1
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Earley CJ, Jones BC, Ferré S. Brain-iron deficiency models of restless legs syndrome. Exp Neurol 2022; 356:114158. [PMID: 35779614 PMCID: PMC9357217 DOI: 10.1016/j.expneurol.2022.114158] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2022] [Revised: 06/24/2022] [Accepted: 06/25/2022] [Indexed: 11/04/2022]
Abstract
Restless legs syndrome (RLS) is a common sensorimotor disorder for which two main pathological elements are fairly well accepted: Brain iron deficiency (BID) and an altered dopaminergic system. The ability to better understand the causal and consequential factors related to these two pathological elements, would hopefully lead to the development of better therapeutic strategies for treating, if not curing, this disease. The current understanding of the relationship between these two elements is that BID leads to some alterations in neurotransmitters and subsequent changes in the dopaminergic system. Therefore, rodent models based on diet-induced BID, provide a biological substrate to understand the consequences of BID on dopaminergic pathway and on alternative pathways that may be involved. In this review, we present the current research on dopaminergic changes found in RLS subjects and compare that to what is seen in the BID rodent model to provide a validation of the BID rodent model. We also demonstrate the ability of the BID model to predict changes in other neurotransmitter systems and how that has led to new treatment options. Finally, we will present arguments for the utility of recombinant inbred mouse strains that demonstrate natural variation in brain iron, to explore the genetic basis of altered brain iron homeostasis as a model to understand why in idiopathic RLS there can exist a BID despite normal peripheral iron store. This review is the first to draw on 25 years of human and basic research into the pathophysiology of RLS to provide strong supportive data as to the validity of BID model as an important translational model of the disease. As we will demonstrate here, not only does the BID model closely and accurately mimic what we see in the dopaminergic system of RLS, it is the first model to identify alternative systems from which new treatments have recently been developed.
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Affiliation(s)
- Christopher J Earley
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
| | - Byron C Jones
- Department of Genetics, Genomics and Informatics, University of Tennessee Health Science Center, Memphis, TN, USA
| | - Sergi Ferré
- Integrative Neurobiology Section, National Institutes of Health/National Institute on Drug Abuse, Baltimore, MD, USA
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2
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Rabiner EA, Uz T, Mansur A, Brown T, Chen G, Wu J, Atienza J, Schwarz AJ, Yin W, Lewis Y, Searle GE, Dennison JMTJ, Passchier J, Gunn RN, Tauscher J. Endogenous dopamine release in the human brain as a pharmacodynamic biomarker: evaluation of the new GPR139 agonist TAK-041 with [ 11C]PHNO PET. Neuropsychopharmacology 2022; 47:1405-1412. [PMID: 34675381 PMCID: PMC9117280 DOI: 10.1038/s41386-021-01204-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/19/2021] [Revised: 09/03/2021] [Accepted: 09/29/2021] [Indexed: 01/01/2023]
Abstract
The use of positron emission tomography (PET) in early-phase development of novel drugs targeting the central nervous system, is well established for the evaluation of brain penetration and target engagement. However, when novel targets are involved a suitable PET ligand is not always available. We demonstrate an alternative approach that evaluates the attenuation of amphetamine-induced synaptic dopamine release by a novel agonist of the orphan G-protein-coupled receptor GPR139 (TAK-041). GPR139 agonism is a novel candidate mechanism for the treatment of schizophrenia and other disorders associated with social and cognitive dysfunction. Ten healthy volunteers underwent [11C]PHNO PET at baseline, and twice after receiving an oral dose of d-amphetamine (0.5 mg/kg). One of the post-d-amphetamine scans for each subject was preceded by a single oral dose of TAK-041 (20 mg in five; 40 mg in the other five participants). D-amphetamine induced a significant decrease in [11C]PHNO binding potential relative to the non-displaceable component (BPND) in all regions examined (16-28%), consistent with increased synaptic dopamine release. Pre-treatment with TAK-041 significantly attenuated the d-amphetamine-induced reduction in BPND in the a priori defined regions (putamen and ventral striatum: 26% and 18%, respectively). The reduction in BPND was generally higher after the 40 mg than the 20 mg TAK-041 dose, with the difference between doses reaching statistical significance in the putamen. Our findings suggest that TAK-041 enters the human brain and interacts with GPR139 to affect endogenous dopamine release. [11C]PHNO PET is a practical method to detect the effects of novel drugs on the brain dopaminergic system in healthy volunteers, in the early stages of drug development.
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Affiliation(s)
- Eugenii A. Rabiner
- grid.498414.40000 0004 0548 3187Invicro, London, UK ,grid.13097.3c0000 0001 2322 6764Centre for Neuroimaging Sciences, Institute of Psychiatry, Psychology and Neuroscience, King’s College London, London, UK
| | - Tolga Uz
- grid.419849.90000 0004 0447 7762Takeda Pharmaceuticals Ltd, Cambridge, MA USA
| | - Ayla Mansur
- grid.498414.40000 0004 0548 3187Invicro, London, UK
| | - Terry Brown
- grid.419849.90000 0004 0447 7762Takeda Pharmaceuticals Ltd, Cambridge, MA USA
| | - Grace Chen
- grid.419849.90000 0004 0447 7762Takeda Pharmaceuticals Ltd, Cambridge, MA USA
| | - Jingtao Wu
- grid.419849.90000 0004 0447 7762Takeda Pharmaceuticals Ltd, Cambridge, MA USA
| | - Joy Atienza
- grid.419849.90000 0004 0447 7762Takeda Pharmaceuticals Ltd, Cambridge, MA USA
| | - Adam J. Schwarz
- grid.419849.90000 0004 0447 7762Takeda Pharmaceuticals Ltd, Cambridge, MA USA
| | - Wei Yin
- grid.419849.90000 0004 0447 7762Takeda Pharmaceuticals Ltd, Cambridge, MA USA
| | - Yvonne Lewis
- grid.498414.40000 0004 0548 3187Invicro, London, UK
| | | | | | | | | | - Johannes Tauscher
- grid.419849.90000 0004 0447 7762Takeda Pharmaceuticals Ltd, Cambridge, MA USA
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3
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Varrone A, Bundgaard C, Bang-Andersen B. PET as a Translational Tool in Drug Development for Neuroscience Compounds. Clin Pharmacol Ther 2022; 111:774-785. [PMID: 35201613 PMCID: PMC9305164 DOI: 10.1002/cpt.2548] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2021] [Accepted: 01/29/2022] [Indexed: 11/05/2022]
Abstract
In central nervous system drug discovery programs, early development of new chemical entities (NCEs) requires a multidisciplinary strategy and a translational approach to obtain proof of distribution, proof of occupancy, and proof of function in specific brain circuits. Positron emission tomography (PET) provides a way to assess in vivo the brain distribution of NCEs and their binding to the target of interest, provided that radiolabeling of the NCE is possible or that a suitable radioligand is available. PET is therefore a key tool for early phases of drug discovery programs. This review will summarize the main applications of PET in early drug development and discuss the usefulness of PET microdosing studies performed with direct labelling of the NCE and PET occupancy studies. The purpose of this review is also to propose an alignment of the nomenclatures used by drug metabolism and pharmacokinetic scientists and PET imaging scientists to indicate key pharmacokinetic parameters and to provide guidance in the performance and interpretation of PET studies.
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Affiliation(s)
- Andrea Varrone
- Translational Biomarkers and Imaging, H. Lundbeck A/S, Copenhagen, Denmark
| | | | - Benny Bang-Andersen
- Translational Biomarkers and Imaging, H. Lundbeck A/S, Copenhagen, Denmark.,Medicinal Chemistry & Translational DMPK, H. Lundbeck A/S, Copenhagen, Denmark
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4
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Smart K, Naganawa M, Baldassarri SR, Nabulsi N, Ropchan J, Najafzadeh S, Gao H, Navarro A, Barth V, Esterlis I, Cosgrove KP, Huang Y, Carson RE, Hillmer AT. PET Imaging Estimates of Regional Acetylcholine Concentration Variation in Living Human Brain. Cereb Cortex 2021; 31:2787-2798. [PMID: 33442731 PMCID: PMC8355478 DOI: 10.1093/cercor/bhaa387] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2020] [Revised: 11/06/2020] [Accepted: 12/01/2020] [Indexed: 11/13/2022] Open
Abstract
Acetylcholine (ACh) has distinct functional roles in striatum compared with cortex, and imbalance between these systems may contribute to neuropsychiatric disease. Preclinical studies indicate markedly higher ACh concentrations in the striatum. The goal of this work was to leverage positron emission tomography (PET) imaging estimates of drug occupancy at cholinergic receptors to explore ACh variation across the human brain, because these measures can be influenced by competition with endogenous neurotransmitter. PET scans were analyzed from healthy human volunteers (n = 4) and nonhuman primates (n = 2) scanned with the M1-selective radiotracer [11C]LSN3172176 in the presence of muscarinic antagonist scopolamine, and human volunteers (n = 10) scanned with the α4β2* nicotinic ligand (-)-[18F]flubatine during nicotine challenge. In all cases, occupancy estimates within striatal regions were consistently lower (M1/scopolamine human scans, 31 ± 3.4% occupancy in striatum, 43 ± 2.9% in extrastriatal regions, p = 0.0094; nonhuman primate scans, 42 ± 26% vs. 69 ± 28%, p < 0.0001; α4β2*/nicotine scans, 67 ± 15% vs. 74 ± 16%, p = 0.0065), indicating higher striatal ACh concentration. Subject-level measures of these concentration differences were estimated, and whole-brain images of regional ACh concentration gradients were generated. These results constitute the first in vivo estimates of regional variation in ACh concentration in the living brain and offer a novel experimental method to assess potential ACh imbalances in clinical populations.
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Affiliation(s)
- Kelly Smart
- Yale PET Center, Yale School of Medicine, New Haven, CT 06510, USA
- Department of Radiology & Biomedical Imaging, Yale School of Medicine, New Haven, CT 06520, USA
| | - Mika Naganawa
- Yale PET Center, Yale School of Medicine, New Haven, CT 06510, USA
- Department of Radiology & Biomedical Imaging, Yale School of Medicine, New Haven, CT 06520, USA
| | - Stephen R Baldassarri
- Department of Internal Medicine, Section of Pulmonary, Critical Care, and Sleep Medicine, Yale School of Medicine, New Haven, CT 06510, USA
| | - Nabeel Nabulsi
- Yale PET Center, Yale School of Medicine, New Haven, CT 06510, USA
- Department of Radiology & Biomedical Imaging, Yale School of Medicine, New Haven, CT 06520, USA
| | - Jim Ropchan
- Yale PET Center, Yale School of Medicine, New Haven, CT 06510, USA
- Department of Radiology & Biomedical Imaging, Yale School of Medicine, New Haven, CT 06520, USA
| | | | - Hong Gao
- Yale PET Center, Yale School of Medicine, New Haven, CT 06510, USA
| | | | | | - Irina Esterlis
- Department of Psychiatry, Yale School of Medicine, New Haven, CT 06511, USA
| | - Kelly P Cosgrove
- Department of Radiology & Biomedical Imaging, Yale School of Medicine, New Haven, CT 06520, USA
- Department of Psychiatry, Yale School of Medicine, New Haven, CT 06511, USA
| | - Yiyun Huang
- Yale PET Center, Yale School of Medicine, New Haven, CT 06510, USA
- Department of Radiology & Biomedical Imaging, Yale School of Medicine, New Haven, CT 06520, USA
| | - Richard E Carson
- Yale PET Center, Yale School of Medicine, New Haven, CT 06510, USA
- Department of Radiology & Biomedical Imaging, Yale School of Medicine, New Haven, CT 06520, USA
- Department of Biomedical Engineering, Yale University, New Haven, CT 06511, USA
| | - Ansel T Hillmer
- Yale PET Center, Yale School of Medicine, New Haven, CT 06510, USA
- Department of Radiology & Biomedical Imaging, Yale School of Medicine, New Haven, CT 06520, USA
- Department of Psychiatry, Yale School of Medicine, New Haven, CT 06511, USA
- Department of Biomedical Engineering, Yale University, New Haven, CT 06511, USA
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5
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Prasad K, de Vries EFJ, Elsinga PH, Dierckx RAJO, van Waarde A. Allosteric Interactions between Adenosine A 2A and Dopamine D 2 Receptors in Heteromeric Complexes: Biochemical and Pharmacological Characteristics, and Opportunities for PET Imaging. Int J Mol Sci 2021; 22:ijms22041719. [PMID: 33572077 PMCID: PMC7915359 DOI: 10.3390/ijms22041719] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2021] [Revised: 02/02/2021] [Accepted: 02/03/2021] [Indexed: 12/17/2022] Open
Abstract
Adenosine and dopamine interact antagonistically in living mammals. These interactions are mediated via adenosine A2A and dopamine D2 receptors (R). Stimulation of A2AR inhibits and blockade of A2AR enhances D2R-mediated locomotor activation and goal-directed behavior in rodents. In striatal membrane preparations, adenosine decreases both the affinity and the signal transduction of D2R via its interaction with A2AR. Reciprocal A2AR/D2R interactions occur mainly in striatopallidal GABAergic medium spiny neurons (MSNs) of the indirect pathway that are involved in motor control, and in striatal astrocytes. In the nucleus accumbens, they also take place in MSNs involved in reward-related behavior. A2AR and D2R co-aggregate, co-internalize, and co-desensitize. They are at very close distance in biomembranes and form heteromers. Antagonistic interactions between adenosine and dopamine are (at least partially) caused by allosteric receptor–receptor interactions within A2AR/D2R heteromeric complexes. Such interactions may be exploited in novel strategies for the treatment of Parkinson’s disease, schizophrenia, substance abuse, and perhaps also attention deficit-hyperactivity disorder. Little is known about shifting A2AR/D2R heteromer/homodimer equilibria in the brain. Positron emission tomography with suitable ligands may provide in vivo information about receptor crosstalk in the living organism. Some experimental approaches, and strategies for the design of novel imaging agents (e.g., heterobivalent ligands) are proposed in this review.
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Affiliation(s)
- Kavya Prasad
- Department of Nuclear Medicine and Molecular Imaging, University Medical Center Groningen, University of Groningen, Hanzeplein 1, 9713GZ Groningen, The Netherlands; (E.F.J.d.V.); (P.H.E.); (R.A.J.O.D.)
- Correspondence: (K.P.); (A.v.W.); Tel.: +31-50-3613215
| | - Erik F. J. de Vries
- Department of Nuclear Medicine and Molecular Imaging, University Medical Center Groningen, University of Groningen, Hanzeplein 1, 9713GZ Groningen, The Netherlands; (E.F.J.d.V.); (P.H.E.); (R.A.J.O.D.)
| | - Philip H. Elsinga
- Department of Nuclear Medicine and Molecular Imaging, University Medical Center Groningen, University of Groningen, Hanzeplein 1, 9713GZ Groningen, The Netherlands; (E.F.J.d.V.); (P.H.E.); (R.A.J.O.D.)
| | - Rudi A. J. O. Dierckx
- Department of Nuclear Medicine and Molecular Imaging, University Medical Center Groningen, University of Groningen, Hanzeplein 1, 9713GZ Groningen, The Netherlands; (E.F.J.d.V.); (P.H.E.); (R.A.J.O.D.)
- Department of Diagnostic Sciences, Ghent University Faculty of Medicine and Health Sciences, C.Heymanslaan 10, 9000 Gent, Belgium
| | - Aren van Waarde
- Department of Nuclear Medicine and Molecular Imaging, University Medical Center Groningen, University of Groningen, Hanzeplein 1, 9713GZ Groningen, The Netherlands; (E.F.J.d.V.); (P.H.E.); (R.A.J.O.D.)
- Correspondence: (K.P.); (A.v.W.); Tel.: +31-50-3613215
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6
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Caravaggio F, Porco N, Kim J, Torres-Carmona E, Brown E, Iwata Y, Nakajima S, Gerretsen P, Remington G, Graff-Guerrero A. Measuring amphetamine-induced dopamine release in humans: A comparative meta-analysis of [ 11 C]-raclopride and [ 11 C]-(+)-PHNO studies. Synapse 2021; 75:e22195. [PMID: 33471400 DOI: 10.1002/syn.22195] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2020] [Revised: 01/02/2021] [Accepted: 01/13/2021] [Indexed: 02/06/2023]
Abstract
The radiotracers [11 C]-raclopride and [11 C]-(+)-PHNO are commonly used to measure differences in amphetamine-induced dopamine release between healthy persons and persons with neuropsychiatric diseases. As an agonist radiotracer, [11 C]-(+)-PHNO should theoretically be roughly 2.7 times more sensitive to displacement by endogenous dopamine than [11 C]raclopride. To date, only one study has been published comparing the sensitivity of these two radiotracers to amphetamine-induced dopamine release in healthy persons. Unfortunately, conflicting findings in the literature suggests that the dose of amphetamine they employed (0.3 mg/kg, p.o.) may not reliably reduce [11 C]-raclopride binding in the caudate. Thus, it is unclear whether the preponderance of evidence supports the theory that [11 C]-(+)-PHNO is more sensitive to displacement by amphetamine in humans than [11 C]-raclopride. In order to clarify these issues, we conducted a comparative meta-analysis summarizing the effects of amphetamine on [11 C]-raclopride and [11 C]-(+)-PHNO binding in healthy humans. Our analysis indicates that amphetamine given at 0.3 mg/kg, p.o. does not reliably reduce [11 C]-raclopride binding in the caudate. Second, the greater sensitivity of [11 C]-(+)-PHNO is evidenced at 0.5 mg/kg, p.o., but not at lower doses of amphetamine. Third, our analysis suggests that [11 C]-(+)-PHNO may be roughly 1.5 to 2.5 times more sensitive to displacement by amphetamine than [11 C]-raclopride in healthy persons. We recommend that future displacement studies with these radiotracers employ 0.5 mg/kg, p.o. of amphetamine with a dose, post-scan interval of at least 3 hr. Using this dose of amphetamine, [11 C]-raclopride studies should employ at least n = 34 participants per group, while [11 C]-(+)-PHNO studies should employ at least n = 6 participants per group, in order to be sufficiently powered (80%) to detect changes in radiotracer binding within the caudate.
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Affiliation(s)
- Fernando Caravaggio
- Brain Health Imaging Centre, Centre for Addiction and Mental Health, Toronto, ON, Canada.,Department of Psychiatry, University of Toronto, Toronto, ON, Canada
| | - Natasha Porco
- Brain Health Imaging Centre, Centre for Addiction and Mental Health, Toronto, ON, Canada
| | - Julia Kim
- Brain Health Imaging Centre, Centre for Addiction and Mental Health, Toronto, ON, Canada
| | - Edgardo Torres-Carmona
- Brain Health Imaging Centre, Centre for Addiction and Mental Health, Toronto, ON, Canada
| | - Eric Brown
- Brain Health Imaging Centre, Centre for Addiction and Mental Health, Toronto, ON, Canada.,Department of Psychiatry, University of Toronto, Toronto, ON, Canada
| | - Yusuke Iwata
- Department of Neuropsychiatry, University of Yamanashi, Chuo, Japan
| | | | - Philip Gerretsen
- Brain Health Imaging Centre, Centre for Addiction and Mental Health, Toronto, ON, Canada.,Department of Psychiatry, University of Toronto, Toronto, ON, Canada
| | - Gary Remington
- Brain Health Imaging Centre, Centre for Addiction and Mental Health, Toronto, ON, Canada.,Department of Psychiatry, University of Toronto, Toronto, ON, Canada
| | - Ariel Graff-Guerrero
- Brain Health Imaging Centre, Centre for Addiction and Mental Health, Toronto, ON, Canada.,Department of Psychiatry, University of Toronto, Toronto, ON, Canada
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7
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Kilbourn MR. 11C- and 18F-Radiotracers for In Vivo Imaging of the Dopamine System: Past, Present and Future. Biomedicines 2021; 9:108. [PMID: 33499179 PMCID: PMC7912183 DOI: 10.3390/biomedicines9020108] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2020] [Revised: 01/17/2021] [Accepted: 01/19/2021] [Indexed: 12/17/2022] Open
Abstract
The applications of positron emission tomography (PET) imaging to study brain biochemistry, and in particular the aspects of dopamine neurotransmission, have grown significantly over the 40 years since the first successful in vivo imaging studies in humans. In vivo PET imaging of dopaminergic functions of the central nervous system (CNS) including dopamine synthesis, vesicular storage, synaptic release and receptor binding, and reuptake processes, are now routinely used for studies in neurology, psychiatry, drug abuse and addiction, and drug development. Underlying these advances in PET imaging has been the development of the unique radiotracers labeled with positron-emitting radionuclides such as carbon-11 and fluorine-18. This review focuses on a selection of the more accepted and utilized PET radiotracers currently available, with a look at their past, present and future.
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Affiliation(s)
- Michael R Kilbourn
- Department of Radiology, University of Michigan Medical School, Ann Arbor, MI 48105, USA
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8
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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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9
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Sander CY, Hansen HD, Wey HY. Advances in simultaneous PET/MR for imaging neuroreceptor function. J Cereb Blood Flow Metab 2020; 40:1148-1166. [PMID: 32169011 PMCID: PMC7238372 DOI: 10.1177/0271678x20910038] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Hybrid imaging using PET/MRI has emerged as a platform for elucidating novel neurobiology, molecular and functional changes in disease, and responses to physiological or pharmacological interventions. For the central nervous system, PET/MRI has provided insights into biochemical processes, linking selective molecular targets and distributed brain function. This review highlights several examples that leverage the strengths of simultaneous PET/MRI, which includes measuring the perturbation of multi-modal imaging signals on dynamic timescales during pharmacological challenges, physiological interventions or behavioral tasks. We discuss important considerations for the experimental design of dynamic PET/MRI studies and data analysis approaches for comparing and quantifying simultaneous PET/MRI data. The primary focus of this review is on functional PET/MRI studies of neurotransmitter and receptor systems, with an emphasis on the dopamine, opioid, serotonin and glutamate systems as molecular neuromodulators. In this context, we provide an overview of studies that employ interventions to alter the activity of neuroreceptors or the release of neurotransmitters. Overall, we emphasize how the synergistic use of simultaneous PET/MRI with appropriate study design and interventions has the potential to expand our knowledge about the molecular and functional dynamics of the living human brain. Finally, we give an outlook on the future opportunities for simultaneous PET/MRI.
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Affiliation(s)
- Christin Y Sander
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, MA, USA
| | - Hanne D Hansen
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, MA, USA.,Neurobiology Research Unit and NeuroPharm, Copenhagen University Hospital (Rigshospitalet), Copenhagen, Denmark
| | - Hsiao-Ying Wey
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, MA, USA
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10
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Moritz AE, Free RB, Weiner WS, Akano EO, Gandhi D, Abramyan A, Keck TM, Ferrer M, Hu X, Southall N, Steiner J, Aubé J, Shi L, Frankowski KJ, Sibley DR. Discovery, Optimization, and Characterization of ML417: A Novel and Highly Selective D 3 Dopamine Receptor Agonist. J Med Chem 2020; 63:5526-5567. [PMID: 32342685 DOI: 10.1021/acs.jmedchem.0c00424] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
To identify novel D3 dopamine receptor (D3R) agonists, we conducted a high-throughput screen using a β-arrestin recruitment assay. Counterscreening of the hit compounds provided an assessment of their selectivity, efficacy, and potency. The most promising scaffold was optimized through medicinal chemistry resulting in enhanced potency and selectivity. The optimized compound, ML417 (20), potently promotes D3R-mediated β-arrestin translocation, G protein activation, and ERK1/2 phosphorylation (pERK) while lacking activity at other dopamine receptors. Screening of ML417 against multiple G protein-coupled receptors revealed exceptional global selectivity. Molecular modeling suggests that ML417 interacts with the D3R in a unique manner, possibly explaining its remarkable selectivity. ML417 was also found to protect against neurodegeneration of dopaminergic neurons derived from iPSCs. Together with promising pharmacokinetics and toxicology profiles, these results suggest that ML417 is a novel and uniquely selective D3R agonist that may serve as both a research tool and a therapeutic lead for the treatment of neuropsychiatric disorders.
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Affiliation(s)
- Amy E Moritz
- Molecular Neuropharmacology Section, National Institute of Neurological Disorders and Stroke, Intramural Research Program, National Institutes of Health, 35 Convent Drive, MSC-3723, Bethesda, Maryland 20892-3723, United States
| | - R Benjamin Free
- Molecular Neuropharmacology Section, National Institute of Neurological Disorders and Stroke, Intramural Research Program, National Institutes of Health, 35 Convent Drive, MSC-3723, Bethesda, Maryland 20892-3723, United States
| | - Warren S Weiner
- University of Kansas Specialized Chemistry Center, University of Kansas, Lawrence, Kansas 66047, United States
| | - Emmanuel O Akano
- Molecular Neuropharmacology Section, National Institute of Neurological Disorders and Stroke, Intramural Research Program, National Institutes of Health, 35 Convent Drive, MSC-3723, Bethesda, Maryland 20892-3723, United States
| | - Disha Gandhi
- Center for Integrative Chemical Biology and Drug Discovery, UNC Eshelman School of Pharmacy, 125 Mason Farm Road, Chapel Hill, North Carolina 27599, United States
| | - Ara Abramyan
- Computational Chemistry and Molecular Biophysics Unit, Molecular Targets and Medications Discovery Branch, National Institute on Drug Abuse, Intramural Research Program, National Institutes of Health, Baltimore, Maryland, 333 Cassell Drive, Baltimore, Maryland 21224, United States
| | - Thomas M Keck
- Department of Chemistry & Biochemistry, Department of Molecular & Cellular Biosciences, College of Science and Mathematics, Rowan University, 201 Mullica Hill Road, Glassboro, New Jersey 08028, United States
| | - Marc Ferrer
- NIH Chemical Genomics Center, Division of Preclinical Innovation, National Center for Advancing Translational Sciences, National Institutes of Health, 9800 Medical Center Drive, Rockville, Maryland 20850, United States
| | - Xin Hu
- NIH Chemical Genomics Center, Division of Preclinical Innovation, National Center for Advancing Translational Sciences, National Institutes of Health, 9800 Medical Center Drive, Rockville, Maryland 20850, United States
| | - Noel Southall
- NIH Chemical Genomics Center, Division of Preclinical Innovation, National Center for Advancing Translational Sciences, National Institutes of Health, 9800 Medical Center Drive, Rockville, Maryland 20850, United States
| | - Joseph Steiner
- NeuroTherapeutics Development Unit, National Institute for Neurological Disorders and Stroke, Intramural Research Program, National Institutes of Health, Bethesda, Maryland 20892, United States
| | - Jeffrey Aubé
- University of Kansas Specialized Chemistry Center, University of Kansas, Lawrence, Kansas 66047, United States.,Center for Integrative Chemical Biology and Drug Discovery, UNC Eshelman School of Pharmacy, 125 Mason Farm Road, Chapel Hill, North Carolina 27599, United States
| | - Lei Shi
- Computational Chemistry and Molecular Biophysics Unit, Molecular Targets and Medications Discovery Branch, National Institute on Drug Abuse, Intramural Research Program, National Institutes of Health, Baltimore, Maryland, 333 Cassell Drive, Baltimore, Maryland 21224, United States
| | - Kevin J Frankowski
- University of Kansas Specialized Chemistry Center, University of Kansas, Lawrence, Kansas 66047, United States.,Center for Integrative Chemical Biology and Drug Discovery, UNC Eshelman School of Pharmacy, 125 Mason Farm Road, Chapel Hill, North Carolina 27599, United States
| | - David R Sibley
- Molecular Neuropharmacology Section, National Institute of Neurological Disorders and Stroke, Intramural Research Program, National Institutes of Health, 35 Convent Drive, MSC-3723, Bethesda, Maryland 20892-3723, United States
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11
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Hansson AC, Gründer G, Hirth N, Noori HR, Spanagel R, Sommer WH. Dopamine and opioid systems adaptation in alcoholism revisited: Convergent evidence from positron emission tomography and postmortem studies. Neurosci Biobehav Rev 2019; 106:141-164. [DOI: 10.1016/j.neubiorev.2018.09.010] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2018] [Revised: 09/08/2018] [Accepted: 09/14/2018] [Indexed: 12/20/2022]
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12
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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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13
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Measuring endogenous changes in serotonergic neurotransmission with [ 11C]Cimbi-36 positron emission tomography in humans. Transl Psychiatry 2019; 9:134. [PMID: 30975977 PMCID: PMC6459901 DOI: 10.1038/s41398-019-0468-8] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/05/2019] [Accepted: 03/24/2019] [Indexed: 12/28/2022] Open
Abstract
Developing positron emission tomography (PET) radioligands for the detection of endogenous serotonin release will enable the investigation of serotonergic deficits in many neuropsychiatric disorders. The present study investigates how acute challenges that aim to increase or decrease cerebral serotonin levels affect binding of the serotonin 2A receptor (5-HT2AR) agonist radioligand [11C]Cimbi-36. In a randomized, double-blind, placebo-controlled, three-arm design, 23 healthy volunteers were PET scanned twice with [11C]Cimbi-36: at baseline and following double-blind assignment to one of three interventions (1) infusion of the selective serotonin reuptake inhibitor (SSRI) citalopram preceded by oral dosing of the 5-HT1AR antagonist pindolol, (n = 8) (2) acute tryptophan depletion (ATD) (n = 7) and (3) placebo (n = 8). Two-sample t-tests revealed no significant group differences in percent change of neocortical [11C]Cimbi-36 binding from baseline to intervention between placebo and citalopram/pindolol (p = 0.4) or between placebo and ATD (p = 0.5). Notably, there was a significantly larger within-group variation in 5-HT2AR binding after intervention with citalopram/pindolol, as compared with placebo (p = 0.007). These findings suggest that neither ATD nor a combination of citalopram and pindolol elicit acute unidirectional changes in serotonin levels sufficient to be detected with [11C]Cimbi-36 PET in neocortex. We suggest that the large interindividual variation in 5-HT2AR binding after citalopram/pindolol reflects that after an acute SSRI intervention, individuals respond substantially different in terms of their brain serotonin levels. Our observation has a potential impact for the understanding of patient responses to SSRI.
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14
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Caravaggio F, Iwata Y, Kim J, Shah P, Gerretsen P, Remington G, Graff-Guerrero A. What proportion of striatal D2 receptors are occupied by endogenous dopamine at baseline? A meta-analysis with implications for understanding antipsychotic occupancy. Neuropharmacology 2019; 163:107591. [PMID: 30940535 DOI: 10.1016/j.neuropharm.2019.03.034] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2019] [Revised: 03/25/2019] [Accepted: 03/27/2019] [Indexed: 11/30/2022]
Abstract
Using molecular imaging techniques - positron emission tomography (PET) and single-photon emission computed tomography (SPECT) - in conjunction with an acute dopamine depletion challenge (alpha-methyl-para-tyrosine) it is possible to estimate endogenous dopamine levels occupying striatal dopamine D2 receptors (D2R) in humans in vivo. However, it is unclear what proportion of striatal D2R are occupied by endogenous dopamine under normal conditions. This is important since it has been suggested that in schizophrenia there may be a substantial proportion of striatal D2R which are occupied by endogenous dopamine and not accessible by therapeutic doses of antipsychotics. In order to clarify these issues, we conducted a meta-analysis of dopamine depletion studies using substituted benzamide radiotracers in healthy persons. This meta-analysis suggests that anywhere from 8 to 21% (weighted average 11%) of striatal D2R may be occupied by endogenous dopamine at baseline. Using these estimates, we propose an updated occupancy model and tentatively suggest that antipsychotics inhibit a smaller proportion of the total pool of striatal D2R in vivo than previously acknowledged. This article is part of the issue entitled 'Special Issue on Antipsychotics'.
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Affiliation(s)
- Fernando Caravaggio
- Research Imaging Centre, Centre for Addiction and Mental Health, 250 College Street, Toronto, Ontario, M5T 1R8, Canada; Department of Psychiatry, University of Toronto, 250 College Street, Toronto, Ontario, M5T 1R8, Canada.
| | - Yusuke Iwata
- Research Imaging Centre, Centre for Addiction and Mental Health, 250 College Street, Toronto, Ontario, M5T 1R8, Canada; Department of Psychiatry, University of Toronto, 250 College Street, Toronto, Ontario, M5T 1R8, Canada
| | - Julia Kim
- Research Imaging Centre, Centre for Addiction and Mental Health, 250 College Street, Toronto, Ontario, M5T 1R8, Canada; Institute of Medical Science, University of Toronto, 1 Kings College Circle, Toronto, Ontario, M5S 1A8, Canada
| | - Parita Shah
- Research Imaging Centre, Centre for Addiction and Mental Health, 250 College Street, Toronto, Ontario, M5T 1R8, Canada; Institute of Medical Science, University of Toronto, 1 Kings College Circle, Toronto, Ontario, M5S 1A8, Canada
| | - Philip Gerretsen
- Research Imaging Centre, Centre for Addiction and Mental Health, 250 College Street, Toronto, Ontario, M5T 1R8, Canada; Department of Psychiatry, University of Toronto, 250 College Street, Toronto, Ontario, M5T 1R8, Canada; Institute of Medical Science, University of Toronto, 1 Kings College Circle, Toronto, Ontario, M5S 1A8, Canada
| | - Gary Remington
- Research Imaging Centre, Centre for Addiction and Mental Health, 250 College Street, Toronto, Ontario, M5T 1R8, Canada; Department of Psychiatry, University of Toronto, 250 College Street, Toronto, Ontario, M5T 1R8, Canada; Institute of Medical Science, University of Toronto, 1 Kings College Circle, Toronto, Ontario, M5S 1A8, Canada
| | - Ariel Graff-Guerrero
- Research Imaging Centre, Centre for Addiction and Mental Health, 250 College Street, Toronto, Ontario, M5T 1R8, Canada; Department of Psychiatry, University of Toronto, 250 College Street, Toronto, Ontario, M5T 1R8, Canada; Institute of Medical Science, University of Toronto, 1 Kings College Circle, Toronto, Ontario, M5S 1A8, Canada
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15
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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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16
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Andersson JD, Matuskey D, Finnema SJ. Positron emission tomography imaging of the γ-aminobutyric acid system. Neurosci Lett 2018; 691:35-43. [PMID: 30102960 DOI: 10.1016/j.neulet.2018.08.010] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2018] [Revised: 08/06/2018] [Accepted: 08/09/2018] [Indexed: 01/08/2023]
Abstract
In this review, we summarize the recent development of positron emission tomography (PET) radioligands for γ-aminobutyric acid A (GABAA) receptors and their potential to measure changes in endogenous GABA levels and highlight the clinical and translational applications of GABA-sensitive PET radioligands. We review the basic physiology of the GABA system with a focus on the importance of GABAA receptors in the brain and specifically the benzodiazepine binding site. Challenges for the development of central nervous system radioligands and particularly for radioligands with increased GABA sensitivity are outlined, as well as the status of established benzodiazepine site PET radioligands and agonist GABAA radioligands. We underline the challenge of using allosteric interactions to measure GABA concentrations and review the current state of PET imaging of changes in GABA levels. We conclude that PET tracers with increased GABA sensitivity are required to efficiently measure GABA release and that such a tool could be broadly applied to assess GABA transmission in vivo across several disorders.
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Affiliation(s)
- Jan D Andersson
- University of Alberta, Medical Isotope and Cyclotron Facility, Edmonton, Canada
| | - David Matuskey
- PET Center, Department of Radiology and Biomedical Imaging, Yale University, New Haven, CT, USA
| | - Sjoerd J Finnema
- PET Center, Department of Radiology and Biomedical Imaging, Yale University, New Haven, CT, USA; Center for Psychiatric Research, Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden.
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17
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Yang KC, Takano A, Halldin C, Farde L, Finnema SJ. Serotonin concentration enhancers at clinically relevant doses reduce [ 11C]AZ10419369 binding to the 5-HT 1B receptors in the nonhuman primate brain. Transl Psychiatry 2018; 8:132. [PMID: 30013068 PMCID: PMC6048172 DOI: 10.1038/s41398-018-0178-7] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/26/2017] [Revised: 02/14/2018] [Accepted: 04/03/2018] [Indexed: 12/25/2022] Open
Abstract
The serotonin (5-HT) system plays an important role in the pathophysiology and treatment of several major psychiatric disorders. Currently, no suitable positron emission tomography (PET) imaging paradigm is available to assess 5-HT release in the living human brain. [11C]AZ10419369 binds to 5-HT1B receptors and is one of the most 5-HT-sensitive radioligands available. This study applied 5-HT concentration enhancers which can be safely studied in humans, and examined their effect on [11C]AZ10419369 binding at clinically relevant doses, including amphetamine (1 mg/kg), 3,4-methylenedioxymethamphetamine (MDMA; 1 mg/kg) or 5-hydroxy-L-tryptophan (5-HTP; 5 mg/kg). Twenty-six PET measurements (14 for amphetamine, 6 for MDMA and 6 for 5-HTP) using a bolus and constant infusion protocol were performed in four cynomolgus monkeys before or after drug administration. Binding potential (BPND) values were determined with the equilibrium method (integral interval: 63-123 min) using cerebellum as the reference region. BPND values were significantly decreased in several examined brain regions after administration of amphetamine (range: 19-31%), MDMA (16-25%) or 5-HTP (13-31%). Reductions in [11C]AZ10419369 binding were greater in striatum than cortical regions after administration of 5-HTP, while no prominent regional differences were found for amphetamine and MDMA. In conclusion, [11C]AZ10419369 binding is sensitive to changes in 5-HT concentration induced by amphetamine, MDMA or 5-HTP. The robust changes in BPND, following pretreatment drugs administered at clinically relevant doses, indicate that the applied PET imaging paradigms hold promise to be successfully used in future human studies.
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Affiliation(s)
- Kai-Chun Yang
- Department of Clinical Neuroscience, Center for Psychiatric Research, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden.
| | - Akihiro Takano
- Department of Clinical Neuroscience, Center for Psychiatric Research, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden
| | - Christer Halldin
- Department of Clinical Neuroscience, Center for Psychiatric Research, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden
| | - Lars Farde
- Department of Clinical Neuroscience, Center for Psychiatric Research, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden
- Personalized Health Care and Biomarkers, AstraZeneca PET Science Center at Karolinska Institutet, Stockholm, Sweden
| | - Sjoerd J Finnema
- Department of Clinical Neuroscience, Center for Psychiatric Research, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden
- Department of Radiology and Biomedical Imaging, Yale University, New Haven, CT, USA
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18
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Weinstein JJ, van de Giessen E, Rosengard RJ, Xu X, Ojeil N, Brucato G, Gil RB, Kegeles LS, Laruelle M, Slifstein M, Abi-Dargham A. PET imaging of dopamine-D2 receptor internalization in schizophrenia. Mol Psychiatry 2018; 23:1506-1511. [PMID: 28507321 PMCID: PMC5690884 DOI: 10.1038/mp.2017.107] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/06/2017] [Revised: 03/22/2017] [Accepted: 04/04/2017] [Indexed: 02/07/2023]
Abstract
Recent genetic, molecular and post-mortem studies suggest impaired dopamine (DA)-D2 receptor (D2R) trafficking in patients with schizophrenia (SZ). Imaging and preclinical studies have shown agonist-induced D2R internalization can be imaged with positron emission tomography (PET) using D2R radiotracers combined with psychostimulant challenge. This is feasible if radiotracer binding is measured when postchallenge DA levels have returned to baseline, following the initial competition phase between DA and radiotracer for binding to D2R. Here we used 'late-phase' imaging after challenge to test the hypothesis that impaired D2R internalization in SZ leads to blunted late-phase displacement, or a faster return to baseline, in patients compared with healthy controls (HCs). We imaged 10 patients with SZ and 9 HCs with PET and [11C]raclopride at baseline and two times (3-5 and 6-10 h) following 0.5 mg kg-1 dextroamphetamine. We measured binding potential relative to non-displaceable compartment (BPND) and derived percent reduction from baseline (ΔBPND) for each postamphetamine scan. To test the hypothesis that time course of return of striatal BPND to baseline differed between SZ and HCs, we implemented a linear model with ΔBPND as dependent variable, time after amphetamine as repeated measure and time after amphetamine and diagnostic group as fixed effects. Neither diagnostic group nor interaction of diagnostic group-by-time after amphetamine significantly affected striatal ΔBPND (F=1.38, P=0.26; F=0.51, P=0.61). These results show similar pattern of return of BPND to baseline as a function of time in patients with SZ and HC, suggesting that striatal D2R internalization as measured by our imaging paradigm is normal in patients with SZ.
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Affiliation(s)
- Jodi J. Weinstein
- Department of Psychiatry, Stony Brook University School of Medicine, Stony Brook, New York,Department of Psychiatry, Columbia University College of Physicians and Surgeons, New York, New York
| | | | | | - Xiaoyan Xu
- New York State Psychiatric Institute, New York, New York
| | - Najate Ojeil
- New York State Psychiatric Institute, New York, New York
| | - Gary Brucato
- Department of Psychiatry, Columbia University College of Physicians and Surgeons, New York, New York,New York State Psychiatric Institute, New York, New York
| | - Roberto B. Gil
- Department of Psychiatry, Stony Brook University School of Medicine, Stony Brook, New York
| | - Lawrence S. Kegeles
- Department of Psychiatry, Columbia University College of Physicians and Surgeons, New York, New York,New York State Psychiatric Institute, New York, New York
| | - Marc Laruelle
- Department of Psychiatry, Columbia University College of Physicians and Surgeons, New York, New York
| | - Mark Slifstein
- Department of Psychiatry, Stony Brook University School of Medicine, Stony Brook, New York
| | - Anissa Abi-Dargham
- Department of Psychiatry, Stony Brook University School of Medicine, Stony Brook, New York
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19
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Frankle WG, Paris J, Himes M, Mason NS, Mathis CA, Narendran R. Amphetamine-Induced Striatal Dopamine Release Measured With an Agonist Radiotracer in Schizophrenia. Biol Psychiatry 2018; 83:707-714. [PMID: 29325847 PMCID: PMC5862747 DOI: 10.1016/j.biopsych.2017.11.032] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/17/2017] [Revised: 11/29/2017] [Accepted: 11/30/2017] [Indexed: 02/07/2023]
Abstract
BACKGROUND Receptor imaging studies have reported increased amphetamine-induced dopamine release in subjects with schizophrenia (SCH) relative to healthy control subjects (HCs). A limitation of these studies, performed with D2/3 antagonist radiotracers, is the failure to provide information about D2/3 receptors configured in a state of high affinity for the agonists (i.e., D2/3 receptors coupled to G proteins [D2/3 HIGH]). The endogenous agonist dopamine binds with preference to D2/3 HIGH receptors relative to D2/3 LOW receptors, making it critical to understand the status of D2/3 HIGH receptors in SCH. METHODS D2/3 agonist positron emission tomography radiotracer [11C]N-propyl-norapomorphine ([11C]NPA) binding potential (BPND) was measured in 14 off-medication subjects with SCH and 14 matched HCs at baseline and after the administration of 0.5 mg kg-1 oral D-amphetamine. The amphetamine-induced change in BPND (ΔBPND) was calculated as the difference between BPND in the postamphetamine condition and BPND in the baseline condition and was expressed as a percentage of BPND at baseline. RESULTS A trend-level increase was observed in comparing baseline [11C]NPA BPND (repeated-measures analysis of variance, F1,26 = 3.34, p = .08) between the SCH and HC groups. Amphetamine administration significantly decreased BPND in all striatal regions across all subjects in both groups. No differences were observed in [11C]NPA ΔBPND (repeated-measures analysis of variance, F1,26 = 1.9, p = .18) between HCs and subjects with SCH. Amphetamine significantly increased positive symptoms in subjects with SCH (19.5 ± 5.3 vs. 23.7 ± 4.1, paired t test, p < .0001); however, no correlations were noted with [11C]NPA BPND or ΔBPND. CONCLUSIONS This study provides in vivo indication of a role for postsynaptic factors in amphetamine-induced psychosis in SCH.
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Affiliation(s)
- W Gordon Frankle
- Department of Psychiatry, NYU Langone Medical Center, New York, New York.
| | - Jennifer Paris
- Department of Psychiatry, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Michael Himes
- Department of Psychiatry, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - N Scott Mason
- Department of Radiology, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Chester A Mathis
- Department of Radiology, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Rajesh Narendran
- Department of Psychiatry, University of Pittsburgh, Pittsburgh, Pennsylvania; Department of Radiology, University of Pittsburgh, Pittsburgh, Pennsylvania
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20
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Caravaggio F, Ku Chung J, Plitman E, Boileau I, Gerretsen P, Kim J, Iwata Y, Patel R, Chakravarty MM, Remington G, Graff-Guerrero A. The relationship between subcortical brain volume and striatal dopamine D 2/3 receptor availability in healthy humans assessed with [ 11 C]-raclopride and [ 11 C]-(+)-PHNO PET. Hum Brain Mapp 2017; 38:5519-5534. [PMID: 28752565 DOI: 10.1002/hbm.23744] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2017] [Revised: 06/21/2017] [Accepted: 07/16/2017] [Indexed: 01/18/2023] Open
Abstract
BACKGROUND Abnormalities in dopamine (DA) and brain morphology are observed in several neuropsychiatric disorders. However, it is not fully understood how these abnormalities may relate to one another. For such in vivo findings to be used as biomarkers for neuropsychiatric disease, it must be understood how variability in DA relates to brain structure under healthy conditions. We explored how the availability of striatal DA D2/3 receptors (D2/3 R) is related to the volume of subcortical brain structures in a sample of healthy humans. Differences in D2/3 R availability measured with an antagonist radiotracer ([11 C]-raclopride) versus an agonist radiotracer ([11 C]-(+)-PHNO) were examined. METHODS Data from 62 subjects scanned with [11 C]-raclopride (mean age = 38.98 ± 14.45; 23 female) and 68 subjects scanned with [11 C]-(+)-PHNO (mean age = 38.54 ± 14.59; 25 female) were used. Subcortical volumes were extracted from T1-weighted images using the Multiple Automatically Generated Templates (MAGeT-Brain) algorithm. Partial correlations were used controlling for age, gender, and total brain volume. RESULTS For [11 C]-(+)-PHNO, ventral caudate volumes were positively correlated with BPND in the dorsal caudate and globus pallidus (GP). Ventral striatum (VS) volumes were positively correlated with BPND in the VS. With [11 C]-raclopride, BPND in the VS was negatively correlated with subiculum volume of the hippocampus. Moreover, BPND in the GP was negatively correlated with the volume of the lateral posterior nucleus of the thalamus. CONCLUSION Findings are purely exploratory and presented corrected and uncorrected for multiple comparisons. We hope they will help inform the interpretation of future PET studies where concurrent changes in D2/3 R and brain morphology are observed. Hum Brain Mapp 38:5519-5534, 2017. © 2017 Wiley Periodicals, Inc.
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Affiliation(s)
- Fernando Caravaggio
- Research Imaging Centre, Centre for Addiction and Mental Health, 250 College Street, Toronto, Ontario, M5T 1R8, Canada.,Department of Psychiatry, University of Toronto, 250 College Street, Toronto, Ontario, M5T 1R8, Canada
| | - Jun Ku Chung
- Research Imaging Centre, Centre for Addiction and Mental Health, 250 College Street, Toronto, Ontario, M5T 1R8, Canada
| | - Eric Plitman
- Research Imaging Centre, Centre for Addiction and Mental Health, 250 College Street, Toronto, Ontario, M5T 1R8, Canada
| | - Isabelle Boileau
- Research Imaging Centre, Centre for Addiction and Mental Health, 250 College Street, Toronto, Ontario, M5T 1R8, Canada.,Department of Psychiatry, University of Toronto, 250 College Street, Toronto, Ontario, M5T 1R8, Canada
| | - Philip Gerretsen
- Research Imaging Centre, Centre for Addiction and Mental Health, 250 College Street, Toronto, Ontario, M5T 1R8, Canada.,Department of Psychiatry, University of Toronto, 250 College Street, Toronto, Ontario, M5T 1R8, Canada
| | - Julia Kim
- Research Imaging Centre, Centre for Addiction and Mental Health, 250 College Street, Toronto, Ontario, M5T 1R8, Canada
| | - Yusuke Iwata
- Research Imaging Centre, Centre for Addiction and Mental Health, 250 College Street, Toronto, Ontario, M5T 1R8, Canada.,Department of Psychiatry, University of Toronto, 250 College Street, Toronto, Ontario, M5T 1R8, Canada
| | - Raihaan Patel
- Department of Biological & Biomedical Engineering, McGill University, Montreal, Quebec, H4H 1R3, Canada.,Cerebral Imaging Centre, Douglas Mental Health Institute, McGill University, Montreal, Quebec, H4H 1R3, Canada
| | - M Mallar Chakravarty
- Department of Biological & Biomedical Engineering, McGill University, Montreal, Quebec, H4H 1R3, Canada.,Cerebral Imaging Centre, Douglas Mental Health Institute, McGill University, Montreal, Quebec, H4H 1R3, Canada.,Department of Psychiatry, McGill University, Montreal, Quebec, H4H 1R3, Canada
| | - Gary Remington
- Research Imaging Centre, Centre for Addiction and Mental Health, 250 College Street, Toronto, Ontario, M5T 1R8, Canada.,Department of Psychiatry, University of Toronto, 250 College Street, Toronto, Ontario, M5T 1R8, Canada
| | - Ariel Graff-Guerrero
- Research Imaging Centre, Centre for Addiction and Mental Health, 250 College Street, Toronto, Ontario, M5T 1R8, Canada.,Department of Psychiatry, University of Toronto, 250 College Street, Toronto, Ontario, M5T 1R8, Canada
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21
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Moritz AE, Free RB, Sibley DR. Advances and challenges in the search for D 2 and D 3 dopamine receptor-selective compounds. Cell Signal 2017; 41:75-81. [PMID: 28716664 DOI: 10.1016/j.cellsig.2017.07.003] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2017] [Revised: 07/07/2017] [Accepted: 07/10/2017] [Indexed: 12/30/2022]
Abstract
Compounds that target D2-like dopamine receptors (DRs) are currently used as therapeutics for several neuropsychiatric disorders including schizophrenia (antagonists) and Parkinson's disease (agonists). However, as the D2R and D3R subtypes are highly homologous, creating compounds with sufficient subtype-selectivity as well as drug-like properties for therapeutic use has proved challenging. This review summarizes the progress that has been made in developing D2R- or D3R-selective antagonists and agonists, and also describes the experimental conditions that need to be considered when determining the selectivity of a given compound, as apparent selectivity can vary widely depending on assay conditions. Future advances in this field may take advantage of currently available structural data to target alternative secondary binding sites through creating bivalent or bitopic chemical structures. Alternatively, the use of high-throughput screening techniques to identify novel scaffolds that might bind to the D2R or D3R in areas other than the highly conserved orthosteric site, such as allosteric sites, followed by iterative medicinal chemistry will likely lead to exceptionally selective compounds in the future. More selective compounds will provide a better understanding of the normal and pathological functioning of each receptor subtype, as well as offer the potential for improved therapeutics.
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Affiliation(s)
- Amy E Moritz
- Molecular Neuropharmacology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, 35 Convent Drive, MSC-3723, Bethesda, MD 20892-3723, United States
| | - R Benjamin Free
- Molecular Neuropharmacology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, 35 Convent Drive, MSC-3723, Bethesda, MD 20892-3723, United States
| | - David R Sibley
- Molecular Neuropharmacology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, 35 Convent Drive, MSC-3723, Bethesda, MD 20892-3723, United States.
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22
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Yang KC, Stepanov V, Martinsson S, Ettrup A, Takano A, Knudsen GM, Halldin C, Farde L, Finnema SJ. Fenfluramine Reduces [11C]Cimbi-36 Binding to the 5-HT2A Receptor in the Nonhuman Primate Brain. Int J Neuropsychopharmacol 2017; 20:683-691. [PMID: 28911007 PMCID: PMC5581490 DOI: 10.1093/ijnp/pyx051] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/25/2017] [Accepted: 06/18/2017] [Indexed: 12/24/2022] Open
Abstract
BACKGROUND [11C]Cimbi-36 is a serotonin 2A receptor agonist positron emission tomography radioligand that has recently been examined in humans. The binding of agonist radioligand is expected to be more sensitive to endogenous neurotransmitter concentrations than antagonist radioligands. In the current study, we compared the effect of serotonin releaser fenfluramine on the binding of [11C]Cimbi-36, [11C]MDL 100907 (a serotonin 2A receptor antagonist radioligand), and [11C]AZ10419369 (a serotonin 1B receptor partial agonist radioligand with established serotonin sensitivity) in the monkey brain. METHODS Eighteen positron emission tomography measurements, 6 for each radioligand, were performed in 3 rhesus monkeys before or after administration of 5.0 mg/kg fenfluramine. Binding potential values were determined with the simplified reference tissue model using cerebellum as the reference region. RESULTS Fenfluramine significantly decreased [11C]Cimbi-36 (26-62%) and [11C]AZ10419369 (35-58%) binding potential values in most regions (P < 0.05). Fenfluramine-induced decreases in [11C]MDL 100907 binding potential were 8% to 30% and statistically significant in 3 regions. Decreases in [11C]Cimbi-36 binding potential were larger than for [11C]AZ10419369 in neocortical and limbic regions (~35%) but smaller in striatum and thalamus (~40%). Decreases in [11C]Cimbi-36 binding potential were 0.9 to 2.8 times larger than for [11C]MDL 100907, and the fraction of serotonin 2A receptor in the high-affinity state was estimated as 54% in the neocortex. CONCLUSIONS The serotonin sensitivity of serotonin 2A receptor agonist radioligand [11C]Cimbi-36 was higher than for antagonist radioligand [11C]MDL 100907. The serotonin sensitivity of [11C]Cimbi-36 was similar to [11C]AZ10419369, which is one of the most sensitive radioligands. [11C]Cimbi-36 is a promising radioligand to examine serotonin release in the primate brain.
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Affiliation(s)
- Kai-Chun Yang
- Karolinska Institutet and Stockholm County Council, Department of Clinical Neuroscience, Center for Psychiatric Research, Stockholm, Sweden (Drs Yang and Stepanov, Mr Martinsson, and Drs Takano, Halldin, Farde, and Finnema); Rigshospitalet, Center for Integrated Molecular Brain Imaging, Copenhagen, Denmark and University of Copenhagen, Faculty of Health and Medicine Sciences, Copenhagen, Denmark (Drs Ettrup and Knudsen); AstraZeneca, PET Science Center at Karolinska Institutet, Personalized Health Care and Biomarkers, Stockholm, Sweden (Dr Farde).,Correspondence: Kai-Chun Yang, MD, Karolinska Institutet and Stockholm County Council, Department of Clinical Neuroscience, Center for Psychiatric Research, Karolinska University Hospital, Building R5:02, SE-171 76 Stockholm, Sweden ()
| | - Vladimir Stepanov
- Karolinska Institutet and Stockholm County Council, Department of Clinical Neuroscience, Center for Psychiatric Research, Stockholm, Sweden (Drs Yang and Stepanov, Mr Martinsson, and Drs Takano, Halldin, Farde, and Finnema); Rigshospitalet, Center for Integrated Molecular Brain Imaging, Copenhagen, Denmark and University of Copenhagen, Faculty of Health and Medicine Sciences, Copenhagen, Denmark (Drs Ettrup and Knudsen); AstraZeneca, PET Science Center at Karolinska Institutet, Personalized Health Care and Biomarkers, Stockholm, Sweden (Dr Farde)
| | - Stefan Martinsson
- Karolinska Institutet and Stockholm County Council, Department of Clinical Neuroscience, Center for Psychiatric Research, Stockholm, Sweden (Drs Yang and Stepanov, Mr Martinsson, and Drs Takano, Halldin, Farde, and Finnema); Rigshospitalet, Center for Integrated Molecular Brain Imaging, Copenhagen, Denmark and University of Copenhagen, Faculty of Health and Medicine Sciences, Copenhagen, Denmark (Drs Ettrup and Knudsen); AstraZeneca, PET Science Center at Karolinska Institutet, Personalized Health Care and Biomarkers, Stockholm, Sweden (Dr Farde)
| | - Anders Ettrup
- Karolinska Institutet and Stockholm County Council, Department of Clinical Neuroscience, Center for Psychiatric Research, Stockholm, Sweden (Drs Yang and Stepanov, Mr Martinsson, and Drs Takano, Halldin, Farde, and Finnema); Rigshospitalet, Center for Integrated Molecular Brain Imaging, Copenhagen, Denmark and University of Copenhagen, Faculty of Health and Medicine Sciences, Copenhagen, Denmark (Drs Ettrup and Knudsen); AstraZeneca, PET Science Center at Karolinska Institutet, Personalized Health Care and Biomarkers, Stockholm, Sweden (Dr Farde)
| | - Akihiro Takano
- Karolinska Institutet and Stockholm County Council, Department of Clinical Neuroscience, Center for Psychiatric Research, Stockholm, Sweden (Drs Yang and Stepanov, Mr Martinsson, and Drs Takano, Halldin, Farde, and Finnema); Rigshospitalet, Center for Integrated Molecular Brain Imaging, Copenhagen, Denmark and University of Copenhagen, Faculty of Health and Medicine Sciences, Copenhagen, Denmark (Drs Ettrup and Knudsen); AstraZeneca, PET Science Center at Karolinska Institutet, Personalized Health Care and Biomarkers, Stockholm, Sweden (Dr Farde)
| | - Gitte M Knudsen
- Karolinska Institutet and Stockholm County Council, Department of Clinical Neuroscience, Center for Psychiatric Research, Stockholm, Sweden (Drs Yang and Stepanov, Mr Martinsson, and Drs Takano, Halldin, Farde, and Finnema); Rigshospitalet, Center for Integrated Molecular Brain Imaging, Copenhagen, Denmark and University of Copenhagen, Faculty of Health and Medicine Sciences, Copenhagen, Denmark (Drs Ettrup and Knudsen); AstraZeneca, PET Science Center at Karolinska Institutet, Personalized Health Care and Biomarkers, Stockholm, Sweden (Dr Farde)
| | - Christer Halldin
- Karolinska Institutet and Stockholm County Council, Department of Clinical Neuroscience, Center for Psychiatric Research, Stockholm, Sweden (Drs Yang and Stepanov, Mr Martinsson, and Drs Takano, Halldin, Farde, and Finnema); Rigshospitalet, Center for Integrated Molecular Brain Imaging, Copenhagen, Denmark and University of Copenhagen, Faculty of Health and Medicine Sciences, Copenhagen, Denmark (Drs Ettrup and Knudsen); AstraZeneca, PET Science Center at Karolinska Institutet, Personalized Health Care and Biomarkers, Stockholm, Sweden (Dr Farde)
| | - Lars Farde
- Karolinska Institutet and Stockholm County Council, Department of Clinical Neuroscience, Center for Psychiatric Research, Stockholm, Sweden (Drs Yang and Stepanov, Mr Martinsson, and Drs Takano, Halldin, Farde, and Finnema); Rigshospitalet, Center for Integrated Molecular Brain Imaging, Copenhagen, Denmark and University of Copenhagen, Faculty of Health and Medicine Sciences, Copenhagen, Denmark (Drs Ettrup and Knudsen); AstraZeneca, PET Science Center at Karolinska Institutet, Personalized Health Care and Biomarkers, Stockholm, Sweden (Dr Farde)
| | - Sjoerd J Finnema
- Karolinska Institutet and Stockholm County Council, Department of Clinical Neuroscience, Center for Psychiatric Research, Stockholm, Sweden (Drs Yang and Stepanov, Mr Martinsson, and Drs Takano, Halldin, Farde, and Finnema); Rigshospitalet, Center for Integrated Molecular Brain Imaging, Copenhagen, Denmark and University of Copenhagen, Faculty of Health and Medicine Sciences, Copenhagen, Denmark (Drs Ettrup and Knudsen); AstraZeneca, PET Science Center at Karolinska Institutet, Personalized Health Care and Biomarkers, Stockholm, Sweden (Dr Farde)
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23
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Jørgensen LM, Weikop P, Villadsen J, Visnapuu T, Ettrup A, Hansen HD, Baandrup AO, Andersen FL, Bjarkam CR, Thomsen C, Jespersen B, Knudsen GM. Cerebral 5-HT release correlates with [ 11C]Cimbi36 PET measures of 5-HT2A receptor occupancy in the pig brain. J Cereb Blood Flow Metab 2017; 37:425-434. [PMID: 26825776 PMCID: PMC5381441 DOI: 10.1177/0271678x16629483] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Positron emission tomography (PET) can, when used with appropriate radioligands, non-invasively generate temporal and spatial information about acute changes in brain neurotransmitter systems. We for the first time evaluate the novel 5-HT2A receptor agonist PET radioligand, [11C]Cimbi-36, for its sensitivity to detect changes in endogenous cerebral 5-HT levels, as induced by different pharmacological challenges. To enable a direct translation of PET imaging data to changes in brain 5-HT levels, we calibrated the [11C]Cimbi-36 PET signal in the pig brain by simultaneous measurements of extracellular 5-HT levels with microdialysis and [11C]Cimbi-36 PET after various acute interventions (saline, citalopram, citalopram + pindolol, fenfluramine). In a subset of pigs, para-chlorophenylalanine pretreatment was given to deplete cerebral 5-HT. The interventions increased the cerebral extracellular 5-HT levels to 2-11 times baseline, with fenfluramine being the most potent pharmacological enhancer of 5-HT release, and induced a varying degree of decline in [11C]Cimbi-36 binding in the brain, consistent with the occupancy competition model. The observed correlation between changes in the extracellular 5-HT level in the pig brain and the 5-HT2A receptor occupancy indicates that [11C]Cimbi-36 binding is sensitive to changes in endogenous 5-HT levels, although only detectable with PET when the 5-HT release is sufficiently high.
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Affiliation(s)
- Louise M Jørgensen
- 1 Neurobiology Research Unit, Rigshospitalet, Copenhagen, Denmark.,2 Faculty of Health and Medical Sciences, University of Copenhagen, Denmark
| | - Pia Weikop
- 3 The Laboratory of Neuropsychiatry, Department of Neuroscience and Pharmacology, University of Copenhagen, Denmark.,4 Psychiatric Centre Copenhagen, University of Copenhagen, Denmark
| | - Jonas Villadsen
- 1 Neurobiology Research Unit, Rigshospitalet, Copenhagen, Denmark
| | - Tanel Visnapuu
- 3 The Laboratory of Neuropsychiatry, Department of Neuroscience and Pharmacology, University of Copenhagen, Denmark.,5 Center for Excellence in Translational Medicine, University of Tartu, Estonia
| | - Anders Ettrup
- 1 Neurobiology Research Unit, Rigshospitalet, Copenhagen, Denmark
| | - Hanne D Hansen
- 1 Neurobiology Research Unit, Rigshospitalet, Copenhagen, Denmark
| | - Anders O Baandrup
- 6 Research Center for Advanced Imaging, Hospital of Køge and Roskilde, Roskilde, Denmark
| | | | | | - Carsten Thomsen
- 2 Faculty of Health and Medical Sciences, University of Copenhagen, Denmark.,9 Department of Radiology, Rigshospitalet, Copenhagen, Denmark
| | - Bo Jespersen
- 10 Department of Neurosurgery, Rigshospitalet, Copenhagen, Denmark
| | - Gitte M Knudsen
- 1 Neurobiology Research Unit, Rigshospitalet, Copenhagen, Denmark.,2 Faculty of Health and Medical Sciences, University of Copenhagen, Denmark
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24
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Caravaggio F, Kegeles LS, Wilson AA, Remington G, Borlido C, Mamo DC, Graff-Guerrero A. Estimating the effect of endogenous dopamine on baseline [(11) C]-(+)-PHNO binding in the human brain. Synapse 2016; 70:453-60. [PMID: 27341789 DOI: 10.1002/syn.21920] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2016] [Revised: 06/03/2016] [Accepted: 06/20/2016] [Indexed: 11/10/2022]
Abstract
Endogenous dopamine (DA) levels at dopamine D2/3 receptors (D2/3 R) have been quantified in the living human brain using the agonist radiotracer [(11) C]-(+)-PHNO. As an agonist radiotracer, [(11) C]-(+)-PHNO is more sensitive to endogenous DA levels than antagonist radiotracers. We sought to determine the proportion of the variance in baseline [(11) C]-(+)-PHNO binding to D2/3 Rs which can be accounted for by variation in endogenous DA levels. This was done by computing the Pearson's coefficient for the correlation between baseline binding potential (BPND ) and the change in BPND after acute DA depletion, using previously published data. All correlations were inverse, and the proportion of the variance in baseline [(11) C]-(+)-PHNO BPND that can be accounted for by variation in endogenous DA levels across the striatal subregions ranged from 42-59%. These results indicate that lower baseline values of [(11) C]-(+)-PHNO BPND reflect greater stimulation by endogenous DA. To further validate this interpretation, we sought to examine whether these data could be used to estimate the dissociation constant (Kd) of DA at D2/3 R. In line with previous in vitro work, we estimated the in vivo Kd of DA to be around 20 nM. In summary, the agonist radiotracer [(11) C]-(+)-PHNO can detect the impact of endogenous DA levels at D2/3 R in the living human brain from a single baseline scan, and may be more sensitive to this impact than other commonly employed radiotracers.
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Affiliation(s)
- Fernando Caravaggio
- Centre for Addiction and Mental Health, Research Imaging Centre, Toronto, Ontario, M5T 1R8, Canada.,Institute of Medical Science, University of Toronto, Toronto, Ontario, M5S 1A8, Canada
| | - Lawrence S Kegeles
- Department of Psychiatry and Radiology, Columbia University College of Physicians and Surgeons, New York State Psychiatric Institute, New York
| | - Alan A Wilson
- Centre for Addiction and Mental Health, Research Imaging Centre, Toronto, Ontario, M5T 1R8, Canada.,Institute of Medical Science, University of Toronto, Toronto, Ontario, M5S 1A8, Canada.,Department of Psychiatry, University of Toronto, Ontario, M5T 1R8, Canada
| | - Gary Remington
- Centre for Addiction and Mental Health, Research Imaging Centre, Toronto, Ontario, M5T 1R8, Canada.,Institute of Medical Science, University of Toronto, Toronto, Ontario, M5S 1A8, Canada.,Department of Psychiatry, University of Toronto, Ontario, M5T 1R8, Canada
| | - Carol Borlido
- Centre for Addiction and Mental Health, Research Imaging Centre, Toronto, Ontario, M5T 1R8, Canada
| | - David C Mamo
- Department of Psychiatry, Faculties of Medicine and Health Science, University of Malta, Msida, Malta
| | - Ariel Graff-Guerrero
- Centre for Addiction and Mental Health, Research Imaging Centre, Toronto, Ontario, M5T 1R8, Canada. .,Institute of Medical Science, University of Toronto, Toronto, Ontario, M5S 1A8, Canada. .,Department of Psychiatry, University of Toronto, Ontario, M5T 1R8, Canada.
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25
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Shalgunov V, van Wieringen JP, Janssen HM, Fransen PM, Dierckx RAJO, Michel MC, Booij J, Elsinga PH. Synthesis and evaluation in rats of homologous series of [(18)F]-labeled dopamine D 2/3 receptor agonists based on the 2-aminomethylchroman scaffold as potential PET tracers. EJNMMI Res 2015. [PMID: 26205538 PMCID: PMC4512978 DOI: 10.1186/s13550-015-0119-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
Background Agonist positron emission tomography (PET) tracers for dopamine D2/3 receptors (D2/3Rs) offer greater sensitivity to changes in endogenous dopamine levels than D2/3R antagonist tracers. D2/3R agonist tracers currently available for clinical research are labeled with the short-lived isotope carbon-11, which limits their use. We aimed to develop high-affinity D2R agonists amenable for labeling with the longer-living fluorine-18. Here, we report the evaluation as potential PET tracers of two homologous series of [18F]fluorinated tracers based on the 2-aminomethylchroman-7-ol (AMC) scaffold: (R)-2-((4-(2-fluoroalkoxy)benzylamino)methyl)chroman-7-ols (AMC13 homologues) and (R)-2-((2-(4-(4-(fluoroalkoxy)phenyl)piperazin-1-yl)ethylamino)methyl)chroman-7-ols (AMC15 homologues). We varied the length of the 18F-fluoroalkyl chain in these structures to balance brain penetration and non-specific binding of the radioligands by adjusting their lipophilicity. Methods The tracers were evaluated in brain slices of Sprague-Dawley rats by in vitro autoradiography and in living rats by microPET imaging and ex vivo autoradiography. PET data were analyzed with one- and two-tissue compartmental models (1TCM/2TCM), simplified reference tissue model (SRTM), and Logan graphical analysis. Specificity of binding was tested by blocking D2/3R with raclopride. Results Homologues with a shorter fluoroalkyl chain consistently showed greater D2/3R-specific-to-total binding ratios in the striatum than those with longer chains. The fluoroethoxy homologue of AMC13 ([18F]FEt-AMC13) demonstrated the highest degree of D2/3R-specific binding among the evaluated tracers: mean striatum-to-cerebellum uptake ratio reached 4.4 in vitro and 2.1/2.8 in vivo/ex vivo (PET/autoradiography). Striatal binding potential (BPND) relative to cerebellum was 0.51–0.63 depending on the estimation method. Radiometabolites of [18F]FEt-AMC13 did not enter the brain. In vitro, application of 10 μmol/L raclopride reduced D2/3R-specific binding of [18F]FEt-AMC13 in the striatum by 81 %. In vivo, pre-treatment with 1 mg/kg (2.9 μmol/kg) raclopride led to 17–39 % decrease in D2/3R-specific binding in the striatum. Conclusions Varying the length of the [18F]fluoroalkyl chain helped improve the characteristics of the original candidate tracers. Further modifications of the current lead [18F]FEt-AMC13 can provide an agonist radiopharmaceutical suitable for D2/3R imaging by PET. Electronic supplementary material The online version of this article (doi:10.1186/s13550-015-0119-x) contains supplementary material, which is available to authorized users.
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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,
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Imaging in vivo glutamate fluctuations with [(11)C]ABP688: a GLT-1 challenge with ceftriaxone. J Cereb Blood Flow Metab 2015; 35:1169-74. [PMID: 25806702 PMCID: PMC4640271 DOI: 10.1038/jcbfm.2015.35] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/20/2014] [Revised: 12/16/2014] [Accepted: 12/30/2014] [Indexed: 01/06/2023]
Abstract
Molecular imaging offers unprecedented opportunities for investigating dynamic changes underlying neuropsychiatric conditions. Here, we evaluated whether [(11)C]ABP688, a positron emission tomography (PET) ligand that binds to the allosteric site of the metabotropic glutamate receptor type 5 (mGluR5), is sensitive to glutamate fluctuations after a pharmacological challenge. For this, we used ceftriaxone (CEF) administration in rats, an activator of the GLT-1 transporter (EAAT2), which is known to decrease extracellular levels of glutamate. MicroPET [(11)C]ABP688 dynamic acquisitions were conducted in rats after a venous injection of either saline (baseline) or CEF 200 mg/kg (challenge). Binding potentials (BP(ND)) were obtained using the simplified reference tissue method. Between-condition statistical parametric maps indicating brain regions showing the highest CEF effects guided placement of microdialysis probes for subsequent assessment of extracellular levels of glutamate. The CEF administration increased [(11)C]ABP688 BP(ND) in the thalamic ventral anterior (VA) nucleus bilaterally. Subsequent microdialysis assessment revealed declines in extracellular glutamate concentrations in the VA. The present results support the concept that availability of mGluR5 allosteric binding sites is sensitive to extracellular concentrations of glutamate. This interesting property of mGluR5 allosteric binding sites has potential applications for assessing the role of glutamate in the pathogenesis of neuropsychiatric conditions.
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27
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Ex Vivo Characterization of a Novel Iodine-123-Labelled Aminomethylchroman as a Potential Agonist Ligand for SPECT Imaging of Dopamine D2/3 Receptors. INTERNATIONAL JOURNAL OF MOLECULAR IMAGING 2015; 2014:507012. [PMID: 25610643 PMCID: PMC4291083 DOI: 10.1155/2014/507012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/29/2014] [Revised: 11/18/2014] [Accepted: 11/27/2014] [Indexed: 11/17/2022]
Abstract
For imaging of dopamine D2/3 receptors, agonist tracers are favoured over antagonists because they are more sensitive to detection of dopamine release and because they may selectively label the high-affinity receptor state. We have developed novel D2/3 receptor selective agonists that can be radiolabelled with [(123)I], which label is advantageous over most other labels, such as carbon-11, as it has a longer half-life. Particularly, we considered (R) N-[7-hydroxychroman-2-yl]-methyl 4-iodobenzyl amine (compound 1) as an attractive candidate for development as it shows high binding affinity to D2/3 receptors in vitro, and here we report on the characterization of this first [(123)I]-labelled D2/3 receptor agonist radiopharmaceutical intended for SPECT imaging. The appropriate tin precursor for [(123)I]-1 was developed and was successfully radiolabelled with iodine-123 giving a moderate yield (30-35%) and a good purity (>95%) for [(123)I]-1. In biodistribution experiments in Wistar rats intravenous injection of [(123)I]-1 resulted in a fast brain uptake, where the observed binding in the D2/3 receptor-rich striatum was slightly higher than that in the cerebellum 30 min to 4 h p.i. Storage phosphor imaging experiments, however, did not show specific D2/3 receptor binding. In conclusion, despite promising in vitro data for 1, neither specific ex vivo binding nor high signal-to-noise ratios were found in rodents for [(123)I]-1.
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In vivo characterization of metabotropic glutamate receptor type 5 abnormalities in behavioral variant FTD. Brain Struct Funct 2015; 221:1387-402. [PMID: 25596865 DOI: 10.1007/s00429-014-0978-3] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2014] [Accepted: 12/22/2014] [Indexed: 10/24/2022]
Abstract
Although the pathogenesis underlying behavioral variant frontotemporal dementia (bvFTD) has yet to be fully understood, glutamatergic abnormalities have been hypothesized to play an important role. The aim of the present study was to determine the availability of the metabotropic glutamate receptor type 5 (mGluR5) using a novel positron emission tomography (PET) radiopharmaceutical with high selectivity for mGluR5 ([(11)C]ABP688) in a sample of bvFTD patients. In addition, we sought to determine the overlap between availability of mGluR5 and neurodegeneration, as measured using [(18)F]FDG-PET and voxel-based morphometry (VBM). Availability of mGluR5 and glucose metabolism ([(18)F]FDG) were measured in bvFTD (n = 5) and cognitively normal (CN) subjects (n = 10). [(11)C]ABP688 binding potential maps (BPND) were calculated using the cerebellum as a reference region, with [(18)F]FDG standardized uptake ratio maps (SUVR) normalized to the pons. Grey matter (GM) concentrations were determined using VBM. Voxel-based group differences were obtained using RMINC. BvFTD patients showed widespread decrements in [(11)C]ABP688 BPND throughout frontal, temporal and subcortical areas. These areas were likewise characterized by significant hypometabolism and GM loss, with overlap between reduced [(11)C]ABP688 BPND and hypometabolism superior to that for GM atrophy. Several regions were characterized only by decreased binding of [(11)C]ABP688. The present findings represent the first in vivo report of decreased availability of mGluR5 in bvFTD. This study suggests that glutamate excitotoxicity may play a role in the pathogenesis of bvFTD and that [(11)C]ABP688 may prove a suitable marker of glutamatergic neurotransmission in vivo.
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Finnema SJ, Scheinin M, Shahid M, Lehto J, Borroni E, Bang-Andersen B, Sallinen J, Wong E, Farde L, Halldin C, Grimwood S. Application of cross-species PET imaging to assess neurotransmitter release in brain. Psychopharmacology (Berl) 2015; 232:4129-57. [PMID: 25921033 PMCID: PMC4600473 DOI: 10.1007/s00213-015-3938-6] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/21/2015] [Accepted: 04/09/2015] [Indexed: 01/03/2023]
Abstract
RATIONALE This review attempts to summarize the current status in relation to the use of positron emission tomography (PET) imaging in the assessment of synaptic concentrations of endogenous mediators in the living brain. OBJECTIVES Although PET radioligands are now available for more than 40 CNS targets, at the initiation of the Innovative Medicines Initiative (IMI) "Novel Methods leading to New Medications in Depression and Schizophrenia" (NEWMEDS) in 2009, PET radioligands sensitive to an endogenous neurotransmitter were only validated for dopamine. NEWMEDS work-package 5, "Cross-species and neurochemical imaging (PET) methods for drug discovery", commenced with a focus on developing methods enabling assessment of changes in extracellular concentrations of serotonin and noradrenaline in the brain. RESULTS Sharing the workload across institutions, we utilized in vitro techniques with cells and tissues, in vivo receptor binding and microdialysis techniques in rodents, and in vivo PET imaging in non-human primates and humans. Here, we discuss these efforts and review other recently published reports on the use of radioligands to assess changes in endogenous levels of dopamine, serotonin, noradrenaline, γ-aminobutyric acid, glutamate, acetylcholine, and opioid peptides. The emphasis is on assessment of the availability of appropriate translational tools (PET radioligands, pharmacological challenge agents) and on studies in non-human primates and human subjects, as well as current challenges and future directions. CONCLUSIONS PET imaging directed at investigating changes in endogenous neurochemicals, including the work done in NEWMEDS, have highlighted an opportunity to further extend the capability and application of this technology in drug development.
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Affiliation(s)
- Sjoerd J. Finnema
- />Department of Clinical Neuroscience, Center for Psychiatric Research, Karolinska Institutet, Stockholm, Sweden
| | - Mika Scheinin
- />Department of Pharmacology, Drug Development and Therapeutics, University of Turku, Turku, Finland , />Unit of Clinical Pharmacology, Turku University Hospital, Turku, Finland
| | - Mohammed Shahid
- />Research and Development, Orion Corporation, Orion Pharma, Turku, Finland
| | - Jussi Lehto
- />Department of Pharmacology, Drug Development and Therapeutics, University of Turku, Turku, Finland
| | - Edilio Borroni
- />Neuroscience Department, Hoffman-La Roche, Basel, Switzerland
| | | | - Jukka Sallinen
- />Research and Development, Orion Corporation, Orion Pharma, Turku, Finland
| | - Erik Wong
- />Neuroscience Innovative Medicine Unit, AstraZeneca, Wilmington, DE USA
| | - Lars Farde
- />Department of Clinical Neuroscience, Center for Psychiatric Research, Karolinska Institutet, Stockholm, Sweden , />Translational Science Center at Karolinska Institutet, AstraZeneca, Stockholm, Sweden
| | - Christer Halldin
- />Department of Clinical Neuroscience, Center for Psychiatric Research, Karolinska Institutet, Stockholm, Sweden
| | - Sarah Grimwood
- Neuroscience Research Unit, Pfizer Inc, Cambridge, MA, USA. .,, 610 Main Street, Cambridge, MA, 02139, USA.
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van Wieringen JP, Michel MC, Janssen HM, Janssen AG, Elsinga PH, Booij J. Agonist signalling properties of radiotracers used for imaging of dopamine D2/3 receptors. EJNMMI Res 2014; 4:53. [PMID: 25977878 PMCID: PMC4422956 DOI: 10.1186/s13550-014-0053-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2014] [Accepted: 09/23/2014] [Indexed: 01/11/2023] Open
Abstract
Background Dopamine D2/3 receptor (D2/3R) agonist radiopharmaceuticals are considered superior to antagonists to detect dopamine release, e.g. induced by amphetamines. Agonists bind preferentially to the high-affinity state of the dopamine D2R, which has been proposed as the reason why agonists are more sensitive to detect dopamine release than antagonist radiopharmaceuticals, but this theory has been challenged. Interestingly, not all agonists similarly activate the classic cyclic adenosine mono phosphate (cAMP) and the ?-arrestin-2 pathway, some stimulate preferentially one of these pathways; a phenomenon called biased agonism. Because these pathways can be affected separately by pathologies or drugs (including dopamine releasers), it is important to know how agonist radiotracers act on these pathways. Therefore, we characterized the intracellular signalling of the well-known D2/3R agonist radiopharmaceuticals NPA and PHNO and of several novel D2/3R agonists. Methods cAMP accumulation and ?-arrestin-2 recruitment were measured on cells expressing human D2R. Results All tested agonists showed (almost) full agonism in both pathways. Conclusions The tested D2/3R agonist radiopharmaceuticals did not exhibit biased agonism in vitro. Consequently, it is likely that drugs (including psychostimulants like amphetamines) and/or pathologies that influence the cAMP and/or the ?-arrestin-2 pathway may influence the binding of these radiopharmaceuticals.
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Affiliation(s)
- Jan-Peter van Wieringen
- Department of Nuclear Medicine, Academic Medical Center, University of Amsterdam, Meibergdreef 9, Amsterdam, 1105, AZ, The Netherlands
| | - Martin C Michel
- Department of Pharmacology, Johannes Gutenberg University, Mainz, Germany
| | | | | | - Philip H Elsinga
- Department of Nuclear Medicine and Molecular Imaging, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Jan Booij
- Department of Nuclear Medicine, Academic Medical Center, University of Amsterdam, Meibergdreef 9, Amsterdam, 1105, AZ, The Netherlands
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Khanapur S, Paul S, Shah A, Vatakuti S, Koole MJB, Zijlma R, Dierckx RAJO, Luurtsema G, Garg P, van Waarde A, Elsinga PH. Development of [18F]-labeled pyrazolo[4,3-e]-1,2,4- triazolo[1,5-c]pyrimidine (SCH442416) analogs for the imaging of cerebral adenosine A2A receptors with positron emission tomography. J Med Chem 2014; 57:6765-80. [PMID: 25061687 DOI: 10.1021/jm500700y] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Cerebral adenosine A2A receptors (A2ARs) are attractive therapeutic targets for the treatment of neurodegenerative and psychiatric disorders. We developed high affinity and selective compound 8 (SCH442416) analogs as in vivo probes for A2ARs using PET. We observed the A2AR-mediated accumulation of [18F]fluoropropyl ([18F]-10b) and [18F]fluoroethyl ([18F]-10a) derivatives of 8 in the brain. The striatum was clearly visualized in PET and in vitro autoradiography images of control animals and was no longer visible after pretreatment with the A2AR subtype-selective antagonist KW6002. In vitro and in vivo metabolite analyses indicated the presence of hydrophilic (radio)metabolite(s), which are not expected to cross the blood-brain-barrier. [18F]-10b and [18F]-10a showed comparable striatum-to- cerebellum ratios (4.6 at 25 and 37 min post injection, respectively) and reversible binding in rat brains. We concluded that these compounds performed equally well, but their kinetics were slightly different. These molecules are potential tools for mapping cerebral A2ARs with PET.
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Affiliation(s)
- Shivashankar Khanapur
- Department of Nuclear Medicine and Molecular Imaging, University Medical Center Groningen, University of Groningen , Groningen, The Netherlands
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Schoultz BW, Hjørnevik T, Reed BJ, Marton J, Coello CS, Willoch F, Henriksen G. Synthesis and evaluation of three structurally related ¹⁸F-labeled orvinols of different intrinsic activities: 6-O-[¹⁸F]fluoroethyl-diprenorphine ([¹⁸F]FDPN), 6-O-[¹⁸F]fluoroethyl-buprenorphine ([¹⁸F]FBPN), and 6-O-[¹⁸F]fluoroethyl-phenethyl-orvinol ([¹⁸F]FPEO). J Med Chem 2014; 57:5464-9. [PMID: 24933507 DOI: 10.1021/jm500503k] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
We report the synthesis and biological evaluation of a triplet of 6-O-(18)F-fluoroethylated derivatives of structurally related orvinols that span across the full range of intrinsic activities, the antagonist diprenorphine, the partial agonist buprenorphine, and the full agonist phenethyl-orvinol. [(18)F]fluoroethyl-diprenorphine, [(18)F]fluoroethyl-buprenorphine, and [(18)F]fluoroethyl-phenethyl-orvinol were prepared in high yields and quality from their 6-O-desmethyl-precursors. The results indicate suitable properties of the three 6-O-(18)F-fluoroethylated derivatives as functional analogues to the native carbon-11 labeled versions with similar pharmacological properties.
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Affiliation(s)
- Bent W Schoultz
- Department of Chemistry, University of Oslo , P.O. Box 1033, Blindern, N-0315 Oslo, Norway
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In vivo imaging of cerebral dopamine D3 receptors in alcoholism. Neuropsychopharmacology 2014; 39:1703-12. [PMID: 24469594 PMCID: PMC4023144 DOI: 10.1038/npp.2014.18] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/22/2013] [Revised: 11/13/2013] [Accepted: 12/11/2013] [Indexed: 01/12/2023]
Abstract
Animal studies support the role of the dopamine D3 receptor (DRD3) in alcohol reinforcement or liking. Sustained voluntary alcohol drinking in rats has been associated with an upregulation of striatal DRD3 gene expression and selective blockade of DRD3 reduces ethanol preference, consumption, and cue-induced reinstatement. In vivo measurement of DRD3 in the living human brain has not been possible until recently owing to a lack of suitable tools. In this study, DRD3 status was assessed for the first time in human alcohol addiction. Brain DRD3 availability was compared between 16 male abstinent alcohol-dependent patients and 13 healthy non-dependent age-matched males using the DRD3-preferring agonist positron emission tomography (PET) radioligand [(11)C]PHNO with and without blockade with a selective DRD3 antagonist (GSK598809 60 mg p.o.). In striatal regions of interest, where the [(11)C]PHNO PET signal represents primarily DRD2 binding, no differences were seen in [(11)C]PHNO binding between the groups at baseline. However, baseline [(11)C]PHNO binding was higher in alcohol-dependent patients in hypothalamus (VT: 16.5 ± 4 vs 13.7 ± 2.9, p = 0.040), a region in which the [(11)C]PHNO signal almost entirely reflects DRD3 availability. The reductions in regional receptor binding (VT) following a single oral dose of GSK598809 (60 mg) were consistent with those observed in previous studies across all regions. There were no differences in regional changes in VT following DRD3 blockade between the two groups, indicating that the regional fractions of DRD3 are similar in the two groups, and the increased [(11)C]PHNO binding in the hypothalamus in alcohol-dependent patients is explained by elevated DRD3 in this group. Although we found no difference between alcohol-dependent patients and controls in striatal DRD3 levels, increased DRD3 binding in the hypothalamus of alcohol-dependent patients was observed. This may be relevant to the development of future therapeutic strategies to treat alcohol abuse.
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Finnema SJ, Stepanov V, Nakao R, Sromek AW, Zhang T, Neumeyer JL, George SR, Seeman P, Stabin MG, Jonsson C, Farde L, Halldin C. (18)F-MCL-524, an (18)F-Labeled Dopamine D2 and D3 Receptor Agonist Sensitive to Dopamine: A Preliminary PET Study. J Nucl Med 2014; 55:1164-70. [PMID: 24790219 DOI: 10.2967/jnumed.113.133876] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2013] [Accepted: 03/17/2014] [Indexed: 02/02/2023] Open
Abstract
UNLABELLED PET has been used to examine changes in neurotransmitter concentrations in the living brain. Pioneering PET studies on the dopamine system have used D2 and D3 receptor (D2/D3) antagonists such as (11)C-raclopride. However, more recently developed agonist radioligands have shown enhanced sensitivity to endogenous dopamine. A limitation of available agonist radioligands is that they incorporate the short-lived radioisotope (11)C. In the current study, we developed the (18)F-labeled D2/D3 receptor agonist (R)-(-)-2-(18)F-fluoroethoxy-N-n-propylnorapomorphine ((18)F-MCL-524). METHODS In total, 10 PET measurements were conducted on 5 cynomolgus monkeys. Initially, the binding of (18)F-MCL-524 was compared with that of (11)C-MNPA in 3 monkeys. Second, the specificity of (18)F-MCL-524 binding was examined in pretreatment studies using raclopride (1.0 mg/kg) and d-amphetamine (1.0 mg/kg). Third, a preliminary kinetic analysis was performed using the radiometabolite-corrected arterial input function of the baseline studies. Finally, 2 whole-body PET measurements were conducted to evaluate biodistribution and radiation dosimetry after intravenous injection of (18)F-MCL-524. RESULTS (18)F-MCL-524 entered the brain and provided striatum-to-cerebellum ratios suitable for reliable quantification of receptor binding using the multilinear reference tissue model. Mean striatal nondisplaceable binding potential (BPND) values were 2.0 after injection of (18)F-MCL-524 and 1.4 after (11)C-MNPA. The ratio of the BPND values of (18)F-MCL-524 and (11)C-MNPA was 1.5 across striatal subregions. After administration of raclopride and d-amphetamine, the (18)F-MCL-524 BPND values were reduced by 89% and 56%, respectively. Preliminary kinetic analysis demonstrated that BPND values obtained with the 1-tissue- and 2-tissue-compartment models were similar to values obtained with the multilinear reference tissue model. Estimated radiation doses were highest for gallbladder (0.27 mSv/MBq), upper large intestine (0.19 mSv/MBq), and small intestine (0.17 mSv/MBq). The estimated effective dose was 0.035 mSv/MBq. CONCLUSION The (18)F-labeled agonist (18)F-MCL-524 appears suitable for quantification of D2/D3 receptor binding in vivo, and the results encourage extension to human studies. The longer half-life of (18)F makes (18)F-MCL-524 attractive for studies on modulation of the dopamine concentration-for example, in combination with simultaneous measurement of changes in blood-oxygen-level-dependent signal using bimodal PET/functional MRI.
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Affiliation(s)
- Sjoerd J Finnema
- Karolinska Institutet, Department of Clinical Neuroscience, Center for Psychiatric Research, Stockholm, Sweden
| | - Vladimir Stepanov
- Karolinska Institutet, Department of Clinical Neuroscience, Center for Psychiatric Research, Stockholm, Sweden
| | - Ryuji Nakao
- Karolinska Institutet, Department of Clinical Neuroscience, Center for Psychiatric Research, Stockholm, Sweden
| | - Anna W Sromek
- McLean Hospital, Harvard Medical School, Belmont, Massachusetts
| | - Tangzhi Zhang
- McLean Hospital, Harvard Medical School, Belmont, Massachusetts
| | - John L Neumeyer
- McLean Hospital, Harvard Medical School, Belmont, Massachusetts
| | | | | | - Michael G Stabin
- Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, Tennessee
| | - Cathrine Jonsson
- Department of Nuclear Medicine, Karolinska University Hospital, Stockholm, Sweden; and
| | - Lars Farde
- Karolinska Institutet, Department of Clinical Neuroscience, Center for Psychiatric Research, Stockholm, Sweden AstraZeneca, Translational Science Center at Karolinska Institutet, Stockholm, Sweden
| | - Christer Halldin
- Karolinska Institutet, Department of Clinical Neuroscience, Center for Psychiatric Research, Stockholm, Sweden
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Kuntner C. Kinetic modeling in pre-clinical positron emission tomography. Z Med Phys 2014; 24:274-85. [PMID: 24629308 DOI: 10.1016/j.zemedi.2014.02.003] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2013] [Revised: 02/11/2014] [Accepted: 02/11/2014] [Indexed: 12/11/2022]
Abstract
Pre-clinical positron emission tomography (PET) has evolved in the last few years from pure visualization of radiotracer uptake and distribution towards quantification of the physiological parameters. For reliable and reproducible quantification the kinetic modeling methods used to obtain relevant parameters of radiotracer tissue interaction are important. Here we present different kinetic modeling techniques with a focus on compartmental models including plasma input models and reference tissue input models. The experimental challenges off deriving the plasma input function in rodents and the effect of anesthesia are discussed. Finally, in vivo application of kinetic modeling in various areas of pre-clinical research is presented and compared to human data.
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Affiliation(s)
- Claudia Kuntner
- Biomedical Systems, Health & Environment Department, AIT Austrian Institute of Technology GmbH, Seibersdorf, Austria.
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van Wieringen JP, Shalgunov V, Janssen HM, Fransen PM, Janssen AGM, Michel MC, Booij J, Elsinga PH. Synthesis and characterization of a novel series of agonist compounds as potential radiopharmaceuticals for imaging dopamine D₂/₃ receptors in their high-affinity state. J Med Chem 2014; 57:391-410. [PMID: 24325578 DOI: 10.1021/jm401384w] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Imaging of dopamine D2/3 receptors (D2/3R) can shed light on the nature of several neuropsychiatric disorders in which dysregulation of D2/3R signaling is involved. Agonist D2/3 tracers for PET/SPECT imaging are considered to be superior to antagonists because they are more sensitive to dopamine concentrations and may selectively label the high-affinity receptor state. Carbon-11-labeled D2/3R agonists have been developed, but these short-lived tracers can be used only in centers with a cyclotron. Here, we report the development of a series of novel D2R agonist compounds based on the 2-aminomethylchromane (AMC) scaffold that provides ample opportunities for the introduction of longer-lived [(18)F] or [(123)I]. Binding experiments showed that several AMC compounds have a high affinity and selectivity for D2/3R and act as agonists. Two fluorine-containing compounds were [(18)F]-labeled, and both displayed specific binding to striatal D2/3R in rat brain slices in vitro. These findings encourage further in vivo evaluations.
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Affiliation(s)
- Jan-Peter van Wieringen
- Department of Nuclear Medicine, Academic Medical Center, University of Amsterdam , Amsterdam, The Netherlands
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Characterization of [11C]Cimbi-36 as an agonist PET radioligand for the 5-HT2A and 5-HT2C receptors in the nonhuman primate brain. Neuroimage 2014; 84:342-53. [DOI: 10.1016/j.neuroimage.2013.08.035] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2013] [Revised: 08/12/2013] [Accepted: 08/15/2013] [Indexed: 11/18/2022] Open
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Improved HPLC purification strategy for [11C]raclopride and [11C]DASB leading to high radiochemical yields and more practical high quality radiopharmaceutical formulations. Appl Radiat Isot 2013; 78:62-7. [DOI: 10.1016/j.apradiso.2013.04.009] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2012] [Revised: 02/19/2013] [Accepted: 04/05/2013] [Indexed: 11/21/2022]
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Ye N, Neumeyer JL, Baldessarini RJ, Zhen X, Zhang A. Update 1 of: Recent Progress in Development of Dopamine Receptor Subtype-Selective Agents: Potential Therapeutics for Neurological and Psychiatric Disorders. Chem Rev 2013; 113:PR123-78. [DOI: 10.1021/cr300113a] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Na Ye
- CAS Key Laboratory of Receptor Research, and Synthetic Organic & Medicinal Chemistry Laboratory (SOMCL), Shanghai Institute of Materia Medica (SIMM), Chinese Academy of Sciences, Shanghai, China 201203
| | - John L. Neumeyer
- Medicinal Chemistry Laboratory,
McLean Hospital, Harvard Medical School, Massachusetts 02478, United States
| | | | - Xuechu Zhen
- Department of Pharmacology, College of Pharmaceutical Sciences, Soochow University, Suzhou, China 215123
| | - Ao Zhang
- CAS Key Laboratory of Receptor Research, and Synthetic Organic & Medicinal Chemistry Laboratory (SOMCL), Shanghai Institute of Materia Medica (SIMM), Chinese Academy of Sciences, Shanghai, China 201203
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Suridjan I, Rusjan P, Addington J, Wilson AA, Houle S, Mizrahi R. Dopamine D2 and D3 binding in people at clinical high risk for schizophrenia, antipsychotic-naive patients and healthy controls while performing a cognitive task. J Psychiatry Neurosci 2013; 38:98-106. [PMID: 23010256 PMCID: PMC3581597 DOI: 10.1503/jpn.110181] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
BACKGROUND The dopamine (DA) D2 receptors exist in 2 states: a high-affinity state (D2 high) that is linked to second messenger systems, responsible for functional effects, exhibits high affinity for agonists (e.g., DA), and a low-affinity state that is functionally inert exhibits lower affinity for agonists. The DA D3 receptor subtype exhibits high agonist affinity, whereas the existence of the multiple affinity states is controversial. Preclinical studies in animal models of psychosis have shown a selective increase of D2 high as the common factor in psychosis, and the D3 receptor has been suggested to be involved in the pathophysiology of schizophrenia. METHODS We studied D2 high and D3 in people at clinical high risk (CHR) for schizophrenia and in antipsychotic-naive patients with schizophrenia using the novel positron emission tomography radiotracer, [11C]-(+)-PHNO. The binding potential nondisplaceable (BP(ND)) was examined in the regions of interest (ROI; caudate, putamen, ventral striatum, globus pallidus, substantia nigra and thalamus) using an ROI and a voxel-wise approach while participants performed a cognitive task. RESULTS We recruited 12 CHR individuals and 13 antipsychotic-naive patients with schizophrenia-spectrum disorder, whom we compared with 12 age- and sex-matched healthy controls. The BP(ND) between patients and controls did not differ in any of the ROIs, consistent with the voxel-wise analysis. Correlations between the BP(ND) in D3-rich regions and psychopathology warrant further investigation. LIMITATIONS In the absence of resting-state (baseline) BP(ND) data, or following a depletion paradigm (i.e., α-methyl partyrosine), it is not possible to ascertain whether the lack of difference among the groups is owing to different levels of baseline DA or to release during the cognitive task. CONCLUSION To our knowledge, the present study represents the first effort to measure the D2 and D3 receptors under a cognitive challenge in individuals putative/prodromal for schizophrenia using [11C]-(+)-PHNO.
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Affiliation(s)
| | | | | | | | | | - Romina Mizrahi
- Correspondence to: R. Mizrahi, PET Centre, Centre for Addiction and Mental Health, 250 College St., Toronto ON M5T 1R8;
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Kumar JSD, Parsey RV, Kassir SA, Majo VJ, Milak MS, Prabhakaran J, Simpson NR, Underwood MD, Mann JJ, Arango V. Autoradiographic evaluation of [3H]CUMI-101, a novel, selective 5-HT1AR ligand in human and baboon brain. Brain Res 2013; 1507:11-8. [PMID: 23454434 DOI: 10.1016/j.brainres.2013.02.035] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2012] [Revised: 02/14/2013] [Accepted: 02/20/2013] [Indexed: 01/01/2023]
Abstract
[11C]CUMI-101 is the first selective serotonin receptor (5-HT1AR) partial agonist radiotracer for positron emission tomography (PET) tested in vivo in nonhuman primates and humans. We evaluated specific binding of [3H]CUMI-101 by quantitative autoradiography studies in postmortem baboon and human brain sections using the 5-HT1AR antagonist WAY-100635 as a displacer. The regional and laminar distributions of [3H]CUMI-101 binding in baboon and human brain sections matched the known distribution of [3H]8-OH-DPAT and [3H]WAY-100635. Prazosin did not measurably displace [3H]CUMI-101 binding in baboon or human brain sections, thereby ruling out [3H]CUMI-101 binding to α1-adrenergic receptors. This study demonstrates that [11C]CUMI-101 is a selective 5-HT1AR ligand for in vivo and in vitro studies in baboon and human brain.
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Affiliation(s)
- J S Dileep Kumar
- Division of Molecular Imaging and Neuropathology, New York State Psychiatric Institute, New York, USA.
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Xu J, Vangveravong S, Li S, Fan J, Jones LA, Cui J, Wang R, Tu Z, Chu W, Perlmutter JS, Mach RH. Positron emission tomography imaging of dopamine D2 receptors using a highly selective radiolabeled D2 receptor partial agonist. Neuroimage 2013; 71:168-74. [PMID: 23333701 DOI: 10.1016/j.neuroimage.2013.01.007] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2012] [Revised: 12/19/2012] [Accepted: 01/08/2013] [Indexed: 11/16/2022] Open
Abstract
A series of microPET imaging studies were conducted in anesthetized rhesus monkeys using the dopamine D2-selective partial agonist, [(11)C]SV-III-130. There was a high uptake in regions of brain known to express a high density of D2 receptors under baseline conditions. Rapid displacement in the caudate and putamen, but not in the cerebellum, was observed after injection of the dopamine D2/3 receptor nonselective ligand S(-)-eticlopride at a low dosage (0.025mg/kg/i.v.); no obvious displacement in the caudate, putamen and cerebellum was observed after the treatment with a dopamine D3 receptor selective ligand WC-34 (0.1mg/kg/i.v.). Pretreatment with lorazepam (1mg/kg, i.v. 30min) to reduce endogenous dopamine prior to tracer injection resulted in unchanged binding potential (BP) values, a measure of D2 receptor binding in vivo, in the caudate and putamen. d-Amphetamine challenge studies indicate that there is a significant displacement of [(11)C]SV-III-130 by d-Amphetamine-induced increases in synaptic dopamine levels.
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Affiliation(s)
- Jinbin Xu
- Department of Radiology, Washington University School of Medicine, 510 S. Kingshighway Blvd., St. Louis, MO 63110, USA
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Tziortzi AC, Haber SN, Searle GE, Tsoumpas C, Long CJ, Shotbolt P, Douaud G, Jbabdi S, Behrens TEJ, Rabiner EA, Jenkinson M, Gunn RN. Connectivity-based functional analysis of dopamine release in the striatum using diffusion-weighted MRI and positron emission tomography. ACTA ACUST UNITED AC 2013; 24:1165-77. [PMID: 23283687 DOI: 10.1093/cercor/bhs397] [Citation(s) in RCA: 230] [Impact Index Per Article: 20.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The striatum acts in conjunction with the cortex to control and execute functions that are impaired by abnormal dopamine neurotransmission in disorders such as Parkinson's and schizophrenia. To date, in vivo quantification of striatal dopamine has been restricted to structure-based striatal subdivisions. Here, we present a multimodal imaging approach that quantifies the endogenous dopamine release following the administration of d-amphetamine in the functional subdivisions of the striatum of healthy humans with [(11)C]PHNO and [(11)C]Raclopride positron emission tomography ligands. Using connectivity-based (CB) parcellation, we subdivided the striatum into functional subregions based on striato-cortical anatomical connectivity information derived from diffusion magnetic resonance imaging (MRI) and probabilistic tractography. Our parcellation showed that the functional organization of the striatum was spatially coherent across individuals, congruent with primate data and previous diffusion MRI studies, with distinctive and overlapping networks. d-amphetamine induced the highest dopamine release in the limbic followed by the sensory, motor, and executive areas. The data suggest that the relative regional proportions of D2-like receptors are unlikely to be responsible for this regional dopamine release pattern. Notably, the homogeneity of dopamine release was significantly higher within the CB functional subdivisions in comparison with the structural subdivisions. These results support an association between local levels of dopamine release and cortical connectivity fingerprints.
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Hillmer AT, Wooten DW, Slesarev MS, Ahlers EO, Barnhart TE, Murali D, Schneider ML, Mukherjee J, Christian BT. PET imaging of α4β2* nicotinic acetylcholine receptors: quantitative analysis of 18F-nifene kinetics in the nonhuman primate. J Nucl Med 2012; 53:1471-80. [PMID: 22851633 DOI: 10.2967/jnumed.112.103846] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
UNLABELLED The PET radioligand 2-fluoro-3-[2-((S)-3-pyrrolinyl)methoxy]pyridine ((18)F-nifene) is an α4β2* nicotinic acetylcholine receptor (nAChR) agonist developed to provide accelerated in vivo equilibrium compared with existing α4β2* radioligands. The goal of this work was to analyze the in vivo kinetic properties of (18)F-nifene with both kinetic modeling and graphical analysis techniques. METHODS Dynamic PET experiments were performed on 4 rhesus monkeys (female; age range, 9-13 y) using a small-animal PET scanner. Studies began with a high-specific-activity (18)F-nifene injection, followed by a coinjection of (18)F-nifene and unlabeled nifene at 60 min. Sampling of arterial blood with metabolite analysis was performed throughout the experiment to provide a parent radioligand input function. In vivo kinetics were characterized with both a 1-tissue-compartment model (1TCM) and a 2-tissue-compartment model, Logan graphical methods (both with and without blood sampling), and the multilinear reference tissue model. Total distribution volumes and nondisplaceable binding potentials (BP(ND)) were used to compare regional binding of (18)F-nifene. Regions examined include the anteroventral thalamus, lateral geniculate body, frontal cortex, subiculum, and cerebellum. RESULTS The rapid uptake and binding of (18)F-nifene in nAChR-rich regions of the brain was appropriately modeled using the 1TCM. No evidence for specific binding of (18)F-nifene in the cerebellum was detected on the basis of the coinjection studies, suggesting the suitability of the cerebellum as a reference region. Total distribution volumes in the cerebellum were 6.91 ± 0.61 mL/cm(3). BP(ND) values calculated with the 1TCM were 1.60 ± 0.17, 1.35 ± 0.16, 0.26 ± 0.08, and 0.30 ± 0.07 in the anteroventral thalamus, lateral geniculate body, frontal cortex, and subiculum, respectively. For all brain regions, there was a less than 0.04 absolute difference in the average BP(ND) values calculated with each of the 1TCM, multilinear reference tissue model, and Logan methods. CONCLUSION The fast kinetic properties and specific regional binding of (18)F-nifene promote extension of the radioligand into preclinical animal models and human subjects.
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Affiliation(s)
- Ansel T Hillmer
- Department of Medical Physics, University of Wisconsin-Madison, Madison, Wisconsin 53705, USA.
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Narendran R, Martinez D, Mason NS, Lopresti BJ, Himes ML, Chen CM, May MA, Price JC, Mathis CA, Frankle WG. Imaging of dopamine D2/3 agonist binding in cocaine dependence: a [11C]NPA positron emission tomography study. Synapse 2012; 65:1344-9. [PMID: 21780185 DOI: 10.1002/syn.20970] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
OBJECTIVE Positron emission tomography (PET) studies performed with [(11) C]raclopride have consistently reported lower binding to D(2/3) receptors and lower amphetamine-induced dopamine (DA) release in cocaine abusers relative to healthy controls. A limitation of these studies that were performed with D(2/3) antagonist radiotracers such as [(11) C]raclopride is the failure to provide information that is specific to D(2/3) receptors configured in a state of high affinity for the agonists (i.e., D(2/3) receptors coupled to G-proteins, D(2/3 HIGH) ). As the endogenous agonist DA binds with preference to D(2/3 HIGH) relative to D(2/3 LOW) receptors (i.e., D(2/3) receptors uncoupled to G-proteins) it is critical to understand the in vivo status of D(2/3 HIGH) receptors in cocaine dependence. Thus, we measured the available fraction of D(2/3) (HIGH) receptors in 10 recently abstinent cocaine abusers (CD) and matched healthy controls (HC) with the D(2/3) antagonist and agonist PET radiotracers [(11) C]raclopride and [(11) C]NPA. METHODS [(11) C]raclopride and [(11) C]NPA binding potential (BP) (BP(ND) ) in the striatum were measured with kinetic analysis using the arterial input function. The available fraction of D(2/3 HIGH) receptors, i.e., % R(HIGH) available = D(2/3 HIGH) /(D(2/3 HIGH) + D(2/3 LOW) ) was then computed as the ratio of [(11) C]NPA BP(ND) /[(11) C]raclopride BP(ND) . RESULTS No differences in striatal [(11) C]NPA BP(ND) (HC = 1.00 ± 0.17; CD = 0.97 ± 0.17, P = 0.67) or available % R(HIGH) (HC = 39% ± 5%; CD = 41% ± 5%, P = 0.50) was observed between cocaine abusers and matched controls. CONCLUSIONS The results of this [(11) C]NPA PET study do not support alterations in D(2/3 HIGH) binding in the striatum in cocaine dependence.
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Affiliation(s)
- Rajesh Narendran
- Department of Radiology, University of Pittsburgh, Pittsburgh, Pennsylvania; Department of Psychiatry, University of Pittsburgh, Pittsburgh, Pennsylvania 15213, USA.
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Buiter HJ, Leysen JE, Schuit RC, Fisher A, Lammertsma AA, Windhorst AD. Radiosynthesis and biological evaluation of the M1 muscarinic acetylcholine receptor agonist ligand [11C]AF150(S). J Labelled Comp Radiopharm 2012. [DOI: 10.1002/jlcr.2932] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Hans J.C. Buiter
- Department of Nuclear Medicine & PET Research; VU University Medical Center; PO Box 7057; 1007 MB; Amsterdam; The Netherlands
| | - Josée E. Leysen
- Department of Nuclear Medicine & PET Research; VU University Medical Center; PO Box 7057; 1007 MB; Amsterdam; The Netherlands
| | - Robert C. Schuit
- Department of Nuclear Medicine & PET Research; VU University Medical Center; PO Box 7057; 1007 MB; Amsterdam; The Netherlands
| | - Abraham Fisher
- Israel Institute for Biological Research; Ness-Ziona; Israel
| | - Adriaan A. Lammertsma
- Department of Nuclear Medicine & PET Research; VU University Medical Center; PO Box 7057; 1007 MB; Amsterdam; The Netherlands
| | - Albert D. Windhorst
- Department of Nuclear Medicine & PET Research; VU University Medical Center; PO Box 7057; 1007 MB; Amsterdam; The Netherlands
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Mizrahi R, Addington J, Rusjan PM, Suridjan I, Ng A, Boileau I, Pruessner JC, Remington G, Houle S, Wilson AA. Increased stress-induced dopamine release in psychosis. Biol Psychiatry 2012; 71:561-7. [PMID: 22133268 DOI: 10.1016/j.biopsych.2011.10.009] [Citation(s) in RCA: 194] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/30/2011] [Accepted: 10/02/2011] [Indexed: 10/28/2022]
Abstract
BACKGROUND A pathologic response to common life stressors, in which a hyperresponsive dopaminergic system is thought to play a key role, is a potential etiologic factor in the triggering and relapse of psychosis. However, there is no direct evidence that brain dopaminergic response to stress is exaggerated in psychosis. METHODS Using the ability of endogenous dopamine (DA) to compete with [(11)C]-(+)-PHNO binding, as measured with positron emission tomography, we examined stress-induced DA release in response to a validated psychosocial stress task. We studied 12 clinical high-risk (CHR), 10 antipsychotic-naive subjects with schizophrenia (SCZ), and 12 matched healthy volunteers (HV). Stress-induced DA release was estimated as the percent change in binding potential between conditions (stress and control scan) in the striatal subdivisions: limbic striatum (LST), associative striatum (AST), and sensorimotor striatum (SMST). RESULTS We found a significant difference between groups in the AST (F = 8.13, df = 2,31, p = .001), and at the SMST (F = 3,64, df = 2,31, p = .03) but not in the LST (F = .43, df = 2,31, p = .40) with CHR and SCZ having larger [(11)C]-(+)-PHNO displacement in response to the stress. Bonferroni-corrected comparisons confirmed that HV displacement (-2.86%) in the AST was significantly different in CHR (6.97%) and SCZ (11.44%) (with no significant difference between CHR and SCZ). CONCLUSIONS This study reveals a sensitized dopaminergic response to stress in a psychiatric condition and may have important theoretical and clinical implications regarding efforts to abort or delay relapse and/or conversion to psychosis.
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Affiliation(s)
- Romina Mizrahi
- Positron Emission Tomography Centre, Centre for Addiction and Mental Health, University of Toronto, Toronto, Canada.
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Vauquelin G, Bostoen S, Vanderheyden P, Seeman P. Clozapine, atypical antipsychotics, and the benefits of fast-off D2 dopamine receptor antagonism. Naunyn Schmiedebergs Arch Pharmacol 2012; 385:337-72. [PMID: 22331262 DOI: 10.1007/s00210-012-0734-2] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2011] [Accepted: 01/25/2012] [Indexed: 12/20/2022]
Abstract
Drug-receptor interactions are traditionally quantified in terms of affinity and efficacy, but there is increasing awareness that the drug-on-receptor residence time also affects clinical performance. While most interest has hitherto been focused on slow-dissociating drugs, D(2) dopamine receptor antagonists show less extrapyramidal side effects but still have excellent antipsychotic activity when they dissociate swiftly. Fast dissociation of clozapine, the prototype of the "atypical antipsychotics", has been evidenced by distinct radioligand binding approaches both on cell membranes and intact cells. The surmountable nature of clozapine in functional assays with fast-emerging responses like calcium transients is confirmatory. Potential advantages and pitfalls of the hitherto used techniques are discussed, and recommendations are given to obtain more precise dissociation rates for such drugs. Surmountable antagonism is necessary to allow sufficient D(2) receptor stimulation by endogenous dopamine in the striatum. Simulations are presented to find out whether this can be achieved during sub-second bursts in dopamine concentration or rather during much slower, activity-related increases thereof. While the antagonist's dissociation rate is important to distinguish between both mechanisms, this becomes much less so when contemplating time intervals between successive drug intakes, i.e., when pharmacokinetic considerations prevail. Attention is also drawn to the divergent residence times of hydrophobic antagonists like haloperidol when comparing radioligand binding data on cell membranes with those on intact cells and clinical data.
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Affiliation(s)
- Georges Vauquelin
- Department of Molecular and Biochemical Pharmacology, Vrije Universiteit Brussel, Pleinlaan 2, 1050, Brussels, Belgium.
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Shotbolt P, Tziortzi AC, Searle GE, Colasanti A, van der Aart J, Abanades S, Plisson C, Miller SR, Huiban M, Beaver JD, Gunn RN, Laruelle M, Rabiner EA. Within-subject comparison of [(11)C]-(+)-PHNO and [(11)C]raclopride sensitivity to acute amphetamine challenge in healthy humans. J Cereb Blood Flow Metab 2012; 32:127-36. [PMID: 21878947 PMCID: PMC3323295 DOI: 10.1038/jcbfm.2011.115] [Citation(s) in RCA: 134] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
[(11)C]PHNO is a D(2)/D(3) agonist positron emission tomography radiotracer, with higher in vivo affinity for D(3) than for D(2) receptors. As [(11)C]-(+)-PHNO is an agonist, its in vivo binding is expected to be more affected by acute fluctuations in synaptic dopamine than that of antagonist radiotracers such as [(11)C]raclopride. In this study, the authors compared the effects of an oral dose of the dopamine releaser amphetamine (0.3 mg/kg) on in vivo binding of [(11)C]-(+)-PHNO and [(11)C]raclopride in healthy subjects, using a within-subjects, counterbalanced, open-label design. In the dorsal striatum, where the density of D(3) receptors is negligible and both tracers predominantly bind to D(2) receptors, the reduction of [(11)C]-(+)-PHNO binding potential (BP(ND)) was 1.5 times larger than that of [(11)C]raclopride. The gain in sensitivity associated with the agonist [(11)C]-(+)-PHNO implies that ∼65% of D(2) receptors are in the high-affinity state in vivo. In extrastriatal regions, where [(11)C]-(+)-PHNO predominantly binds to D(3) receptors, the amphetamine effect on [(11)C]-(+)-PHNO BP(ND) was even larger, consistent with the higher affinity of dopamine for D(3). This study indicates that [(11)C]-(+)-PHNO is superior to [(11)C]raclopride for studying acute fluctuations in synaptic dopamine in the human striatum. [(11)C]-(+)-PHNO also enables measurement of synaptic dopamine in D(3) regions.
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Affiliation(s)
- Paul Shotbolt
- GlaxoSmithKline Clinical Imaging Centre, Hammersmith Hospital, London, UK.
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Measuring Dopamine Synaptic Transmission with Molecular Imaging and Pharmacological Challenges: The State of the Art. MOLECULAR IMAGING IN THE CLINICAL NEUROSCIENCES 2012. [DOI: 10.1007/7657_2012_45] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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