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Krohn KA, Vera DR. Concepts for design and analysis of receptor radiopharmaceuticals: The Receptor-Binding Radiotracers series of meetings provided the foundation. Nucl Med Biol 2021; 92:5-23. [PMID: 32331709 PMCID: PMC8049838 DOI: 10.1016/j.nucmedbio.2020.03.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2020] [Accepted: 03/08/2020] [Indexed: 12/14/2022]
Abstract
A symposium at George Washington University on Receptor-Binding Radiotracers in 1980 and three follow-up meetings held at University of California, San Diego provided a forum for debating the critical concepts involved in the new field of designing and evaluating radiotracers for imaging receptors and transporters. This review is intended to educate young investigators who may be relatively new to receptor radiopharmaceutical development. Our anticipated audience includes researchers in basic pharmacology, radiochemistry, imaging technology and kinetic data analysis and how these disciplines have worked together to build our understanding of the human biology of transporters and receptor signaling in health and disease. We have chosen to focus on radiochemical design of a useful imaging agent and how design is coupled to analysis of data collected from dynamic imaging with that agent. Some pharmacology may be required for designing the imaging agent and some imaging physics may be important in optimizing the quality of data that is collected. However, the key to a successful imaging agent is matching the radiotracer to the target receptor and to analysis of the time-course data that is used to parse delivery from specific binding and subsequent metabolism or degradation. Properly designed imaging agents are providing critical information about human biology in health and disease as well as pharmacodynamic response to drug interventions. The review emphasizes some of the ideas that were controversial at the 1980 conference and chronicles with literature examples how they have resolved over the four decades of using radiotracers to study transporters and receptors in human subjects. These examples show that there are situations where a very small KD, i.e. high affinity, has the potential to yield an image that reflects blood flow more than receptor density. The examples also show that by combining two studies, one with high specific activity and a second with low specific activity injections one can unravel the pseudo-first order rate B'max into the true second-order rate constant, k3, and the unoccupied receptor density. The final section describes how mathematical methods first presented to the receptor-imaging community in 1980 are now being used to provide confidence in the analysis of kinetic biodistribution studies. Our hope is that by bringing these concepts together in a single review, the next generation of scientists developing receptor imaging agents can be much more efficient than their pioneers in developing useful imaging methods.
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Affiliation(s)
- Kenneth A Krohn
- Center for Radiochemistry Research, Department of Diagnostic Radiology, Mail Code L104, Oregon Health & Science University, 3181 SW Sam Jackson Park Rd, Portland, OR 97239, United States of America.
| | - David R Vera
- UCSD Moores Cancer Center, Department of Radiology, Mail Code 0819, University of California, San Diego, CA 92037, United States of America
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Schildt A, Walker MD, Dinelle K, Miao Q, Schulzer M, O'Kusky J, Farrer MJ, Doudet DJ, Sossi V. Single Inflammatory Trigger Leads to Neuroinflammation in LRRK2 Rodent Model without Degeneration of Dopaminergic Neurons. JOURNAL OF PARKINSONS DISEASE 2020; 9:121-139. [PMID: 30452424 DOI: 10.3233/jpd-181446] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
BACKGROUND Leucine-rich repeat kinase 2 (LRRK2) mutations are the most common genetic risk factor for Parkinson's disease (PD). While the corresponding pathogenic mechanisms remain largely unknown, LRRK2 has been implicated in the immune system. OBJECTIVE To assess whether LRRK2 mutations alter the sensitivity to a single peripheral inflammatory trigger, with ultimate impact on dopaminergic integrity, using a longitudinal imaging-based study design. METHODS Rats carrying LRRK2 p.G2019S and non-transgenic (NT) littermates were treated peripherally with lipopolysaccharide (LPS). They were monitored over 10 months with PET markers for neuroinflammation and dopaminergic integrity, and with behavioral testing. Tyrosine hydroxylase and CD68 expression were assessed postmortem, 12 months after LPS treatment, in the striatum and substantia nigra. RESULTS Longitudinal [11C]PBR28 PET imaging revealed that LPS treatment caused inflammation in the brain, increasing over time, as compared to saline (corrected p = 0.008). LPS treated LRRK2 animals exhibited significantly increased neuroinflammation in the cortex and ventral-regions compared to saline treated animals (LRRK2 and NT) at 10 months post treatment, with the increase in [11C]PBR28 binding from baseline averaging 0.128±0.045 g/mL. For LPS treated NT animals, the increase was not significant. CD68 immunohistochemistry data supported the imaging results, but without reaching statistical significance. No dopaminergic degeneration was observed. CONCLUSION A single peripheral inflammatory trigger elicited long lasting, progressive neuroinflammation. A trend for an exacerbated inflammatory response in LRRK2 animals compared to NT controls was observed. Translationally, this implies that repeated exposure to inflammatory triggers may be needed for LRRK2 mutation carriers to develop active PD.
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Affiliation(s)
- Anna Schildt
- Department of Physics and Astronomy, University of British Columbia, Vancouver, BC, Canada.,Department of Nuclear Medicine and Molecular Imaging, University of Groningen, University Medical Centre Groningen, Groningen, The Netherlands
| | - Matthew D Walker
- Department of Physics and Astronomy, University of British Columbia, Vancouver, BC, Canada
| | - Katherine Dinelle
- Pacific Parkinson's Research Centre, University of British Columbia, Vancouver, BC, Canada
| | | | - Michael Schulzer
- Pacific Parkinson's Research Centre, University of British Columbia, Vancouver, BC, Canada
| | - John O'Kusky
- Department of Pathology, University of British Columbia, Vancouver, BC, Canada
| | - Matthew J Farrer
- Department of Medical Genetics, Centre for Applied Neurogenetics, University of British Columbia, Vancouver, BC, Canada
| | - Doris J Doudet
- Department of Medicine, Division of Neurology, University of British Columbia, Vancouver, BC, Canada
| | - Vesna Sossi
- Department of Physics and Astronomy, University of British Columbia, Vancouver, BC, Canada
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3
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Phan JA, Stokholm K, Zareba-Paslawska J, Jakobsen S, Vang K, Gjedde A, Landau AM, Romero-Ramos M. Early synaptic dysfunction induced by α-synuclein in a rat model of Parkinson's disease. Sci Rep 2017; 7:6363. [PMID: 28743955 PMCID: PMC5526979 DOI: 10.1038/s41598-017-06724-9] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2017] [Accepted: 06/15/2017] [Indexed: 02/08/2023] Open
Abstract
Evidence suggests that synapses are affected first in Parkinson’s disease (PD). Here, we tested the claim that pathological accumulation of α-synuclein, and subsequent synaptic disruption, occur in absence of dopaminergic neuron loss in PD. We determined early synaptic changes in rats that overexpress human α-synuclein by local injection of viral-vectors in midbrain. We aimed to achieve α-synuclein levels sufficient to induce terminal pathology without significant loss of nigral neurons. We tested synaptic disruption in vivo by analyzing motor defects and binding of a positron emission tomography (PET) radioligand to the vesicular monoamine transporter 2, (VMAT2), [11C]dihydrotetrabenazine (DTBZ). Animals overexpressing α-synuclein had progressive motor impairment and, 12 weeks post-surgery, showed asymmetric in vivo striatal DTBZ binding. The PET images matched ligand binding in post-mortem tissue, and histological markers of dopaminergic integrity. Histology confirmed the absence of nigral cell death with concomitant significant loss of striatal terminals. Progressive aggregation of proteinase-K resistant and Ser129-phosphorylated α-synuclein was observed in dopaminergic terminals, in dystrophic swellings that resembled axonal spheroids and contained mitochondria and vesicular proteins. In conclusion, pathological α-synuclein in nigro-striatal axonal terminals leads to early axonal pathology, synaptic disruption, dysfunction of dopaminergic neurotransmission, motor impairment, and measurable change of VMAT2 in the absence of cell loss.
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Affiliation(s)
- Jenny-Ann Phan
- Department of Biomedicine, NEURODIN AU IDEAS Center, Aarhus University, Wilhelm Meyers Allé 4, bldg. 1242, Aarhus C, 8000, Denmark.,Department of Nuclear Medicine and PET Centre, Aarhus University and Hospital, Norrebrogade 44, bldg. 10G, Aarhus C, 8000, Denmark
| | - Kathrine Stokholm
- Department of Biomedicine, NEURODIN AU IDEAS Center, Aarhus University, Wilhelm Meyers Allé 4, bldg. 1242, Aarhus C, 8000, Denmark.,Department of Nuclear Medicine and PET Centre, Aarhus University and Hospital, Norrebrogade 44, bldg. 10G, Aarhus C, 8000, Denmark
| | - Justyna Zareba-Paslawska
- Department of Biomedicine, NEURODIN AU IDEAS Center, Aarhus University, Wilhelm Meyers Allé 4, bldg. 1242, Aarhus C, 8000, Denmark
| | - Steen Jakobsen
- Department of Nuclear Medicine and PET Centre, Aarhus University and Hospital, Norrebrogade 44, bldg. 10G, Aarhus C, 8000, Denmark
| | - Kim Vang
- Department of Nuclear Medicine and PET Centre, Aarhus University and Hospital, Norrebrogade 44, bldg. 10G, Aarhus C, 8000, Denmark
| | - Albert Gjedde
- Department of Neuroscience and Pharmacology, University of Copenhagen, Blegdamsvej 3, Copenhagen, 2200, Denmark.,Center of Neuroscience, University of Copenhagen, Copenhagen, Denmark.,Dept of Radiology & Radiological Science, Johns Hopkins University, Baltimore, MD, USA.,Department of Neurology and Neurosurgery, McGill University, Montreal, Quebec, Canada.,Neurosciences Research Center, Tabriz University of Medical Sciences, Tabriz, Iran.,Department of Clinical Medicine, University of Southern Denmark, Odense, Denmark
| | - Anne M Landau
- Department of Nuclear Medicine and PET Centre, Aarhus University and Hospital, Norrebrogade 44, bldg. 10G, Aarhus C, 8000, Denmark. .,Translational Neuropsychiatry Unit, Aarhus University, Skovagervej 2, Risskov, 8240, Denmark.
| | - Marina Romero-Ramos
- Department of Biomedicine, NEURODIN AU IDEAS Center, Aarhus University, Wilhelm Meyers Allé 4, bldg. 1242, Aarhus C, 8000, Denmark.
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4
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Mejias M, Yu J, Mackey S, Dinelle K, Sossi V, Doudet DJ. Interpreting DTBZ binding data in rodent: Inherent variability and compensation. Synapse 2016; 70:147-52. [PMID: 26749375 DOI: 10.1002/syn.21883] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2015] [Revised: 12/17/2015] [Accepted: 01/04/2016] [Indexed: 12/16/2022]
Abstract
[11C]-dihydrotetrabenazine (DTBZ) Positron Emission Tomography was used to evaluate the vesicular monoamine transporter type 2 as an index of dopaminergic function in the striatum of adult Sprague-Dawley rats obtained from two different animal sources (Charles River Laboratories [CR] or UBC's Animal Care Centre [ACC]) and later submitted to two different unilateral lesions of the nigro-striatal pathway. The results showed a significant difference in the striatal binding potential (BP(ND)) at baseline (before lesioning) between the CR and ACC groups providing evidence that the origin of the animals, possibly due to differences in early environmental factors or breeding conditions associated with different animal vendors plays a role in the development of the adult dopaminergic system. Further, in both animal models, an increase in DTBZ BP(ND) was observed, after unilateral intervention, in the striatum contralateral to the lesion, likely reflecting compensatory effects. Based on these findings, we conclude that in unilateral models, the unlesioned side/hemisphere may not be an appropriate control and that care should be taken to control for the origin of the animals in any given study, especially in longitudinal and replication studies.
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Affiliation(s)
- Miguel Mejias
- Department of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
| | - Jing Yu
- Department of Medicine, University of British Columbia, Vancouver, British Columbia, Canada.,Department of Nuclear Medicine, Da Lian Medical University Affiliated Hospital No 2, China
| | - Scott Mackey
- Department of Medicine, University of British Columbia, Vancouver, British Columbia, Canada.,Department of Psychiatry, University of Vermont, Burlington, Vermont
| | - Katie Dinelle
- Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia, Canada
| | - Vesna Sossi
- Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia, Canada
| | - Doris J Doudet
- Department of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
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Bannon D, Landau AM, Doudet DJ. How Relevant Are Imaging Findings in Animal Models of Movement Disorders to Human Disease? Curr Neurol Neurosci Rep 2015; 15:53. [DOI: 10.1007/s11910-015-0571-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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Molinet-Dronda F, Gago B, Quiroga-Varela A, Juri C, Collantes M, Delgado M, Prieto E, Ecay M, Iglesias E, Marín C, Peñuelas I, Obeso JA. Monoaminergic PET imaging and histopathological correlation in unilateral and bilateral 6-hydroxydopamine lesioned rat models of Parkinson's disease: A longitudinal in-vivo study. Neurobiol Dis 2015; 77:165-72. [DOI: 10.1016/j.nbd.2015.01.007] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2014] [Revised: 12/25/2014] [Accepted: 01/30/2015] [Indexed: 10/24/2022] Open
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Salo R, Fassbender C. Structural, functional and spectroscopic MRI studies of methamphetamine addiction. Curr Top Behav Neurosci 2015; 11:321-64. [PMID: 22094881 DOI: 10.1007/7854_2011_172] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/16/2023]
Abstract
This chapter reviews selected neuroimaging findings related to long-term amphetamine and methamphetamine (MA) use. An overview of structural and functional (fMRI) MR studies, Diffusion Tensor Imaging (DTI), Magnetic Resonance Spectroscopy (MRS) and Positron Emission Tomography (PET) studies conducted in long-term MA abusers is presented. The focus of this chapter is to present the relevant studies as tools to understand brain changes following drug abstinence and recovery from addiction. The behavioral relevance of these neuroimaging studies is discussed as they relate to clinical symptoms and treatment. Within each imaging section this chapter includes a discussion of the relevant imaging studies as they relate to patterns of drug use (i.e., duration of MA use, cumulative lifetime dose and time MA abstinent) as well as an overview of studies that link the imaging findings to cognitive measures. In our conclusion we discuss some of the future directions of neuroimaging as it relates to the pathophysiology of addiction.
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Affiliation(s)
- Ruth Salo
- UC Davis Imaging Research Center, 4701 X Street, Sacramento, CA, USA,
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Walker MD, Dinelle K, Kornelsen R, Lee A, Farrer MJ, Stoessl AJ, Sossi V. Measuring dopaminergic function in the 6-OHDA-lesioned rat: a comparison of PET and microdialysis. EJNMMI Res 2013; 3:69. [PMID: 24088510 PMCID: PMC3875899 DOI: 10.1186/2191-219x-3-69] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2013] [Accepted: 09/23/2013] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND [18 F]fluorodopa (FDOPA) positron emission tomography (PET) allows assessment of levodopa (LDOPA) metabolism and is widely used to study Parkinson's disease. We examined how [18 F]FDOPA PET-derived kinetic parameters relate the dopamine (DA) and DA metabolite content of extracellular fluid measured by microdialysis to aid in the interpretation of data from both techniques. METHODS [18 F]FDOPA PET imaging and microdialysis measurements were performed in unilaterally 6-hydroxydopamine-lesioned rats (n = 8) and normal control rats (n = 3). Microdialysis testing included baseline measurements and measurements following acute administration of LDOPA. PET imaging was also performed using [11C]dihydrotetrabenazine (DTBZ), which is a ligand for the vesicular monoamine transporter marker and allowed assessment of denervation severity. RESULTS The different methods provided highly correlated data. Lesioned rats had reduced DA metabolite concentrations ipsilateral to the lesion (p < 0.05 compared to controls), with the concentration being correlated with FDOPA's effective distribution volume ratio (EDVR; r = 0.86, p < 0.01) and DTBZ's binding potential (BPND; r = 0.89, p < 0.01). The DA metabolite concentration in the contralateral striatum of severely (>80%) lesioned rats was lower (p < 0.05) than that of less severely lesioned rats (<80%) and was correlated with the ipsilateral PET measures (r = 0.89, p < 0.01 for BPND) but not with the contralateral PET measures. EDVR and BPND in the contralateral striatum were not different from controls and were not correlated with the denervation severity. CONCLUSIONS The demonstrated strong correlations between the PET and microdialysis measures can aid in the interpretation of [18 F]FDOPA-derived kinetic parameters and help compare results from different studies. The contralateral striatum was affected by the lesioning and so cannot always serve as an unaffected control.
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Affiliation(s)
- Matthew D Walker
- Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver, British Columbia V6T 1Z1, Canada
| | - Katherine Dinelle
- Pacific Parkinson's Research Centre, University of British Columbia, 2221 Wesbrook Mall, Vancouver, British Columbia V6T 2B5, Canada
| | - Rick Kornelsen
- Pacific Parkinson's Research Centre, University of British Columbia, 2221 Wesbrook Mall, Vancouver, British Columbia V6T 2B5, Canada
| | - Anna Lee
- Pacific Parkinson's Research Centre, University of British Columbia, 2221 Wesbrook Mall, Vancouver, British Columbia V6T 2B5, Canada
| | - Matthew J Farrer
- Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia V6H 3N1, Canada
| | - A Jon Stoessl
- Pacific Parkinson's Research Centre, University of British Columbia, 2221 Wesbrook Mall, Vancouver, British Columbia V6T 2B5, Canada
| | - Vesna Sossi
- Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver, British Columbia V6T 1Z1, Canada
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Pharmacological imaging as a tool to visualise dopaminergic neurotoxicity. Neuropharmacology 2013; 84:159-69. [PMID: 23851258 DOI: 10.1016/j.neuropharm.2013.06.029] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2012] [Revised: 06/06/2013] [Accepted: 06/27/2013] [Indexed: 11/20/2022]
Abstract
Dopamine abnormalities underlie a wide variety of psychopathologies, including ADHD and schizophrenia. A new imaging technique, pharmacological magnetic resonance imaging (phMRI), is a promising non-invasive technique to visualize the dopaminergic system in the brain. In this review we explore the clinical potential of phMRI in detecting dopamine dysfunction or neurotoxicity, assess its strengths and weaknesses and identify directions for future research. Preclinically, phMRI is able to detect severe dopaminergic abnormalities quite similar to conventional techniques such as PET and SPECT. phMRI benefits from its high spatial resolution and the possibility to visualize both local and downstream effects of dopaminergic neurotransmission. In addition, it allows for repeated measurements and assessments in vulnerable populations. The major challenge is the complex interpretation of phMRI results. Future studies in patients with dopaminergic abnormalities need to confirm the currently reviewed preclinical findings to validate the technique in a clinical setting. Eventually, based on the current review we expect that phMRI can be of use in a clinical setting involving vulnerable populations (such as children and adolescents) for diagnosis and monitoring treatment efficacy. This article is part of the Special Issue Section entitled 'Neuroimaging in Neuropharmacology'.
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Mackey S, Jing Y, Flores J, Dinelle K, Doudet DJ. Direct intranigral administration of an ubiquitin proteasome system inhibitor in rat: behavior, positron emission tomography, immunohistochemistry. Exp Neurol 2013; 247:19-24. [PMID: 23557600 DOI: 10.1016/j.expneurol.2013.03.021] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2012] [Revised: 03/12/2013] [Accepted: 03/14/2013] [Indexed: 01/10/2023]
Abstract
Several independent lines of research suggest that disruption of the ubiquitin proteasome system (UPS) may play a role in the pathophysiology of Parkinson's disease. Direct intracerebral injection of UPS inhibitors (e.g. lactacystin) in animals has consistently produced important features of the disease. In this study, a range of lactacystin doses (0.5, 1, 2, 10 and 20 μg) were injected into the right substantia nigra in rats to determine the ideal dose required to produce a robust and specific lesion of the dopamine nigro-striatal system and motor deficits. Motor behavior, assessed with the tapered ledged beam task, was severely affected in animals that received high doses (10 and 20 μg) but only mild, impairments were observed in animals that received low doses (0.5, 1, and 2 μg). Positron emission tomography was performed with a dedicated small animal scanner on the rats following the injection of the radio-labeled tracer (±)[(11)C]dihydrotetrabenazine (DTBZ) which labels vesicular monoamine transporter type 2. Severe loss of [(11)C]DTBZ binding in the ipsilateral striatum was observed in the higher dose groups and mild loss was observed in the low dose groups. Stereological cell counting of tyrosine hydroxylase immunoreactive cells in the substantia nigra and the ventral tegmental area indicated a dose dependent loss of dopaminergic neurons. Significant correlations were found between the behavioral motor deficits, striatal [(11)C]DTBZ binding and cell counts of tyrosine hydroxylase immunoreactive cells. Taken together these results indicate that intranigral injection of lactacystin produces dose dependent effects on the dopamine nigro-striatal system and a dose of 10 μg will produce a consistent severe lesion.
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Affiliation(s)
- Scott Mackey
- Department of Psychiatry, University of California, San Diego, La Jolla, CA 92037, USA.
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11
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In-vivo measurement of LDOPA uptake, dopamine reserve and turnover in the rat brain using [18F]FDOPA PET. J Cereb Blood Flow Metab 2013; 33:59-66. [PMID: 22929441 PMCID: PMC3597374 DOI: 10.1038/jcbfm.2012.120] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Longitudinal measurements of dopamine (DA) uptake and turnover in transgenic rodents may be critical when developing disease-modifying therapies for Parkinson's disease (PD). We demonstrate methodology for such measurements using [(18)F]fluoro-3,4-dihydroxyphenyl-L-alanine ([(18)F]FDOPA) positron emission tomography (PET). The method was applied to 6-hydroxydopamine lesioned rats, providing the first PET-derived estimates of DA turnover for this species. Control (n=4) and unilaterally lesioned (n=11) rats were imaged multiple times. Kinetic modeling was performed using extended Patlak, incorporating a k(loss) term for metabolite washout, and modified Logan methods. Dopaminergic terminal loss was measured via [(11)C]-(+)-dihydrotetrabenazine (DTBZ) PET. Clear striatal [(18)F]FDOPA uptake was observed. In the lesioned striatum the effective DA turnover increased, shown by a reduced effective distribution volume ratio (EDVR) for [(18)F]FDOPA. Effective distribution volume ratio correlated (r>0.9) with the [(11)C]DTBZ binding potential (BP(ND)). The uptake and trapping rate (k(ref)) decreased after lesioning, but relatively less so than [(11)C]DTBZ BP(ND). For normal controls, striatal estimates were k(ref)=0.037±0.005 per minute, EDVR=1.07±0.22 and k(loss)=0.024±0.003 per minute (30 minutes turnover half-time), with repeatability (coefficient of variation) ≤11%. [(18)F]fluoro-3,4-dihydroxyphenyl-L-alanine PET enables measurements of DA turnover in the rat, which is useful for developing novel therapies for PD.
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12
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Landau AM, Doudet DJ, Jakobsen S. Amphetamine challenge decreases yohimbine binding to α2 adrenoceptors in Landrace pig brain. Psychopharmacology (Berl) 2012; 222:155-63. [PMID: 22227612 DOI: 10.1007/s00213-011-2632-6] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/21/2011] [Accepted: 12/21/2011] [Indexed: 11/29/2022]
Abstract
RATIONALE The noradrenaline (NA) system is implicated in neurodegenerative and psychiatric disorders; however, our understanding is impaired by the lack of well-validated radioligands to assess NA function and release. Yohimbine, an α2 adrenoceptor antagonist, has recently been developed as a carbon-11 [11C]-labeled radioligand for positron emission tomography (PET) imaging studies. OBJECTIVES Here we explore the hypothesis that yohimbine can be used as an in vivo tracer of NA receptor binding and release during amphetamine challenges in Landrace pigs. METHODS Pigs underwent baseline PET scans with [11C]yohimbine and were then challenged with 10 mg/kg d-amphetamine 20 min prior to a second [11C]yohimbine scan. Using the Logan analysis model, volumes of distribution were calculated from fits of the kinetic data 25-90 min post-yohimbine injection. RESULTS Amphetamine decreased [11C]yohimbine volume of distribution in the brain regions under investigation, including the thalamus, caudate nucleus, and cortical regions. CONCLUSION These data suggest that the binding of [11C]yohimbine to α2 adrenoceptors may be displaceable by increases in synaptic concentrations of the endogenous ligand, NA, and possibly dopamine, suggesting the possibility that [11C]yohimbine may be used as a surrogate marker of NA release in vivo.
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Affiliation(s)
- Anne M Landau
- Department of Nuclear Medicine and PET Center, Aarhus University Hospital, Norrebrogade 44, Building 10G, Aarhus C 8000, Denmark
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13
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Sossi V, Dinelle K, Jivan S, Fischer K, Holden JE, Doudet D. In vivo dopamine transporter imaging in a unilateral 6-hydroxydopamine rat model of Parkinson disease using 11C-methylphenidate PET. J Nucl Med 2012; 53:813-22. [PMID: 22492730 DOI: 10.2967/jnumed.111.101436] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
UNLABELLED Dopamine transporter (DAT) function is altered by many neurodegenerative diseases. For instance, in Parkinson disease DAT density has been shown to decrease in early disease and to play a role in the occurrence of motor complications. DAT is thus an important imaging target with potential therapeutic relevance in humans and animal models of disease. The PET DAT marker (11)C-methylphenidate is commonly used to quantify DAT function. Here we investigate the characteristics of the (11)C-methylphenidate-derived quantification of DAT in rodents using the 6-hydroxydopamine Parkinson disease rat model. METHODS Seven unilaterally 6-hydroxydopamine-lesioned rats (dopaminergic denervation [DD] range, 36%-94%) were injected with 3.7 MBq/100 g of body weight and tracer masses ranging from 93.8 to 0.0041 μg/100 g of body weight. We evaluated the maximum available transporter density and the in vivo (apparent) ligand-transporter dissociation constant (B(max) and K app d, respectively) with an in vivo Scatchard method using several modeling approaches and estimated the transporter occupancy as a function of the amount of tracer injected and tracer specific activity (SA). RESULTS Strong evidence of different nonspecific binding in the striatal region, compared with the reference region, leading to bias in the estimate of DD severity was found. One percent transporter occupancy was reached with 0.14 μg of tracer/100 g of body weight, corresponding to an SA of 5.7 kBq/pmol for the given radioactivity dose, and 10% occupancy was reached at 1.5 μg of tracer/100 g of body weight, corresponding to an SA of 0.57 kBq/pmol. The 6-hydroxydopamine lesion affected B(max) (control, 402 ± 94 pmol/mL; lesioned, 117 ± 120 pmol/mL; P = 0.003) but not K app d (control, 331 ± 63 pmol/mL; lesioned, 362 ± 119 pmol/mL; P = 0.63). CONCLUSION Although DAT imaging can be performed at a relatively high mass of (11)C-methylphenidate (low SA), the additional nonspecific binding found in the striatum can introduce a DD severity-dependent bias in the estimate of tissue-derived binding potential and care must be taken in comparing (11)C-methylphenidate-derived assessment of DD with that obtained using other dopaminergic tracers.
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Affiliation(s)
- Vesna Sossi
- Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia, Canada.
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14
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Kyono K, Takashima T, Katayama Y, Kawasaki T, Zochi R, Gouda M, Kuwahara Y, Takahashi K, Wada Y, Onoe H, Watanabe Y. Use of [18F]FDOPA-PET for in vivo evaluation of dopaminergic dysfunction in unilaterally 6-OHDA-lesioned rats. EJNMMI Res 2011; 1:25. [PMID: 22214344 PMCID: PMC3251329 DOI: 10.1186/2191-219x-1-25] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2011] [Accepted: 11/10/2011] [Indexed: 11/22/2022] Open
Abstract
Background We evaluated the utility of L-3,4-dihydroxy-6-[18F]fluoro-phenylalanine ([18F]FDOPA) positron emission tomography (PET) as a method for assessing the severity of dopaminergic dysfunction in unilaterally 6-hydroxydopamine (6-OHDA)-lesioned rats by comparing it with quantitative biochemical, immunohistochemical, and behavioral measurements. Methods Different doses of 6-OHDA (0, 7, 14, and 28 μg) were unilaterally injected into the right striatum of male Sprague-Dawley rats. Dopaminergic functional activity in the striatum was assessed by [18F]FDOPA-PET, measurement of striatal dopamine (DA) and DA metabolite levels, tyrosine hydroxylase (TH) immunostaining, and methamphetamine-induced rotational testing. Results Accumulation of [18F]FDOPA in the bilateral striatum was observed in rats pretreated with both aromatic L-amino acid decarboxylase and catechol-O-methyltransferase (COMT) inhibitors. Unilateral intrastriatal injection of 6-OHDA produced a significant site-specific reduction in [18F]FDOPA accumulation. The topological distribution pattern of [18F]FDOPA accumulation in the ipsilateral striatum agreed well with the pattern in TH-stained corresponding sections. A significant positive relationship was found between Patlak plot Ki values and striatal levels of DA and its metabolites (r = 0.958). A significant negative correlation was found between both Ki values (r = -0.639) and levels of DA and its metabolites (r = -0.719) and the number of methamphetamine-induced rotations. Conclusions Ki values determined using [18F]FDOPA-PET correlated significantly with the severity of dopaminergic dysfunction. [18F]FDOPA-PET makes it possible to perform longitudinal evaluation of dopaminergic function in 6-OHDA-lesioned rats, which is useful in the development of new drugs and therapies for Parkinson's disease (PD).
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Affiliation(s)
- Kiyoshi Kyono
- RIKEN Center for Molecular Imaging Science, Hyogo, Japan.
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15
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Abstract
In the last 25 years there have been enormous advances in brain imaging. In addition to utility in diagnosis, these have led to novel insights into the pathogenesis of basal ganglia disease and the role of dopamine and the basal ganglia in normal health. The authors review highlights of this work, with a focus on advances in Parkinson's disease, the dystonias, Huntington's disease, and the role of dopamine in cognition and reward signaling. Emerging areas for future development include studies of functional connectivity, the analysis of default mode networks, studies of novel neurochemical pathways, methods to study disease pathogenesis, and the application of imaging techniques to investigate animal models of disease.
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Affiliation(s)
- A Jon Stoessl
- Pacific Parkinson's Research Centre, University of British Columbia & Vancouver Coastal Health, Vancouver, British Columbia, Canada.
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16
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Fischer K, Sossi V, von Ameln-Mayerhofer A, Reischl G, Pichler BJ. In vivo quantification of dopamine transporters in mice with unilateral 6-OHDA lesions using [11C]methylphenidate and PET. Neuroimage 2011; 59:2413-22. [PMID: 21945469 DOI: 10.1016/j.neuroimage.2011.08.109] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2011] [Revised: 08/24/2011] [Accepted: 08/30/2011] [Indexed: 01/28/2023] Open
Abstract
UNLABELLED Quantification of the binding of [11C]methylphenidate to the dopamine transporter (DAT) using positron emission tomography (PET) is often used to evaluate the integrity of dopaminergic neurons in the striatal regions of the brain. Over the past decade, many genetically engineered mouse models of human disease have been developed and have become particularly useful for the study of disease onset and progression over time. Quantitative imaging of small structures such as the mouse brain is especially challenging. Thus, the aims of this study were (1) to evaluate the accuracy of quantifying DAT binding using in vivo PET and (2) to examine the impact of different methodologies. METHODS Eight mice were scanned with [11C]methylphenidate under true or transient equilibrium conditions using a bolus and constant infusion protocol or a bolus injection protocol to evaluate the accuracy of the Logan graphical approach for [11C]methylphenidate imaging in mice. Displacement with unlabeled methylphenidate (0.1, 3 and 10 mg/kg) was used to verify specific binding. In a second experiment, 30 mice were lesioned by injection of 6-hydroxydopamine (6-OHDA) at doses of 0, 2 or 4 μg (n=10) into the right striatum to assess the dose-dependent correlation between the PET signal and dopaminergic degeneration. In addition, we performed test-retest experiments and used ex vivo autoradiography (AR) to validate the effect of partial volume on the accuracy of the [11C]methylphenidate PET quantification in the mouse striatum. RESULTS The binding potentials (BPND) calculated from the Logan graphical analysis under transient equilibrium conditions (1.03±0.1) were in excellent agreement with those calculated at true equilibrium (1.07±0.1). Displacement of specific binding with 0.1, 3 and 10mg/kg methylphenidate resulted in 38%, 77% and 81% transporter occupancy in the striatum. Intra-striatal injections of 6-OHDA caused a dose-dependent decrease in the specific binding of [11C]methylphenidate to the DAT in the striatum. The BPND was reduced by 49% and 61% after injection with 2 and 4 μg of 6-OHDA, respectively. The test-retest reproducibility was 6% in the healthy striatum and 27% in the lesioned striatum. In addition, only a small (15%) difference was found between the [11C]methylphenidate DVR-1 values determined by PET and AR on the healthy side, and no differences were observed on the lesioned side. CONCLUSION The present work demonstrates for the first time that [11C]methylphenidate PET is useful for the quantification of striatal dopamine transporters at the dopaminergic nerve terminals in the mouse striatum; therefore, this marker may be used as a biomarker in genetically engineered mouse models of neurodegenerative disorders. However, only changes resulting in greater than 10% differences in BPND values can reliably be detected in vivo.
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Affiliation(s)
- Kristina Fischer
- Department of Preclinical Imaging and Radiopharmacy, Laboratory for Preclinical Imaging and Imaging Technology of the Werner Siemens-Foundation, Eberhard-Karls University of Tübingen, Germany.
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17
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Nikolaus S, Larisch R, Vosberg H, Beu M, Hautzel H, Wirrwar A, Mueller HW, Antke C. In vivo imaging neurotransmitter function. The rat 6-hydroxydopamine model and its relevance for human Parkinson's disease. Nuklearmedizin 2011; 50:155-66. [PMID: 21409317 DOI: 10.3413/nukmed-0371-10-12] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2010] [Accepted: 02/14/2011] [Indexed: 01/13/2023]
Abstract
This article gives an overview of those small animal imaging studies which have been conducted on neurotransmitter function in the rat 6-hydoxydopamine (6-OHDA) model of Parkinson's disease, and discusses findings with respect to the outcome of clinical studies on Parkinsonian patients.
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Affiliation(s)
- S Nikolaus
- Clinic of Nuclear Medicine, University Hospital Düsseldorf, 40225 Düsseldorf, Germany.
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18
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Xi W, Tian M, Zhang H. Molecular imaging in neuroscience research with small-animal PET in rodents. Neurosci Res 2011; 70:133-43. [PMID: 21241748 DOI: 10.1016/j.neures.2010.12.017] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2010] [Revised: 12/21/2010] [Accepted: 12/24/2010] [Indexed: 10/18/2022]
Abstract
Cognitive neuroscience, which studies the biological basis of mental processes, widely uses neuroimaging technologies like functional magnetic resonance imaging and positron emission tomography (PET) to study the human brain. Small laboratory animals, like rodents, are commonly used in brain research and provide abundant models of human brain diseases. The development of high-resolution small-animal PET and various radiotracers together with sophisticated methods for analyzing functional brain imaging data have accelerated research on brain function and neurotransmitter release during behavioral tasks in rodents. In this review, we first summarize advances in the methodology of cognitive research brought about by the development of sophisticated methods for whole-brain imaging analysis and improvements in neuroimaging protocols. Then, we discuss basic mechanisms related to metabolic changes and the expression of neurotransmitters in various brain areas during task-induced neural activity. In particular, we discuss glucose metabolism imaging and brain receptor imaging for various receptor systems. Finally, we discuss the current status and future perspectives. Mechanisms of neurotransmitter expression will probably become an increasingly important field of study in the future, leading to more collaboration between investigators in fields such as computational and theoretical neuroscience.
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Affiliation(s)
- Wang Xi
- Department of Nuclear Medicine, Second Affiliated Hospital of Zhejiang University, School of Medicine, Hangzhou, China
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19
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Landau AM, Chakravarty MM, Clark CM, Zis AP, Doudet DJ. Electroconvulsive therapy alters dopamine signaling in the striatum of non-human primates. Neuropsychopharmacology 2011; 36:511-8. [PMID: 20944554 PMCID: PMC3055667 DOI: 10.1038/npp.2010.182] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Electroconvulsive therapy (ECT) is one of the most effective therapies for depression and has beneficial motor effects in parkinsonian patients. However, little is known about the mechanisms of therapeutic action of ECT for either condition. The aim of this work was to explore the impact of ECT on dopaminergic function in the striatum of non-human primates. Rhesus monkeys underwent a course of six ECT treatments under a human clinical protocol. Longitudinal effects on the dopaminergic nigrostriatal system were studied over 6 weeks using the in vivo capabilities of positron emission tomography (PET). PET scans were performed prior to the onset of ECT treatments and at 24-48 h, 8-10 days, and 6 weeks after the final ECT treatment. Early increases in dopamine transporter and vesicular monoamine transporter 2 binding returned to baseline levels by 6 weeks post-ECT. Transient increases in D1 receptor binding were also observed, whereas the binding potential to D2 receptors was unaltered. The increase in dopaminergic neurotransmission suggested by our results may account in part for the therapeutic effect of ECT in mood disorders and Parkinson's disease.
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Affiliation(s)
- Anne M Landau
- Aarhus PET Center and Center of Functionally Integrative Neuroscience, Aarhus University Hospital, Aarhus, Denmark,Department of Medicine/Neurology, University of British Columbia, Vancouver, BC, Canada
| | - M Mallar Chakravarty
- Aarhus PET Center and Center of Functionally Integrative Neuroscience, Aarhus University Hospital, Aarhus, Denmark,Rotman Research Institute, Baycrest Hospital and Mouse Imaging Centre, Sick Children's Hospital, Toronto, ON, Canada
| | - Campbell M Clark
- Department of Psychiatry, University of British Columbia, Vancouver, BC, Canada
| | - Athanasios P Zis
- Department of Psychiatry, University of British Columbia, Vancouver, BC, Canada
| | - Doris J Doudet
- Aarhus PET Center and Center of Functionally Integrative Neuroscience, Aarhus University Hospital, Aarhus, Denmark,Department of Medicine/Neurology, University of British Columbia, Vancouver, BC, Canada,Department of Medicine/Neurology, University of British Columbia, 2221 Wesbrook Mall, Purdy Pavilion M36, Vancouver, BC, V6T 2B5, Canada. Tel: +6 04 822 7163; Fax: +6 04 822 7866; E-mail:
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20
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Levodopa and pramipexole effects on presynaptic dopamine PET markers and estimated dopamine release. Eur J Nucl Med Mol Imaging 2010; 37:2364-70. [DOI: 10.1007/s00259-010-1581-3] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2010] [Accepted: 07/23/2010] [Indexed: 02/06/2023]
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21
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Elmenhorst D, Minuzzi L, Aliaga A, Rowley J, Massarweh G, Diksic M, Bauer A, Rosa-Neto P. In vivo and in vitro validation of reference tissue models for the mGluR(5) ligand [(11)C]ABP688. J Cereb Blood Flow Metab 2010; 30:1538-49. [PMID: 20531460 PMCID: PMC2949244 DOI: 10.1038/jcbfm.2010.65] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The primary objective of this study was to verify the suitability of reference tissue-based quantification methods of the metabotropic glutamate receptor type 5 (mGluR(5)) with [(11)C]ABP688. This study presents in vivo (Positron Emission Tomography (PET)) and in vitro (autoradiography) measurements of mGluR(5) densities in the same rats and evaluates both noninvasive and blood-dependent pharmacokinetic models for the quantification of [(11)C]ABP688 binding. Eleven rats underwent [(11)C]ABP688 PET scans. In five animals, baseline scans were compared with blockade experiments with the antagonist 1,2-methyl-6-(phenylethynyl)-pyridine (MPEP), and arterial blood samples were drawn and corrected for metabolites. Afterward, saturation-binding autoradiography was performed. Blocking with MPEP resulted in an average decrease of the total distribution volume (V(T)) between 43% and 58% (thalamus and caudate-putamen, respectively) but had no significant effect on cerebellar V(T) (mean reduction: -0.01%). Comparing binding potential (BP(ND)) based on the V(T) with noninvasively determined BP(ND) revealed an average negative bias of 0.7% in the caudate-putamen and an average positive bias of 3.1% in the low-binding regions. Scan duration of 50 minutes is required. The cerebellum is a suitable reference region for the quantification of mGluR(5) availability as measured with [(11)C]ABP688 PET in rats. Blood-based and reference region-based PET quantification shows a significant linear relationship to autoradiographic determinations.
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Affiliation(s)
- David Elmenhorst
- Institute of Neurosciences and Medicine, INM-2, Research Center Juelich, Juelich, Germany
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22
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Quantitative PET imaging of radioligands with slow kinetics in human brain. Eur J Nucl Med Mol Imaging 2010; 37:1613-5. [DOI: 10.1007/s00259-010-1518-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2010] [Accepted: 06/03/2010] [Indexed: 11/25/2022]
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23
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Topping GJ, Dinelle K, Kornelsen R, McCormick S, Holden JE, Sossi V. Positron emission tomography kinetic modeling algorithms for small animal dopaminergic system imaging. Synapse 2010; 64:200-8. [DOI: 10.1002/syn.20716] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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24
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Riss PJ, Debus F, Hummerich R, Schmidt U, Schloss P, Lueddens H, Roesch F. Ex vivo and in vivo evaluation of [18F]PR04.MZ in rodents: a selective dopamine transporter imaging agent. ChemMedChem 2009; 4:1480-7. [PMID: 19588472 DOI: 10.1002/cmdc.200900177] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
N-4-Fluorobut-2-yn-1-yl-2beta-carbomethoxy-3beta-phenyltropane (PR04.MZ) has been developed as dopamine transporter (DAT) ligand for molecular imaging. It contains a terminally fluorinated, conformationally constrained nitrogen substituent that is well suited for the introduction of fluorine-18. The present report describes the pharmacological characterisation of [18F]PR04.MZ. The ligand shows an IC50 value of 2 nM against human DAT, whereas the IC50 value against human serotonin transporter and human noradrenalin transporter are lower (110 nM and 22 nM, respectively). Furthermore, its ex vivo organ distribution, its binding profile in the rat brain and reversibility of binding were examined. A muPET study illuminates a fast kinetic profile and specific binding to rat DAT.
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Affiliation(s)
- Patrick J Riss
- Universität Mainz-Institut für Kernchemie, Fritz Strassmann Weg 2, 55128 Mainz, Germany.
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25
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Rishel MJ, Amarasinghe KKD, Dinn SR, Johnson BF. Asymmetric synthesis of tetrabenazine and dihydrotetrabenazine. J Org Chem 2009; 74:4001-4. [PMID: 19374381 DOI: 10.1021/jo900480n] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The enantioselective synthesis of (+)-tetrabenazine (TBZ) and (+)-dihydrotetrabenazine (DTBZ), agents of significant interest for therapeutic and molecular imaging applications, has been completed in 21% (TBZ) and 16% (DTBZ) overall yield and in >97% ee from the starting dihydroisoquinoline. The synthesis utilizes Sodeoka's palladium-catalyzed asymmetric malonate addition to set the initial stereocenter followed by a number of diastereoselective transformations to incorporate the remaining asymmetric centers.
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Affiliation(s)
- Michael J Rishel
- GE Global Research, One Research Circle, Niskayuna, New York 12309, USA.
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26
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Klein RL, Dayton RD, Terry TL, Vascoe C, Sunderland JJ, Tainter KH. PET imaging in rats to discern temporal onset differences between 6-hydroxydopamine and tau gene vector neurodegeneration models. Brain Res 2009; 1259:113-22. [PMID: 19368808 DOI: 10.1016/j.brainres.2009.01.063] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2008] [Revised: 01/27/2009] [Accepted: 01/29/2009] [Indexed: 10/21/2022]
Abstract
We attempted to monitor the nigrostriatal dopaminergic system in rats with positron emission tomography (PET) during the progression of two experimental disease states. One model was 6-hydroxydopamine (6-OHDA) lesioning and the other was direct gene transfer of the microtubule-associated protein tau to the substantia nigra using an adeno-associated virus vector (AAV9). The PET ligand was 6-[18F]fluoro-L-m-tyrosine (FMT), imaged prior to, and at two intervals after initiating dopaminergic neurodegeneration. The striatum was delineated with the aid of repeated PET imaging (FMT and sodium fluoride for bone), realignment to subsequent computed axial tomography scans, and registration to an atlas, which proved essential to tracking disease progression. The striata on the two sides of the brain were compared over time after unilateral lesioning treatments. 6-OHDA reduced uptake on the ipsilateral side relative to the untreated contralateral side at both 1 and 4 weeks after lesioning, while the AAV9 tau led to reduced uptake of the tracer in the striatum at 4 weeks, but not 1 week after treatment. The amplitude of the loss of FMT uptake in striatum at 4 weeks with either model was subtle relative to the postmortem histological analysis of the tissue, but the multi-modal imaging analysis yielded statistical effects that matched well with the histology in terms of the timing of the loss of dopaminergic markers. Live longitudinal imaging successfully tracked two distinct types of disease progression in individual rats, although the FMT is not a sensitive ligand to monitor the extent of the lesion.
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Affiliation(s)
- Ronald L Klein
- Department of Pharmacology, LSUHSC, Shreveport, LA 71130, USA.
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27
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Sossi V, Dinelle K, Topping GJ, Holden JE, Doudet D, Schulzer M, Ruth TJ, Stoessl AJ, de la Fuente-Fernandez R. Dopamine transporter relation to levodopa-derived synaptic dopamine in a rat model of Parkinson's: an in vivo imaging study. J Neurochem 2009; 109:85-92. [PMID: 19183257 DOI: 10.1111/j.1471-4159.2009.05904.x] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Studies showed that the dopamine (DA) transporter (DAT) modulates changes in levodopa-derived synaptic dopamine levels (Delta(DA)) in Parkinson's disease (PD). Here we evaluate the relationship between DAT and Delta(DA) in the 6-hydroxydopamine model of Parkinson's disease to investigate these mechanisms as a function of dopaminergic denervation and in relation to other denervation-induced regulatory changes. 27 rats with a unilateral 6-hydroxydopamine lesion (denervation approximately 20-97%) were imaged with (11)C-dihydrotetrabenazine (VMAT2 marker), (11)C-methylphenidate (DAT marker) and (11)C-raclopride (D2-type receptor marker). For denervation <75%Delta(DA) was significantly correlated with a combination of relatively preserved terminal density and lower DAT. For denervation <90%, Delta(DA) was significantly negatively correlated with DAT with a weaker dependence on VMAT2. For the entire data set, no dependence on pre-synaptic markers was observed; Delta(DA) was significantly positively correlated with (11)C-raclopride binding-derived estimates of DA loss. These findings parallel observations in humans, and show that (i) regulatory changes attempt to normalize synaptic DA levels (ii) a lesion-induced functional dependence of Delta(DA) on DAT occurs up to approximately 90% denervation (iii) for denervation < 75% relative lower DAT levels may relate to effective compensation; for higher denervation, lower DAT levels likely contribute to oscillations in synaptic DA associated with dyskinesias.
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Affiliation(s)
- Vesna Sossi
- Pacific Parkinson's Research Centre, Wesbrook Mall, Vancouver, British Columbia, Canada
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Increased vesicular monoamine transporter binding during early abstinence in human methamphetamine users: Is VMAT2 a stable dopamine neuron biomarker? J Neurosci 2008; 28:9850-6. [PMID: 18815269 DOI: 10.1523/jneurosci.3008-08.2008] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Animal data indicate that methamphetamine can damage striatal dopamine terminals. Efforts to document dopamine neuron damage in living brain of methamphetamine users have focused on the binding of [(11)C]dihydrotetrabenazine (DTBZ), a vesicular monoamine transporter (VMAT2) positron emission tomography (PET) radioligand, as a stable dopamine neuron biomarker. Previous PET data report a slight decrease in striatal [(11)C]DTBZ binding in human methamphetamine users after prolonged (mean, 3 years) abstinence, suggesting that the reduction would likely be substantial in early abstinence. We measured striatal VMAT2 binding in 16 recently withdrawn (mean, 19 d; range, 1-90 d) methamphetamine users and in 14 healthy matched-control subjects during a PET scan with (+)[(11)C]DTBZ. Unexpectedly, striatal (+)[(11)C]DTBZ binding was increased in methamphetamine users relative to controls (+22%, caudate; +12%, putamen; +11%, ventral striatum). Increased (+)[(11)C]DTBZ binding in caudate was most marked in methamphetamine users abstinent for 1-3 d (+41%), relative to the 7-21 d (+15%) and >21 d (+9%) groups. Above-normal VMAT2 binding in some drug users suggests that any toxic effect of methamphetamine on dopamine neurons might be masked by an increased (+)[(11)C]DTBZ binding and that VMAT2 radioligand binding might not be, as is generally assumed, a "stable" index of dopamine neuron integrity in vivo. One potential explanation for increased (+)[(11)C]DTBZ binding is that VMAT2 binding is sensitive to changes in vesicular dopamine storage levels, presumably low in drug users. If correct, (+)[(11)C]DTBZ might be a useful imaging probe to correlate changes in brain dopamine stores and behavior in users of methamphetamine.
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29
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Tupala E, Häkkinen M, Storvik M, Tiihonen J. Striatal dopaminergic terminals in type 1 and type 2 alcoholics measured with [3H]dihydrotetrabenazine and human whole hemisphere autoradiography. Psychiatry Res 2008; 163:70-5. [PMID: 18394867 DOI: 10.1016/j.pscychresns.2007.12.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/09/2007] [Revised: 07/18/2007] [Accepted: 12/03/2007] [Indexed: 10/22/2022]
Abstract
A number of studies have pointed to the importance of dopamine system in the context of alcoholism. Previous studies have shown lower dopamine transporter levels on late-onset Cloninger type 1 alcoholics. However, whether this lower level is due to a lower level of dopamine transporter protein or a lower level of dopaminergic nerve terminals remains unclear. The aim of this study was to compare putative alterations of dopaminergic terminals in caudate, putamen and nucleus accumbens of type 1 and type 2 alcoholics and healthy controls by using [(3)H]dihydrotetrabenazine as a radioligand in postmortem human whole hemisphere autoradiography. We compared the present results with the findings of our earlier studies on the dopamine transporter in these same subjects, demonstrating that alcoholics do not differ significantly from controls in striatal [(3)H]dihydrotetrabenazine binding. Although type 1 alcoholics have been reported to have up to 36% lower striatal dopamine transporter levels than controls, the results suggest that the density of their dopaminergic nerve terminals is not altered.
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Affiliation(s)
- Erkki Tupala
- Department of Forensic Psychiatry, University of Kuopio, Niuvanniemi Hospital, Kuopio, Finland
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30
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Strome EM, Doudet DJ. Animal Models of Neurodegenerative Disease: Insights from In vivo Imaging Studies. Mol Imaging Biol 2007; 9:186-95. [PMID: 17357857 DOI: 10.1007/s11307-007-0093-4] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Animal models have been used extensively to understand the etiology and pathophysiology of human neurodegenerative diseases, and are an essential component in the development of therapeutic interventions for these disorders. In recent years, technical advances in imaging modalities such as positron emission tomography (PET) and magnetic resonance imaging (MRI) have allowed the use of these techniques for the evaluation of functional, neurochemical, and anatomical changes in the brains of animals. Combining animal models of neurodegenerative disorders with neuroimaging provides a powerful tool to follow the disease process, to examine compensatory mechanisms, and to investigate the effects of potential treatments preclinically to derive knowledge that will ultimately inform our clinical decisions. This article reviews the literature on the use of PET and MRI in animal models of Parkinson's disease, Huntington's disease, and Alzheimer's disease, and evaluates the strengths and limitations of brain imaging in animal models of neurodegenerative diseases.
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Affiliation(s)
- Elissa M Strome
- Pacific Parkinson's Research Centre, University of British Columbia, Vancouver, Canada.
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