve transection enrichment and training resulted in statistically significantly increased AChE activity only in lateral visual association cortex. Our findings provide evidence for intra- and supramodal influences of the neonatal removal of retinal input on neural activity- and use-dependent modifications of cortical AChE activity. The laminar distribution of the AChE reaction product suggests that the observed changes in AChE activity were mainly related to cholinergic basal forebrain afferents. These afferents may facilitate the stabilization of transient connections between the somatic sensory and the visual pathway.
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Affiliation(s)
- Peter Melzer
- Deparment of Psychology, Vanderbilt University, 301 Wilson Hall, 111 21st Ave. S., Nashville, Tennessee 37203, USA.
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Kiesewetter DO, Jagoda EM, Shimoji K, Ma Y, Eckelman WC. Evaluation of [18F]fluoroxanomeline {5-{4-[(6-[18F]fluorohexyl)oxy]-1,2,5-thiadiazol-3-yl}-1-methyl-1,2,3,6-tetrahydropyridine} in muscarinic knockout mice. Nucl Med Biol 2007; 34:141-52. [PMID: 17307122 DOI: 10.1016/j.nucmedbio.2006.11.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2006] [Revised: 11/17/2006] [Accepted: 11/25/2006] [Indexed: 11/25/2022]
Abstract
INTRODUCTION We set out to develop a muscarinic M1-selective agonist (based on the structure of the functionally M1-selective xanomeline) that could be radiolabeled with fluorine-18 for use as an imaging agent for positron emission tomography. METHODS The radiochemical synthesis was achieved, employing the arts of organic and radiochemical syntheses. Binding selectivity studies employed biodistribution studies, using autoradiography and/or tissue dissection, in wild-type or muscarinic receptor knockout mice. RESULTS [(18)F]Fluoroxanomeline shows rather uniform uptake in all mouse brain regions and high specific binding, with a brain-to-blood ratio of 32 at 60 min postinjection. In addition, the specific binding is demonstrated by a 58% to 75% decrease in brain uptake upon coinjection with 5 nmol of unlabeled fluoroxanomeline or xanomeline. Brain uptake studies with [(3)H]xanomeline in muscarinic knockout mice show decreased uptake in M1 (17-34%) and M2 (2-20%) knockout mice compared with control. However, statistical significance was observed in only a few regions. Comparison of [(18)F]fluoroxanomeline in knockout mice showed no difference in M1 or M4 knockout mice but a general decrease in M2 (2-24%) knockout mice. The decrease of [(18)F]fluoroxanomeline uptake in M2 knockout mice reached statistical significance in brain stem, cerebellum, frontal cortex, hippocampus, inferior colliculus and superior colliculus. CONCLUSION Although xanomeline displays highly selective M1 agonist activity in functional assays, little selectivity for muscarinic subtype binding was observed for xanomeline or its fluorine-containing analogue, fluoroxanomeline. This emphasizes the lack of correlation between functional selectivity and binding selectivity.
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Affiliation(s)
- Dale O Kiesewetter
- Positron Emission Tomography Radiochemistry Group, NIBIB, NIH, Bethesda, MD 20892, USA.
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Cohen RM, Carson RE, Filbey F, Szczepanik J, Sunderland T. Age and APOE-epsilon4 genotype influence the effect of physostigmine infusion on the in-vivo distribution volume of the muscarinic-2-receptor dependent tracer [18F]FP-TZTP. Synapse 2006; 60:86-92. [PMID: 16598702 DOI: 10.1002/syn.20276] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The apolipoprotein E-epsilon4 allele (APOE-epsilon4) confers greater susceptibility to age-related memory disorders. Abnormalities in the cholinergic system are likely contributors to these disorders with both age and APOE-epsilon4 genotype modifying behavioral and physiological responses to drugs that alter cholinergic pathway function. Recently, we reported a greater in vivo distribution volume of the F-18 labeled muscarinic-2 (M2) selective agonist, 3-(3-(3-[18F]Flouropropyl)thio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine ([18F]FP-TZTP), in aging healthy subjects with an APOE-epsilon4 allele. To examine the effects of aging and the APOE-epsilon4 allele on the response of the muscarinic component of cholinergic pathway to pharmacologic augmentation, two [18F]FP-TZTP PET scans were conducted in 19 subjects varying in age from 22 to 74 years, the first served as baseline for the second scan that was performed while the subjects were either infused with saline (n = 6) or with the acetylcholinesterase inhibitor physostigmine (6 with an APOE-epsilon4 allele and 7 without an APOE-epsilon4 allele). Using a multiple regression analysis, both AGE (beta = 0.621 +/- 0.135, B = 0.353 +/- 0.077, t(10) = 4.61, P < 0.001) and APOE-epsilon4 genotype (beta = 0.742, B = 14.8 +/- 2.69, t(10) = 5.51, P < 0.0003) were found to be significant contributors to subject response to physostigmine. The adjusted R2 for the model as a whole was 0.786 (F(2,10) = 23.00, P < 0.0002) with both increasing age and the presence of the APOE-epsilon4 allele modifying the response to physostigmine in the direction of larger decreases in [18F]FP-TZTP distribution volumes in all brain regions examined. The findings, particularly the absence of an interaction between AGE and APOE-epsilon4 genotype, contribute to the growing body of evidence that suggests that the APOE-epsilon4 genotype is likely to contribute to brain structure and function prior to aging.
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Affiliation(s)
- Robert M Cohen
- Geriatric Psychiatry Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland 20892, USA.
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Ravasi L, Kiesewetter DO, Shimoji K, Lucignani G, Eckelman WC. Why does the agonist [18F]FP-TZTP bind preferentially to the M2 muscarinic receptor? Eur J Nucl Med Mol Imaging 2005; 33:292-300. [PMID: 16333673 DOI: 10.1007/s00259-005-1966-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2005] [Accepted: 09/14/2005] [Indexed: 11/28/2022]
Abstract
PURPOSE Preferential binding of FP-TZTP at the M(2) receptor in vivo led to investigation of [(18)F]FP-TZTP as a potential PET tracer for Alzheimer's disease, in which a substantial reduction of M(2) receptors has been observed in autopsy studies. We hereby investigated in vitro the FP-TZTP behavior to further elucidate the properties of FP-TZTP that lead to its M(2) selectivity. METHODS Chinese hamster ovarian cells expressing the five subtypes of human muscarinic receptor as well as the wild type were harvested in culture to assess equilibrium binding. Specific binding was calculated by subtraction of non-specific binding from total binding. Internal specific binding was calculated by subtraction of external specific binding from the total specific binding. Saturation assays were also performed to calculate B(max), K(i), and IC(50). In addition, equilibrium binding and dissociation kinetic studies were performed on rat brain tissue. Selected regions of interest were drawn on the digital autoradiograms and [(18)F]FP-TZTP off-rates were determined by measurement of the rate of release into a buffer solution of [(18)F]FP-TZTP from slide-bound cells that had been preincubated with [(18)F]FP-TZTP. RESULTS At equilibrium in vitro, M(2) subtype selectivity of [(18)F]FP-TZTP was not evident. We demonstrated that ATP-dependent mechanisms are not responsible for FP-TZTP M(2) selectivity. In vitro off-rate studies from rat brain tissue showed that the off-rate of FP-TZTP varied with the percentage of M(2) subtype in the tissue region. CONCLUSION The slower dissociation kinetics of FP-TZTP from M(2) receptors compared with the four other muscarinic receptor subtypes may be a factor in its M(2) selectivity.
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Affiliation(s)
- L Ravasi
- PET Radiochemistry Group, National Institute for Biomedical Imaging and Bioengineering, National Institutes of Health, 10 Center Drive, Bethesda, MD 20892, USA
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Sunderland T, Gur RE, Arnold SE. The use of biomarkers in the elderly: current and future challenges. Biol Psychiatry 2005; 58:272-6. [PMID: 16018985 DOI: 10.1016/j.biopsych.2005.05.016] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/02/2004] [Revised: 05/04/2005] [Accepted: 05/10/2005] [Indexed: 10/25/2022]
Abstract
Biomarkers are hypothesized but not frequently used in research with the elderly because of a general paucity of supportive scientific data. However, there is an obvious need for greater diagnostic specificity and sensitivity across many diagnoses in the elderly, as well as good targets for therapeutic trials. The authors reviewed the available information in this field as part of a general review of geriatric research for the . Potential biomarkers with pathophysiologic significance have been studied in the field of Alzheimer disease research with some success, especially in the area of genetic markers (apolipoprotein E [APOE] epsilon4 allele), neuroimaging, and cerebrospinal fluid markers (beta-amyloid and tau). While some progress has been made in the search for adequate biomarkers in the elderly, in particular with Alzheimer disease, much more work is needed before these potential biomarkers can be reliably used in clinical practice.
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Affiliation(s)
- Trey Sunderland
- Geriatric Psychiatry Branch, National Institute of Mental Health, Bethesda, Maryland 20892, USA.
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Coccini T, Randine G, Castoldi AF, Balloni L, Baiardi P, Manzo L. Lymphocyte muscarinic receptors and platelet monoamine oxidase-B as biomarkers of CNS function: effects of age and gender in healthy humans. ENVIRONMENTAL TOXICOLOGY AND PHARMACOLOGY 2005; 19:715-720. [PMID: 21783547 DOI: 10.1016/j.etap.2004.12.042] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Lymphocyte cholinergic muscarinic receptors (MRs) and platelet monoamine oxidase-B (MAO-B) activity are considered surrogate markers of the same parameters in the central nervous system. Lymphocyte MR binding and platelet MAO-B activity were measured in a consistent number of healthy human adults and analysed according to gender and age. The mean value±S.D. of MR binding neither differed between males (12.2±10.0fmol/10(6)cells, range: 0.5-37.9, n=86) and females (10.7±9.7fmol/10(6)cells, range: 0.5-39.7, n=69) nor among age groups. MAO-B activity was significantly higher in women (geometric mean: 11.3nmol/mgprotein/h, with 65% of values from 7.3 to 17.6; n=43), than in men (7.7nmol/mgprotein/h, with 65% of values from 4.5 to 13; n=95). Males aged 56-66 years displayed a higher, though not statistically significant, basal enzyme activity than younger subjects. Altogether these data indicate gender-related differences in MAO activity, but not in MR binding, and inter-individual differences in the basal values of both peripheral blood markers in healthy subjects.
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Affiliation(s)
- Teresa Coccini
- Toxicology Division, Institute of Pavia, IRCCS Salvatore Maugeri Foundation, Via Ferrata 8, 27100 Pavia, Italy
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Lemaître H, Crivello F, Grassiot B, Alpérovitch A, Tzourio C, Mazoyer B. Age- and sex-related effects on the neuroanatomy of healthy elderly. Neuroimage 2005; 26:900-11. [PMID: 15955500 DOI: 10.1016/j.neuroimage.2005.02.042] [Citation(s) in RCA: 205] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2004] [Revised: 02/04/2005] [Accepted: 02/24/2005] [Indexed: 10/25/2022] Open
Abstract
Effects of age and sex, and their interaction on the structural brain anatomy of healthy elderly were assessed thanks to a cross-sectional study of a cohort of 662 subjects aged from 63 to 75 years. T1- and T2-weighted MRI scans were acquired in each subject and further processed using a voxel-based approach that was optimized for the identification of the cerebrospinal fluid (CSF) compartment. Analysis of covariance revealed a classical neuroanatomy sexual dimorphism, men exhibiting larger gray matter (GM), white matter (WM), and CSF compartment volumes, together with larger WM and CSF fractions, whereas women showed larger GM fraction. GM and WM were found to significantly decrease with age, while CSF volume significantly increased. Tissue probability map analysis showed that the highest rates of GM atrophy in this age range were localized in primary cortices, the angular and superior parietal gyri, the orbital part of the prefrontal cortex, and in the hippocampal region. There was no significant interaction between "Sex" and "Age" for any of the tissue volumes, as well as for any of the tissue probability maps. These findings indicate that brain atrophy during the seventh and eighth decades of life is ubiquitous and proceeds at a rate that is not modulated by "Sex".
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Affiliation(s)
- Hervé Lemaître
- Groupe d'Imagerie Neurofonctionnelle, UMR 6194, CNRS, CEA, Universités de Caen et Paris 5, GIP Cyceron, BP5229, F-14074 Caen, France
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Orth M, Amann B, Robertson MM, Rothwell JC. Excitability of motor cortex inhibitory circuits in Tourette syndrome before and after single dose nicotine. ACTA ACUST UNITED AC 2005; 128:1292-300. [PMID: 15774505 DOI: 10.1093/brain/awh473] [Citation(s) in RCA: 91] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The pathophysiology underlying the involuntary tics of Gilles de la Tourette syndrome (GTS) remains unknown. Here we used transcranial magnetic stimulation (TMS) to examine the excitability of two different inhibitory systems in the human motor cortex: short interval intracortical inhibition (SICI) and short interval afferent inhibition (SAI) in 10 healthy non-smoking controls and eight untreated non-smoking patients with GTS. Compared with the healthy control group, both SICI (measured at a range of conditioning intensities) and SAI were reduced in patients. This is consistent with the suggestion that reduced excitability of cortical inhibition is one factor that contributes to the difficulty that patients have in suppressing involuntary tics. In addition, the reduced SAI indicates that impaired intracortical inhibition may not be limited to the motor cortex but also involves circuits linking sensory input and motor output. A single dose of nicotine reduced tic severity as assessed by blind video scoring in the majority of patients. In addition, it abolished the difference between patients and controls in SICI and SAI. There was no effect of nicotine, and no difference between controls and patients in measures of motor or SICI threshold. This indicates that cholinergic input can modulate the efficiency of SICI and SAI differently in GTS and healthy controls.
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Affiliation(s)
- M Orth
- Sobell Department of Motor Neuroscience and Movement Disorders,The National Hospital for Neurology and Neurosurgery, Royal Free and University College Medical School, Queen Square, London WC1N 3BG, UK.
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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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Scott Mason N, Mathis CA. Positron Emission Tomography Agents for Central Nervous System Drug Development Applications. ANNUAL REPORTS IN MEDICINAL CHEMISTRY 2005. [DOI: 10.1016/s0065-7743(05)40004-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/20/2023]
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Décossas M, Doudnikoff E, Bloch B, Bernard V. Aging and subcellular localization of m2 muscarinic autoreceptor in basalocortical neurons in vivo. Neurobiol Aging 2004; 26:1061-72. [PMID: 15748786 DOI: 10.1016/j.neurobiolaging.2004.09.007] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2004] [Revised: 09/07/2004] [Accepted: 09/24/2004] [Indexed: 10/26/2022]
Abstract
By using immunohistochemical approaches at the light and electron microscopic levels, we have shown that aging modifies the subcellular distribution of the m2 muscarinic autoreceptor (m2R) differentially at somato-dendritic postsynaptic sites and at axonal presynaptic sites in cholinergic basalocortical neurons, in vivo. In cholinergic perikarya and dendrites of the nucleus basalis magnocellularis (NBM), aging is associated with a decrease of the density of m2R at the plasma membrane and in the cytoplasm, suggesting a decrease of the total number of m2R in the somato-dendritic field. In contrast, the number of substance P receptors per somato-dendritic surface was not affected. In the frontal cortex (FC), we have shown a decrease of cytoplasmic m2R density also leading to a decrease of the number of m2R per surface of varicosities but with no change of the density of m2R at the membrane. Our results suggest that the decrease of m2R in the somato-dendritic field of the NBM, but not a modification of the number of presynaptic m2 autoreceptors at the plasma membrane in the FC, could contribute to the decrease of the efficacy of cholinergic transmission observed with aging in the rat.
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Affiliation(s)
- Marion Décossas
- Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5541, Laboratoire d'Histologie-Embryologie, Université Victor Ségalen-Bordeaux 2, 146 rue Léo-Saignat, 33076 Bordeaux Cedex, France
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Eckelman WC, Rice KC, Contoreggi C. New tools to monitor stress using non-invasive PET imaging. Ann N Y Acad Sci 2004; 1018:487-94. [PMID: 15240406 DOI: 10.1196/annals.1296.060] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Noninvasive imaging using positron emission tomography (PET) is playing an increasing role in monitoring biochemical changes in vivo in various diseases. For example, many of the neurochemical systems activated by stress can be monitored using this technique. Examples of neurotransmitter interactions with CRH, serotonin, dopamine, and muscarinic cholinergic receptors demonstrate this approach.
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Affiliation(s)
- William C Eckelman
- PET Department, Warren G. Magnuson Clinical Center, 10 Center Drive, Rm. 1C401, Bethesda, MD 20892, USA.
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Norbury R, Travis MJ, Erlandsson K, Waddington W, Owens J, Ell PJ, Murphy DG. SPET imaging of central muscarinic receptors with (R,R)[123I]-I-QNB: methodological considerations. Nucl Med Biol 2004; 31:583-90. [PMID: 15219276 DOI: 10.1016/j.nucmedbio.2004.01.003] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2003] [Revised: 01/23/2004] [Accepted: 01/24/2004] [Indexed: 11/21/2022]
Abstract
Investigations on the effect of normal healthy ageing on the muscarinic system have shown conflicting results. Also, in vivo determination of muscarinic receptor binding has been hampered by a lack of subtype selective ligands and differences in methods used for quantification of receptor densities. Recent in vitro and in vivo work with the muscarinic antagonist (R,R)-I-QNB indicates this ligand has selectivity for m(1) and m(4) muscarinic receptor subtypes. Therefore, we used (R,R)[(123)I]-I-QNB and single photon emission tomography to study brain m(1) and m(4) muscarinic receptors in 25 healthy female subjects (11 younger subjects, age range 26-32 years and 14 older subjects, age range 57-82 years). Our aims were to ascertain the viability of tracer administration and imaging within the same day, and to evaluate whether normalization to whole brain, compared to normalization to cerebellum, could alter the clinical interpretation of results. Images were analyzed using the simplified reference tissue model and by two ratio methods: normalization to whole brain and normalization to cerebellum. Significant correlations were observed between kinetic analysis and normalization to cerebellum, but not to whole brain. Both the kinetic analysis and normalization to cerebellum showed age-related reductions in muscarinic binding in frontal, orbitofrontal, and parietal regions. Normalization to whole brain, however, failed to detect age-related changes in any region. Here we show that, for this radiotracer, normalizing to a region of negligible specific binding (cerebellum) significantly improves sensitivity when compared to global normalization.
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Affiliation(s)
- R Norbury
- Psychological Medicine, Institute of Psychiatry, Denmark Hill, London, United Kingdom.
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Abstract
Factors that place constraints on radio-chemists who are seeking to design and develop radiopharmaceuticals for PET imaging studies include the short half-lives of 11C and 18F, minimum radiochemical yield and specific activity requirements, and high radiation fields that are associated with multi-Curie quantities of PET radionuclides. Nevertheless, during the past 20 years, considerable progress has been made in the development and application of a variety of PET radiotracers for a range of imaging studies in human subjects. We have highlighted a few areas of radiochemistry that focused on PET radiotracers that are described in this issue. Although the number of PET radiotracers synthesized is in the hundreds [6], much work remains to develop specific and useful PET radiotracers for a host of new and exciting noninvasive imaging applications.
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Affiliation(s)
- N Scott Mason
- Positron Emission Tomography Facility, Department of Radiology, University of Pittsburgh, B-938, UPMC Presbyterian, 200 Lothrop Street, Pittsburgh, PA 15213-2582, USA.
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Adams KH, Pinborg LH, Svarer C, Hasselbalch SG, Holm S, Haugbøl S, Madsen K, Frøkjaer V, Martiny L, Paulson OB, Knudsen GM. A database of [18F]-altanserin binding to 5-HT2A receptors in normal volunteers: normative data and relationship to physiological and demographic variables. Neuroimage 2004; 21:1105-13. [PMID: 15006678 DOI: 10.1016/j.neuroimage.2003.10.046] [Citation(s) in RCA: 97] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2003] [Revised: 10/29/2003] [Accepted: 10/31/2003] [Indexed: 11/29/2022] Open
Abstract
This study presents the results of an analysis of 5-hydroxytryptamine (5-HT)(2A) receptors in 52 healthy subjects. Thirty men and twenty-two women aged between 21 and 79 years were investigated with magnetic resonance imaging (MRI) and [(18)F]-altanserin positron emission tomography (PET). The distribution volumes of specific tracer binding (DV(3)') was calculated for 15 brain regions using either cerebellum or pons as reference regions and correlations between DV(3)' and physiological and demographic variables were made. The regional distribution of [(18)F]-altanserin binding in the healthy human brain was in agreement with existing in vitro post-mortem human 5-HT(2A) data. Apart from nonspecific cerebellar binding (DV(2)), there was no gender difference in 5-HT(2A) binding. A positive correlation between cerebellar binding and age was observed and negative correlations between age and DV(3)' were found in all cortical regions, except occipital cortex, corresponding to a decrease in DV(3)' of 6% or 4% per decade with cerebellum or pons as reference regions, respectively. In several temporal and frontal cortical regions, positive correlations were found between body mass index (BMI) and DV(3)'. Our findings provide a resource to aid design of clinical studies of the 5-HT(2A) receptors. [(18)F]-altanserin binding appears to be unaffected by gender, but the effects of ageing must be considered for clinical studies. The correlations between different cortical regions' 5-HT(2A) binding and BMI should be explored in future studies.
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Affiliation(s)
- Karen H Adams
- Neurobiology Research Unit, University Hospital of Copenhagen, Rigshospitalet, Denmark
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Knol RJJ, Doornbos T, van den Bos JC, de Bruin K, Pfaffendorf M, Aanhaanen W, Janssen AGM, Vekemans JAJM, van Eck-Smit BLF, Booij J. Synthesis and evaluation of iodinated TZTP-derivatives as potential radioligands for imaging of muscarinic M2 receptors with SPET. Nucl Med Biol 2004; 31:111-23. [PMID: 14741576 DOI: 10.1016/s0969-8051(03)00095-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
A series of iodinated thiadiazolyltetrahydro-1-methyl-pyridine (TZTP) compounds was synthesized and evaluated in vitro and in vivo as potential radioligands for imaging of the muscarinic M2 receptor subtype with SPET. One of these compounds, 5-(E)-iodopentenylthio-TZTP, has high in vitro affinity (Ki = 4.9 nM) and moderate selectivity for the muscarinic M2 receptor subtype. Although the uptake pattern in the biodistribution studies in rats is consistent with muscarinic M2 receptor disribution, specific in vivo binding to these receptors could not be demonstrated. The usefulness of this tracer in human SPET imaging may therefore be limited.
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Affiliation(s)
- Remco J J Knol
- Graduate School of Neurosciences, Department of Nuclear Medicine, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
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Herholz K, Weisenbach S, Zündorf G, Lenz O, Schröder H, Bauer B, Kalbe E, Heiss WD. In vivo study of acetylcholine esterase in basal forebrain, amygdala, and cortex in mild to moderate Alzheimer disease. Neuroimage 2004; 21:136-43. [PMID: 14741650 DOI: 10.1016/j.neuroimage.2003.09.042] [Citation(s) in RCA: 102] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
It is currently unclear whether impairment of the cholinergic system is present in Alzheimer disease (AD) already at an early stage and to what extent it depends on degeneration of the nucleus basalis of Meynert (nbM). We examined acetylcholine esterase activity in vivo in the nbM, the amygdala, and cerebral neocortex. Measurements were performed in normal controls and in patients with mild to moderate AD with positron emission tomography (PET) and C-11-labeled N-methyl-4-piperidyl-acetate (MP4A) which is a specific substrate of AChE. AChE activity was reduced significantly in amygdala and cerebral cortex. In contrast, AChE activity and glucose metabolism appeared preserved or even increased in the nbM. The results support the concept that neocortical and amygdaloid functional changes of the cholinergic system are an early and leading event in AD, rather than the consequence of neurodegeneration of basal nuclei.
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Affiliation(s)
- K Herholz
- Department of Neurology, University Cologne, and Max-Planck Institute for Neurological Research, Cologne, Germany.
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Shimoji K, Esaki T, Itoh Y, Ravasi L, Cook M, Jehle J, Jagoda EM, Kiesewetter DO, Schmidt K, Sokoloff L, Eckelman WC. Inhibition of [18F]FP-TZTP binding by loading doses of muscarinic agonists P-TZTP or FP-TZTP in vivo is not due to agonist-induced reduction in cerebral blood flow. Synapse 2003; 50:151-63. [PMID: 12923818 DOI: 10.1002/syn.10257] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
[(18)F][3-(3-(3-Fluoropropyl)thio)-1,2,5-thiadiazol-4-yl]-1,2,5,6-tetrahydro-1-methylpyridine ([(18)F]FP-TZTP) is an M2 selective muscarinic agonist that may allow noninvasive studies of Alzheimer's disease with PET. 3-(3-(Propylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine (P-TZTP), a nonfluorinated analog of FP-TZTP, and unlabeled FP-TZTP inhibited [(18)F]FP-TZTP binding in vivo. Because muscarinic action of the loading dose of P-TZTP administered might have had pharmacological effects, the apparent inhibition might have resulted from reduced delivery rather than competition with receptor-binding. Therefore, we examined the effects of P-TZTP or FP-TZTP administration on cerebral blood flow (CBF) measured by the [(14)C]iodoantipyrine method and laser-Doppler flowmetry in rats. Statistically significant synchronous decreases in both CBF and mean arterial blood pressure (MABP) were observed within the first minute following administration. The decreases in both CBF and MABP were prevented by pretreatment with atropine methyl bromide (M-At), a peripheral muscarinic antagonist, and coadministration of M-At with either FP-TZTP or P-TZTP resulted in the same degree of inhibition of cerebral [(18)F]FP-TZTP-uptake 30 min after administration as observed without M-At. Also, with programmed infusions designed to produce constant arterial concentrations of [(18)F]FP-TZTP and FP-TZTP, which avoid changes in CBF, significant inhibition of [(18)F]FP-TZTP-binding by FP-TZTP was observed. These results indicate that inhibition of [(18)F]FP-TZTP-binding in the brain by P-TZTP or FP-TZTP in vivo occurs independently of their effects on CBF. The methods employed here may also be of interest to evaluate physiological effects of blocking agents utilized to validate other radiopharmaceuticals.
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Affiliation(s)
- Kazuaki Shimoji
- Positron Emission Tomography Department, Clinical Center, NIMH, National Institutes of Health, Bethesda, Maryland 20892, USA
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Eckelman WC. The use of gene-manipulated mice in the validation of receptor binding radiotracer. Nucl Med Biol 2003; 30:851-60. [PMID: 14698789 DOI: 10.1016/s0969-8051(03)00123-9] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- William C Eckelman
- PET Department, Warren G. Magnuson Clinical Center, Bethesda, MD 20892, USA.
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Cohen RM, Podruchny TA, Bokde ALW, Carson RE, Herscovitch P, Kiesewetter DO, Eckelman WC, Sunderland T. Higher in vivo muscarinic-2 receptor distribution volumes in aging subjects with an apolipoprotein E-epsilon4 allele. Synapse 2003; 49:150-6. [PMID: 12774299 DOI: 10.1002/syn.10225] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The apolipoprotein E-epsilon4 allele confers an increased susceptibility to age-related memory problems and Alzheimer's disease. Abnormalities in the cholinergic system are also likely contributors to memory deficits associated with aging and AD. To determine the effect of the APOE-epsilon4 allele on the muscarinic component of the cholinergic system of aging subjects, 10 healthy subjects with APOE-epsilon4 alleles (APOE-epsilon4+) and 10 without (APOE-epsilon4-), ranging in age from 52 to 75 years, were tomographically scanned with the F-18-labeled muscarinic-2 (M2) selective agonist, 3-(3-(3-[(18)F]Flouropropyl)thio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine ([(18)F]FP-TZTP). The distribution volumes (V(T)) of [(18)F]FP-TZTP were determined by compartmental modeling of partial volume and free fraction corrected PET scans. Regional cerebral blood flow (rCBF) measurements with H(2) (15)O were also performed. Global Gray V(T) (840 +/- 155 ml plasma/ml tissue) was greater in APOE-epsilon4+ subjects than APOE-epsilon4- subjects (660 +/- 113 ml plasma/ml tissue, P = 0.01), and previously studied younger subjects. There were no significant differences between the groups with respect to rCBF, but within the APOE-epsilon4+ group there was a trend for subjects with the higher Global Gray V(T)s to have lower Global Gray CBFs (r = -0.65, P < 0.06). A lower concentration of acetylcholine in the synapse of APOE-epsilon4+ older individuals is a likely explanation for the greater [(18)F]FP-TZTP distribution volumes.
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Affiliation(s)
- Robert M Cohen
- Geriatric Psychiatry Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland 20892, USA
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Current awareness in geriatric psychiatry. Int J Geriatr Psychiatry 2003; 18:661-8. [PMID: 12879898 DOI: 10.1002/gps.789] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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