1
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Avendaño-Estrada A, Olarte-Casas MÁ, Ávila-Rodríguez MÁ. Vectorial-based analysis of dual-tracer PET imaging: A proof of concept. Comput Biol Med 2024; 168:107705. [PMID: 37979207 DOI: 10.1016/j.compbiomed.2023.107705] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2023] [Revised: 11/10/2023] [Accepted: 11/13/2023] [Indexed: 11/20/2023]
Abstract
BACKGROUND The diagnosis of neurological diseases is complicated since they often share similar symptoms and occur in different severity levels. Imaging techniques such as PET molecular imaging are helpful for an early and accurate diagnosis and, staging allowing a noninvasive evaluation of the disease. The combination of two radioligands in the same patient could be valuable to achieve these diagnostic goals; nevertheless, the imaging data obtained with two radioligands is commonly interpreted independently. This novel approach to combine the PET data of two radiopharmaceuticals, separately acquired in the same subject, is to obtain new quantitative metrics. PET images of patients with Parkinson's disease (PD) and healthy controls (HC) were analyzed. Voxel-by-voxel uptake is compared by combining the imaging data. Dual-tracer PET imaging analysis was tested with [11C]DTBZ-[11C]Raclopride as proof of concept. RESULTS The new proposed metric based on a resultant vector is capable of efficiently discriminating healthy controls from PD patients (p < 0.0001) allowing the detection of slight changes in patients undergoing therapeutic approaches. Significant differences were found between HC and PD patients for the evaluated radiotracers. CONCLUSIONS The resultant vector appears to deliver useful information that could be helpful to evaluate PD patients under treatment and to improve differential diagnoses.
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Affiliation(s)
- Arturo Avendaño-Estrada
- Unidad Radiofarmacia-Ciclotrón, Facultad de Medicina, División de Investigación, Universidad Nacional Autónoma de México, Mexico; Centro de Investigación sobre el Envejecimiento, Centro de Investigación y de Estudios Avanzados Sede Sur, Mexico.
| | - Miguel Ángel Olarte-Casas
- Unidad PET/CT, Facultad de Medicina, División de Investigación, Universidad Nacional Autónoma de México, Mexico
| | - Miguel Ángel Ávila-Rodríguez
- Unidad Radiofarmacia-Ciclotrón, Facultad de Medicina, División de Investigación, Universidad Nacional Autónoma de México, Mexico; Centro de Investigación sobre el Envejecimiento, Centro de Investigación y de Estudios Avanzados Sede Sur, Mexico.
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2
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Moustapha ME, Geesi MH, Farag ZR, Anouar EH. Electrophilic Aromatic Synthesis of Radioiodinated Aripiprazole: Experimental and DFT Investigations. Curr Org Synth 2020; 17:295-303. [PMID: 32271696 DOI: 10.2174/1570179417666200409145824] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2019] [Revised: 02/06/2020] [Accepted: 02/07/2020] [Indexed: 11/22/2022]
Abstract
BACKGROUND Aripiprazole is a quinolinone derivative. It shows a high affinity for neurotransmitters dopamine and serotonin receptors, which can overcome the blood-brain barrier (BBB) to reach the central nervous system (CNS) to exert therapeutic effects. Its radioiodination may lead to high radiochemical yield and improved its affinity. Aripiprazole radioiodination is an aromatic electrophilic substitution. OBJECTIVE Herein, we investigate the favorable atom site of the aromatic electrophilic substitution of aripiprazole by calculating the Fukui indices of heavy atoms and ESP charges of the parent molecule. METHODS The calculations have been carried out at the B3LYP/LanL2DZ level of theory. The iodinated aripiprazole structure is confirmed by comparing the experimental and the predicted 1H NMR chemical shifts of the parent molecule and its iodinated forms. RESULTS Finally, the electronic properties of aripiprazole and its iodinated form were calculated at the same level of theory. Nucleophilic Fukui indices and ESP charges calculations confirm that C8 is the most favorable site of the electrophilic substitution. The calculated electronic properties (e.g, gap energy, electron affinity, and electronegativity) of aripiprazole and its iodinated form reveal the higher reactivity of iodinated aripiprazole compared with aripiprazole. CONCLUSION This may explain the higher affinity of iodinated aripiprazole and the increase of its radiochemical yield.
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Affiliation(s)
- Moustapha E Moustapha
- Department of Chemistry, College of Science and Humanities in Al-Kharj, Prince Sattam Bin Abdulaziz University, Al-Kharj 11942, Saudi Arabia
| | - Mohammed H Geesi
- Department of Chemistry, College of Science and Humanities in Al-Kharj, Prince Sattam Bin Abdulaziz University, Al-Kharj 11942, Saudi Arabia
| | - Zeinab R Farag
- Chemistry Department, Faculty of Science, Fayoum University, Fayoum, Egypt
| | - El Hassane Anouar
- Department of Chemistry, College of Science and Humanities in Al-Kharj, Prince Sattam Bin Abdulaziz University, Al-Kharj 11942, Saudi Arabia
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Caravaggio F, Iwata Y, Kim J, Shah P, Gerretsen P, Remington G, Graff-Guerrero A. What proportion of striatal D2 receptors are occupied by endogenous dopamine at baseline? A meta-analysis with implications for understanding antipsychotic occupancy. Neuropharmacology 2019; 163:107591. [PMID: 30940535 DOI: 10.1016/j.neuropharm.2019.03.034] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2019] [Revised: 03/25/2019] [Accepted: 03/27/2019] [Indexed: 11/30/2022]
Abstract
Using molecular imaging techniques - positron emission tomography (PET) and single-photon emission computed tomography (SPECT) - in conjunction with an acute dopamine depletion challenge (alpha-methyl-para-tyrosine) it is possible to estimate endogenous dopamine levels occupying striatal dopamine D2 receptors (D2R) in humans in vivo. However, it is unclear what proportion of striatal D2R are occupied by endogenous dopamine under normal conditions. This is important since it has been suggested that in schizophrenia there may be a substantial proportion of striatal D2R which are occupied by endogenous dopamine and not accessible by therapeutic doses of antipsychotics. In order to clarify these issues, we conducted a meta-analysis of dopamine depletion studies using substituted benzamide radiotracers in healthy persons. This meta-analysis suggests that anywhere from 8 to 21% (weighted average 11%) of striatal D2R may be occupied by endogenous dopamine at baseline. Using these estimates, we propose an updated occupancy model and tentatively suggest that antipsychotics inhibit a smaller proportion of the total pool of striatal D2R in vivo than previously acknowledged. This article is part of the issue entitled 'Special Issue on Antipsychotics'.
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Affiliation(s)
- Fernando Caravaggio
- Research Imaging Centre, Centre for Addiction and Mental Health, 250 College Street, Toronto, Ontario, M5T 1R8, Canada; Department of Psychiatry, University of Toronto, 250 College Street, Toronto, Ontario, M5T 1R8, Canada.
| | - Yusuke Iwata
- Research Imaging Centre, Centre for Addiction and Mental Health, 250 College Street, Toronto, Ontario, M5T 1R8, Canada; Department of Psychiatry, University of Toronto, 250 College Street, Toronto, Ontario, M5T 1R8, Canada
| | - Julia Kim
- Research Imaging Centre, Centre for Addiction and Mental Health, 250 College Street, Toronto, Ontario, M5T 1R8, Canada; Institute of Medical Science, University of Toronto, 1 Kings College Circle, Toronto, Ontario, M5S 1A8, Canada
| | - Parita Shah
- Research Imaging Centre, Centre for Addiction and Mental Health, 250 College Street, Toronto, Ontario, M5T 1R8, Canada; Institute of Medical Science, University of Toronto, 1 Kings College Circle, Toronto, Ontario, M5S 1A8, Canada
| | - Philip Gerretsen
- Research Imaging Centre, Centre for Addiction and Mental Health, 250 College Street, Toronto, Ontario, M5T 1R8, Canada; Department of Psychiatry, University of Toronto, 250 College Street, Toronto, Ontario, M5T 1R8, Canada; Institute of Medical Science, University of Toronto, 1 Kings College Circle, Toronto, Ontario, M5S 1A8, Canada
| | - Gary Remington
- Research Imaging Centre, Centre for Addiction and Mental Health, 250 College Street, Toronto, Ontario, M5T 1R8, Canada; Department of Psychiatry, University of Toronto, 250 College Street, Toronto, Ontario, M5T 1R8, Canada; Institute of Medical Science, University of Toronto, 1 Kings College Circle, Toronto, Ontario, M5S 1A8, Canada
| | - Ariel Graff-Guerrero
- Research Imaging Centre, Centre for Addiction and Mental Health, 250 College Street, Toronto, Ontario, M5T 1R8, Canada; Department of Psychiatry, University of Toronto, 250 College Street, Toronto, Ontario, M5T 1R8, Canada; Institute of Medical Science, University of Toronto, 1 Kings College Circle, Toronto, Ontario, M5S 1A8, Canada
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4
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Loiodice S, McGhan P, Gryshkova V, Fleurance R, Dardou D, Hafidi A, Nogueira da Costa A, Durif F. Striatal changes underlie MPEP-mediated suppression of the acquisition and expression of pramipexole-induced place preference in an alpha-synuclein rat model of Parkinson's disease. J Psychopharmacol 2017. [PMID: 28631520 DOI: 10.1177/0269881117714051] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Impulsive-compulsive disorders in Parkinson's disease patients have been described as behavioural or substance addictions including pathological gambling or compulsive medication use of dopamine replacement therapy. A substantial gap remains in the understanding of these disorders. We previously demonstrated that the rewarding effect of the D2/D3 agonist pramipexole was enhanced after repeated exposure to L-dopa and alpha-synuclein mediated dopaminergic nigral loss with specific transcriptional signatures suggesting a key involvement of the glutamatergic pathway. Here, we further investigate the therapeutic potential of metabotropic glutamate receptor 5 antagonism in Parkinson's disease/dopamine replacement therapy related bias of reward-mediated associative learning. We identified protein changes underlying the striatal remodelling associated with the pramipexole-induced conditioned place preference. Acquisition and expression of the pramipexole-induced conditioned place preference were abolished by the metabotropic glutamate receptor 5 antagonist 2-methyl-6-phenylethynyl (pyridine) (conditioned place preference scores obtained with pramipexole conditioning were reduced by 12.5% and 125.8% when 2-methyl-6-phenylethynyl (pyridine) was co-administrated with pramipexole or after the pramipexole conditioning, respectively). Up-regulation of the metabotropic glutamate receptor 5 was found in the dorsomedial-striatum and nucleus accumbens core. Activation of these two brain sub-regions was also highlighted through FosB immunohistochemistry. Convergent molecular and pharmacological data further suggests metabotropic glutamate receptor 5 as a promising therapeutic target for the management of Parkinson's disease/dopamine replacement therapy related reward bias.
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Affiliation(s)
- Simon Loiodice
- 1 EA7280 Neuropsychopharmacology of sub-cortical dopaminergic pathways, Université d'Auvergne, Clermont-Ferrand, France.,2 Department of Non-Clinical Development, UCB Biopharma SPRL, Braine-l'Alleud, Belgium
| | - Portia McGhan
- 2 Department of Non-Clinical Development, UCB Biopharma SPRL, Braine-l'Alleud, Belgium
| | - Vitalina Gryshkova
- 2 Department of Non-Clinical Development, UCB Biopharma SPRL, Braine-l'Alleud, Belgium
| | - Renaud Fleurance
- 2 Department of Non-Clinical Development, UCB Biopharma SPRL, Braine-l'Alleud, Belgium
| | - David Dardou
- 1 EA7280 Neuropsychopharmacology of sub-cortical dopaminergic pathways, Université d'Auvergne, Clermont-Ferrand, France
| | - Aziz Hafidi
- 1 EA7280 Neuropsychopharmacology of sub-cortical dopaminergic pathways, Université d'Auvergne, Clermont-Ferrand, France
| | | | - Franck Durif
- 1 EA7280 Neuropsychopharmacology of sub-cortical dopaminergic pathways, Université d'Auvergne, Clermont-Ferrand, France.,3 Neurology Department, CHU Clermont-Ferrand, Clermont-Ferrand, France
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5
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Arias-Carrión O, Caraza-Santiago X, Salgado-Licona S, Salama M, Machado S, Nardi AE, Menéndez-González M, Murillo-Rodríguez E. Orquestic regulation of neurotransmitters on reward-seeking behavior. Int Arch Med 2014; 7:29. [PMID: 25061480 PMCID: PMC4108978 DOI: 10.1186/1755-7682-7-29] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2014] [Accepted: 05/31/2014] [Indexed: 01/15/2023] Open
Abstract
The ventral tegmental area is strongly associated with the reward system. Dopamine is released in areas such as the nucleus accumbens and prefrontal cortex as a result of rewarding experiences such as food, sex, and neutral stimuli that become associated with them. Electrical stimulation of the ventral tegmental area or its output pathways can itself serve as a potent reward. Different drugs that increase dopamine levels are intrinsically rewarding. Although the dopaminergic system represent the cornerstone of the reward system, other neurotransmitters such as endogenous opioids, glutamate, γ-Aminobutyric acid, acetylcholine, serotonin, adenosine, endocannabinoids, orexins, galanin and histamine all affect this mesolimbic dopaminergic system. Consequently, genetic variations of neurotransmission are thought influence reward processing that in turn may affect distinctive social behavior and susceptibility to addiction. Here, we discuss current evidence on the orquestic regulation of different neurotranmitters on reward-seeking behavior and its potential effect on drug addiction.
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Affiliation(s)
- Oscar Arias-Carrión
- Unidad de Trastornos del Movimiento y Sueño (TMS), Hospital General Dr. Manuel Gea González, Mexico City, Mexico ; Unidad de Trastornos del Movimiento y Sueño (TMS), Hospital General Ajusco Medio, Mexico City, Mexico
| | - Xanic Caraza-Santiago
- Unidad de Trastornos del Movimiento y Sueño (TMS), Hospital General Dr. Manuel Gea González, Mexico City, Mexico
| | - Sergio Salgado-Licona
- Unidad de Trastornos del Movimiento y Sueño (TMS), Hospital General Dr. Manuel Gea González, Mexico City, Mexico
| | - Mohamed Salama
- Toxicology Department and Medical Experimental Research Center (MERC), Faculty of Medicine, Mansoura University, Mansoura, Egypt
| | - Sergio Machado
- Panic and Respiration, Institute of Psychiatry of Federal University of Rio de Janeiro, Rio de Janeiro, Brazil ; Physical Activity Neuroscience Physical Activity Sciences Postgraduate Program, Salgado de Oliveira University, Niterói, Brazil
| | - Antonio Egidio Nardi
- Panic and Respiration, Institute of Psychiatry of Federal University of Rio de Janeiro, Rio de Janeiro, Brazil
| | | | - Eric Murillo-Rodríguez
- Laboratorio de Neurociencias Moleculares e Integrativas, Escuela de Medicina, División Ciencias de la Salud, Universidad Anáhuac Mayab, Mérida, Yucatán, Mexico
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6
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Hu G, Henke A, Karpowicz RJ, Sonders MS, Farrimond F, Edwards R, Sulzer D, Sames D. New fluorescent substrate enables quantitative and high-throughput examination of vesicular monoamine transporter 2 (VMAT2). ACS Chem Biol 2013; 8:1947-54. [PMID: 23859623 DOI: 10.1021/cb400259n] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Vesicular monoamine transporter 2 (VMAT2) is an essential component of the monoaminergic neurotransmission system in the brain as it transports monoamine neurotransmitters from the neuronal cytosol into the synaptic vesicles and thus contributes to modulation of neurotransmitter release. Considering the continuing interest in VMAT2 as a drug target, as well as a target for the design of imaging probes, we have developed a fluorescent substrate well suited for the study of VMAT2 in cell culture. Herein, we report the synthesis and characterization of a new fluorescent probe, FFN206, as an excellent VMAT2 substrate capable of detecting VMAT2 activity in intact cells using fluorescence microscopy, with subcellular localization to VMAT2-expressing acidic compartments without apparent labeling of other organelles. VMAT2 activity can also be measured via microplate reader. The apparent Km of FFN206 at VMAT2 was found to be 1.16 ± 0.10 μM, similar to that of dopamine. We further report the development and validation of a cell-based fluorescence assay amenable to high-throughput screening (HTS) using VMAT2-transfected HEK cells (Z'-factor of 0.7-0.8), enabling rapid identification of VMAT2 inhibitors and measurement of their inhibition constants over a broad range of affinities. FFN206 thus represents a new tool for optical examination of VMAT2 function in cell culture.
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Affiliation(s)
- Gang Hu
- Department
of Chemistry, Columbia University, New
York, New York 10027, United
States
| | - Adam Henke
- Department
of Chemistry, Columbia University, New
York, New York 10027, United
States
| | - Richard J. Karpowicz
- Department
of Chemistry, Columbia University, New
York, New York 10027, United
States
| | - Mark S. Sonders
- Departments of Psychiatry and
Neurology, Columbia University, New York,
New York 10032, United States
| | - Frances Farrimond
- Departments of Neurology and
Physiology, University of California School of Medicine, San Francisco, San Francisco, California 94143, United
States
| | - Robert Edwards
- Departments of Neurology and
Physiology, University of California School of Medicine, San Francisco, San Francisco, California 94143, United
States
| | - David Sulzer
- Departments of
Neurology, Psychiatry,
and Pharmacology, Columbia University,
New York, New York 10032, United States
| | - Dalibor Sames
- Department
of Chemistry, Columbia University, New
York, New York 10027, United
States
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7
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Moustapha ME, Motaleb MA, Ibrahim IT, Moustafa ME. Oxidative radioiodination of aripiprazole by chloramine-T as a route to a potential brain imaging agent: a mechanistic approach. RADIOCHEMISTRY 2013. [DOI: 10.1134/s1066362213010232] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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8
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Fluorescent dopamine tracer resolves individual dopaminergic synapses and their activity in the brain. Proc Natl Acad Sci U S A 2012; 110:870-5. [PMID: 23277566 DOI: 10.1073/pnas.1213569110] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
We recently introduced fluorescent false neurotransmitters (FFNs) as optical tracers that enable the visualization of neurotransmitter release at individual presynaptic terminals. Here, we describe a pH-responsive FFN probe, FFN102, which as a polar dopamine transporter substrate selectively labels dopamine cell bodies and dendrites in ventral midbrain and dopaminergic synaptic terminals in dorsal striatum. FFN102 exhibits greater fluorescence emission in neutral than acidic environments, and thus affords a means to optically measure evoked release of synaptic vesicle content into the extracellular space. Simultaneously, FFN102 allows the measurement of individual synaptic terminal activity by following fluorescence loss upon stimulation. Thus, FFN102 enables not only the identification of dopamine cells and their processes in brain tissue, but also the optical measurement of functional parameters including dopamine transporter activity and dopamine release at the level of individual synapses. As such, the development of FFN102 demonstrates that, by bringing together organic chemistry and neuroscience, molecular entities can be generated that match the endogenous transmitters in selectivity and distribution, allowing for the study of both the microanatomy and functional plasticity of the normal and diseased nervous system.
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9
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Vadola PA, Sames D. Catalytic coupling of arene C-H bonds and alkynes for the synthesis of coumarins: substrate scope and application to the development of neuroimaging agents. J Org Chem 2012; 77:7804-14. [PMID: 22768913 PMCID: PMC3448786 DOI: 10.1021/jo3006842] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
C-H bond functionalization offers strategically novel approaches to complex organic compounds. However, many C-H functionalization reactions suffer from poor compatibility with Lewis basic functional groups, especially amines, which are often essential for biological activity. This study describes a systematic examination of the substrate scope of catalytic hydroarylation in the context of complex amino coumarin synthesis. The choice of substrates was guided by the design and development of the next generation of fluorescent false neurotransmitters (FFNs), neuroimaging probes we recently introduced for optical imaging of neurotransmission in the brain. Comparison of two mild protocols using catalytic PtCl(4) or Au(PPh(3))Cl/AgSbF(6)revealed that each method has a broad and mutually complementary substrate scope. The relatively less active platinum system out-performed the gold catalyst with indole substrates lacking substitution at the C-3 position and provided higher regioselectivity in the case of carbazole-based substrates. On the other hand, the more active gold catalyst demonstrated excellent functional group tolerance, and the ability to catalyze the formation of strained, helical products. The development of these two protocols offers enhanced substrate scope and provides versatile synthetic tools required for the structure-activity examination of FFN neuroimaging probes as well as for the synthesis of complex coumarins in general.
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Affiliation(s)
- Paul A. Vadola
- Department of Chemistry, Columbia University, 3000 Broadway, New York, New York 10027
| | - Dalibor Sames
- Department of Chemistry, Columbia University, 3000 Broadway, New York, New York 10027
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10
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Deignan J, Luján R, Bond C, Riegel A, Watanabe M, Williams JT, Maylie J, Adelman JP. SK2 and SK3 expression differentially affect firing frequency and precision in dopamine neurons. Neuroscience 2012; 217:67-76. [PMID: 22554781 DOI: 10.1016/j.neuroscience.2012.04.053] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2011] [Revised: 03/29/2012] [Accepted: 04/21/2012] [Indexed: 11/30/2022]
Abstract
The firing properties of dopamine (DA) neurons in the substantia nigra (SN) pars compacta are strongly influenced by the activity of apamin-sensitive small conductance Ca(2+)-activated K(+) (SK) channels. Of the three SK channel genes expressed in central neurons, only SK3 expression has been identified in DA neurons. The present findings show that SK2 was also expressed in DA neurons. Immuno-electron microscopy (iEM) showed that SK2 was primarily expressed in the distal dendrites, while SK3 was heavily expressed in the soma and, to a lesser extent, throughout the dendritic arbor. Electrophysiological recordings of the effects of the SK channel blocker apamin on DA neurons from wild type and SK(-/-) mice show that SK2-containing channels contributed to the precision of action potential (AP) timing, while SK3-containing channels influenced AP frequency. The expression of SK2 in DA neurons may endow distinct signaling and subcellular localization to SK2-containing channels.
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Affiliation(s)
- J Deignan
- Vollum Institute, Oregon Health & Science University, Portland, OR 97239, USA
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11
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Scerbina T, Chatterjee D, Gerlai R. Dopamine receptor antagonism disrupts social preference in zebrafish: a strain comparison study. Amino Acids 2012; 43:2059-72. [PMID: 22491827 DOI: 10.1007/s00726-012-1284-0] [Citation(s) in RCA: 82] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2011] [Accepted: 03/31/2012] [Indexed: 01/03/2023]
Abstract
Zebrafish form shoals in nature and in the laboratory. The sight of conspecifics has been found reinforcing in zebrafish learning tasks. However, the mechanisms of shoaling, and those of its reinforcing properties, are not known. The dopaminergic system has been implicated in reward among other functions and it is also engaged by drugs of abuse as shown in a variety of vertebrates including zebrafish. The ontogenetic changes in dopamine levels and, to a lesser degree, in serotonin levels, have been found to accompany the maturation of shoaling in zebrafish. Thus, we hypothesized that the dopaminergic system may contribute to shoaling in zebrafish. To test this we employed a D1-receptor antagonist and quantified behavioral responses of our subjects using a social preference (shoaling) paradigm. We found significant reduction of social preference induced by the D1-R antagonist, SCH23390, in the AB strain of zebrafish, an alteration that was not accompanied by changes in motor function or vision. We also detected D1-R antagonist-induced changes in the level of dopamine, DOPAC, serotonin and 5HIAA, respectively, in the brain of AB zebrafish as quantified by HPLC with electrochemical detection. We found the antagonist-induced behavioral changes to be absent and the levels of these neurochemicals to be lower in another zebrafish population, SF, demonstrating naturally occurring genetic variability in these traits. We conclude that this variability may be utilized to unravel the mechanisms of social behavior in zebrafish, a line of research that may be extended to other vertebrates including our own species.
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Affiliation(s)
- Tanya Scerbina
- Department of Psychology, University of Toronto Mississauga, 3359 Mississauga Road North, Rm 4020C, Mississauga, ON, L5L 1C6, Canada
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12
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Basselin M, Ramadan E, Rapoport SI. Imaging brain signal transduction and metabolism via arachidonic and docosahexaenoic acid in animals and humans. Brain Res Bull 2012; 87:154-71. [PMID: 22178644 PMCID: PMC3274571 DOI: 10.1016/j.brainresbull.2011.12.001] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2011] [Revised: 12/01/2011] [Accepted: 12/02/2011] [Indexed: 02/05/2023]
Abstract
The polyunsaturated fatty acids (PUFAs), arachidonic acid (AA, 20:4n-6) and docosahexaenoic acid (DHA, 22:6n-3), important second messengers in brain, are released from membrane phospholipid following receptor-mediated activation of specific phospholipase A(2) (PLA(2)) enzymes. We developed an in vivo method in rodents using quantitative autoradiography to image PUFA incorporation into brain from plasma, and showed that their incorporation rates equal their rates of metabolic consumption by brain. Thus, quantitative imaging of unesterified plasma AA or DHA incorporation into brain can be used as a biomarker of brain PUFA metabolism and neurotransmission. We have employed our method to image and quantify effects of mood stabilizers on brain AA/DHA incorporation during neurotransmission by muscarinic M(1,3,5), serotonergic 5-HT(2A/2C), dopaminergic D(2)-like (D(2), D(3), D(4)) or glutamatergic N-methyl-d-aspartic acid (NMDA) receptors, and effects of inhibition of acetylcholinesterase, of selective serotonin and dopamine reuptake transporter inhibitors, of neuroinflammation (HIV-1 and lipopolysaccharide) and excitotoxicity, and in genetically modified rodents. The method has been extended for the use with positron emission tomography (PET), and can be employed to determine how human brain AA/DHA signaling and consumption are influenced by diet, aging, disease and genetics.
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Affiliation(s)
- Mireille Basselin
- Brain Physiology and Metabolism Section, National Institute on Aging, National Institutes of Health, Bethesda, MD, USA
| | - Epolia Ramadan
- Brain Physiology and Metabolism Section, National Institute on Aging, National Institutes of Health, Bethesda, MD, USA
| | - Stanley I. Rapoport
- Brain Physiology and Metabolism Section, National Institute on Aging, National Institutes of Health, Bethesda, MD, USA
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13
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Ion channels and schizophrenia: a gene set-based analytic approach to GWAS data for biological hypothesis testing. Hum Genet 2011; 131:373-91. [PMID: 21866342 DOI: 10.1007/s00439-011-1082-x] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2011] [Accepted: 08/08/2011] [Indexed: 01/11/2023]
Abstract
Schizophrenia is a complex genetic disorder. Gene set-based analytic (GSA) methods have been widely applied for exploratory analyses of large, high-throughput datasets, but less commonly employed for biological hypothesis testing. Our primary hypothesis is that variation in ion channel genes contribute to the genetic susceptibility to schizophrenia. We applied Exploratory Visual Analysis (EVA), one GSA application, to analyze European-American (EA) and African-American (AA) schizophrenia genome-wide association study datasets for statistical enrichment of ion channel gene sets, comparing GSA results derived under three SNP-to-gene mapping strategies: (1) GENIC; (2) 500-Kb; (3) 2.5-Mb and three complimentary SNP-to-gene statistical reduction methods: (1) minimum p value (pMIN); (2) a novel method, proportion of SNPs per Gene with p values below a pre-defined α-threshold (PROP); and (3) the truncated product method (TPM). In the EA analyses, ion channel gene set(s) were enriched under all mapping and statistical approaches. In the AA analysis, ion channel gene set(s) were significantly enriched under pMIN for all mapping strategies and under PROP for broader mapping strategies. Less extensive enrichment in the AA sample may reflect true ethnic differences in susceptibility, sampling or case ascertainment differences, or higher dimensionality relative to sample size of the AA data. More consistent findings under broader mapping strategies may reflect enhanced power due to increased SNP inclusion, enhanced capture of effects over extended haplotypes or significant contributions from regulatory regions. While extensive pMIN findings may reflect gene size bias, the extent and significance of PROP and TPM findings suggest that common variation at ion channel genes may capture some of the heritability of schizophrenia.
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Arias-Carrión O, Stamelou M, Murillo-Rodríguez E, Menéndez-González M, Pöppel E. Dopaminergic reward system: a short integrative review. Int Arch Med 2010; 3:24. [PMID: 20925949 PMCID: PMC2958859 DOI: 10.1186/1755-7682-3-24] [Citation(s) in RCA: 209] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2010] [Accepted: 10/06/2010] [Indexed: 11/18/2022] Open
Abstract
Memory is an essential element to adaptive behavior since it allows consolidation of past experience guiding the subject to consider them in future experiences. Among the endogenous molecules that participate in the consolidation of memory, including the drug-seeking reward, considered as a form of learning, is dopamine. This neurotransmitter modulates the activity of specific brain nucleus such as nuclei accumbens, putamen, ventral tegmental area (VTA), among others and synchronizes the activity of these nuclei to establish the neurobiological mechanism to set the hedonic element of learning. We review the experimental evidence that highlights the activity of different brain nuclei modulating the mechanisms whereby dopamine biases memory towards events that are of motivational significance.
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Affiliation(s)
- Oscar Arias-Carrión
- Human Science Center (FESTO-Program for Applied Knowing), Ludwig-Maximilians-Universität, Munich, Germany.
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Arias-Carrión O, Stamelou M, Murillo-Rodríguez E, Menéndez-González M, Pöppel E. Dopaminergic reward system: a short integrative review. Int Arch Med 2010. [PMID: 20925949 DOI: 10.1186/1755-7682-3-24.] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
Memory is an essential element to adaptive behavior since it allows consolidation of past experience guiding the subject to consider them in future experiences. Among the endogenous molecules that participate in the consolidation of memory, including the drug-seeking reward, considered as a form of learning, is dopamine. This neurotransmitter modulates the activity of specific brain nucleus such as nuclei accumbens, putamen, ventral tegmental area (VTA), among others and synchronizes the activity of these nuclei to establish the neurobiological mechanism to set the hedonic element of learning. We review the experimental evidence that highlights the activity of different brain nuclei modulating the mechanisms whereby dopamine biases memory towards events that are of motivational significance.
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Affiliation(s)
- Oscar Arias-Carrión
- Human Science Center (FESTO-Program for Applied Knowing), Ludwig-Maximilians-Universität, Munich, Germany.
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Bridges TM, LeBois EP, Hopkins CR, Wood MR, Jones CK, Conn PJ, Lindsley CW. The antipsychotic potential of muscarinic allosteric modulation. DRUG NEWS & PERSPECTIVES 2010; 23:229-40. [PMID: 20520852 PMCID: PMC4780339 DOI: 10.1358/dnp.2010.23.4.1416977] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The cholinergic hypothesis of schizophrenia emerged over 50 years ago based on clinical observations with both anticholinergics and pan-muscarinic agonists. Not until the 1990s did the cholinergic hypothesis of schizophrenia receive renewed enthusiasm based on clinical data with xanomeline, a muscarinic acetylcholine receptor M(1)/M(4)-preferring orthosteric agonist. In a clinical trial with Alzheimer's patients, xanomeline not only improved cognitive performance, but also reduced psychotic behaviors. This encouraging data spurred a second clinical trial in schizophrenic patients, wherein xanomeline significantly improved the positive, negative and cognitive symptom clusters. However, the question remained: Was the antipsychotic efficacy due to activation of M(1), M(4) or both M(1)/M(4)? Classical orthosteric ligands lacked the muscarinic receptor subtype selectivity required to address this key question. More recently, functional assays have allowed for the discovery of ligands that bind at allosteric sites, binding sites distinct from the orthosteric (acetylcholine) site, which are structurally less conserved and thereby afford high levels of receptor subtype selectivity. Recently, allosteric ligands, with unprecedented selectivity for either M(1) or M(4), have been discovered and have demonstrated comparable efficacy to xanomeline in preclinical antipsychotic and cognition models. These data suggest that selective allosteric activation of either M(1) or M(4) has antipsychotic potential through distinct, yet complimentary mechanisms.
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Affiliation(s)
- Thomas M. Bridges
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Evan P. LeBois
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Corey R. Hopkins
- Department of Pharmacology, Vanderbilt Program in Drug Discovery and Vanderbilt Specialized Chemistry Center (MLPCN), Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Michael R. Wood
- Department of Pharmacology, Vanderbilt Program in Drug Discovery and Vanderbilt Specialized Chemistry Center (MLPCN), Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Carrie K. Jones
- Department of Pharmacology, Vanderbilt Program in Drug Discovery and Vanderbilt Specialized Chemistry Center (MLPCN), Vanderbilt University Medical Center, and U.S. Department of Veterans Affairs, Tennessee Valley Healthcare System (TVHS), Nashville, Tennessee, USA
| | - P. Jeffrey Conn
- Department of Pharmacology, Vanderbilt Program in Drug Discovery and Vanderbilt Specialized Chemistry Center (MLPCN), Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Craig W. Lindsley
- Department of Pharmacology, Vanderbilt Program in Drug Discovery and Vanderbilt Specialized Chemistry Center (MLPCN), Vanderbilt University Medical Center, and Department of Chemistry, Vanderbilt University, Nashville, Tennessee, USA
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Patel NH, Vyas NS, Puri BK, Nijran KS, Al-Nahhas A. Positron emission tomography in schizophrenia: a new perspective. J Nucl Med 2010; 51:511-20. [PMID: 20237027 DOI: 10.2967/jnumed.109.066076] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
UNLABELLED PET is an important functional imaging technique that can be used to investigate neurotransmitter receptors and transporters directly by mapping human brain function. PET is increasingly being used greatly to advance our understanding of the neurobiology and pathophysiology of schizophrenia. METHODS This review focuses on the use of PET tracers and kinetic modeling in identifying regional brain abnormalities and regions associated with cognitive functioning in schizophrenia. A variety of PET tracers have been used to identify brain abnormalities, including (11)C, (15)O-water, (18)F-fallypride, and L-3,4-dihydroxy-6-(18)F-fluorophenylalanine ((18)F-FDOPA). RESULTS Some studies have used compartmental modeling to determine tracer binding kinetics. The most consistent findings show a difference in the dopamine content in the prefrontal cortex, anterior cingulate gyrus, and hippocampus between healthy controls and patients with schizophrenia. Studies also show a higher density of D(2) receptors in the striatum and neural brain dysconnectivity. CONCLUSION Future investigations integrating clinical, imaging, genetic, and cognitive aspects are warranted to gain a better understanding of the pathophysiology of this disorder.
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Affiliation(s)
- Neva H Patel
- Radiological Sciences Unit, Imperial College Healthcare NHS Trust, London, United Kingdom.
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Abstract
The aberrant expression and function of certain receptors in tumours and other diseased tissues make them preferable targets for molecular imaging. PET and SPECT radionuclides can be used to label specific ligands with high affinity for the target receptors. The functional information obtained from imaging these receptors can be used to better understand the systems under investigation and for diagnostic and therapeutic applications. This review discusses some of the aspects of receptor imaging with small molecule tracers by PET and SPECT and reviews some of the tracers for the receptor imaging of tumours and brain, heart and lung disorders.
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Affiliation(s)
- Aviv Hagooly
- Mallinckrodt Institute of Radiology, Washington University School of Medicine, 510 S. Kingshighway Blvd., Campus Box 8225, St. Louis, MO 63110, USA.
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Ginovart N, Willeit M, Rusjan P, Graff A, Bloomfield PM, Houle S, Kapur S, Wilson AA. Positron emission tomography quantification of [11C]-(+)-PHNO binding in the human brain. J Cereb Blood Flow Metab 2007; 27:857-71. [PMID: 17033687 DOI: 10.1038/sj.jcbfm.9600411] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
The kinetic modeling of [11C]-(+)-PHNO binding to the dopamine D2/3 receptors in six human volunteers using positron emission tomography (PET) is described. [11C]-(+)-PHNO is the first agonist radioligand for the D2/3 in humans and as expected showed high uptake in caudate, putamen, globus pallidus (GP) and ventral striatum, and low uptake in cerebellum. A two-tissue compartment model (2CM) with four parameters was necessary to adequately fit time-activity data in all regions. Although a 2CM provided an excellent estimation of total distribution volumes, which were highly correlated with those obtained with the invasive Logan approach, it provided a poor identification of the k3/k4 ratios. Coupling K1/k2 between brain regions (Method C) or fixing K1/k2 to the value obtained in cerebellum (Method D) enabled more stable estimates of k3/k4 as compared with an unconstrained 2CM. The k3/k4 obtained with Method D ranged from 0.12+/-0.03 in cerebellum to 3.93+/-0.77 in GP and were similar to those obtained when coupling K1/k2. Binding potentials (BPs) obtained using the simplified reference tissue model (BP(SRTM)) ranged from 2.08+/-0.34 in caudate to 3.55+/-0.78 in GP and were highly correlated with k3/k4 estimates obtained with Method D (r=0.98). However, BP(SRTM) were 11%+/-5% lower than values obtained with Method D. BPs derived using the noninvasive Logan approach were slightly lower but not significantly different than BP(SRTM). This study demonstrates that [11C]-(+)-PHNO can be used for the quantitative measurement of D2/3 densities and should enable further studies of potential D2/3 dysregulation in several important psychiatric and neurologic illnesses.
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Affiliation(s)
- Nathalie Ginovart
- The Vivian Rakoff Positron Emission Tomography Unit, Centre for Addiction and Mental Health, Toronto, Ontario, Canada.
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Mateos JJ, Lomeña F, Parellada E, Mireia F, Fernandez-Egea E, Pavia J, Prats A, Pons F, Bernardo M. Lower striatal dopamine transporter binding in neuroleptic-naive schizophrenic patients is not related to antipsychotic treatment but it suggests an illness trait. Psychopharmacology (Berl) 2007; 191:805-11. [PMID: 17019564 DOI: 10.1007/s00213-006-0570-5] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/27/2006] [Accepted: 08/08/2006] [Indexed: 11/27/2022]
Abstract
INTRODUCTION Drug induced parkinsonism (DIP) is directly related to dopamine D2 receptor blockade. However, there are many references describing parkinsonian signs (PS) in naive-patients. In our previous study, we observed lower DAT binding in a group of first-episode schizophrenic patients after short-term treatment with risperidone, compared with age-matched healthy controls. AIM To clarify if DAT decrease could be an illness trait, excluding the effect of antipsychotics on DAT availability, and to determine whether DAT availability before treatment with antipsychotics may predict subsequent development of PS. MATERIALS AND METHODS A new series of 20 neuroleptic-naive schizophrenic patients and 15 healthy subjects was recruited. SPECT with [(123)I] FP-CIT (DaTSCAN(R)) was performed before starting antipsychotics and after 4 weeks of treatment. PS and psychopathological status were assessed by the Simpson-Angus (SAS), CGI and PANSS scales. Quantitative analyses of SPECTs were performed using ROIs placed in the caudate, putamen and occipital cortex. RESULTS Schizophrenic patients showed lower DAT binding compared with the healthy subjects at baseline (p<0.001) and after a 4-week-treatment period (p=0.001). Six out of eight schizophrenic patients of the DIP group were symptomatic for PS at baseline, in comparison to two out of 12 in the NoDIP group. Nonetheless, no differences were observed on DAT between DIP and NoDIP, neither at baseline (p=0.360) nor at endpoint (p=0.984). Finally, no differences between baseline-endpoint DAT binding were observed, neither in the DIP group (p=0.767) nor in the NoDIP group (p=0.093). CONCLUSION Our new series of first-episode naive-schizophrenic patients (1) points out DAT dysfunction as an illness trait due to the significantly lower DAT binding in schizophrenic patients in comparison to healthy subjects; (2) supports the results of other authors who describe PS in never-treated patients; (3) confirms that [(123)I] FP-CIT does not allow us to predict which patients will develop parkinsonism due to the lack of differences between DIP and NoDIP patients; and (4) confirms a null effect of antipsychotics on DAT due to the lack of differences in [(123)I] FP-CIT before and after a 4-week-treatment period.
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Affiliation(s)
- Jose J Mateos
- Nuclear Medicine Department, Hospital Clínic of Barcelona, University of Barcelona, Barcelona, Spain.
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22
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Lindsey KP, Gatley SJ. Applications of Clinical Dopamine Imaging. PET Clin 2007; 2:45-65. [DOI: 10.1016/j.cpet.2007.09.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Abstract
Recent technologic advances make it increasingly possible to image neurotransmitter systems in living human brain, The dopamine system has been most intensively studied owing to its involvement in several brain disorders such as Parkinson's disease and Huntington's disease, as well as psychiatric disorders such as schizophrenia, depression, and compulsive behavioral disorders of multiple types. A variety of aspects of dopamine receptor density, function, and dopaminergic terminal status can now be assessed using the minimally invasive neuroimaging techniques of positron emission tomography and single-photon emission computed tomography. Although these techniques are currently used most often in the context of research, clinical applications are rapidly emerging.
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Affiliation(s)
- Kimberly P Lindsey
- Department of Psychiatry, Harvard University Medical School, 115 Mill Street, Belmont, MA 02478, USA
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Mateos JJ, Lomeña F, Parellada E, Font M, Fernández E, Pavia J, Prats A, Bernardo M. Disminución del transportador de dopamina estriatal en primeros episodios psicóticos de pacientes esquizofrénicos tratados con risperidona. ACTA ACUST UNITED AC 2006; 25:159-65. [PMID: 16762269 DOI: 10.1157/13088411] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
UNLABELLED Extrapyramidal symptoms and Parkinsonism (PS) are side effects commonly observed with antipsychotic treatment. However, about 24% of never-treated schizophrenic patients may suffer from PS, which contrast with that 1% observed from the general population. 123I-FP-CIT SPECT has probe useful to differentiate degenerative from non-degenerative PS, so it could be interesting using it for establishing the functional state of presynaptic dopamine neurons of these patients. AIM To determine the dopamine transporter binding (DAT) in a homogeneous group of first-episode schizophrenic patients. METHODS An open, transversal study. Thirty schizophrenic in-patients and 15 healthy subjects were recruited. Patients were treated with similar doses of risperidone and all subjects were scanned with 123I-FP-CIT. Extrapyramidal symptoms and psychopathological status was assessed by Simpson-Angus, CGI and PANSS. Semi-quantitative analyses of SPECT images were performed using ROIs placed in caudate nucleus, anterior, medium and posterior putamen and occipital cortex. RESULTS Whole striatum 123I-FP-CIT binding ratio was significantly lower in patients than healthy subjects (t = 2.56, p < 0.014). This was observed in whole putamen (t = 2.66, p < 0.011), anterior (t = 2.35, p < 0.023), medium (t = 2.38, p < 0.022) and posterior putamen (t = 2.09, p < 0.042). No differences were observed in caudate nucleus (t = 1.81, p = 0.076). Females obtained higher binding ratios than males (t = -3.13, p < 0.003). No correlation was observed between 123I-FP-CIT binding ratios and clinical scales. CONCLUSION In our series, first episode schizophrenic patients treated with risperidone have a decrease striatal DAT binding assessed with 123I-FP-CIT SPECT. This alteration could be related to their own schizophrenia disease or be secondary to the antipsychotic treatment.
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Affiliation(s)
- J J Mateos
- Servicio de Medicina Nuclear, Hospital Clínico de Barcelona, Universidad de Barcelona, España.
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25
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Jackson A, Sedaghat K, Minerds K, James C, Tiberi M. Opposing effects of phorbol-12-myristate-13-acetate, an activator of protein kinase C, on the signaling of structurally related human dopamine D1 and D5 receptors. J Neurochem 2006; 95:1387-400. [PMID: 16313517 DOI: 10.1111/j.1471-4159.2005.03476.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The 'cross-talk' between different types of neurotransmitters through second messenger pathways represents a major regulatory mechanism in neuronal function. We investigated the effects of activation of protein kinase C (PKC) on cAMP-dependent signaling by structurally related human D1-like dopaminergic receptors. Human embryonic kidney 293 (HEK293) cells expressing D1 or D5 receptors were pretreated with phorbol-12-myristate-13-acetate (PMA), a potent activator of PKC, followed by analysis of dopamine-mediated receptor activation using whole cell cAMP assays. Unpredictably, PKC activation had completely opposite effects on D1 and D5 receptor signaling. PMA dramatically augmented agonist-evoked D1 receptor signaling, whereas constitutive and dopamine-mediated D5 receptor activation were rapidly blunted. RT-PCR and immunoblotting analyses showed that phorbol ester-regulated PKC isozymes (conventional: alpha, betaI, betaII, gamma; novel: delta, epsilon, eta, theta) and protein kinase D (PKCmicro) are expressed in HEK293 cells. PMA appears to mediate these contrasting effects through the activation of Ca2+-independent novel PKC isoforms as revealed by specific inhibitors, bisindolylmaleimide I, Gö6976, and Gö6983. The finding that cross-talk between PKC and cAMP pathways can produce such opposite outcomes following the activation of structurally similar D1-like receptor subtypes is novel and further strengthens the view that D1 and D5 receptors serve distinct functions in the mammalian nervous and endocrine systems.
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Affiliation(s)
- Adele Jackson
- Ottawa Health Research Institute, Ottawa Hospital (Civic Campus), and Department of Medicine/Cellular and Molecular Medicine/Psychiatry, University of Ottawa, Ottawa, Ontario, Canada
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Voll RJ, McConathy J, Waldrep MS, Crowe RJ, Goodman MM. Semi-automated preparation of the dopamine transporter ligand [(18)F]FECNT for human PET imaging studies. Appl Radiat Isot 2005; 63:353-61. [PMID: 15985372 DOI: 10.1016/j.apradiso.2005.04.008] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2005] [Revised: 03/25/2005] [Accepted: 04/14/2005] [Indexed: 11/24/2022]
Abstract
The fluorine-18 labeled dopamine transport (DAT) ligand 2 beta-carbomethoxy-3beta-(4-chlorophenyl)-8-(2-fluoroethyl)nortropane (FECNT) has shown promising properties as an in vivo DAT imaging agent in human and monkey PET studies. A semi-automated synthesis has been developed to reliably produce [(18)F]FECNT in a 16% decay corrected yield. This method utilizes a new [(18)F]fluoralkylating agent and provides high purity [(18)F]FECNT in a formulation suitable for human use.
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Affiliation(s)
- Ronald J Voll
- Department of Radiology, EUH, 1364 Clifton Road NE, Atlanta, GA 30322, USA
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27
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Mateos JJ, Lomeña F, Parellada E, Font M, Fernandez E, Pavia J, Prats A, Pons F, Bernardo M. Decreased striatal dopamine transporter binding assessed with [123I] FP-CIT in first-episode schizophrenic patients with and without short-term antipsychotic-induced parkinsonism. Psychopharmacology (Berl) 2005; 181:401-6. [PMID: 15830229 DOI: 10.1007/s00213-005-2250-2] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/18/2005] [Accepted: 02/19/2005] [Indexed: 10/25/2022]
Abstract
RATIONALE Drug-induced parkinsonism (DIP) is one of the main causes of treatment drop-out in schizophrenic patients causing a high incidence of relapse that leads patients to a bad clinical prognosis. The dopaminergic nigrostriatal pathway is involved in the movement control, so the study of the dopamine transporter (DAT) could be of great value to determine its implication in the appearance of DIP. OBJECTIVE The goal of the study is to determine the striatal DAT binding assessed with [(123)I] FP-CIT SPECT in first-episode neuroleptic-naive schizophrenic in-patients with DIP after short-term antipsychotic treatment. METHOD The [(123)I] FP-CIT binding ratios of ten schizophrenic in-patients who developed DIP during the first 4-week period of risperidone treatment (6+/-2 mg/day) were compared with ten schizophrenic in-patients treated with the same doses of risperidone and who do not developed DIP and with ten age-matched healthy subjects. Quantitative analyses of SPECTs were performed using regions of interest located in caudate, putamen and occipital cortex. Parkinsonism was assessed by the Simpson-Angus Scale and the psychopathological status by the Clinical General Impression and Positive and Negative Syndrome Scales. RESULTS Whole striatal [(123)I] FP-CIT binding ratios were significantly lower in patients with and without DIP than in healthy subjects (p<0.001). This was also observed in whole putamen (p<0.001) and caudate nucleus (p<0.001). Females showed higher whole striatal [(123)I] FP-CIT binding ratios than males (p<0.05). No differences in psychopathological scales were observed between patients with and without DIP. CONCLUSION Our first-episode schizophrenic patients with and without DIP after short-term risperidone treatment have a decreased striatal DAT binding assessed with [(123)I] FP-CIT. This alteration could be related to the schizophrenic disease or may be secondary to the antipsychotic treatment.
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Affiliation(s)
- Jose J Mateos
- Nuclear Medicine Department, Hospital Clinic of Barcelona, University of Barcelona, Spain.
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Abstract
The measurement of regional cerebral blood flow (rCBF) by single-photon emission computed tomography (SPECT) is a powerful clinical and research tool. There are several clinical applications now documented, a substantial number under active investigation, and a larger number yet to be studied. Standards regarding patient imaging environment and image presentation are becoming established. This article reviews key aspects of SPECT functional brain imaging in clinical practice, with a particular emphasis on therapeutics, including 1) the quality of the tomographic device, 2) the radiopharmaceutical employed, 3) environmental conditions at the time of radiotracer administration, 4) characteristics of the subject, 5) the format used for image presentation, and 6) the essential components of image processing necessary to the achievement of high-quality SPECT brain images. Next, a brief description of relevant radiation safety issues is provided. Finally, applications in molecular imaging, especially in small animal imaging for research as well as drug discovery and development are discussed. The gamut of SPECT studies from currently routine clinical applications to molecular imaging offers a wonderful frontier for opportunities to employ functional brain imaging in neurotherapeutics.
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Affiliation(s)
- Michael D Devous
- Nuclear Medicine Center and Department of Radiology, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9061, USA.
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McTavish SFB, Mannie ZN, Harmer CJ, Cowen PJ. Lack of effect of tyrosine depletion on mood in recovered depressed women. Neuropsychopharmacology 2005; 30:786-91. [PMID: 15702140 DOI: 10.1038/sj.npp.1300665] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The role of dopamine (DA) pathways in the pathophysiology of depressive disorder is poorly understood. However, because DA plays a key role in motivational behavior, it is important to study in a disorder characterized by anhedonia, lack of energy and psychomotor retardation. A recently developed dietary manipulation ('tyrosine (TYR) depletion') offers a novel method to assess the role of DA in major depression. We studied 15 euthymic women with a past history of recurrent depression, who received a 74 g amino-acid drink lacking TYR and phenylalanine (PHE) (TYR-free) and a balanced (BAL) amino acid drink on two separate occasions in a double-blind, random-order, crossover design. Plasma prolactin levels rose following the TYR-free drink relative to the balanced mixture, while performance on a spatial recognition memory task was impaired. However, relative to the BAL drink, the TYR-free drink did not lower objective or subjective measures of mood. We conclude that as in healthy volunteers, TYR depletion in euthymic subjects, with a past history of major depression, attenuated DA function, as reflected in increased plasma prolactin levels and decreased spatial memory performance. However ratings of depression were unaffected, suggesting that disruption of dopaminergic function by this manipulation does not induce a lowering of mood in individuals vulnerable to depression.
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Tipre DN, Fujita M, Chin FT, Seneca N, Vines D, Liow JS, Pike VW, Innis RB. Whole-body biodistribution and radiation dosimetry estimates for the PET dopamine transporter probe 18F-FECNT in non-human primates. Nucl Med Commun 2005; 25:737-42. [PMID: 15208503 PMCID: PMC4133981 DOI: 10.1097/01.mnm.0000133074.64669.60] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
BACKGROUND AND AIM 2 beta-Carbomethoxy-3-(4-chlorophenyl)-8-(2-[18F]fluoroethyl)nortropane (18F-FECNT) is a selective radioligand for the in vivo quantification of dopamine transporters by using positron emission tomography. The aim of the current study was to quantify the distribution of radioactivity in three rhesus monkeys after the injection of approximately 185 MBq (5 mCi) of 18F-FECNT. METHOD Whole-body images were acquired at 23-30 time points for a total of 220 min following injection of the radioligand. Source organs were identified at each time point from planar images. RESULTS The peak activities in planar images in the six identified source organs (expressed as per cent injected dose (%ID)) were lungs (16.5%ID at 2 min), kidneys (12.5%ID at 3 min), brain (9.5%ID at 6 min), liver (7.5%ID at 3 min), red bone marrow (3.5%ID at 12 min), and urinary bladder (2%ID at 98 min). Radiation absorbed doses were calculated using the gastrointestinal tract model in two ways: (1) assuming no urine voiding, and (2) using a dynamic bladder model with voiding intervals of 2.4 and 4.8 h. Using the gastrointestinal tract model and dynamic bladder model with a voiding interval 4.8 h, the three organs with highest exposure (in mu Gy.MBq(-1) (mrad.mCi(-1)) were kidneys 75.68 (280), lungs 44.86 (166) and urinary bladder 58.38 (216). Effective doses estimated with and without urine voiding were in the range 21.35-22.70 mu Gy.MBq(-1) (79-84 mrad.mCi(-1)). CONCLUSION The estimated radiation burden of 18F-FECNT is relatively modest and would allow multiple scans per research subject per year.
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Affiliation(s)
- Dnyanesh N Tipre
- Molecular Imaging Branch, National Institute of Mental Health, National Institutes of Health, Bldg 1 Rm. B3-10, 1 Center Drive, Bethesda, MD 20892-0135, USA.
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Airaksinen AJ, Huotari M, Shvetsov A, Vainiotalo P, Männisto PT, Tuomisto L, Bergström KA, Vepsäläinen J. Synthesis and biological evaluation of 6/7-exo-methyl-3β-(4-iodo)phenyltropane-2β-carboxylic acid methyl esters. Eur J Med Chem 2005; 40:299-304. [PMID: 15725499 DOI: 10.1016/j.ejmech.2004.11.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2004] [Revised: 11/08/2004] [Accepted: 11/09/2004] [Indexed: 10/26/2022]
Abstract
6beta/7beta-Methyl-2-methoxycarbonyltropinones (3a, 3b) were synthesized and used as starting materials in the synthesis of 6beta/7beta-methyl-2beta-methoxycarbonyl-3beta-phenyltropanes (6a, 6b), 6beta/7beta-methyl-2beta-methoxycarbonyl-3beta-(4-iodo)phenyltropanes (7a, 7b) and 6beta-methyl-2beta-methoxycarbonyl-3beta-(4-iodo)phenylnortropane (8). The effect of 6/7-groups was evaluated by in vitro receptor binding to dopamine (DAT), serotonin (SERT) and norepinephrine (NET) transporters. Introduction of a methyl group at the 6- or 7-position diminished the overall affinity for the transporters, though mostly to NET. In vivo locomotor tests were performed in mice for compounds 7a and 8. Compound 8 had no apparent effect on locomotor activity. Compound 7a increased locomotion in a wide dose range, but was much less potent than a reference compound, 2beta-carbomethoxy-3beta-(4-iodo)phenyl-tropane (beta-CIT).
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Affiliation(s)
- Anu J Airaksinen
- Department of Chemistry, University of Kuopio, P.O.B. 1627, 70211 Kuopio, Finland.
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Mukherjee J, Christian BT, Narayanan TK, Shi B, Collins D. Measurement of d-amphetamine-induced effects on the binding of dopamine D-2/D-3 receptor radioligand, 18F-fallypride in extrastriatal brain regions in non-human primates using PET. Brain Res 2005; 1032:77-84. [PMID: 15680944 DOI: 10.1016/j.brainres.2004.11.005] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/06/2004] [Indexed: 11/25/2022]
Abstract
The ability to measure amphetamine-induced dopamine release in extrastriatal brain regions in the non-human primates was evaluated by using the dopamine D-2/D-3 receptor radioligand, (18)F-fallypride. These regions included the thalamus, amygdala, pituitary, temporal cortex and frontal cortex as well as putamen, caudate and ventral striatum. The positron emission tomography (PET) studies involved control studies, which extended to 3 h, and the amphetamine-challenge studies, which involved administration of d-amphetamine (approx. 0.5-1 mg/kg, i.v.). PET data analysis employed the distribution volume ratio method (DVR) in which the cerebellum was used as a reference region. Our results show a substantial decrease in the binding potential of (18)F-fallypride in extrastriatal regions: thalamus (-20%), amygdala (-39%) and pituitary (-14%). Putamen, caudate and ventral striatum also exhibited significant decreases (-20%). The decrease in (18)F-fallypride binding in the extrastriatal regions points to the importance of dopaminergic neurotransmission in these brain regions. Furthermore, our findings support the use of (18)F-fallypride to measure extrastriatal dopamine release.
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Affiliation(s)
- Jogeshwar Mukherjee
- Brain Imaging Center, Department of Psychiatry and Human Behavior, University of California-Irvine, 162 Irvine Hall, Irvine, CA 92697, USA.
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Abstract
Insomnia is a common feature in schizophrenia. However, it seldom is the predominant complaint. Nevertheless, severe insomnia is often seen during exacerbations of schizophrenia, and may actually precede the appearance of other symptoms of relapse. The sleep disturbances of either never-medicated or previously treated schizophrenia patients are characterized by a sleep-onset and maintenance insomnia. In addition, stage 4 sleep, slow wave sleep (stages 3 and 4), non-REM (NREM) sleep in minutes and REM latency are decreased. The atypical antipsychotics olanzapine, risperidone, and clozapine significantly increase total sleep time and stage 2 sleep. Moreover, olanzapine and risperidone enhance slow wave sleep. On the other hand, the typical antipsychotics haloperidol, thiothixene, and flupentixol significantly reduce stage 2 sleep latency and increase sleep efficiency. Future research should address: (1) the sleep patterns in subtypes of schizophrenia patients; (2) the role of neurotransmitters other than dopamine in the disruption of sleep in schizophrenia; (3) the functional alterations in CNS areas related to the pathophysiology of schizophrenia during NREM sleep and REM sleep (brain imaging studies); (4) the short-term, intermediate-term, and long-term effects of atypical antisychotics on sleep variables.
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Affiliation(s)
- Jaime M Monti
- Department of Pharmacology and Therapeutics, Clinics Hospital, 2833/602 Zudanez Street, Montevideo 11300, Uruguay.
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34
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Scheler G. Regulation of neuromodulator receptor efficacy—implications for whole-neuron and synaptic plasticity. Prog Neurobiol 2004; 72:399-415. [PMID: 15177784 DOI: 10.1016/j.pneurobio.2004.03.008] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2003] [Accepted: 03/26/2004] [Indexed: 11/20/2022]
Abstract
Membrane receptors for neuromodulators (NM) are highly regulated in their distribution and efficacy-a phenomenon which influences the individual cell's response to central signals of NM release. Even though NM receptor regulation is implicated in the pharmacological action of many drugs, and is also known to be influenced by various environmental factors, its functional consequences and modes of action are not well understood. In this paper we summarize relevant experimental evidence on NM receptor regulation (specifically dopamine D1 and D2 receptors) in order to explore its significance for neural and synaptic plasticity. We identify the relevant components of NM receptor regulation (receptor phosphorylation, receptor trafficking and sensitization of second-messenger pathways) gained from studies on cultured cells. Key principles in the regulation and control of short-term plasticity (sensitization) are identified, and a model is presented which employs direct and indirect feedback regulation of receptor efficacy. We also discuss long-term plasticity which involves shifts in receptor sensitivity and loss of responsivity to NM signals. Finally, we discuss the implications of NM receptor regulation for models of brain plasticity and memorization. We emphasize that a realistic model of brain plasticity will have to go beyond Hebbian models of long-term potentiation and depression. Plasticity in the distribution and efficacy of NM receptors may provide another important source of functional plasticity with implications for learning and memory.
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Affiliation(s)
- Gabriele Scheler
- International Computer Science Institute, 1947 Center Street, Suite 600, Berkeley, CA 94704, USA.
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35
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Lomeña Caballero FJ, Simó Perdigó M. [Indications of PET imaging]. Med Clin (Barc) 2003; 120:742-9. [PMID: 12781085 DOI: 10.1016/s0025-7753(03)73831-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Affiliation(s)
- Francisco Juan Lomeña Caballero
- Servicio de Medicina Nuclear. Hospital Clínic de Barcelona. Institut d'Investigació Biomèdica Agustí Pi i Sunyer (IDIBAPS). Universitat de Barcelona. Barcelona. Spain.
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36
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Kung HF, Kung MP, Choi SR. Radiopharmaceuticals for single-photon emission computed tomography brain imaging. Semin Nucl Med 2003; 33:2-13. [PMID: 12605353 DOI: 10.1053/snuc.2003.127296] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
In the past 10 years, significant progress on the development of new brain-imaging agents for single-photon emission computed tomography has been made. Most of the new radiopharmaceuticals are designed to bind specific neurotransmitter receptor or transporter sites in the central nervous system. Most of the site-specific brain radiopharmaceuticals are labeled with (123)I. Results from imaging of benzodiazepine (gamma-aminobutyric acid) receptors by [(123)I]iomazenil are useful in identifying epileptic seizure foci and changes of this receptor in psychiatric disorders. Imaging of dopamine D2/D3 receptors ([(123)I]iodobenzamide and [(123)I]epidepride) and transporters [(123)I]CIT (2-beta-carboxymethoxy-3-beta(4-iodophenyl)tropane) and [(123)I]FP-beta-CIT (N-propyl-2-beta-carboxymethoxy-3-beta(4-iodophenyl)-nortropane has proven to be a simple but powerful tool for differential diagnosis of Parkinson's and other neurodegenerative diseases. A (99m)Tc-labeled agent, [(99m)Tc]TRODAT (technetium, 2-[[2-[[[3-(4-chlorophenyl)-8-methyl-8-azabicyclo [3,2,1]oct-2-yl]methyl](2-mercaptoethyl)amino]ethyl]amino] ethanethiolato(3-)]oxo-[1R-(exo-exo)]-), for imaging dopamine transporters in the brain has been successfully applied in the diagnosis of Parkinson's disease. Despite the fact that (123)I radiopharmaceuticals have been widely used in Japan and in Europe, clinical application of (123)I-labeled brain radiopharmaceuticals in the United States is limited because of the difficulties in supplying such agents. Development of (99m)Tc agents will likely extend the application of site-specific brain radiopharmaceuticals for routine applications in aiding the diagnosis and monitoring treatments of various neurologic and psychiatric disorders.
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Affiliation(s)
- Hank F Kung
- Department of Radiology, University of Pennsylvania, Philadelphia, PA 19104, USA
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37
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Mukherjee J, Christian BT, Dunigan KA, Shi B, Narayanan TK, Satter M, Mantil J. Brain imaging of 18F-fallypride in normal volunteers: blood analysis, distribution, test-retest studies, and preliminary assessment of sensitivity to aging effects on dopamine D-2/D-3 receptors. Synapse 2002; 46:170-88. [PMID: 12325044 DOI: 10.1002/syn.10128] [Citation(s) in RCA: 199] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Human studies of dopamine D2/D3 receptors using 18F-fallypride-PET in normal volunteers were performed to evaluate brain distribution in striatal and extrastriatal regions, evaluate metabolites in blood plasma, establish PET imaging protocol for this new radiotracer, evaluate graphical methods of analysis to quantitate D2/D3 receptors, and assess the ability of 18F-fallypride to measure changes in D2/D3 receptors with aging as a model. Subjects (6; 21-63 years) had a PET scan on a Siemens HR+ scanner with 18F-fallypride and a T1-weighted MRI scan on a 1.5T GE scanner for purposes of anatomical coregistration with PET. A 3-h PET scan with 18F-fallypride (0.07 mCi/Kg) was carried out on each subject and repeated in 4-6 weeks. Arterial or arterialized venous blood was obtained in all subjects in order to evaluate blood activity levels and analyze metabolites in the plasma. Brain regions-of-interest were identified and drawn using PET and PET-MR coregistered images. PET data was analyzed using graphical methods in which cerebellum was used as the reference region providing distribution volume ratios (DVR) from which binding potential (BP) was derived and used as a measure of concentration of receptors. Distribution of 18F-fallypride was consistent in all subjects studied and the rank order of receptor concentration was putamen > caudate > thalamus = pituitary > amygdala > colliculi > substantia nigra > hippocampus = temporal cortex > parietal cortex = occipital cortex = orbitofrontal cortex. For younger subjects, BP ranged from 37 for the putamen to 0.4 for orbitofrontal cortex, with a test-retest error of about 10%. Both hydrophilic and lipophilic metabolites were observed in arterial blood plasma and analyses showed approx. 30-40% of plasma radioactivity at 3 h was 18F-fallypride. With aging, all brain regions exhibited a significant decrease (>10% per decade) in binding of 18F-fallypride. PET studies with 18F-fallypride are thus suitable to study changes in D2/D3 receptors in striatal and extrastriatal brain regions.
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Affiliation(s)
- Jogeshwar Mukherjee
- Department of Nuclear Medicine/PET, Kettering Medical Center, Dayton, Ohio 45429, USA.
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38
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Sánchez-Pernaute R, Brownell AL, Isacson O. Functional imaging of the dopamine system: in vivo evaluation of dopamine deficiency and restoration. Neurotoxicology 2002; 23:469-78. [PMID: 12428719 DOI: 10.1016/s0161-813x(02)00064-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Dopamine deficiency causes a severe impairment in motor function in patients with Parkinson's disease (PD) and in experimental animal models. Recent developments in neuroimaging techniques provide a means to assess in vivo the state of the dopamine system. From a functional perspective, four levels need to be operative and integrated in the system: the dopamine cell (pre-synaptic), the striatal dopamine receptors (post-synaptic), adequate release of dopamine (intra-synaptic), and the cortico-subcortical motor projections. Neuroimaging functional methods can be used to estimate, at these four levels, dopamine cell degeneration, adaptive responses to injury and, importantly, the effect of therapeutic interventions. In this respect, data from functional imaging studies at clinical and pre-clinical stages, support the idea that cell replacement therapy might achieve a more physiological restoration of the dopamine motor system than other therapies (such as ablative surgery, administration of precursor, deep brain stimulation) that currently are equally or more effective in relieving motor symptoms.
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Affiliation(s)
- R Sánchez-Pernaute
- Udall Parkinson's Disease Research Center of Excellence, Neuroregeneration Laboratory, McLean Hospital/Harvard Medical School, Belmont, MA 02478, USA
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39
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Jackson A, Iwasiow RM, Chaar ZY, Nantel MF, Tiberi M. Homologous regulation of the heptahelical D1A receptor responsiveness: specific cytoplasmic tail regions mediate dopamine-induced phosphorylation, desensitization and endocytosis. J Neurochem 2002; 82:683-97. [PMID: 12153492 DOI: 10.1046/j.1471-4159.2002.01001.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
In the present study, we investigate the role of specific cytoplasmic tail (CT) regions of the D1A receptor in mediating dopamine (DA)-induced phosphorylation, desensitization and endocytosis. Results obtained in human embryonic kidney (HEK) cells expressing the wild-type (WT) or truncation forms (Delta425, Delta379 and Delta351) of the D1A receptor show that sequences located downstream of Gly379 regulate DA-mediated phosphorylation-dependent desensitization of D1A receptors. However, the longer truncation mutant Delta351 failed to undergo detectable DA-induced phosphorylation while exhibiting DA-induced desensitization features similar to the shorter truncation mutant Delta379. These data potentially suggest a novel role for a receptor phosphorylation-independent process in the DA-promoted D1A subtype desensitization. Our immunofluorescence data also suggest that sequences located between Cys351 and Gly379 play an important role in DA-mediated receptor endocytosis. Additionally, time-course studies were done in intact cells expressing WT or truncation receptors to measure the observed rate constant for adenylyl cyclase (AC) activation or k(obs), a parameter linked to the receptor-G protein coupling status. In agreement with the desensitization data, Delta425- and Delta379-expressing cells exhibit an increase of kobs in comparison with WT-expressing cells. Nevertheless, Delta351-expressing cells, which harbor similar desensitization features of Delta379-expressing cells, display no change in k(obs) when compared with WT-expressing cells. Our results suggest that a defective DA-induced endocytosis may hamper Delta351 resensitization and concomitant increase in k(obs). Thus, our study showing that specific D1A receptor CT sequences regulate DA-induced phosphorylation, desensitization, and endocytosis highlights the underlying molecular complexity of signaling at dopaminergic synapses.
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Affiliation(s)
- Adele Jackson
- Ottawa Health Research Institute, Department of Medicine/Cellular, University of Ottawa, Ontario, Canada
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40
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Madras BK, Miller GM, Fischman AJ. The dopamine transporter: relevance to attention deficit hyperactivity disorder (ADHD). Behav Brain Res 2002; 130:57-63. [PMID: 11864718 DOI: 10.1016/s0166-4328(01)00439-9] [Citation(s) in RCA: 81] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The dopamine transporter is elevated in adults with attention deficit hyperactivity disorder (ADHD) compared with healthy controls [Lancet 354 (1999) 2132]. The findings have been confirmed by others in a different population using a different probe for the dopamine transporter. Notwithstanding the need to confirm these findings in a multi-center trial, several hypotheses are presented to account for these observations. A premise that elevated transporter levels result from medication is not supported by current data. Other possibilities, including hypertrophy of dopamine neuronal terminals in the striatum, dysfunctional regulation of dopamine or dopamine receptors, or anomalies in the dopamine transporter gene are presented as hypotheses. The feasibility of exploring these mechanisms in animal models or in human subjects is explored.
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Affiliation(s)
- Bertha K Madras
- Department of Psychiatry, New England Regional Primate Research Center, Harvard Medical School, 1 Pine Hill Drive, Southborough, MA 01772-9102, USA.
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41
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I(h) channels contribute to the different functional properties of identified dopaminergic subpopulations in the midbrain. J Neurosci 2002. [PMID: 11850457 DOI: 10.1523/jneurosci.22-04-01290.2002] [Citation(s) in RCA: 267] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Dopaminergic (DA) midbrain neurons in the substantia nigra (SN) and ventral tegmental area (VTA) are involved in various brain functions such as voluntary movement and reward and are targets in disorders such as Parkinson's disease and schizophrenia. To study the functional properties of identified DA neurons in mouse midbrain slices, we combined patch-clamp recordings with either neurobiotin cell-filling and triple labeling confocal immunohistochemistry, or single-cell RT-PCR. We discriminated four DA subpopulations based on anatomical and neurochemical differences: two calbindin D28-k (CB)-expressing DA populations in the substantia nigra (SN/CB+) or ventral tegmental area (VTA/CB+), and respectively, two calbindin D28-k negative DA populations (SN/CB-, VTA/CB-). VTA/CB+ DA neurons displayed significantly faster pacemaker frequencies with smaller afterhyperpolarizations compared with other DA neurons. In contrast, all four DA populations possessed significant differences in I(h) channel densities and I(h) channel-mediated functional properties like sag amplitudes and rebound delays in the following order: SN/CB- --> VTA/CB- --> SN/CB+ --> VTA/CB+. Single-cell RT-multiplex PCR experiments demonstrated that differential calbindin but not calretinin expression is associated with differential I(h) channel densities. Only in SN/CB- DA neurons, however, I(h) channels were actively involved in pacemaker frequency control. In conclusion, diversity within the DA system is not restricted to distinct axonal projections and differences in synaptic connectivity, but also involves differences in postsynaptic conductances between neurochemically and topographically distinct DA neurons.
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42
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Morgan D, Grant KA, Gage HD, Mach RH, Kaplan JR, Prioleau O, Nader SH, Buchheimer N, Ehrenkaufer RL, Nader MA. Social dominance in monkeys: dopamine D2 receptors and cocaine self-administration. Nat Neurosci 2002; 5:169-74. [PMID: 11802171 DOI: 10.1038/nn798] [Citation(s) in RCA: 419] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Disruption of the dopaminergic system has been implicated in the etiology of many pathological conditions, including drug addiction. Here we used positron emission tomography (PET) imaging to study brain dopaminergic function in individually housed and in socially housed cynomolgus macaques (n = 20). Whereas the monkeys did not differ during individual housing, social housing increased the amount or availability of dopamine D2 receptors in dominant monkeys and produced no change in subordinate monkeys. These neurobiological changes had an important behavioral influence as demonstrated by the finding that cocaine functioned as a reinforcer in subordinate but not dominant monkeys. These data demonstrate that alterations in an organism's environment can produce profound biological changes that have important behavioral associations, including vulnerability to cocaine addiction.
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Affiliation(s)
- Drake Morgan
- Department of Physiology and Pharmacology, Wake Forest University School of Medicine, Medical Center Boulevard, Winston-Salem, North Carolina 27157, USA
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43
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Chaar ZY, Jackson A, Tiberi M. The cytoplasmic tail of the D1A receptor subtype: identification of specific domains controlling dopamine cellular responsiveness. J Neurochem 2001; 79:1047-58. [PMID: 11739618 DOI: 10.1046/j.1471-4159.2001.00648.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In this study the rat D1A receptor (wild-type, WT) and truncation mutants thereof, are utilized to delineate specific cytoplasmic tail (CT) domains responsible for regulating ligand binding and receptor-mediated adenylyl cyclase activation. In human embryonic kidney (HEK) cells, all truncation mutants of the D1A receptor (Delta425, Delta379, Delta351) display cell surface localization and express at high but different receptor numbers. Binding studies suggest that residues located between Cys(351) and Asp(425) may serve to restrain the agonist binding conformation of the D1A receptor. This contention is supported by the observation that the constitutive activation of Delta351 is significantly increased in comparison with WT, Delta425 and Delta379. Furthermore, we demonstrate that the extent of dopamine-mediated maximal activation of adenylyl cyclase is significantly augmented in cells expressing Delta351 when compared with WT or mutants harboring shorter truncations. These results suggest that in addition to restraining receptor conformation, determinants located downstream of Cys(351) may act as negative regulators of the G protein coupling efficiency and adenylyl cyclase activation. Interestingly, all truncated receptors used in the present study display a decrease in dopamine potency when compared with WT. We show that inhibition of protein kinase A (PKA) activity leads also to a reduction in dopamine potency in cells expressing WT but not Delta351 receptors. These results hint at a potential previously unanticipated role for PKA in facilitating D1A receptor coupling efficiency in HEK cells. Overall, the present study has uncovered specific CT domains involved in regulating discrete aspects of the D1A receptor signaling.
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Affiliation(s)
- Z Y Chaar
- Ottawa Health Research Institute, and Departments of Medicine/Cellular and Molecular Medicine, University of Ottawa, Ottawa, Ontario, Canada
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44
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Verhoeff NPLG, Kapur S. The Role of Neuroimaging in Development of and Treatment With Antipsychotics. J Pharm Pract 2001. [DOI: 10.1106/ryyj-eemb-9ka4-d5dh] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
This article addresses how neuroimaging can impact the development of and therapy with antipsychotics. The article explains how drug development, disease pathophysiology and neuroimaging approaches can be understood within a single neurobiological framework. It then highlights the relative strengths and applicability of the two streams of neuroimaging: neurochemical neuroimaging that reveals regional concentrations of particular neurochemical species (receptors, transporters or enzymes) and functional neuroimaging that reveals the effects of drug or disease on regional indices of neuronal function such as blood flow and oxygen and glucose metabolism. The application of these techniques is exemplified with recent examples from development and therapeutic use of antipsychotics. To assist decision making in the context of these imaging possibilities, the article presents an algorithm that can be used to guide decisions regarding the application of neuroimaging in the development of and treatment with antipsychotics.
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Affiliation(s)
- Nicolaas P. L. G. Verhoeff
- Schizophrenia Program and PET Centre, CAMH, Toronto, The Clarke Division of the CAMH, 250 College Street, Toronto, ON Canada, M5T 1R8 and the Department of Psychiatry, University of Toronto,
| | - Shitij Kapur
- Schizophrenia Program and PET Centre, CAMH, Toronto, The Clarke Division of the CAMH, 250 College Street, Toronto, ON Canada, M5T 1R8 and Department of Psychiatry, University of Toronto
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45
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McConathy J, Kilts CD, Goodman MM. Radioligands for PET and SPECT Imaging of the central noradrenergic system. CNS Spectr 2001; 6:704-9. [PMID: 15520617 DOI: 10.1017/s1092852900001401] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
In the central nervous system, the neurotransmitter norepinephrine is involved in normal physiology, neuropsychiatric disorders, and the effects of numerous drugs. Although alterations of the central noradrenergic system are involved in the pathophysiology and pharmacotherapy of mood disorders, the basis and nature of these changes remain unresolved. Positron emission tomography (PET) and single photon emission computed tomography (SPECT) imaging agents will be valuable for further elucidating the roles of norepinephrine in health and disease. This review discusses PET and SPECT radioligands that have been developed for the enzymes, receptors, and transporters involved in noradrenergic neurotransmission. Currently, imaging agents that exhibit specific in vivo uptake in the brain have been described for monoamine oxidase A and beta-adrenergic receptors, but have not undergone detailed evaluation or experimental application. Based on the successful development and utilization of in vivo imaging agents for elements of the central dopaminergic and serotoninergic systems, PET and SPECT radioligands are expected to serve as new tools for studying the physiology, pathophysiology, and pharmacology of the central noradrenergic system.
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Affiliation(s)
- J McConathy
- Neuroscience Program, Emory University, Atlanta, GA, USA.
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46
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Differential expression of the small-conductance, calcium-activated potassium channel SK3 is critical for pacemaker control in dopaminergic midbrain neurons. J Neurosci 2001. [PMID: 11331374 DOI: 10.1523/jneurosci.21-10-03443.2001] [Citation(s) in RCA: 233] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The physiological activity of dopaminergic midbrain (DA) neurons is important for movement, cognition, and reward. Altered activity of DA neurons is a key finding in schizophrenia, but the cellular mechanisms have not been identified. Recently, KCNN3, a gene that encodes a member (SK3) of the small-conductance, calcium-activated potassium (SK) channels, has been proposed as a candidate gene for schizophrenia. However, the functional role of SK3 channels in DA neurons is unclear. We combined patch-clamp recordings with single-cell RT-PCR and confocal immunohistochemistry in mouse midbrain slices to study the function of molecularly defined SK channels in DA neurons. Biophysical and pharmacological analysis, single-cell mRNA, and protein expression profiling strongly suggest that SK3 channels mediate the calcium-dependent afterhyperpolarization in DA neurons. Perforated patch recordings of DA neurons in the substantia nigra (SN) demonstrated that SK3 channels dynamically control the frequency of spontaneous firing. In addition, SK3 channel activity was essential to maintain the high precision of the intrinsic pacemaker of DA SN neurons. In contrast, in the ventral tegmental area, DA neurons displayed significantly smaller SK currents and lower SK3 protein expression. In these DA neurons, SK3 channels were not involved in pacemaker control. Accordingly, they discharged in a more irregular manner compared with DA SN neurons. Thus, our study shows that differential SK3 channel expression is a critical molecular mechanism in DA neurons to control neuronal activity. This provides a cellular framework to understand the functional consequences of altered SK3 expression, a candidate disease mechanism for schizophrenia.
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47
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Verhoeff NPLG. Radiotracer imaging of dopamine transporters and presynaptic dopamine synthesis in parkinsonian syndromes. BRAZILIAN JOURNAL OF PSYCHIATRY 2001. [DOI: 10.1590/s1516-44462001000500015] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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48
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Hurley MJ, Mash DC, Jenner P. Dopamine D(1) receptor expression in human basal ganglia and changes in Parkinson's disease. BRAIN RESEARCH. MOLECULAR BRAIN RESEARCH 2001; 87:271-9. [PMID: 11245931 DOI: 10.1016/s0169-328x(01)00022-5] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The expression of the human dopamine D(1) receptor was examined by reverse transcription polymerase chain reaction (RT-PCR) and radioligand binding using [(3)H]-SCH23390 in post-mortem brain tissue that was obtained from normal subjects and patients dying with Parkinson's disease who were receiving treatment with dopaminergic drugs. D(1) receptor mRNA and specific [(3)H]-SCH23390 binding sites were found in both striatal (nucleus accumbens, caudate nucleus and putamen) and extrastriatal (globus pallidus and substantia nigra) brain regions. In parkinsonian brain, D(1) receptor mRNA was increased in the nucleus accumbens, while a decrease was detected in the substantia nigra pars compacta. No change in D(1) mRNA levels was found in the other brain areas examined. An increase in the density of specific [(3)H]-SCH23390 binding sites was found in the anterior putamen and a decrease in the external segment of the globus pallidus, no changes were detected elsewhere. This study demonstrates that regulation of D(1) receptor expression in the brain of patients dying with Parkinson's disease that were treated with L-DOPA is confined to small alterations in restricted brain regions.
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Affiliation(s)
- M J Hurley
- Neurology Department, University of Miami School of Medicine, Miami, FL 31336, USA.
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Abstract
The expression of the human adenosine A(2A) receptor was examined by reverse transcription polymerase chain reaction in post-mortem human brain tissue that was obtained from normal subjects and patients who died with Parkinson's disease. Adenosine A(2A) receptor mRNA was detected in both striatal (nucleus accumbens, caudate nucleus and putamen) and extrastriatal (globus pallidus and substantia nigra) brain regions. A significant decrease in the level of adenosine A(2A) receptor mRNA was found in the anterior and posterior caudate nucleus and anterior dorsal putamen, whereas a significant increase was observed in the substantia nigra pars reticulata of Parkinsonian brain when compared to age-matched controls. No change in adenosine A(2A) receptor mRNA levels was seen in any other brain region examined. This study demonstrates that A(2A) receptor mRNA expression is altered in the basal ganglia of patients who died with Parkinson's disease and who were receiving treatment with dopaminergic drugs. The adenosine A(2A) receptor appears subject to regulation by dopaminergic systems in human brain, though these data do not permit a distinction to be made between the effects of neuronal degeneration or drug treatment. The adenosine A(2A) receptor may therefore form a target for the treatment of basal ganglia disease.
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Affiliation(s)
- M J Hurley
- Neurology Department, University of Miami School of Medicine, 1501 NW 9th Avenue, FL, 33136, Miami, USA.
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