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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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Learning, memory and the expression of cholinergic components in mice are modulated by the pesticide chlorpyrifos depending upon age at exposure and apolipoprotein E (APOE) genotype. Arch Toxicol 2019; 93:693-707. [DOI: 10.1007/s00204-019-02387-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2018] [Accepted: 01/10/2019] [Indexed: 12/20/2022]
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Jiang S, Tang L, Zhao N, Yang W, Qiu Y, Chen HZ. A Systems View of the Differences between APOE ε4 Carriers and Non-carriers in Alzheimer's Disease. Front Aging Neurosci 2016; 8:171. [PMID: 27462267 PMCID: PMC4941795 DOI: 10.3389/fnagi.2016.00171] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2016] [Accepted: 06/27/2016] [Indexed: 12/19/2022] Open
Abstract
APOE ε4 is the strongest genetic risk factor for late-onset Alzheimer's disease (AD) and accounts for 50-65% of late-onset AD. Late-onset AD patients carrying or not carrying APOE ε4 manifest many clinico-pathological distinctions. Thus, we applied a weighted gene co-expression network analysis to identify specific co-expression modules in AD based on APOE ε4 stratification. Two specific modules were identified in AD APOE ε4 carriers and one module was identified in non-carriers. The hub genes of one module of AD APOE ε4 carriers were ISOC1, ENO3, GDF10, GNB3, XPO4, ACLY and MATN2. The other module of AD APOE ε4 carriers consisted of 10 hub genes including ANO3, ARPP21, HPCA, RASD2, PCP4 and ADORA2A. The module of AD APOE ε4 non-carriers consisted of 16 hub genes including DUSP5, TNFRSF18, ZNF331, DNAJB5 and RIN1. The module of AD APOE ε4 carriers including ISOC1 and ENO3 and the module of non-carriers contained the most highly connected hub gene clusters. mRNA expression of the genes in the cluster of the ISOC1 and ENO3 module of carriers was shown to be correlated in a time-dependent manner under APOE ε4 treatment but not under APOE ε3 treatment. In contrast, mRNA expression of the genes in the cluster of non-carriers' module was correlated under APOE ε3 treatment but not under APOE ε4 treatment. The modules of carriers demonstrated genetic bases and were mainly enriched in hereditary disorders and neurological diseases, energy metabolism-associated signaling and G protein-coupled receptor-associated pathways. The module including ISOC1 and ENO3 harbored two conserved promoter motifs in its hub gene cluster that could be regulated by common transcription factors and miRNAs. The module of non-carriers was mainly enriched in neurological, immunological and cardiovascular diseases and was correlated with Parkinson's disease. These data demonstrate that AD in APOE ε4 carriers involves more genetic factors and particular biological processes, whereas AD in APOE ε4 non-carriers shares more common pathways with other types of diseases. The study reveals differential genetic bases and pathogenic and pathological processes between carriers and non-carriers, providing new insight into the mechanisms of the differences between APOE ε4 carriers and non-carriers in AD.
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Affiliation(s)
- Shan Jiang
- Department of Pharmacology, Institute of Medical Sciences, Shanghai Jiao Tong University School of Medicine, Shanghai China
| | - Ling Tang
- Department of Pharmacology, Institute of Medical Sciences, Shanghai Jiao Tong University School of Medicine, Shanghai China
| | - Na Zhao
- Department of Pharmacology, Institute of Medical Sciences, Shanghai Jiao Tong University School of Medicine, Shanghai China
| | - Wanling Yang
- Department of Paediatrics and Adolescent Medicine, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam Hong Kong
| | - Yu Qiu
- Department of Pharmacology, Institute of Medical Sciences, Shanghai Jiao Tong University School of Medicine, Shanghai China
| | - Hong-Zhuan Chen
- Department of Pharmacology, Institute of Medical Sciences, Shanghai Jiao Tong University School of Medicine, Shanghai China
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Peris-Sampedro F, Reverte I, Basaure P, Cabré M, Domingo JL, Colomina MT. Apolipoprotein E (APOE) genotype and the pesticide chlorpyrifos modulate attention, motivation and impulsivity in female mice in the 5-choice serial reaction time task. Food Chem Toxicol 2016; 92:224-35. [PMID: 27106138 DOI: 10.1016/j.fct.2016.03.029] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2016] [Revised: 03/02/2016] [Accepted: 03/21/2016] [Indexed: 02/08/2023]
Abstract
Organophosphate pesticides - and chlorpyrifos (CPF) in particular - contribute to a wide range of neurobehavioural disorders. Most experimental research focuses on learning and memory processes, while other behaviours remain understudied. The isoforms of the human apolipoprotein E (apoE) confer different cognitive skills on their carriers, but data on this topic are still limited. The current study was performed to assess whether the APOE genotypic variability differently modulates the effects of CPF on attentional performance, inhibitory control and motivation. Human apoE targeted replacement adult female mice (apoE2, apoE3 and apoE4) were trained to stably perform the 5-choice serial reaction time task (5-CSRTT). Animals were then subjected to daily dietary CPF (3.75 mg/kg body weight) for 4 weeks. After CPF exposure, we established a 4-week CPF-free period to assess recovery. All individuals acquired the task, apoE2 mice showed enhanced learning, while apoE4 mice displayed increased premature and perseverative responding. This genotype-dependent lack of inhibitory control was reversed by CPF. Overall, the pesticide induced protracted impairments in sustained attention and motivation, and it reduced anticipatory responding. ApoE3 mice exhibited delayed attentional disruptions throughout the wash-out period. Taken together, these findings provide notable evidence on the emergence of CPF-related attentional and motivational deficits.
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Affiliation(s)
- Fiona Peris-Sampedro
- Research in Neurobehaviour and Health (NEUROLAB), Universitat Rovira i Virgili, Tarragona, Spain; Department of Psychology and Research Center for Behavioural Assessment (CRAMC), Universitat Rovira i Virgili, Tarragona, Spain; Laboratory of Toxicology and Environmental Health, School of Medicine, IISPV, Universitat Rovira i Virgili, Reus, Spain.
| | - Ingrid Reverte
- Research in Neurobehaviour and Health (NEUROLAB), Universitat Rovira i Virgili, Tarragona, Spain
| | - Pia Basaure
- Research in Neurobehaviour and Health (NEUROLAB), Universitat Rovira i Virgili, Tarragona, Spain; Department of Psychology and Research Center for Behavioural Assessment (CRAMC), Universitat Rovira i Virgili, Tarragona, Spain; Laboratory of Toxicology and Environmental Health, School of Medicine, IISPV, Universitat Rovira i Virgili, Reus, Spain
| | - Maria Cabré
- Research in Neurobehaviour and Health (NEUROLAB), Universitat Rovira i Virgili, Tarragona, Spain; Department of Biochemistry and Biotechnology, Universitat Rovira i Virgili, Tarragona, Spain
| | - José L Domingo
- Laboratory of Toxicology and Environmental Health, School of Medicine, IISPV, Universitat Rovira i Virgili, Reus, Spain
| | - Maria Teresa Colomina
- Research in Neurobehaviour and Health (NEUROLAB), Universitat Rovira i Virgili, Tarragona, Spain; Department of Psychology and Research Center for Behavioural Assessment (CRAMC), Universitat Rovira i Virgili, Tarragona, Spain.
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Reverte I, Peris-Sampedro F, Basaure P, Campa L, Suñol C, Moreno M, Domingo JL, Colomina MT. Attentional performance, impulsivity, and related neurotransmitter systems in apoE2, apoE3, and apoE4 female transgenic mice. Psychopharmacology (Berl) 2016; 233:295-308. [PMID: 26497539 DOI: 10.1007/s00213-015-4113-9] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/02/2015] [Accepted: 10/06/2015] [Indexed: 12/27/2022]
Abstract
RATIONALE The apolipoprotein E (apoE) genotype influences cognitive performance in humans depending on age and sex. While the detrimental role of the apoE4 isoform on spatial learning and memory has been well-established in humans and rodents, less is known on its impact on the executive functions. OBJECTIVES We aimed to evaluate the effect of apoE isoforms (apoE2, apoE3, apoE4) on visuospatial attention and inhibitory control performance in female transgenic mice, and to determine the neurochemical and neuropharmacological basis of this potential relationship. METHODS Female mice carrying apoE2, apoE3, and apoE4 were trained in the five-choice serial reaction time task (5-CSRTT). Upon a stable performance, we manipulated the inter-trial interval and the stimulus duration to elicit impulsive responding and engage attention respectively. We further performed a pharmacological challenge by administering cholinergic and GABAergic agents. Finally, we analyzed the levels of brain amino acids and monoamines by using reversed phase high-performance liquid chromatography (HPLC). RESULTS ApoE4 mice showed a deficient inhibitory control as revealed by increased perseveration and premature responding. When attention was challenged, apoE4 mice also showed a higher drop in accuracy. The adverse effect of scopolamine on the task was attenuated in apoE4 mice compared to apoE2 and apoE3. Furthermore, apoE4 mice showed less dopamine in the frontal cortex than apoE2 mice. CONCLUSIONS We confirmed that the apoE genotype influences attention and inhibitory control in female transgenic mice. The influence of apoE isoforms in the brain neuromodulatory system may explain the cognitive and behavioral differences attributable to the genotype.
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Schilling LP, Leuzy A, Zimmer ER, Gauthier S, Rosa-Neto P. Nonamyloid PET biomarkers and Alzheimer's disease: current and future perspectives. FUTURE NEUROLOGY 2014. [DOI: 10.2217/fnl.14.40] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
ABSTRACT Recent advances in neurobiology and PET have helped redefine Alzheimer's disease (AD) as a dynamic pathophysiological process, clinically characterized by preclinical, mild cognitive impairment due to AD and dementia stages. Though a majority of PET studies conducted within these populations have to date focused on β-amyloid, various ‘nonamyloid’ radiopharmaceuticals exist for evaluating neurodegeneration, neuroinflammation and perturbations in neurotransmission across the spectrum of AD. Importantly, findings using such tracers have been shown to correlate with various clinical, cognitive and behavioral measures. In the context of a growing shift toward early diagnosis and symptomatic and disease-modifying clinical trials, nonamyloid PET radiotracers will prove of use, and, potentially, contribute to improved therapeutic prospects for AD.
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Affiliation(s)
- Lucas Porcello Schilling
- Translational Neuroimaging Laboratory (TNL), McGill Center for Studies in Aging (MCSA), Douglas Mental Health Research Institute, Montreal, Canada
- Alzheimer's Disease Research Unit, McGill Center for Studies in Aging (MCSA), Douglas Mental Health Research Institute, Montreal, Canada
- Brain Institute of Rio Grande do Sul, Pontifical Catholic University of Rio Grande do Sul (PUCRS), Porto Alegre, Brazil
| | - Antoine Leuzy
- Translational Neuroimaging Laboratory (TNL), McGill Center for Studies in Aging (MCSA), Douglas Mental Health Research Institute, Montreal, Canada
- Alzheimer's Disease Research Unit, McGill Center for Studies in Aging (MCSA), Douglas Mental Health Research Institute, Montreal, Canada
| | - Eduardo Rigon Zimmer
- Translational Neuroimaging Laboratory (TNL), McGill Center for Studies in Aging (MCSA), Douglas Mental Health Research Institute, Montreal, Canada
- Alzheimer's Disease Research Unit, McGill Center for Studies in Aging (MCSA), Douglas Mental Health Research Institute, Montreal, Canada
- Department of Biochemistry, Federal University of Rio Grande do Sul (UFRGS), Porto Alegre, Brazil
| | - Serge Gauthier
- Alzheimer's Disease Research Unit, McGill Center for Studies in Aging (MCSA), Douglas Mental Health Research Institute, Montreal, Canada
| | - Pedro Rosa-Neto
- Translational Neuroimaging Laboratory (TNL), McGill Center for Studies in Aging (MCSA), Douglas Mental Health Research Institute, Montreal, Canada
- Alzheimer's Disease Research Unit, McGill Center for Studies in Aging (MCSA), Douglas Mental Health Research Institute, Montreal, Canada
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Roberts PD, Spiros A, Geerts H. Simulations of symptomatic treatments for Alzheimer's disease: computational analysis of pathology and mechanisms of drug action. ALZHEIMERS RESEARCH & THERAPY 2012. [PMID: 23181523 PMCID: PMC3580459 DOI: 10.1186/alzrt153] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Introduction A substantial number of therapeutic drugs for Alzheimer's disease (AD) have failed in late-stage trials, highlighting the translational disconnect with pathology-based animal models. Methods To bridge the gap between preclinical animal models and clinical outcomes, we implemented a conductance-based computational model of cortical circuitry to simulate working memory as a measure for cognitive function. The model was initially calibrated using preclinical data on receptor pharmacology of catecholamine and cholinergic neurotransmitters. The pathology of AD was subsequently implemented as synaptic and neuronal loss and a decrease in cholinergic tone. The model was further calibrated with clinical Alzheimer's Disease Assessment Scale-cognitive subscale (ADAS-Cog) results on acetylcholinesterase inhibitors and 5-HT6 antagonists to improve the model's prediction of clinical outcomes. Results As an independent validation, we reproduced clinical data for apolipoprotein E (APOE) genotypes showing that the ApoE4 genotype reduces the network performance much more in mild cognitive impairment conditions than at later stages of AD pathology. We then demonstrated the differential effect of memantine, an N-Methyl-D-aspartic acid (NMDA) subunit selective weak inhibitor, in early and late AD pathology, and show that inhibition of the NMDA receptor NR2C/NR2D subunits located on inhibitory interneurons compensates for the greater excitatory decline observed with pathology. Conclusions This quantitative systems pharmacology approach is shown to be complementary to traditional animal models, with the potential to assess potential off-target effects, the consequences of pharmacologically active human metabolites, the effect of comedications, and the impact of a small number of well described genotypes.
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Affiliation(s)
- Patrick D Roberts
- Department of Biomedical Engineering, Oregon Health & Science University, 3303 SW Bond Avenue, Portland, OR 97239 USA ; In Silico Biosciences, Inc., 405 Waltham Street, Lexington, MA 02421 USA
| | - Athan Spiros
- In Silico Biosciences, Inc., 405 Waltham Street, Lexington, MA 02421 USA
| | - Hugo Geerts
- In Silico Biosciences, Inc., 405 Waltham Street, Lexington, MA 02421 USA
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Nebes RD, Pollock BG, Perera S, Halligan EM, Saxton JA. The greater sensitivity of elderly APOE ε4 carriers to anticholinergic medications is independent of cerebrovascular disease risk. ACTA ACUST UNITED AC 2012; 10:185-92. [PMID: 22534472 DOI: 10.1016/j.amjopharm.2012.03.003] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2011] [Revised: 03/07/2012] [Accepted: 03/16/2012] [Indexed: 11/16/2022]
Abstract
BACKGROUND Recent studies found use of anticholinergic medications to be associated with greater performance decrements in older persons who carry an ε4 allele of the apolipoprotein E (APOE) gene than in those carrying only ε2 or ε3 alleles. OBJECTIVES The present study examined whether the apparently greater behavioral toxicity of anticholinergic drugs in ε4 carriers may result from an increased risk of cerebrovascular disease, which is more common in ε4 carriers. METHODS Cross-sectional data were available from 240 elderly community volunteers who had participated in 2 different studies of the cognitive and motor effects of normal aging. As part of these studies, information was gathered on subjects' use of anticholinergic medications (based on an inventory of medications taken within 24 hours of testing), risk of cerebrovascular disease (Framingham Stroke Risk Profile), and APOE genotype. Performance data were also available from measures of general cognitive status (Mini-Mental State Examination), executive function (Trail Making Test), mood (Geriatric Depression Scale), sleep (Pittsburgh Sleep Quality Index), and walking speed. Logistic and linear regression models were used to examine how outcomes differed between genotypes and drug use, independent of the risk of cerebrovascular disease. RESULTS In persons with a non-ε4 genotype, anticholinergic medication use did not significantly affect any of the behavioral measures. By contrast, among ε4 carriers, those taking anticholinergic drugs performed significantly worse than did those not taking such drugs on tests of general cognitive status, executive function, mood, and sleep. Adjusting for participants' stroke risk had a minimal effect on these results. CONCLUSIONS Anticholinergic medication use was associated with poorer performance on measures of cognition, sleep, and mood only in older persons who carried 1 or more ε4 alleles of the APOE gene; this effect did not appear to be the result of an increased risk of cerebrovascular disease.
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Affiliation(s)
- Robert D Nebes
- Department of Psychiatry, University of Pittsburgh Medical School, Pennsylvania, USA.
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Imaging of the muscarinic acetylcholine neuroreceptor in rats with the M2 selective agonist [18F]FP-TZTP. Nucl Med Biol 2011; 39:45-55. [PMID: 21831648 DOI: 10.1016/j.nucmedbio.2011.06.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2011] [Revised: 06/03/2011] [Accepted: 06/07/2011] [Indexed: 11/21/2022]
Abstract
INTRODUCTION [(18)F]FP-TZTP is an M2 muscarinic subtype selective receptor-binding radiotracer used in vivo to image human and nonhuman primate brain following both bolus injection and infusion. In order to carry out repeated studies in rodents, the techniques developed for primates must be transferred to rodents with the same precision. This includes obtaining a metabolite-corrected input function. METHODS We compared bolus injection with constant infusion in rats that were awake or under isoflurane anesthesia. Brain-plasma and brain-blood distribution ratios were calculated by dividing brain (18)F concentrations, determined in vivo by positron emission tomography imaging with the Advanced Technology Laboratory Animal Scanner, ex vivo by direct counting in excised brain tissue or by quantitative autoradiography by the plasma or whole blood concentrations that had been corrected for metabolite contents. RESULTS Blood volume constraints prevented adequate blood sampling to define a precise input function after bolus injection, thus preventing full kinetic analysis. Constant infusion, however, required fewer blood samples to define the input function, allowing calculation of distribution ratios, but complete equilibrium between plasma and tissue had not yet been reached after 120 min. CONCLUSION Our results showed that the blood clearance and metabolism were too rapid to obtain a reproducible input function after bolus injection. The equilibrium distribution ratios did not lead to precise biochemical parameters, but the constant infusion was more suitable in that distribution ratios between tissue and plasma were statistically more precise. Constant infusion is the better approach for studying [(18)F]FP-TZTP by small animal imaging.
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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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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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Kadir A, Nordberg A. Target-specific PET probes for neurodegenerative disorders related to dementia. J Nucl Med 2010; 51:1418-30. [PMID: 20810758 DOI: 10.2967/jnumed.110.077164] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Dementia is a highly prevalent problem causing considerable disability and mortality and exacting great costs to individuals, their families, and society. The 4 most common neurodegenerative disorders that cause dementia-Alzheimer disease, frontotemporal dementia, dementia with Lewy bodies, and dementia in Parkinson disease-have different underlying etiologies and pathogenetic mechanisms. There is a great need for early diagnostic markers; functional brain imaging may therefore assist in the detection and differential diagnosis of dementia due to neurodegenerative diseases. Functional imaging such as PET allows in vivo imaging of functional brain activity indicating cerebral blood flow and cerebral glucose metabolism, and PET allows imaging of neurotransmitter activity, including that of the cholinergic, dopaminergic, and serotonergic systems. New PET neuroimaging tracers are being developed for detecting pathologic parameters such as amyloid plaque and microglial activity. The development of molecular imaging is important for early diagnosis of dementia, selection of patients for therapies, and evaluation of therapies.
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Affiliation(s)
- Ahmadul Kadir
- Division of Alzheimer Neurobiology, Department of Neurobiology, Care Sciences and Society, Karolinska Institutet, Karolinska University Hospital Huddinge, Stockholm, Sweden
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Failing compensatory mechanisms during working memory in older apolipoprotein E-epsilon4 healthy adults. Brain Imaging Behav 2010; 4:177-88. [PMID: 20502990 DOI: 10.1007/s11682-010-9097-9] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
How and when the known genetic risk allele, apolipoprotein E-epsilon4 (APOEepsilon4), confers risk to Alzheimer's disease has yet to be determined. We studied older adults and found that APOEepsilon4 carriers had greater neural activation in the medial frontal and parahippocampal gyrus during a memory task (cluster-corrected p < .01). When compared to a group of younger adults, interactive effects of age and APOEepsilon4 were found in the inferior frontal-anterior temporal region, one of the first areas to develop amyloid plaques in patients with Alzheimer's disease, and, in the posterior cingulate, one of the earliest areas to show decreased cerebral metabolism in Alzheimer's disease. Thus, abnormally high activation in fronto-temporal areas are present in both younger and older APOEepsilon4 carriers confronted with a working memory task when compared to non-APOEepsilon4 carriers. This effect, however, appears to diminish with age.
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Abstract
In Alzheimer disease (AD), which is the most common cause of dementia, the underlying disease pathology most probably precedes the onset of cognitive symptoms by many years. Thus, efforts are underway to find early diagnostic markers as well as disease-modifying treatments for this disorder. PET enables various brain systems to be monitored in living individuals. In patients with AD, PET can be used to investigate changes in cerebral glucose metabolism, various neurotransmitter systems, neuroinflammation, and the protein aggregates that are characteristic of the disease, notably the amyloid deposits. These investigations are helping to further our understanding of the complex pathophysiological mechanisms that underlie AD, as well as aiding the early and differential diagnosis of the disease in the clinic. In the future, PET studies will also be useful for identifying new therapeutic targets and monitoring treatment outcomes. Amyloid imaging could be useful as early diagnostic marker of AD and for selecting patients for anti-amyloid-beta therapy, while cerebral glucose metabolism could be a suitable PET marker for monitoring disease progression. For the near future, multitracer PET studies are unlikely to be used routinely in the clinic for AD, being both burdensome and expensive; however, such studies are very informative in a research context.
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Affiliation(s)
- Agneta Nordberg
- Division of Alzheimer Neurobiology, Department of Neurobiology, Care Sciences and Society, Karolinska Institute, Karolinska University Hospital Huddinge, Novum, Stockholm, Sweden.
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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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Negash S, Greenwood PM, Sunderland T, Parasuraman R, Geda YE, Knopman DS, Boeve BF, Ivnik RJ, Petersen RC, Smith GE. The influence of apolipoprotein E genotype on visuospatial attention dissipates after age 80. Neuropsychology 2009; 23:81-9. [PMID: 19210035 DOI: 10.1037/a0014014] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Although it is established that apolipoprotein E (APOE) e4 allele increases the risk of Alzheimer's disease (AD), epidemiological studies indicate that genetic risk decreases late in life. This raises the question of whether the effects of APOE on cognition that are seen in midlife arise from a cognitive phenotype of APOE or from the presence of early AD in some APOE-e4 carriers. The authors addressed this question by comparing the cognitive consequences of variation in the APOE gene between individuals over the age of 80 (old-old) and middle-aged and young-old individuals. A spatially cued discrimination paradigm--previously shown to be sensitive to AD and to APOE genotype--required a speeded categorization of a target letter following cues that were valid, invalid, or neutral in predicting target location. Results revealed greater costs of invalid cues in the APOE-e4 carriers of middle-aged and young-old, but not old-old, groups. The dissipation of the APOE effect in old-old individuals at lower risk of AD suggests that visuospatial attention impairments seen as early as midlife in APOE-e4 carriers may be a preclinical marker of AD.
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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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Mattay VS, Goldberg TE, Sambataro F, Weinberger DR. Neurobiology of cognitive aging: insights from imaging genetics. Biol Psychol 2008; 79:9-22. [PMID: 18511173 PMCID: PMC3127547 DOI: 10.1016/j.biopsycho.2008.03.015] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2007] [Revised: 03/11/2008] [Accepted: 03/25/2008] [Indexed: 12/25/2022]
Abstract
Over the last several years, neuroscientists have been increasingly using neuroimaging techniques to unravel the neurobiology underlying cognitive aging, and in more recent years to explore the role of genes on the variability of the aging process. One of the primary goals of this research is to identify proteins involved in cognitive aging with the hope that this would facilitate the development of novel treatments to combat cognitive impairment. Further, it is likely with early identification of susceptible individuals, early intervention through life-style changes and other methods could increase an individual's resilience to the effects of aging.
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Affiliation(s)
- Venkata S Mattay
- Genes, Cognition and Psychosis Program, National Institute of Mental Health, National Institute of Health, Department of Health and Human Services, Bethesda, MD 20892, USA.
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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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Eckelman WC, Reba RC, Kelloff GJ. Targeted imaging: an important biomarker for understanding disease progression in the era of personalized medicine. Drug Discov Today 2008; 13:748-59. [PMID: 18617011 DOI: 10.1016/j.drudis.2008.05.009] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2008] [Revised: 04/30/2008] [Accepted: 05/22/2008] [Indexed: 11/16/2022]
Abstract
The key to applying targeted imaging to personalized medicine is the choice of the right radiolabeled probe for the right target for the right disease following the lead of pharmaceutical development. The imaging approach differs depending on whether the target is a single disease control point (e.g. a specific receptor or transport protein linked to the mechanistic activity of a drug) or a general disease control point applicable to a number of treatment paradigms (e.g. proliferation, angiogenesis, inflammation). But in either case, the number of control points must be small given the time constraints on molecular imaging procedures in the clinic. Regardless of the choice, the radiotracer must be validated as binding to the target with the appropriate pharmacokinetics and pharmacodynamics for effective external imaging. Such an imaging agent developed in concert with drug development has a built in synergy that will accelerate the drug development process, targeted imaging and personalized medicine as well.
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Small GW, Bookheimer SY, Thompson PM, Cole GM, Huang SC, Kepe V, Barrio JR. Current and future uses of neuroimaging for cognitively impaired patients. Lancet Neurol 2008; 7:161-72. [PMID: 18207114 DOI: 10.1016/s1474-4422(08)70019-x] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Technological advances have led to greater use of both structural and functional brain imaging to assist with the diagnosis of dementia for the increasing numbers of people with cognitive decline as they age. In current clinical practice, structural imaging (CT or MRI) is used to identify space-occupying lesions and stroke. Functional methods, such as PET scanning of glucose metabolism, could be used to differentiate Alzheimer's disease from frontotemporal dementia, which helps to guide clinicians in symptomatic treatment strategies. New neuroimaging methods that are currently being developed can measure specific neurotransmitter systems, amyloid plaque and tau tangle concentrations, and neuronal integrity and connectivity. Successful co-development of neuroimaging surrogate markers and preventive treatments might eventually lead to so-called brain-check scans for determining risk of cognitive decline, so that physicians can administer disease-modifying medications, vaccines, or other interventions to avoid future cognitive losses and to delay onset of disease.
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Affiliation(s)
- Gary W Small
- Department of Psychiatry and Biobehavioral Sciences and Semel Institute for Neuroscience and Human Behavior, University of California-Los Angeles, Los Angeles, California, USA.
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Ichise M, Cohen RM, Carson RE. Noninvasive estimation of normalized distribution volume: application to the muscarinic-2 ligand [(18)F]FP-TZTP. J Cereb Blood Flow Metab 2008; 28:420-30. [PMID: 17653129 DOI: 10.1038/sj.jcbfm.9600530] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Reference tissue methods to estimate neuroreceptor binding are not applicable to [(18)F]FP-TZTP (a muscarinic-2 cholinergic receptor ligand), because there is no suitable receptor-free reference region. We evaluated a new method to estimate, without using arterial data or a receptor-free reference region, a receptor parameter called the normalized distribution volume, V(T)(*), using a region containing receptors as the input tissue. V(T)(*) is defined as V(T)/K'(1) (distribution volume (V(T)) normalized by K'(1) of the input region). We used a two-parameter multilinear reference tissue model (MRTM2) to generate parametric images of V(T)(*) and R(1) (R(1)=K(1)/K'(1)) from [(18)F]FP-TZTP PET data of healthy aged subjects (10 with apolipoprotein E-epsilon4 alleles (APOE-epsilon4(+)) and nine without (APOE-epsilon4(-)). V(T)(*) and V(T) were normalized by plasma-free fraction, f(P). By one-tissue kinetic analysis (1TKA) with metabolite-corrected plasma data, V(T) was previously reported as higher in the APOE-epsilon4(+) group. The noise magnitude of MRTM2 V(T)(*) and R(1) images were nearly identical to those of 1TKA V(T) and K(1) images. K'(1) or f(P) was not different between the two groups. V(T)(*) (mins) (1,659+/-497) and V(T) (mL/cm(3)) (701+/-99) in APOE-epsilon4(+) were higher by 38 and 22% than those (1,209+/-233 and 577+/-112) in APOE-epsilon4(-), respectively. The statistical significance for V(T)(*) (0.041) was lower than that for V(T) (0.025), due to the higher intersubject variability of V(T)(*) (25%) than that of V(T) (17%). We conclude that MRTM2 V(T)(*) allows detection of group differences in receptor binding without arterial blood or a receptor-free reference region.
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Affiliation(s)
- Masanori Ichise
- Kreitchman PET Center, Department of Radiology, Columbia University College of Physicians, New York, New York 10032, USA.
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Petrella JR, Mattay VS, Doraiswamy PM. Imaging genetics of brain longevity and mental wellness: the next frontier? Radiology 2008; 246:20-32. [PMID: 18096526 DOI: 10.1148/radiol.2461061994] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The advent of new "omics" technologies (genomics, proteomics, and metabolomics) has ushered in a new era of biomedical discovery that is already affecting every field of medicine. With the rapid growth of the older population worldwide, there is great interest in applying these technologies not only to diagnose and prevent disease, but also to enhance brain longevity and mental wellness. Nearly two-thirds of the approximately 30,000 genes in the human genome are related to brain function, and up to half of the variance in age-related changes in cognition, brain volume, and neuronal function appears to be genetically determined. Selected examples will be used to illustrate how neuroimaging is being employed to study the effects of genes and how neurogenetics may affect future radiology research and practice.
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Affiliation(s)
- Jeffrey R Petrella
- Alzheimer Imaging Research Laboratory, Department of Radiology, Duke University Medical Center, Box 3808, Durham, NC 27710, USA.
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Herholz K, Weisenbach S, Kalbe E. Deficits of the cholinergic system in early AD. Neuropsychologia 2007; 46:1642-7. [PMID: 18201734 DOI: 10.1016/j.neuropsychologia.2007.11.024] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2007] [Revised: 11/07/2007] [Accepted: 11/28/2007] [Indexed: 10/22/2022]
Abstract
Impairment of cholinergic neurotransmission is a well-established fact in Alzheimer's disease (AD) but there is controversy about its relevance at the early stages of the disease. In the recent years new techniques for in vivo imaging of key components of the cholinergic system in humans have developed. They are beginning to be applied to the very early stages of AD. Preliminary results suggest that there is early impairment of presynaptic receptors and acetylcholine esterase, the main degrading enzyme for acetylcholine, in cerebral cortex. The relation of these findings to neuronal function and post-mortem findings is being discussed.
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Cohen RM. The application of positron-emitting molecular imaging tracers in Alzheimer's disease. Mol Imaging Biol 2007; 9:204-16. [PMID: 17354042 DOI: 10.1007/s11307-007-0094-3] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The symptomatology and known pathology of Alzheimer's disease are restricted to the central nervous system. This review details studies of PET tracers aimed at interrogating cholinergic, serotonergic, opiate, benzodiazepine, and inflammatory pathways as well as PET tracers that illuminate amyloid plaques and neurofibrillary tangles in AD. Progress has been remarkable. Together with studies of brain structure with MRI and of functional regional brain activity, e.g., through measures of blood flow and glucose metabolic rate, molecular imaging promises to dramatically alter our understanding of the structural and physiological abnormalities underlying AD symptomatology. A more immediate impact on the diagnosis and treatment evaluation of AD patients in clinical trials is predicted while the possibility of personalized treatment or prevention of AD may not be that far away.
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Affiliation(s)
- Robert M Cohen
- Department of Psychiatry and Behavioral Neurosciences, Cedars-Sinai Medical Center, Thalians E-135, Los Angeles, CA 90048, USA.
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Ritland JS, Utheim TP, Utheim OA, Espeseth T, Lydersen S, Semb SO, Rootwelt H, Elsås T. Effects of APOE and CHRNA4 genotypes on retinal nerve fibre layer thickness at the optic disc and on risk for developing exfoliation syndrome. ACTA ACUST UNITED AC 2007; 85:257-61. [PMID: 17488453 DOI: 10.1111/j.1600-0420.2006.00824.x] [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] [Indexed: 01/12/2023]
Abstract
PURPOSE To investigate whether CHRNA4 and APOE genotypes influence retinal nerve fibre layer (RNFL) thickness at the optic disc, intraocular pressure (IOP) and the development of exfoliation syndrome (XFS). METHODS A sample of 88 healthy adults (aged 50-75 years) genotyped for polymorphisms of APOE and CHRNA4 underwent an eye examination including slit-lamp examination and fundus photography, as well as measurements of visual acuity, refraction, IOP and RNFL thickness at the optic disc by optical coherence tomography. The Fisher-Boschloo unconditional full multinomial test and two sample t-tests were used in the statistical analyses. RESULTS There was no correlation between CHRNA4 and APOE genotypes and average RNFL thickness at the optic disc in the two eyes. Mean IOP in the eyes of APOE2 carriers was 13.18 mmHg, whereas that in the eyes of non-APOE2 carriers, at 14.82 mmHg, was significantly higher (p = 0.014). Exfoliation syndrome was found in one or both eyes in 15 persons. The presence of XFS was less likely in CC carriers of the CHRNA4 gene than in TT and TC carriers (p = 0.049). CONCLUSIONS We found no significant difference in RNFL thickness at the optic disc in the different genotype carriers of the APOE and CHRNA4 genes, and thereby no evidence for increased loss of ganglion cells in the retina as an effect of these genes. APOE2 carriers had significantly lower IOP than non-APOE2 carriers. However, both values are within the normal range and RNFL thickness measurements at the optic disc showed no difference between these two groups. In our study population, CC carriers of the CHRNA4 gene were less likely to develop XFS.
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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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Gosso MF, van Belzen M, de Geus EJC, Polderman JC, Heutink P, Boomsma DI, Posthuma D. Association between the CHRM2 gene and intelligence in a sample of 304 Dutch families. GENES BRAIN AND BEHAVIOR 2006; 5:577-84. [PMID: 17081262 DOI: 10.1111/j.1601-183x.2006.00211.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The CHRM2 gene is thought to be involved in neuronal excitability, synaptic plasticity and feedback regulation of acetylcholine release and has previously been implicated in higher cognitive processing. In a sample of 667 individuals from 304 families, we genotyped three single-nucleotide polymorphisms (SNPs) in the CHRM2 gene on 7q31-35. From all individuals, standardized intelligence measures were available. Using a test of within-family association, which controls for the possible effects of population stratification, a highly significant association was found between the CHRM2 gene and intelligence. The strongest association was between rs324650 and performance IQ (PIQ), where the T allele was associated with an increase of 4.6 PIQ points. In parallel with a large family-based association, we observed an attenuated - although still significant - population-based association, illustrating that population stratification may decrease our chances of detecting allele-trait associations. Such a mechanism has been predicted earlier, and this article is one of the first to empirically show that family-based association methods are not only needed to guard against false positives, but are also invaluable in guarding against false negatives.
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Affiliation(s)
- M F Gosso
- Department of Biological Psychology, Vrije Universiteit, Amsterdam, the Netherlands.
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Eggers C, Herholz K, Kalbe E, Heiss WD. Cortical acetylcholine esterase activity and ApoE4-genotype in Alzheimer disease. Neurosci Lett 2006; 408:46-50. [PMID: 16996687 DOI: 10.1016/j.neulet.2006.08.061] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2006] [Revised: 08/12/2006] [Accepted: 08/14/2006] [Indexed: 10/24/2022]
Abstract
Positron emission tomography (PET) studies have demonstrated reduced acetylcholine esterase (AChE) activity as an indicator of cholinergic impairment, which is a main pathogenic process in Alzheimer's disease (AD). The E4 allele of apolipoprotein epsilon (ApoE4) is a major risk factor for AD. We examined the relation between ApoE-genotype and cortical AChE activity. In 19 patients (mean age 64) with mild to moderate AD (mean MMSE 22) PET with C-11-labeled N-methyl-4-piperidyl-acetate (MP4A) was performed and the ApoE4-genotype was determined. Parametric images of AChE hydrolysis were generated using a non-invasive technique and analysed globally and regionally. A neuropsychological battery testing memory, attention, executive functions, visuoconstruction, and language was administered. The mean cortical AChE activity was reduced significantly in both groups compared to reference values. The ApoE4 positive subjects (two homozygotes, nine heterozygotes) had significantly higher (p<0.05) AChE levels (MP4A hydrolysis rate 0.0753+/-0.0088min(-1)) than the ApoE4 negative subjects (n=8, 0.0654+/-0.0090min(-1)). Both groups were comparable with regard to age (63 versus 65) and dementia severity (MMSE 20 versus MMSE 22). AChE-impairment correlated significantly with the word fluency task (r=0.041, p<0.05) in the ApoE4 negative group only. These results indicate that cortical AChE activity is relatively well preserved in ApoE4 carriers, either by preservation of its cellular expression or as AChE activity in amyloid plaques.
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Espeseth T, Greenwood PM, Reinvang I, Fjell AM, Walhovd KB, Westlye LT, Wehling E, Lundervold A, Rootwelt H, Parasuraman R. Interactive effects of APOE and CHRNA4 on attention and white matter volume in healthy middle-aged and older adults. COGNITIVE AFFECTIVE & BEHAVIORAL NEUROSCIENCE 2006; 6:31-43. [PMID: 16869227 DOI: 10.3758/cabn.6.1.31] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
In the present study, we investigated age-related changes in interactions between efficiency of neuronal repair mechanisms and efficiency of cholinergic neurotransmission in the context of attentional orienting. In addition, we explored white matter volume changes as possible neuronal underpinnings. A sample of 230 healthy middle-aged (53-64 years) and older (65-75 years) adults was genotyped for polymorphisms of APOE and CHRNA4, a nicotinic receptor subunit gene. Participants were administered a visuospatial attention task involving letter discrimination with location cues of varying validity. Genotype effects on white matter volume were also investigated in a subset of participants who received MRI scans. APOE interacted with CHRNA4, such that APOE-epsilon4 carriers who were also CHRNA4 TT homozygotes showed disproportionately slowed reaction time (RT) following invalid location cues. The interaction was stronger in the middle-aged participants than in the older participants. There was also a trend for individuals with combined APOE-epsilon4/CHRNA4 TT genotypes to show both lower white matter volume and slower overall RT on the attention task The interaction of a neurotransmission gene (CHRNA4) and a susceptibility gene (APOE) suggests that the efficiency of neuronal repair mechanisms may modulate the cholinergic system to influence attentional function.
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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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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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Abstract
The association between genes and brain function using functional brain imaging techniques is an emerging and promising area of research that will help to better characterize the influence of genes on cognition and behavior as well as the link between genetic susceptibility and neuropsychiatric disorders. Neurophysiological imaging provides information regarding the effect of genes on brain function at the level of information processing, and neurochemical imaging provides information on the intrinsic mechanisms on how these genes affect the brain response. In this review, we highlight recent studies that have begun to explore the influence of genetic mutations on brain function with these techniques. The results, even from these few studies, illustrate the potential of these techniques to provide a more sensitive assay than behavioral measures used alone. The results also show that neuroimaging techniques can elucidate the influence of genes on brain function in relatively small sample populations, sometimes even in the absence of significant differences in behavioral measures.
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Affiliation(s)
- Venkata S Mattay
- Clinical Brain Disorders Branch, National Institute of Mental Health, National Institute of Health, Department of Health and Human Services, Building 10, Center Drive, Room 4S-235, Bethesda, MD 20892-1379, 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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