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Lillethorup TP, Noer O, Alstrup AKO, Real CC, Stokholm K, Thomsen MB, Zaer H, Orlowski D, Mikkelsen TW, Glud AN, Nielsen EHT, Schacht AC, Winterdahl M, Brooks DJ, Sørensen JCH, Landau AM. Spontaneous Partial Recovery of Striatal Dopaminergic Uptake Despite Nigral Cell Loss in Asymptomatic MPTP-Lesioned Female Minipigs. Neurotoxicology 2022; 91:166-176. [DOI: 10.1016/j.neuro.2022.05.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2022] [Revised: 04/06/2022] [Accepted: 05/09/2022] [Indexed: 11/16/2022]
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Cholinergic systems, attentional-motor integration, and cognitive control in Parkinson's disease. PROGRESS IN BRAIN RESEARCH 2022; 269:345-371. [PMID: 35248201 PMCID: PMC8957710 DOI: 10.1016/bs.pbr.2022.01.011] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Dysfunction and degeneration of CNS cholinergic systems is a significant component of multi-system pathology in Parkinson's disease (PD). We review the basic architecture of human CNS cholinergic systems and the tools available for studying changes in human cholinergic systems. Earlier post-mortem studies implicated abnormalities of basal forebrain corticopetal cholinergic (BFCC) and pedunculopontine-laterodorsal tegmental (PPN-LDT) cholinergic projections in cognitive deficits and gait-balance deficits, respectively. Recent application of imaging methods, particularly molecular imaging, allowed more sophisticated correlation of clinical features with regional cholinergic deficits. BFCC projection deficits correlate with general and domain specific cognitive deficits, particularly for attentional and executive functions. Detailed analyses suggest that cholinergic deficits within the salience and cingulo-opercular task control networks, including both neocortical, thalamic, and striatal nodes, are a significant component of cognitive deficits in non-demented PD subjects. Both BFCC and PPN-LDT cholinergic projection systems, and striatal cholinergic interneuron (SChI), abnormalities are implicated in PD gait-balance disorders. In the context of experimental studies, these results indicate that disrupted attentional functions of BFCC and PPN-LDT cholinergic systems underlie impaired gait-balance functions. SChI dysfunction likely impairs intra-striatal integration of attentional and motor information. Thalamic and entorhinal cortex cholinergic deficits may impair multi-sensory integration. Overt degeneration of CNS systems may be preceded by increased activity of cholinergic neurons compensating for nigrostriatal dopaminergic deficits. Subsequent dysfunction and degeneration of cholinergic systems unmasks and exacerbates functional deficits secondary to dopaminergic denervation. Research on CNS cholinergic systems dysfunctions in PD requires a systems-level approach to understanding PD pathophysiology.
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Tseng KY, Kuo TT, Wang V, Huang EYK, Ma KH, Olson L, Hoffer BJ, Chen YH. Tetrabenazine Mitigates Aberrant Release and Clearance of Dopamine in the Nigrostriatal System, and Alleviates L-DOPA-Induced Dyskinesia in a Mouse Model of Parkinson's Disease. JOURNAL OF PARKINSON'S DISEASE 2022; 12:1545-1565. [PMID: 35599497 DOI: 10.3233/jpd-223195] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
BACKGROUND L-DOPA-induced dyskinesia (LID), occurring with aberrant processing of exogenous L-DOPA in the dopamine-denervated striatum, is a main complication of levodopa treatment in Parkinson's disease. OBJECTIVE To characterize the effects of the vesicular antagonist tetrabenazine (TBZ) on L-DOPA-induced behavior, neurochemical signals, and underlying protein expressions in an animal model of Parkinson's disease. METHODS 20-week-old MitoPark mice were co-treated or separately administered TBZ and L-DOPA for 14 days. Abnormal involuntary movements (AIMs) and locomotor activity were analyzed. To explore dopamine (DA) transmission, fast scan cyclic voltammetry was used to assess presynaptic DA dynamics in striatal slices following treatments. PET imaging with 4-[18F]-PE2I, ADAM and immunoblotting assays were used to detect receptor protein changes in the DA-denervated striatum. Finally, nigrostriatal tissues were collected for HPLC measures of DA, serotonin and their metabolites. RESULTS A single injection of TBZ given in the interval between the two L-DOPA/Carbidopa treatments significantly attenuated L-DOPA-induced AIMs expression and locomotor hyperactivity. TBZ was shown to reduce tonic and phasic release of DA following L-DOPA treatment in DA-denervated striatal tissue. In the DA-depleted striatum, TBZ decreased the expression of L-DOPA-enhanced D1 receptors and the serotonin reuptake transporter. Neurochemical analysis indicated that TBZ attenuated L-DOPA-induced surges of DA levels by promoting DA turnover in the nigrostriatal system. CONCLUSIONS Our findings demonstrate that TBZ diminishes abnormal striatal DA transmission, which involves the ability of TBZ to modulate the presymptomatic dynamics of DA, and then mitigate aberrant release of exogenous L-DOPA from nerve terminals. The results support the potential of repositioning TBZ to counteract LID development.
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Affiliation(s)
- Kuan-Yin Tseng
- National Defense Medical Center, Taipei, Taiwan, R.O.C
- Department of Neurological Surgery, Tri-Service General Hospital, Taipei, Taiwan, R.O.C
| | - Tung-Tai Kuo
- Department of Neurological Surgery, Tri-Service General Hospital, Taipei, Taiwan, R.O.C
| | - Vicki Wang
- Ph.D. Program in Translational Medicine, National Defense Medical Center and Academia Sinica, Taipei, Taiwan
| | - Eagle Yi-Kung Huang
- Department of Pharmacology, National Defense Medical Center, Taipei, Taiwan, R.O.C
| | - Kuo-Hsing Ma
- Graduate Institute of Biology and Anatomy, National Defense Medical Center, Taipei, Taiwan, R.O.C
| | - Lars Olson
- Department of Neuroscience, Karolinska Institute, Stockholm, Sweden
| | - Barry J Hoffer
- Department of Neurosurgery, University Hospitals of Cleveland, Case Western Reserve University School of Medicine, Cleveland, OH, USA
| | - Yuan-Hao Chen
- National Defense Medical Center, Taipei, Taiwan, R.O.C
- Department of Neurological Surgery, Tri-Service General Hospital, Taipei, Taiwan, R.O.C
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Lohoff FW, Carr GV, Brookshire B, Ferraro TN, Lucki I. Deletion of the vesicular monoamine transporter 1 (vmat1/slc18a1) gene affects dopamine signaling. Brain Res 2019; 1712:151-157. [PMID: 30685272 DOI: 10.1016/j.brainres.2019.01.029] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2018] [Revised: 01/18/2019] [Accepted: 01/23/2019] [Indexed: 10/27/2022]
Abstract
The vesicular monoamine transporter is involved in presynaptic catecholamine storage and neurotransmission. Two isoforms of the transporter exist, VMAT1 and VMAT2, and both are expressed in the brain, though VMAT2 expression is more robust and has been more widely studied. In this study we investigated the role of VMAT1 KO on markers of dopaminergic function and neurotransmission, and dopamine-related behaviors. Null-mutant VMAT1 mice were studied behaviorally using the tail suspension test, elevated zero maze and locomotor activity assessments. Tissue monoamines were measured both ex vivo and by using in vivo microdialysis. Protein expression of tyrosine hydroxylase and D2 dopamine receptors was measured using western blot analysis. Results show that VMAT1 KO mice have decreased dopamine levels in the frontal cortex, increased postsynaptic D2 expression, and lower frontal cortex tyrosine hydroxylase expression compared to WT mice. VMAT1 KO mice also show an exaggerated behavioral locomotor response to acute amphetamine treatment. We conclude that dopaminergic signaling is robustly altered in the frontal cortex of VMAT1 null-mutant mice and suggest that VMAT1 may be relevant to the pathogenesis and/or treatment of psychiatric illnesses including schizophrenia and bipolar disease.
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Affiliation(s)
- Falk W Lohoff
- Section on Clinical Genomics and Experimental Therapeutics, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, MD, USA.
| | - Gregory V Carr
- Lieber Institute for Brain Development, Baltimore, MD, USA; Department of Pharmacology and Molecular Sciences, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Bethany Brookshire
- Center for Neurobiology and Behavior, Department of Psychiatry, University of Pennsylvania School of Medicine Translational Research Laboratories, Philadelphia, PA, USA
| | - Thomas N Ferraro
- Department of Biomedical Sciences, Rowan University, Camden, NJ, USA
| | - Irwin Lucki
- Department of Pharmacology, Uniformed Services University, Bethesda, MD, USA
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5
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Lillethorup TP, Glud AN, Alstrup AKO, Noer O, Nielsen EHT, Schacht AC, Landeck N, Kirik D, Orlowski D, Sørensen JCH, Doudet DJ, Landau AM. Longitudinal monoaminergic PET imaging of chronic proteasome inhibition in minipigs. Sci Rep 2018; 8:15715. [PMID: 30356172 PMCID: PMC6200778 DOI: 10.1038/s41598-018-34084-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2018] [Accepted: 10/11/2018] [Indexed: 02/08/2023] Open
Abstract
Impairment of the ubiquitin proteasome system has been implicated in Parkinson’s disease. We used positron emission tomography to investigate longitudinal effects of chronic intracerebroventricular exposure to the proteasome inhibitor lactacystin on monoaminergic projections and neuroinflammation. Göttingen minipigs were implanted in the cisterna magna with a catheter connected to a subcutaneous injection port. Minipigs were imaged at baseline and after cumulative doses of 200 and 400 μg lactacystin, respectively. Main radioligands included [11C]-DTBZ (vesicular monoamine transporter type 2) and [11C]-yohimbine (α2-adrenoceptor). [11C]-DASB (serotonin transporter) and [11C]-PK11195 (activated microglia) became available later in the study and we present their results in a smaller subset of animals for information purposes only. Striatal [11C]-DTBZ binding potentials decreased significantly by 16% after 200 μg compared to baseline, but the decrease was not sustained after 400 μg (n = 6). [11C]-yohimbine volume of distribution increased by 18–25% in the pons, grey matter and the thalamus after 200 μg, which persisted at 400 μg (n = 6). In the later subset of minipigs, we observed decreased [11C]-DASB (n = 5) and increased [11C]-PK11195 (n = 3) uptake after 200 μg. These changes may mimic monoaminergic changes and compensatory responses in early Parkinson’s disease.
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Affiliation(s)
- Thea P Lillethorup
- Department of Nuclear Medicine and PET Center, Department of Clinical Medicine, Aarhus University and Hospital, Aarhus, Denmark
| | - Andreas N Glud
- Center for Experimental Neuroscience (CENSE), Department of Clinical Medicine, Aarhus University, Aarhus, Denmark
| | - Aage K O Alstrup
- Department of Nuclear Medicine and PET Center, Department of Clinical Medicine, Aarhus University and Hospital, Aarhus, Denmark
| | - Ove Noer
- Department of Nuclear Medicine and PET Center, Department of Clinical Medicine, Aarhus University and Hospital, Aarhus, Denmark
| | - Erik H T Nielsen
- Department of Nuclear Medicine and PET Center, Department of Clinical Medicine, Aarhus University and Hospital, Aarhus, Denmark
| | - Anna C Schacht
- Department of Nuclear Medicine and PET Center, Department of Clinical Medicine, Aarhus University and Hospital, Aarhus, Denmark
| | - Natalie Landeck
- Brain Repair and Imaging in Neural Systems (BRAINS) Unit, Department of Experimental Medical Science, Lund University, Lund, Sweden
| | - Deniz Kirik
- Brain Repair and Imaging in Neural Systems (BRAINS) Unit, Department of Experimental Medical Science, Lund University, Lund, Sweden
| | - Dariusz Orlowski
- Center for Experimental Neuroscience (CENSE), Department of Clinical Medicine, Aarhus University, Aarhus, Denmark
| | - Jens Christian H Sørensen
- Center for Experimental Neuroscience (CENSE), Department of Clinical Medicine, Aarhus University, Aarhus, Denmark
| | - Doris J Doudet
- Department of Medicine/Neurology, University of British Columbia, Vancouver, BC, Canada
| | - Anne M Landau
- Department of Nuclear Medicine and PET Center, Department of Clinical Medicine, Aarhus University and Hospital, Aarhus, Denmark. .,Translational Neuropsychiatry Unit, Department of Clinical Medicine, Aarhus University, Aarhus, Denmark.
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Emamzadeh FN, Surguchov A. Parkinson's Disease: Biomarkers, Treatment, and Risk Factors. Front Neurosci 2018; 12:612. [PMID: 30214392 PMCID: PMC6125353 DOI: 10.3389/fnins.2018.00612] [Citation(s) in RCA: 276] [Impact Index Per Article: 46.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2018] [Accepted: 08/13/2018] [Indexed: 12/14/2022] Open
Abstract
Parkinson's disease (PD) is a progressive neurodegenerative disorder caused mainly by lack of dopamine in the brain. Dopamine is a neurotransmitter involved in movement, motivation, memory, and other functions; its level is decreased in PD brain as a result of dopaminergic cell death. Dopamine loss in PD brain is a cause of motor deficiency and, possibly, a reason of the cognitive deficit observed in some PD patients. PD is mostly not recognized in its early stage because of a long latency between the first damage to dopaminergic cells and the onset of clinical symptoms. Therefore, it is very important to find reliable molecular biomarkers that can distinguish PD from other conditions, monitor its progression, or give an indication of a positive response to a therapeutic intervention. PD biomarkers can be subdivided into four main types: clinical, imaging, biochemical, and genetic. For a long time protein biomarkers, dopamine metabolites, amino acids, etc. in blood, serum, cerebrospinal liquid (CSF) were considered the most promising. Among the candidate biomarkers that have been tested, various forms of α-synuclein (α-syn), i.e., soluble, aggregated, post-translationally modified, etc. were considered potentially the most efficient. However, the encouraging recent results suggest that microRNA-based analysis may bring considerable progress, especially if it is combined with α-syn data. Another promising analysis is the advanced metabolite profiling of body fluids, called "metabolomics" which may uncover metabolic fingerprints specific for various stages of PD. Conventional pharmacological treatment of PD is based on the replacement of dopamine using dopamine precursors (levodopa, L-DOPA, L-3,4 dihydroxyphenylalanine), dopamine agonists (amantadine, apomorphine) and MAO-B inhibitors (selegiline, rasagiline), which can be used alone or in combination with each other. Potential risk factors include environmental toxins, drugs, pesticides, brain microtrauma, focal cerebrovascular damage, and genomic defects. This review covers molecules that might act as the biomarkers of PD. Then, PD risk factors (including genetics and non-genetic factors) and PD treatment options are discussed.
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Affiliation(s)
- Fatemeh N. Emamzadeh
- Division of Biomedical and Life Sciences, Faculty of Health and Medicine, University of Lancaster, Lancaster, United Kingdom
| | - Andrei Surguchov
- Department of Neurology, Kansas University Medical Center, Kansas City, KS, United States
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Lillethorup TP, Glud AN, Alstrup AKO, Mikkelsen TW, Nielsen EH, Zaer H, Doudet DJ, Brooks DJ, Sørensen JCH, Orlowski D, Landau AM. Nigrostriatal proteasome inhibition impairs dopamine neurotransmission and motor function in minipigs. Exp Neurol 2018; 303:142-152. [PMID: 29428213 DOI: 10.1016/j.expneurol.2018.02.005] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2017] [Revised: 01/29/2018] [Accepted: 02/06/2018] [Indexed: 01/09/2023]
Abstract
Parkinson's disease (PD) is characterized by degeneration of dopaminergic neurons in the substantia nigra leading to slowness and stiffness of limb movement with rest tremor. Using ubiquitin proteasome system inhibitors, rodent models have shown nigrostriatal degeneration and motor impairment. We translated this model to the Göttingen minipig by administering lactacystin into the medial forebrain bundle (MFB). Minipigs underwent positron emission tomography (PET) imaging with (+)-α-[11C]dihydrotetrabenazine ([11C]DTBZ), a marker of vesicular monoamine transporter 2 availability, at baseline and three weeks after the unilateral administration of 100 μg lactacystin into the MFB. Compared to their baseline values, minipigs injected with lactacystin showed on average a 36% decrease in ipsilateral striatal binding potential corresponding to impaired presynaptic dopamine terminals. Behaviourally, minipigs displayed asymmetrical motor disability with spontaneous rotations in one of the animals. Immunoreactivity for tyrosine hydroxylase (TH) and HLA-DR-positive microglia confirmed asymmetrical reduction in nigral TH-positive neurons with an inflammatory response in the lactacystin-injected minipigs. In conclusion, direct injection of lactacystin into the MFB of minipigs provides a model of PD with reduced dopamine neurotransmission, TH-positive neuron reduction, microglial activation and behavioural deficits. This large animal model could be useful in studies of symptomatic and neuroprotective therapies with translatability to human PD.
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Affiliation(s)
- Thea P Lillethorup
- Department of Nuclear Medicine and PET Center, Institute of Clinical Medicine, Aarhus University and Hospital, Denmark
| | - Andreas N Glud
- Center for Experimental Neuroscience (CENSE), Department of Neurosurgery, Institute of Clinical Medicine, Aarhus University, Denmark
| | - Aage K O Alstrup
- Department of Nuclear Medicine and PET Center, Institute of Clinical Medicine, Aarhus University and Hospital, Denmark
| | - Trine W Mikkelsen
- Center for Experimental Neuroscience (CENSE), Department of Neurosurgery, Institute of Clinical Medicine, Aarhus University, Denmark
| | - Erik H Nielsen
- Department of Nuclear Medicine and PET Center, Institute of Clinical Medicine, Aarhus University and Hospital, Denmark
| | - Hamed Zaer
- Center for Experimental Neuroscience (CENSE), Department of Neurosurgery, Institute of Clinical Medicine, Aarhus University, Denmark
| | - Doris J Doudet
- Department of Medicine/Neurology, University of British Columbia, Vancouver, BC, Canada
| | - David J Brooks
- Department of Nuclear Medicine and PET Center, Institute of Clinical Medicine, Aarhus University and Hospital, Denmark; Division of Neuroscience, Department of Medicine, Imperial College London, UK; Division of Neuroscience, Newcastle University, UK
| | - Jens Christian H Sørensen
- Center for Experimental Neuroscience (CENSE), Department of Neurosurgery, Institute of Clinical Medicine, Aarhus University, Denmark
| | - Dariusz Orlowski
- Center for Experimental Neuroscience (CENSE), Department of Neurosurgery, Institute of Clinical Medicine, Aarhus University, Denmark
| | - Anne M Landau
- Department of Nuclear Medicine and PET Center, Institute of Clinical Medicine, Aarhus University and Hospital, Denmark; Translational Neuropsychiatry Unit, Institute of Clinical Medicine, Aarhus University, Denmark.
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8
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Kish SJ, Boileau I, Callaghan RC, Tong J. Brain dopamine neurone 'damage': methamphetamine users vs. Parkinson's disease - a critical assessment of the evidence. Eur J Neurosci 2017; 45:58-66. [PMID: 27519465 PMCID: PMC5209286 DOI: 10.1111/ejn.13363] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2016] [Revised: 07/28/2016] [Accepted: 08/09/2016] [Indexed: 12/31/2022]
Abstract
The objective of this review is to evaluate the evidence that recreational methamphetamine exposure might damage dopamine neurones in human brain, as predicted by experimental animal findings. Brain dopamine marker data in methamphetamine users can now be compared with those in Parkinson's disease, for which the Oleh Hornykiewicz discovery in Vienna of a brain dopamine deficiency is established. Whereas all examined striatal (caudate and putamen) dopamine neuronal markers are decreased in Parkinson's disease, levels of only some (dopamine, dopamine transporter) but not others (dopamine metabolites, synthetic enzymes, vesicular monoamine transporter 2) are below normal in methamphetamine users. This suggests that loss of dopamine neurones might not be characteristic of methamphetamine exposure in at least some human drug users. In methamphetamine users, dopamine loss was more marked in caudate than in putamen, whereas in Parkinson's disease, the putamen is distinctly more affected. Substantia nigra loss of dopamine-containing cell bodies is characteristic of Parkinson's disease, but similar neuropathological studies have yet to be conducted in methamphetamine users. Similarly, it is uncertain whether brain gliosis, a common feature of brain damage, occurs after methamphetamine exposure in humans. Preliminary epidemiological findings suggest that methamphetamine use might increase risk of subsequent development of Parkinson's disease. We conclude that the available literature is insufficient to indicate that recreational methamphetamine exposure likely causes loss of dopamine neurones in humans but does suggest presence of a striatal dopamine deficiency that, in principle, could be corrected by dopamine substitution medication if safety and subject selection considerations can be resolved.
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Affiliation(s)
- Stephen J. Kish
- Human Brain Laboratory, Research Imaging Centre, Centre for Addiction and Mental Health, Toronto, Ontario, Canada
| | - Isabelle Boileau
- Addiction Imaging Research Group, Campbell Family Mental Health Research Institute, Centre for Addiction and Mental Health, Toronto, Ontario, Canada
| | - Russell C. Callaghan
- Northern Medical Program, University of Northern British Columbia (UNBC), Prince George, British Columbia, Canada
| | - Junchao Tong
- Human Brain Laboratory, Research Imaging Centre, Centre for Addiction and Mental Health, Toronto, Ontario, Canada
- Addiction Imaging Research Group, Campbell Family Mental Health Research Institute, Centre for Addiction and Mental Health, Toronto, Ontario, Canada
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Asser A, Kõks S, Snellman A, Haaparanta-Solin M, Arponen E, Grönroos T, Nairismägi J, Bergquist J, Soomets U, Piip P, Eltermaa M, Sauk M, Lindmäe H, Rinne JO, Taba P. Increased striatal VMAT2 binding in mice after chronic administration of methcathinone and manganese. Brain Res 2016; 1652:97-102. [PMID: 27693414 DOI: 10.1016/j.brainres.2016.09.034] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2016] [Revised: 09/24/2016] [Accepted: 09/26/2016] [Indexed: 11/30/2022]
Abstract
Intravenous use of a psychostimulant drug containing methcathinone (ephedrone) and manganese causes an irreversible extrapyramidal syndrome in drug abusers. We aimed to reproduce the syndrome in mice to evaluate dopaminergic damage. C57/B6 mice were intraperitoneally injected once a day with the study drug or saline for a period of 27 weeks. Motor activity was recorded in an automated motility-box. After 13 and 27 weeks of treatment, ex vivo digital autoradiography was performed using [11C]dihydrotetrabenazine ([11C]DTBZ). After 27 weeks of treatment [11C]DTBZ autoradiography demonstrated a significant increase in the striatum-to-cerebellum binding ratio compared with saline treated controls. At the same time point, there was no evident change in motor activity. Increased [11C]DTBZ binding may indicate vesicular monoamine transporter type 2 (VMAT2) function is altered. The lack of extrapyramidal symptoms in animals could be attributed to low dosing regimen or high metabolic rate.
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Affiliation(s)
- Andres Asser
- Department of Neurology and Neurosurgery, University of Tartu, Tartu, Estonia
| | - Sulev Kõks
- Department of Pathophysiology, University of Tartu, Tartu, Estonia
| | | | | | | | - Tove Grönroos
- Turku PET Centre, University of Turku, Turku, Finland
| | - Jaak Nairismägi
- Institute of Gene Technology, Tallinn Technical University, Tallinn, Estonia
| | - Jonas Bergquist
- Department of Chemistry, Uppsala University, Uppsala, Sweden
| | - Ursel Soomets
- Department of Biochemistry, University of Tartu, Tartu, Estonia
| | - Piret Piip
- Department of Neurology and Neurosurgery, University of Tartu, Tartu, Estonia
| | - Mall Eltermaa
- Department of Neurology and Neurosurgery, University of Tartu, Tartu, Estonia
| | - Martin Sauk
- Department of Neurology and Neurosurgery, University of Tartu, Tartu, Estonia
| | - Hanna Lindmäe
- Department of Neurology and Neurosurgery, University of Tartu, Tartu, Estonia
| | - Juha O Rinne
- Turku PET Centre, University of Turku, Turku, Finland; Department of Neurology, Turku University Hospital, Turku, Finland
| | - Pille Taba
- Department of Neurology and Neurosurgery, University of Tartu, Tartu, Estonia.
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Huang ZR, Tsai CL, Huang YY, Shiue CY, Tzen KY, Yen RF, Hsin LW. A Novel Potential Positron Emission Tomography Imaging Agent for Vesicular Monoamine Transporter Type 2. PLoS One 2016; 11:e0161295. [PMID: 27612194 PMCID: PMC5017712 DOI: 10.1371/journal.pone.0161295] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2016] [Accepted: 07/06/2016] [Indexed: 12/02/2022] Open
Abstract
In the early 1990s, 9-(+)-11C-dihydrotetrabenazine (9-(+)-11C-DTBZ) was shown to be a useful positron emission tomography (PET) imaging agent for various neurodegenerative disorders. Here, we described the radiosynthesis and evaluation of the 9-(+)-11C-DTBZ analog, 10-(+)-11C-DTBZ, as a vesicular monoamine transporter 2 (VMAT2) imaging agent and compare it with 9-(+)-11C-DTBZ. 10-(+)-11C-DTBZ was obtained by 11C-MeI methylation with its 10 hydroxy precursor in the presence of 5 M NaOH. It had a slightly better average radiochemical yield of 35.3 ± 3.6% (decay-corrected to end of synthesis (EOS)) than did 9-(+)-11C-DTBZ (30.5 ± 2.3%). MicroPET studies showed that 10-(+)-11C-DTBZ had a striatum-to-cerebellum ratio of 3.74 ± 0.21 at 40 min post-injection, while the ratio of 9-(+)-11C-DTBZ was 2.50 ± 0.33. This indicated that 10-(+)-11C-DTBZ has a higher specific uptake in VMAT2-rich brain regions, and 10-(+)-11C-DTBZ may be a potential VMAT2 radioligand. Our experiment is the first study of 10-(+)-11C-DTBZ to include dynamic brain distribution in rat brains.
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Affiliation(s)
- Zih-Rou Huang
- School of Pharmacy, College of Medicine, National Taiwan University, Taipei, Taiwan
| | - Chia-Ling Tsai
- PET Center, Department of Nuclear Medicine, National Taiwan University Hospital, Taipei, Taiwan
| | - Ya-Yao Huang
- PET Center, Department of Nuclear Medicine, National Taiwan University Hospital, Taipei, Taiwan
| | - Chyng-Yann Shiue
- PET Center, Department of Nuclear Medicine, National Taiwan University Hospital, Taipei, Taiwan
- Molecular Imaging Center, National Taiwan University, Taipei, Taiwan
- PET Center, Department of Nuclear Medicine, Tri-Service General Hospital, Taipei, Taiwan
| | - Kai-Yuan Tzen
- PET Center, Department of Nuclear Medicine, National Taiwan University Hospital, Taipei, Taiwan
| | - Ruoh-Fang Yen
- PET Center, Department of Nuclear Medicine, National Taiwan University Hospital, Taipei, Taiwan
- Molecular Imaging Center, National Taiwan University, Taipei, Taiwan
| | - Ling-Wei Hsin
- School of Pharmacy, College of Medicine, National Taiwan University, Taipei, Taiwan
- Molecular Imaging Center, National Taiwan University, Taipei, Taiwan
- Center for Innovative Therapeutics Discovery, National Taiwan University, Taipei, Taiwan
- * E-mail:
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Rapid Recovery of Vesicular Dopamine Levels in Methamphetamine Users in Early Abstinence. Neuropsychopharmacology 2016; 41:1179-87. [PMID: 26321315 PMCID: PMC4748442 DOI: 10.1038/npp.2015.267] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/08/2015] [Revised: 07/30/2015] [Accepted: 08/21/2015] [Indexed: 11/08/2022]
Abstract
We previously reported very low levels of dopamine in post-mortem striatum of chronic methamphetamine users, raising the possibility that restoration of normal dopamine levels could help in this addiction and perhaps prevent early relapse. To establish relevance of this finding to the living brain, we tested whether striatal [(11)C]-(+)-dihydrotetrabenazine binding, a vesicular monoamine transporter probe sensitive to changes in (stored) vesicular dopamine, is elevated in methamphetamine users. Chronic methamphetamine users underwent [(11)C]-(+)-dihydrotetrabenazine positron emission tomography scans during early (mean 2.6 days) and later (~10 days) abstinence. Striatal [(11)C]-(+)-dihydrotetrabenazine binding was elevated (suggesting low stored dopamine) in methamphetamine users (n=28; 2.6 days after last use) relative to controls (n=22) (+28%, p<0.0001) and correlated with severity and recency of drug use and with cognitive impairment and withdrawal symptoms. Mean [(11)C]-(+)-dihydrotetrabenazine binding levels in the subgroup of methamphetamine users who could remain abstinent ~10 days following last use (n=17) were normal at the follow-up scan. Our imaging data support post-mortem findings and suggest that chronic methamphetamine users have low brain levels of stored dopamine during very early abstinence from MA, which could contribute to behavioral and cognitive deficits. Findings also suggest a rapid recovery of stored dopamine in some methamphetamine users who become abstinent and who therefore might not benefit from dopamine replacement medication (eg, levodopa). Further study is necessary to establish whether those users who could not maintain abstinence for the second scan might have a more severe and persistent dopamine deficiency and who could benefit from this medication.
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Algarni MA, Stoessl AJ. The role of biomarkers and imaging in Parkinson’s disease. Expert Rev Neurother 2016; 16:187-203. [DOI: 10.1586/14737175.2016.1135056] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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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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Chen Z, Tang J, Liu C, Li X, Huang H, Xu X, Yu H. Effects of anesthetics on vesicular monoamine transporter type 2 binding to ¹⁸F-FP-(+)-DTBZ: a biodistribution study in rat brain. Nucl Med Biol 2015; 43:124-129. [PMID: 26526872 DOI: 10.1016/j.nucmedbio.2015.09.009] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2015] [Revised: 09/14/2015] [Accepted: 09/28/2015] [Indexed: 11/30/2022]
Abstract
OBJECTIVES The in vivo binding analysis of vesicular monoamine transporter type 2 (VMAT2) to radioligand has provided a means of investigating related disorders. Anesthesia is often inevitable when the investigations are performed in animals. In the present study, we tested effects of four commonly-used anesthetics: isoflurane, pentobarbital, chloral hydrate and ketamine, on in vivo VMAT2 binding to (18)F-FP-(+)-DTBZ, a specific VMAT2 radioligand, in rat brain. METHODS The transient equilibrium time window for in vivo binding of (18)F-FP-(+)-DTBZ after a bolus injection was firstly determined. The brain biodistribution studies under anesthetized and awake rats were then performed at the equilibrium time. Standard uptake values (SUVs) of the interest brain regions: the striatum (ST), hippocampus (HP), cortex (CX) and cerebellum (CB) were obtained; and ratios of tissue to cerebellum were calculated. RESULTS Isoflurane and pentobarbital did not alter distribution of (18)F-FP-(+)-DTBZ in the brain relative to the awake group; neither SUVs nor ratios of ST/CB and HP/CB were altered significantly. Chloral hydrate significantly increased SUVs of all the brain regions, but did not significantly alter ratios of ST/CB and HP/CB. Ketamine significantly increased SUVs of the striatum, hippocampus and cortex, and insignificantly increased the SUV of the cerebellum; consequently, ketamine significantly increased ratios of ST/CB and HP/CB. CONCLUSIONS It is concluded that in vivo VMAT2 binding to (18)F-FP-(+)-DTBZ are not altered by isoflurane and pentobarbital, but altered by chloral hydrate and ketamine. Isoflurane and pentobarbital may be promising anesthetic compounds for investigating in vivo VMAT2 binding. Further studies are warranted to investigate the interactions of anesthetics with VMAT2 binding potential with in vivo PET studies.
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Affiliation(s)
- Zhengping Chen
- Key Laboratory of Nuclear Medicine, Ministry of Health, Jiangsu Key Laboratory of Molecular Nuclear Medicine, Jiangsu Institute of Nuclear Medicine, Wuxi, Jiangsu, China, 214063.
| | - Jie Tang
- Key Laboratory of Nuclear Medicine, Ministry of Health, Jiangsu Key Laboratory of Molecular Nuclear Medicine, Jiangsu Institute of Nuclear Medicine, Wuxi, Jiangsu, China, 214063
| | - Chunyi Liu
- Key Laboratory of Nuclear Medicine, Ministry of Health, Jiangsu Key Laboratory of Molecular Nuclear Medicine, Jiangsu Institute of Nuclear Medicine, Wuxi, Jiangsu, China, 214063
| | - Xiaomin Li
- Key Laboratory of Nuclear Medicine, Ministry of Health, Jiangsu Key Laboratory of Molecular Nuclear Medicine, Jiangsu Institute of Nuclear Medicine, Wuxi, Jiangsu, China, 214063
| | - Hongbo Huang
- Key Laboratory of Nuclear Medicine, Ministry of Health, Jiangsu Key Laboratory of Molecular Nuclear Medicine, Jiangsu Institute of Nuclear Medicine, Wuxi, Jiangsu, China, 214063
| | - Xijie Xu
- Key Laboratory of Nuclear Medicine, Ministry of Health, Jiangsu Key Laboratory of Molecular Nuclear Medicine, Jiangsu Institute of Nuclear Medicine, Wuxi, Jiangsu, China, 214063
| | - Huixin Yu
- Key Laboratory of Nuclear Medicine, Ministry of Health, Jiangsu Key Laboratory of Molecular Nuclear Medicine, Jiangsu Institute of Nuclear Medicine, Wuxi, Jiangsu, China, 214063
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15
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Narendran R, Jedema HP, Lopresti BJ, Mason NS, Himes ML, Bradberry CW. Decreased vesicular monoamine transporter type 2 availability in the striatum following chronic cocaine self-administration in nonhuman primates. Biol Psychiatry 2015; 77:488-92. [PMID: 25062684 PMCID: PMC4275417 DOI: 10.1016/j.biopsych.2014.06.012] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/21/2014] [Revised: 05/13/2014] [Accepted: 06/11/2014] [Indexed: 12/16/2022]
Abstract
BACKGROUND Consistent with postmortem data, in a recent positron emission tomography study, we demonstrated less [(11)C]-(+)-dihydrotetrabenazine ([(11)C]DTBZ) binding to striatal vesicular monoamine transporter type 2 (VMAT2) in cocaine abusers compared with control subjects. A major limitation of these between-group comparison human studies is their inability to establish a causal relationship between cocaine abuse and lower VMAT2. Furthermore, studies in rodents that evaluated VMAT2 binding before and after cocaine self-administration do not support a reduction in VMAT2. METHODS To clarify these discrepant VMAT2 findings and attribute VMAT2 reduction to cocaine abuse, we imaged four rhesus monkeys with [(11)C]DTBZ positron emission tomography before and after 16 months of cocaine self-administration. [(11)C]DTBZ binding potential in the striatum was derived using the simplified reference tissue method with the occipital cortex time activity curve as an input function. RESULTS Chronic cocaine self-administration led to a significant (25.8 ± 7.8%) reduction in [(11)C]DTBZ binding potential. CONCLUSIONS In contrast to the cocaine rodent investigations that do not support alterations in VMAT2, these results in nonhuman primates clearly demonstrated a reduction in VMAT2 binding following prolonged exposure to cocaine. Lower VMAT2 implies that fewer dopamine storage vesicles are available in the presynaptic terminals for release, a likely factor contributing to decreased dopamine transmission in cocaine dependence. Future studies should attempt to clarify the clinical significance of lower VMAT2 in cocaine abusers, for example, its relationship to relapse and vulnerability to mood disorders.
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Affiliation(s)
- Rajesh Narendran
- Department of Radiology; Department of Psychiatry, University of Pittsburgh, Pittsburgh, Pennsylvania.
| | - Hank P. Jedema
- Department of Psychiatry, University of Pittsburgh, Pittsburgh, PA
| | | | | | - Michael L. Himes
- Department of Psychiatry, University of Pittsburgh, Pittsburgh, PA
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16
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Christopher L, Marras C, Duff-Canning S, Koshimori Y, Chen R, Boileau I, Segura B, Monchi O, Lang AE, Rusjan P, Houle S, Strafella AP. Combined insular and striatal dopamine dysfunction are associated with executive deficits in Parkinson's disease with mild cognitive impairment. ACTA ACUST UNITED AC 2013; 137:565-75. [PMID: 24334314 DOI: 10.1093/brain/awt337] [Citation(s) in RCA: 111] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The ability to dynamically use various aspects of cognition is essential to daily function, and reliant on dopaminergic transmission in cortico-striatal circuitry. Our aim was to investigate both striatal and cortical dopaminergic changes in patients with Parkinson's disease with mild cognitive impairment, who represent a vulnerable group for the development of dementia. We hypothesized severe striatal dopamine denervation in the associative (i.e. cognitive) region and cortical D2 receptor abnormalities in the salience and executive networks in Parkinson's disease with mild cognitive impairment compared with cognitively normal patients with Parkinson's disease and healthy control subjects. We used positron emission tomography imaging with dopaminergic ligands (11)C-dihydrotetrabenazine, to investigate striatal dopamine neuron integrity in the associative subdivision and (11)C-FLB 457, to investigate cortical D2 receptor availability in patients with Parkinson's disease (55-80 years of age) with mild cognitive impairment (n = 11), cognitively normal patients with Parkinson's disease (n = 11) and age-matched healthy control subjects (n = 14). Subjects were administered a neuropsychological test battery to assess cognitive status and determine the relationship between dopaminergic changes and cognitive performance. We found that patients with mild cognitive impairment had severe striatal dopamine depletion in the associative (i.e. cognitive) subdivision as well as reduced D2 receptor availability in the bilateral insula, a key cognitive hub, compared to cognitively normal patients and healthy subjects after controlling for age, disease severity and daily dopaminergic medication intake. Associative striatal dopamine depletion was predictive of D2 receptor loss in the insula of patients with Parkinson's disease with mild cognitive impairment, demonstrating interrelated striatal and cortical changes. Insular D2 levels also predicted executive abilities in these patients as measured using a composite executive z-score obtained from neuropsychological testing. Furthermore we assessed cortical thickness to ensure that D2 receptor changes were not confounded by brain atrophy. There was no difference between groups in cortical thickness in the insula, or any other cortical region of interest. These findings suggest that striatal dopamine denervation combined with insular D2 receptor loss underlie mild cognitive impairment in Parkinson's disease and in particular decline in executive function. Furthermore, these findings suggest a crucial and direct role for dopaminergic modulation in the insula in facilitating cognitive function.
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Affiliation(s)
- Leigh Christopher
- 1 Morton and Gloria Shulman Movement Disorder Unit and E.J. Safra Parkinson Disease Program, Toronto Western Hospital, UHN, University of Toronto, Ontario, M5T 2S8, Canada
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Podurgiel S, Nunes E, Yohn S, Barber J, Thompson A, Milligan M, Lee C, López-Cruz L, Pardo M, Valverde O, Lendent C, Baqi Y, Müller C, Correa M, Salamone J. The vesicular monoamine transporter (VMAT-2) inhibitor tetrabenazine induces tremulous jaw movements in rodents: Implications for pharmacological models of parkinsonian tremor. Neuroscience 2013; 250:507-19. [DOI: 10.1016/j.neuroscience.2013.07.008] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2013] [Revised: 06/29/2013] [Accepted: 07/03/2013] [Indexed: 11/17/2022]
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Multani PK, Hodge R, Estévez MA, Abel T, Kung H, Alter M, Brookshire B, Lucki I, Nall AH, Talbot K, Doyle GA, Lohoff FW. VMAT1 deletion causes neuronal loss in the hippocampus and neurocognitive deficits in spatial discrimination. Neuroscience 2012. [PMID: 23201251 DOI: 10.1016/j.neuroscience.2012.11.023] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Vesicular monoamine transporters (VMAT) are involved in presynaptic storage and release of neurotransmitters. While it was thought initially that only VMAT2 is brain expressed and VMAT1 is present only in the periphery, recent data have challenged the exclusive expression of VMAT2 in the brain. To further elucidate the role of VMAT1 brain expression and its potential role in neuropsychiatric disorders, we have investigated mice lacking VMAT1. Comparison of wildtype and knock-out (KO) mice using qPCR and immunohistochemistry documents the expression of VMAT1 in the brain. Deletion of VMAT1 leads to increased hippocampal apoptosis and reduced neurogenesis as assessed by caspase-3-labeling and 5-bromo-deoxy-uridine-labeling. Behavioral data show that mice lacking VMAT1 have neurocognitive deficits. VMAT2 expression is not altered in VMAT1 KO mice, suggesting a distinct role of VMAT1. Our data support VMAT1 brain expression and suggest that VMAT1 plays a key role in survival of hippocampal neurons and thus might contribute to neurocognitive deficits observed in neuropsychiatric disorders.
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Affiliation(s)
- P K Multani
- Center for Neurobiology and Behavior, Department of Psychiatry, University of Pennsylvania School of Medicine, Translational Research Laboratories, Philadelphia, PA, USA
| | - R Hodge
- Center for Neurobiology and Behavior, Department of Psychiatry, University of Pennsylvania School of Medicine, Translational Research Laboratories, Philadelphia, PA, USA
| | - M A Estévez
- Department of Biology, University of Pennsylvania, Philadelphia, PA, USA
| | - T Abel
- Center for Neurobiology and Behavior, Department of Psychiatry, University of Pennsylvania School of Medicine, Translational Research Laboratories, Philadelphia, PA, USA; Department of Biology, University of Pennsylvania, Philadelphia, PA, USA
| | - H Kung
- Department of Radiology, University of Pennsylvania School of Medicine, Philadelphia, PA, USA
| | - M Alter
- Center for Neurobiology and Behavior, Department of Psychiatry, University of Pennsylvania School of Medicine, Translational Research Laboratories, Philadelphia, PA, USA
| | - B Brookshire
- Center for Neurobiology and Behavior, Department of Psychiatry, University of Pennsylvania School of Medicine, Translational Research Laboratories, Philadelphia, PA, USA
| | - I Lucki
- Center for Neurobiology and Behavior, Department of Psychiatry, University of Pennsylvania School of Medicine, Translational Research Laboratories, Philadelphia, PA, USA; Department of Pharmacology, University of Pennsylvania School of Medicine, Philadelphia, PA, USA
| | - A H Nall
- Center for Neurobiology and Behavior, Department of Psychiatry, University of Pennsylvania School of Medicine, Translational Research Laboratories, Philadelphia, PA, USA
| | - K Talbot
- Center for Neurobiology and Behavior, Department of Psychiatry, University of Pennsylvania School of Medicine, Translational Research Laboratories, Philadelphia, PA, USA
| | - G A Doyle
- Center for Neurobiology and Behavior, Department of Psychiatry, University of Pennsylvania School of Medicine, Translational Research Laboratories, Philadelphia, PA, USA
| | - F W Lohoff
- Center for Neurobiology and Behavior, Department of Psychiatry, University of Pennsylvania School of Medicine, Translational Research Laboratories, Philadelphia, PA, USA.
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Agarwal PA, Stoessl AJ. Biomarkers for trials of neuroprotection in Parkinson's disease. Mov Disord 2012; 28:71-85. [DOI: 10.1002/mds.25065] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2012] [Revised: 04/19/2012] [Accepted: 04/23/2012] [Indexed: 02/06/2023] Open
Affiliation(s)
- Pankaj A. Agarwal
- Pacific Parkinson's Research Centre; University of British Columbia; Vancouver; British Columbia; Canada
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Zhang J, Zhang X, Li Y, Tian J. Simple, rapid and reliable preparation of [¹¹C]-(+)-α-DTBZ of high quality for routine applications. Molecules 2012; 17:6697-704. [PMID: 22728363 PMCID: PMC6268919 DOI: 10.3390/molecules17066697] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2012] [Revised: 04/28/2012] [Accepted: 04/30/2012] [Indexed: 11/16/2022] Open
Abstract
[¹¹C]-(+)-α-DTBZ has been used as a marker of dopaminergic terminal densities in human striatum and expressed in islet beta cells in the pancreas. We aimed to establish a fully automated and simple procedure for the synthesis of [¹¹C]-(+)-α-DTBZ for routine applications. [¹¹C]-(+)-α-DTBZ was synthesized from a 9-hydroxy precursor in acetone and potassium hydroxide with [¹¹C]-methyl triflate and was purified by solid phase extraction using a Vac tC-18 cartridge. Radiochemical yields based on [¹¹C]-methyl triflate (corrected for decay) were 82.3% ± 3.6%, with a specific radioactivity of 60 GBq/μmol. Time elapsed was less than 20 min from end of bombardment to release of the product for quality control.
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Affiliation(s)
- Jinming Zhang
- Authors to whom correspondence should be addressed; (J.Z.); (J.T.)
| | | | | | - Jiahe Tian
- Authors to whom correspondence should be addressed; (J.Z.); (J.T.)
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21
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Landau AM, Clark C, Jivan S, Doudet DJ. Antiparkinsonian Mechanism of Electroconvulsive Therapy in MPTP-Lesioned Non-Human Primates. NEURODEGENER DIS 2012; 9:128-38. [DOI: 10.1159/000334497] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2011] [Accepted: 10/18/2011] [Indexed: 11/19/2022] Open
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Narendran R, Lopresti BJ, Martinez D, Mason NS, Himes M, May MA, Daley DC, Price JC, Mathis CA, Frankle WG. In vivo evidence for low striatal vesicular monoamine transporter 2 (VMAT2) availability in cocaine abusers. Am J Psychiatry 2012; 169:55-63. [PMID: 22193525 PMCID: PMC3405490 DOI: 10.1176/appi.ajp.2011.11010126] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
OBJECTIVE Positron emission tomography (PET) imaging studies in cocaine abusers have shown that low dopamine release in the striatum following an amphetamine challenge is associated with higher relapse rates. One possible mechanism that might lead to lower amphetamine-induced dopamine release is low availability of dopamine storage vesicles in the presynaptic terminals for release. Consistent with this hypothesis, postmortem studies have shown low levels of vesicular monoamine transporter, type 2 (VMAT2), the membrane protein that regulates the size of the vesicular dopamine pool, in cocaine abusers relative to healthy subjects. To confirm the postmortem findings, the authors used PET and the VMAT2 radioligand [¹¹C]-(+)-dihydrotetrabenazine (DTBZ) to assess the in vivo VMAT2 availability in a group of 12 recently abstinent cocaine-dependent subjects and matched healthy comparison subjects. METHOD [¹¹C]DTBZ nondisplaceable binding potential (BP(ND)) was measured by kinetic analysis using the arterial input function or, if arterial input was unavailable, by the simplified reference tissue method. RESULTS [¹¹C]DTBZ BP(ND) was significantly lower in the cocaine abusers than in the comparison subjects in the limbic striatum (10.0% lower), associative striatum (-13.4%), and sensorimotor striatum (-11.5%). CONCLUSIONS The results of this in vivo PET study confirm previous in vitro reports of low VMAT2 availability in the striatum of cocaine abusers. It also suggests a compensatory down-regulation of the dopamine storage vesicles in response to chronic cocaine abuse and/or a loss of dopaminergic terminals. Further research is necessary to understand the clinical relevance of this observation to relapse and outcome in abstinent cocaine abusers.
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Affiliation(s)
| | | | - Diana Martinez
- Department of Psychiatry, Columbia University Medical Center, New York
| | | | - Michael Himes
- Department of Radiology, University of Pittsburgh, Pittsburgh, PA
| | - Maureen A. May
- Department of Radiology, University of Pittsburgh, Pittsburgh, PA
| | - Dennis C. Daley
- Department of Psychiatry, University of Pittsburgh, Pittsburgh, PA
| | - Julie C. Price
- Department of Radiology, University of Pittsburgh, Pittsburgh, PA
| | | | - W. Gordon Frankle
- Department of Radiology, University of Pittsburgh, Pittsburgh, PA,Department of Psychiatry, University of Pittsburgh, Pittsburgh, PA
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Distribution of vesicular monoamine transporter 2 protein in human brain: implications for brain imaging studies. J Cereb Blood Flow Metab 2011; 31:2065-75. [PMID: 21522164 PMCID: PMC3208151 DOI: 10.1038/jcbfm.2011.63] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The choice of reference region in positron emission tomography (PET) human brain imaging of the vesicular monoamine transporter 2 (VMAT2), a marker of striatal dopamine innervation, has been arbitrary, with cerebellar, whole cerebral, frontal, or occipital cortices used. To establish whether levels of VMAT2 are in fact low in these cortical areas, we measured VMAT2 protein distribution by quantitative immunoblotting in autopsied normal human brain (n=6). Four or five species of VMAT2 immunoreactivity (75, 55, 52, 45, 35 kDa) were detected, which were all markedly reduced in intensity in nigrostriatal regions of patients with parkinsonian conditions versus matched controls (n=9 to 10 each). Using the intact VMAT2 immunoreactivity, cerebellar and cerebral neocortices had levels of the transporter >100-fold lower than the VMAT2-rich striatum and with no significant differences among the cortical regions. We conclude that human cerebellar and cerebral cortices contain negligible VMAT2 protein versus the striatum and, in this respect, all satisfy a criterion for a useful reference region for VMAT2 imaging. The slightly lower PET signal for VMAT2 binding in occipital (the currently preferred reference region) versus cerebellar cortex might not therefore be explained by differences in VMAT2 protein itself but possibly by other imaging variables, for example, partial volume effects.
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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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25
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Wimalasena K. Vesicular monoamine transporters: structure-function, pharmacology, and medicinal chemistry. Med Res Rev 2011; 31:483-519. [PMID: 20135628 PMCID: PMC3019297 DOI: 10.1002/med.20187] [Citation(s) in RCA: 119] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Vesicular monoamine transporters (VMAT) are responsible for the uptake of cytosolic monoamines into synaptic vesicles in monoaminergic neurons. Two closely related VMATs with distinct pharmacological properties and tissue distributions have been characterized. VMAT1 is preferentially expressed in neuroendocrine cells and VMAT2 is primarily expressed in the CNS. The neurotoxicity and addictive properties of various psychostimulants have been attributed, at least partly, to their interference with VMAT2 functions. The quantitative assessment of the VMAT2 density by PET scanning has been clinically useful for early diagnosis and monitoring of the progression of Parkinson's and Alzheimer's diseases and drug addiction. The classical VMAT2 inhibitor, tetrabenazine, has long been used for the treatment of chorea associated with Huntington's disease in the United Kingdom, Canada, and Australia, and recently approved in the United States. The VMAT2 imaging may also be useful for exploiting the onset of diabetes mellitus, as VMAT2 is also expressed in the β-cells of the pancreas. VMAT1 gene SLC18A1 is a locus with strong evidence of linkage with schizophrenia and, thus, the polymorphic forms of the VMAT1 gene may confer susceptibility to schizophrenia. This review summarizes the current understanding of the structure-function relationships of VMAT2, and the role of VMAT2 on addiction and psychostimulant-induced neurotoxicity, and the therapeutic and diagnostic applications of specific VMAT2 ligands. The evidence for the linkage of VMAT1 gene with schizophrenia and bipolar disorder I is also discussed.
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26
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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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27
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Abstract
Parkinson's disease (PD) is a common disorder in which the primary features can be related to dopamine deficiency. Changes on structural imaging are limited, but a wealth of abnormalities can be detected using positron emission tomography, single photon emission computed tomography, or functional magnetic resonance imaging to detect changes in neurochemical pathology or functional connectivity. The changes detected on these studies may reflect the disease process itself and/or compensatory responses to the disease, or they may arise in association with disease- and/or treatment-related complications. This review will focus mainly on neurochemical and metabolic studies and reviews various approaches to the assessment of dopaminergic function as well as the function of other neurotransmitters that may be affected in PD. A number of clinical applications are highlighted, including diagnostic utility, identification of preclinical disease, changes associated with motor and nonmotor complications of PD, and the effects of various therapeutic interventions.
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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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28
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Iritani S, Sekiguchi H, Habuchi C, Torii Y, Yamada S, Waki Y, Noda Y, Furukawa H, Nabeshima T, Ozaki N. Immunohistochemical study of vesicle monoamine transporter 2 in the hippocampal formation of PCP-treated mice. Neurosci Res 2010; 68:125-30. [DOI: 10.1016/j.neures.2010.06.005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2010] [Revised: 06/08/2010] [Accepted: 06/09/2010] [Indexed: 02/08/2023]
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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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Boileau I, Houle S, Rusjan PM, Furukawa Y, Wilkins D, Tong J, Selby P, Wilson AA, Kish SJ. Influence of a low dose of amphetamine on vesicular monoamine transporter binding: a PET (+)[11C]DTBZ study in humans. Synapse 2010; 64:417-20. [PMID: 20169578 DOI: 10.1002/syn.20743] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
We previously reported increased binding of (+)[11C]DTBZ (dihydrotetrabenazine), the vesicular monoamine transporter (VMAT2) positron emission tomography (PET) radioligand, in striatum of some methamphetamine users. This finding might be explained by stimulant-induced vesicular DA depletion resulting in decreased DA (+)[11C]DTBZ competition at VMAT2. In a prospective PET study, we now find that administration of an acute oral dose of amphetamine (0.4 mg/kg) to humans does not cause increased striatal (+)[11C]DTBZ binding but a slight 5% decrease. Our data suggest that a low amphetamine dose is unlikely to cause sufficient DA depletion to detect increased (+)[11C]DTBZ binding and that a higher dose might be required.
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Affiliation(s)
- Isabelle Boileau
- Human Neurochemical Pathology Laboratory, Centre for Addiction and Mental Health, University of Toronto, Toronto, Ontario, Canada.
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Blesa J, Juri C, Collantes M, Peñuelas I, Prieto E, Iglesias E, Martí-Climent J, Arbizu J, Zubieta JL, Rodríguez-Oroz MC, García-García D, Richter JA, Cavada C, Obeso JA. Progression of dopaminergic depletion in a model of MPTP-induced Parkinsonism in non-human primates. An (18)F-DOPA and (11)C-DTBZ PET study. Neurobiol Dis 2010; 38:456-63. [PMID: 20304066 DOI: 10.1016/j.nbd.2010.03.006] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2010] [Revised: 03/05/2010] [Accepted: 03/05/2010] [Indexed: 10/19/2022] Open
Abstract
UNLABELLED Dopaminergic depletion in the nigrostriatal system is the neurochemical hallmark of Parkinson's disease (PD). Although numerous efforts have been made to determine the evolution of dopaminergic depletion in PD, "in vivo" data concerning the stages of this process are still scarce. We evaluated 6-[18F]-fluoro-l-DOPA ((18)F-DOPA) and 11C-(+)-alpha-dihydrotetrabenazine ((11)C-DTBZ) using PET in a model of chronically MPTP-induced parkinsonism in non-human primates. METHODS Sixty-seven cynomolgus monkeys (Macacafascicularis) were included in the study. Progressive parkinsonism was induced by repeated administration of small doses of MPTP (iv) over several months. Animals were classified as controls, asymptomatic, recovered (having exhibited parkinsonian features transiently) and stable parkinsonian, according to their motor status. Analysis of striatal dopaminergic activity was conducted by regions of interest (ROI) and statistical parametric mapping (SPM) over normalized parametric images. RESULTS A progressive loss of striatal uptake was evident among groups for both radiotracers, which correlated significantly with the clinical motor status. Changes occurred earlier, i.e. in the less affected stages, with (11)C-DTBZ. Similar results were achieved by ROI and SPM analysis. Uptake was similar with both radiotracers for the asymptomatic and recovered groups. CONCLUSIONS Serial assessment with (18)F-DOPA and (11)C-DTBZ PETs provides an effective approach to evaluate evolution of dopaminergic depletion in monkeys with MPTP-induced parkinsonism. This approach could be useful to perform studies aiming to test the effect of early therapeutic intervention and putative neuroprotective treatments.
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Affiliation(s)
- Javier Blesa
- Movement Disorders Group, Neurosciences Division, CIMA, and Department of Neurology and Neurosurgery, Clínica Universidad de Navarra, Pamplona, Spain
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Kuriakose R, Stoessl AJ. Imaging the nigrostriatal system to monitor disease progression and treatment-induced complications. PROGRESS IN BRAIN RESEARCH 2010; 184:177-92. [PMID: 20887875 DOI: 10.1016/s0079-6123(10)84009-9] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Radiotracer imaging (RTI) techniques such as positron emission tomography (PET) allow the in vivo assessment of nigrostriatal DA function in Parkinson's disease and have provided valuable insights into the mechanisms of nigrostriatal degeneration and the consequent compensatory changes. Moreover, functional imaging serves as an excellent tool in the assessment of the progression of PD and the evolution of treatment-related complications. However, various studies have shown discordance between clinical progression of PD and nigrostriatal degeneration estimated by PET or SPECT, and no RTI technique can be reliably used as a biomarker for progression of PD. Presynaptic dopaminergic imaging has consistently demonstrated an anterior-posterior gradient of dopaminergic dysfunction predominantly affecting the putamen, with side-to-side asymmetry in tracer binding. Dopaminergic hypofunction in the striatum follows a negative exponential pattern with the fastest rate of decline in early disease. Evaluation of central pharmacokinetics of levodopa action by PET has demonstrated the role of increased synaptic dopamine turnover and downregulation of the dopamine transporter in the pathophysiology of levodopa-induced dyskinesias. In PD with behavioral complications such as impulse control disorders, increased levels of dopamine release have been observed in the ventral striatum during performance of a positive reward task, as well as loss of deactivation in orbitofrontal cortex in response to negative reward prediction errors. This suggests that there is a pathologically heightened "reward" response in the ventral striatum together with loss of the capacity to respond to negative outcomes. Overall, functional imaging with PET is an excellent tool for understanding the disease and its complications; however, caution must be applied in interpretation of the results.
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Affiliation(s)
- Renju Kuriakose
- Pacific Parkinson’s Research Centre, University of British Columbia and Vancouver Coastal Health, Vancouver, BC, Canada
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Kilbourn MR, Butch ER, Desmond T, Sherman P, Harris PE, Frey KA. In vivo [11C]dihydrotetrabenazine binding in rat striatum: sensitivity to dopamine concentrations. Nucl Med Biol 2009; 37:3-8. [PMID: 20122661 DOI: 10.1016/j.nucmedbio.2009.08.013] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2009] [Revised: 08/28/2009] [Accepted: 08/31/2009] [Indexed: 10/20/2022]
Abstract
INTRODUCTION The sensitivity of the in vivo binding of [(11)C]dihydrotetrabenazine ([(11)C]DTBZ) and [(11)C]methylphenidate ([(11)C]MPH) to their respective targets - vesicular monoamine transporter type 2 (VMAT2) and neuronal membrane dopamine transporter - after alterations in endogenous levels of dopamine was examined in the rat brain. METHODS In vivo binding of [(11)C]DTBZ and [(11)C]MPH was determined using a bolus+infusion protocol. The in vitro number of VMAT2 binding sites was determined by autoradiography. RESULTS Repeated dosing with alpha-methyl-p-tyrosine (AMPT) at doses that significantly (-75%) depleted brain tissue dopamine levels resulted in increased (+36%) in vivo [(11)C]DTBZ binding to VMAT2 in the striatum. The increase in binding could be completely reversed via treatment with L-DOPA/benserazide to restore dopamine levels. There were no changes in the total number of VMAT2 binding sites, as measured using in vitro autoradiography. No changes were observed for in vivo [(11)C]MPH binding to the dopamine transporter in the striatum following AMPT pretreatment. CONCLUSION These results indicate that large reductions in dopamine concentrations in the rat brain can produce modest but significant changes in the binding of radioligands to VMAT2, which can be reversed by replenishment of dopamine using exogenous L-DOPA.
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Affiliation(s)
- Michael R Kilbourn
- Department of Radiology, University of Michigan Medical School, Ann Arbor, MI 48109, USA.
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de la Fuente-Fernández R, Sossi V, McCormick S, Schulzer M, Ruth TJ, Stoessl AJ. Visualizing vesicular dopamine dynamics in Parkinson's disease. Synapse 2009; 63:713-6. [DOI: 10.1002/syn.20653] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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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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