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Amato D, Kruyer A, Samaha AN, Heinz A. Hypofunctional Dopamine Uptake and Antipsychotic Treatment-Resistant Schizophrenia. Front Psychiatry 2019; 10:314. [PMID: 31214054 PMCID: PMC6557273 DOI: 10.3389/fpsyt.2019.00314] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/30/2019] [Accepted: 04/23/2019] [Indexed: 01/07/2023] Open
Abstract
Antipsychotic treatment resistance in schizophrenia remains a major issue in psychiatry. Nearly 30% of patients with schizophrenia do not respond to antipsychotic treatment, yet the underlying neurobiological causes are unknown. All effective antipsychotic medications are thought to achieve their efficacy by targeting the dopaminergic system. Here we review early literature describing the fundamental mechanisms of antipsychotic drug efficacy, highlighting mechanistic concepts that have persisted over time. We then reconsider the original framework for understanding antipsychotic efficacy in light of recent advances in our scientific understanding of the dopaminergic effects of antipsychotics. Based on these new insights, we describe a role for the dopamine transporter in the genesis of both antipsychotic therapeutic response and primary resistance. We believe that this discussion will help delineate the dopaminergic nature of antipsychotic treatment-resistant schizophrenia.
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Affiliation(s)
- Davide Amato
- Department of Neuroscience, Medical University of South Carolina, Charleston, SC, United States
| | - Anna Kruyer
- Department of Neuroscience, Medical University of South Carolina, Charleston, SC, United States
| | - Anne-Noël Samaha
- Department of Pharmacology and Physiology, Faculty of Medicine, Université de Montréal, Montreal, QC, Canada
| | - Andreas Heinz
- Department of Psychiatry, Charité University Medicine Berlin, Campus Charité Mitte, Berlin, Germany
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Jauhar S, Veronese M, Nour MM, Rogdaki M, Hathway P, Turkheimer FE, Stone J, Egerton A, McGuire P, Kapur S, Howes OD. Determinants of treatment response in first-episode psychosis: an 18F-DOPA PET study. Mol Psychiatry 2019; 24:1502-1512. [PMID: 29679071 PMCID: PMC6331038 DOI: 10.1038/s41380-018-0042-4] [Citation(s) in RCA: 84] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/23/2017] [Revised: 12/04/2017] [Accepted: 01/15/2018] [Indexed: 11/10/2022]
Abstract
Psychotic illnesses show variable responses to treatment. Determining the neurobiology underlying this is important for precision medicine and the development of better treatments. It has been proposed that dopaminergic differences underlie variation in response, with striatal dopamine synthesis capacity (DSC) elevated in responders and unaltered in non-responders. We therefore aimed to test this in a prospective cohort, with a nested case-control comparison. 40 volunteers (26 patients with first-episode psychosis and 14 controls) received an 18F-DOPA Positron Emission Tomography scan to measure DSC (Kicer) prior to antipsychotic treatment. Clinical assessments (Positive and Negative Syndrome Scale, PANSS, and Global Assessment of Functioning, GAF) occurred at baseline and following antipsychotic treatment for a minimum of 4 weeks. Response was defined using improvement in PANSS Total score of >50%. Patients were followed up for at least 6 months, and remission criteria applied. There was a significant effect of group on Kicer in associative striatum (F(2, 37) = 7.9, p = 0.001). Kicer was significantly higher in responders compared with non-responders (Cohen's d = 1.55, p = 0.01) and controls (Cohen's d = 1.31, p = 0.02). Kicer showed significant positive correlations with improvements in PANSS-positive (r = 0.64, p < 0.01), PANSS negative (rho = 0.51, p = 0.01), and PANSS total (rho = 0.63, p < 0.01) ratings and a negative relationship with change in GAF (r = -0.55, p < 0.01). Clinical response is related to baseline striatal dopaminergic function. Differences in dopaminergic function between responders and non-responders are present at first episode of psychosis, consistent with dopaminergic and non-dopaminergic sub-types in psychosis, and potentially indicating a neurochemical basis to stratify psychosis.
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Affiliation(s)
- Sameer Jauhar
- 0000 0001 2322 6764grid.13097.3cDepartment of Psychosis Studies, Institute of Psychiatry, Psychology and Neuroscience, King’s College, London, UK ,0000 0000 9439 0839grid.37640.36Early Intervention Psychosis Clinical Academic Group, South London & Maudsley NHS Trust, London, UK
| | - Mattia Veronese
- 0000 0001 2322 6764grid.13097.3cCentre for Neuroimaging Sciences, Institute of Psychiatry, Psychology and Neuroscience, King’s College, London, UK
| | - Matthew M Nour
- 0000 0001 2322 6764grid.13097.3cDepartment of Psychosis Studies, Institute of Psychiatry, Psychology and Neuroscience, King’s College, London, UK ,0000 0001 0705 4923grid.413629.bPsychiatric Imaging Group MRC London Institute of Medical Sciences, Hammersmith Hospital, London, W12 0NN UK ,0000 0001 0705 4923grid.413629.bInstitute of Clinical Sciences, Faculty of Medicine, Imperial College, Hammersmith Hospital, London, W12 0NN UK
| | - Maria Rogdaki
- 0000 0001 2322 6764grid.13097.3cDepartment of Psychosis Studies, Institute of Psychiatry, Psychology and Neuroscience, King’s College, London, UK ,0000 0001 0705 4923grid.413629.bPsychiatric Imaging Group MRC London Institute of Medical Sciences, Hammersmith Hospital, London, W12 0NN UK
| | - Pamela Hathway
- 0000 0001 2322 6764grid.13097.3cDepartment of Psychosis Studies, Institute of Psychiatry, Psychology and Neuroscience, King’s College, London, UK
| | - Federico E. Turkheimer
- 0000 0001 2322 6764grid.13097.3cCentre for Neuroimaging Sciences, Institute of Psychiatry, Psychology and Neuroscience, King’s College, London, UK
| | - James Stone
- 0000 0001 2322 6764grid.13097.3cDepartment of Psychosis Studies, Institute of Psychiatry, Psychology and Neuroscience, King’s College, London, UK ,0000 0001 2322 6764grid.13097.3cCentre for Neuroimaging Sciences, Institute of Psychiatry, Psychology and Neuroscience, King’s College, London, UK
| | - Alice Egerton
- 0000 0001 2322 6764grid.13097.3cDepartment of Psychosis Studies, Institute of Psychiatry, Psychology and Neuroscience, King’s College, London, UK
| | - Philip McGuire
- 0000 0001 2322 6764grid.13097.3cDepartment of Psychosis Studies, Institute of Psychiatry, Psychology and Neuroscience, King’s College, London, UK ,0000 0000 9439 0839grid.37640.36Early Intervention Psychosis Clinical Academic Group, South London & Maudsley NHS Trust, London, UK
| | - Shitij Kapur
- 0000 0001 2322 6764grid.13097.3cFiona Pepper, Centre for Neuroimaging Sciences, King’s College, London, UK
| | - Oliver D Howes
- Department of Psychosis Studies, Institute of Psychiatry, Psychology and Neuroscience, King's College, London, UK. .,Psychiatric Imaging Group MRC London Institute of Medical Sciences, Hammersmith Hospital, London, W12 0NN, UK. .,Institute of Clinical Sciences, Faculty of Medicine, Imperial College, Hammersmith Hospital, London, W12 0NN, UK.
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3
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Maia TV, Conceição VA. Dopaminergic Disturbances in Tourette Syndrome: An Integrative Account. Biol Psychiatry 2018; 84:332-344. [PMID: 29656800 DOI: 10.1016/j.biopsych.2018.02.1172] [Citation(s) in RCA: 65] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/16/2017] [Revised: 02/04/2018] [Accepted: 02/25/2018] [Indexed: 12/28/2022]
Abstract
Tourette syndrome (TS) is thought to involve dopaminergic disturbances, but the nature of those disturbances remains controversial. Existing hypotheses suggest that TS involves 1) supersensitive dopamine receptors, 2) overactive dopamine transporters that cause low tonic but high phasic dopamine, 3) presynaptic dysfunction in dopamine neurons, or 4) dopaminergic hyperinnervation. We review evidence that contradicts the first two hypotheses; we also note that the last two hypotheses have traditionally been considered too narrowly, explaining only small subsets of findings. We review all studies that have used positron emission tomography and single-photon emission computerized tomography to investigate the dopaminergic system in TS. The seemingly diverse findings from those studies have typically been interpreted as pointing to distinct mechanisms, as evidenced by the various hypotheses concerning the nature of dopaminergic disturbances in TS. We show, however, that the hyperinnervation hypothesis provides a simple, parsimonious explanation for all such seemingly diverse findings. Dopaminergic hyperinnervation likely causes increased tonic and phasic dopamine. We have previously shown, using a computational model of the role of dopamine in basal ganglia, that increased tonic dopamine and increased phasic dopamine likely increase the propensities to express and learn tics, respectively. There is therefore a plausible mechanistic link between dopaminergic hyperinnervation and TS via increased tonic and phasic dopamine. To further bolster this argument, we review evidence showing that all medications that are effective for TS reduce signaling by tonic dopamine, phasic dopamine, or both.
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Affiliation(s)
- Tiago V Maia
- Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Lisboa, Portugal.
| | - Vasco A Conceição
- Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Lisboa, Portugal
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Lee J, Kim I, Lee J, Knight E, Cheng L, Kang SI, Jang DP, Chang SY. Development of Harmaline-induced Tremor in a Swine Model. Tremor Other Hyperkinet Mov (N Y) 2018; 8:532. [PMID: 29686939 PMCID: PMC5910538 DOI: 10.7916/d8j68tv7] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2017] [Accepted: 02/05/2018] [Indexed: 12/01/2022] Open
Abstract
Background In the field of translational neuroscience research, it is critical to utilize a large animal model to test the feasibility, safety, and functionality of novel therapies. Here, we describe a protocol for the development of a large animal model of tremor. Methods In a pig model, tremor was induced with harmaline and measured with wireless accelerometers attached to the limbs. Three different doses of harmaline were tested and three repetitive injections were made at 72-hour intervals. To fully characterize the drug-induced tremor, onset time, tremor amplitude, maintained duration, and peak tremor frequency were analyzed. Results Harmaline-induced tremor appeared immediately following intravenous injection of harmaline. Tremor was maintained over 2 hours. Its frequency was 10-16 Hz, which was independent of doses. Dose-dependent responses were observed in tremor amplitude, triggering time, and tremor-maintained duration. Repetitive injection of harmaline desensitized the harmaline effect. Discussion We provide a detailed protocol for training, drug injection, device selection, and tremor recording optimized to create a swine model of tremor with harmaline. Our protocol provides reliable tremor in pigs and suggests pig as a valid translational large animal model of tremor.
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Affiliation(s)
- Jihyun Lee
- Department of Neurologic Surgery, Mayo Clinic, Rochester, MN, USA
| | - Inyong Kim
- Department of Neurology, Mayo Clinic, Rochester, MN, USA
| | - Jeyeon Lee
- Department of Neurologic Surgery, Mayo Clinic, Rochester, MN, USA
| | - Emily Knight
- Department of Pediatrics, New York-Presbyterian Weill Cornell Medical Center, New York, NY, USA
| | - Lei Cheng
- Department of Neurosurgery, The Affiliated Hospital of Qingdao University, Qingdao, Shandong, China
| | - Shin il Kang
- Department of Biomedical Engineering, Hanyang University, Hanyang, Korea
| | - Dong Pyo Jang
- Department of Biomedical Engineering, Hanyang University, Hanyang, Korea
| | - Su-Youne Chang
- Department of Neurologic Surgery, Mayo Clinic, Rochester, MN, USA
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN, USA
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5
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Jauhar S, Nour MM, Veronese M, Rogdaki M, Bonoldi I, Azis M, Turkheimer F, McGuire P, Young AH, Howes OD. A Test of the Transdiagnostic Dopamine Hypothesis of Psychosis Using Positron Emission Tomographic Imaging in Bipolar Affective Disorder and Schizophrenia. JAMA Psychiatry 2017; 74:1206-1213. [PMID: 29049482 PMCID: PMC6059355 DOI: 10.1001/jamapsychiatry.2017.2943] [Citation(s) in RCA: 131] [Impact Index Per Article: 18.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
Importance The dopamine hypothesis suggests that dopamine abnormalities underlie psychosis, irrespective of diagnosis, implicating dopamine dysregulation in bipolar affective disorder and schizophrenia, in line with the research domain criteria approach. However, this hypothesis has not been directly examined in individuals diagnosed with bipolar disorder with psychosis. Objectives To test whether dopamine synthesis capacity is elevated in bipolar disorder with psychosis and how this compares with schizophrenia and matched controls and to examine whether dopamine synthesis capacity is associated with psychotic symptom severity, irrespective of diagnostic class. Design, Setting, and Participants This cross-sectional case-control positron emission tomographic study was performed in the setting of first-episode psychosis services in an inner-city area (London, England). Sixty individuals participated in the study (22 with bipolar psychosis [18 antipsychotic naive or free], 16 with schizophrenia [14 antipsychotic naive or free], and 22 matched controls) and underwent fluorodihydroxyphenyl-l-alanine ([18F]-DOPA) positron emission tomography to examine dopamine synthesis capacity. Standardized clinical measures, including the Positive and Negative Syndrome Scale, Young Mania Rating Scale, and Global Assessment of Functioning, were administered. The study dates were March 2013 to November 2016. Main Outcomes and Measures Dopamine synthesis capacity (Kicer) and clinical measures (Positive and Negative Syndrome Scale, Young Mania Rating Scale, and Global Assessment of Functioning). Results The mean (SD) ages of participants were 23.6 (3.6) years in 22 individuals with bipolar psychosis (13 male), 26.3 (4.4) years in 16 individuals with schizophrenia (14 male), and 24.5 (4.5) years in controls (14 male). There was a significant group difference in striatal dopamine synthesis capacity (Kicer) (F2,57 = 6.80, P = .002). Kicer was significantly elevated in both the bipolar group (mean [SD], 13.18 [1.08] × 10-3 min-1; P = .002) and the schizophrenia group (mean [SD], 12.94 [0.79] × 10-3 min-1; P = .04) compared with controls (mean [SD], 12.16 [0.92] × 10-3 min-1). There was no significant difference in striatal Kicer between the bipolar and schizophrenia groups. Kicer was significantly positively correlated with positive psychotic symptom severity in the combined bipolar and schizophrenia sample experiencing a current psychotic episode, explaining 27% of the variance in symptom severity (n = 32, r = 0.52, P = .003). There was a significant positive association between Kicer and positive psychotic symptom severity in individuals with bipolar disorder experiencing a current psychotic episode (n = 16, r = 0.60, P = .01), which remained significant after adjusting for manic symptom severity. Conclusions and Relevance These findings are consistent with a transdiagnostic role for dopamine dysfunction in the pathoetiology of psychosis and suggest dopamine synthesis capacity as a potential novel drug target for bipolar disorder and schizophrenia.
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Affiliation(s)
- Sameer Jauhar
- Department of Psychosis Studies, Institute of Psychiatry, Psychology and Neuroscience, King's College, London, England
- Psychosis Clinical Academic Group, South London and Maudsley National Health Service Foundation Trust, London, England
| | - Matthew M Nour
- Department of Psychosis Studies, Institute of Psychiatry, Psychology and Neuroscience, King's College, London, England
- Medical Research Council London Institute of Medical Sciences, Imperial College, London, England
| | - Mattia Veronese
- Centre for Neuroimaging Studies, Institute of Psychiatry, Psychology and Neuroscience, King's College, London, England
| | - Maria Rogdaki
- Medical Research Council London Institute of Medical Sciences, Imperial College, London, England
| | - Ilaria Bonoldi
- Department of Psychosis Studies, Institute of Psychiatry, Psychology and Neuroscience, King's College, London, England
- Psychosis Clinical Academic Group, South London and Maudsley National Health Service Foundation Trust, London, England
| | - Matilda Azis
- Department of Psychosis Studies, Institute of Psychiatry, Psychology and Neuroscience, King's College, London, England
| | - Federico Turkheimer
- Centre for Neuroimaging Studies, Institute of Psychiatry, Psychology and Neuroscience, King's College, London, England
| | - Philip McGuire
- Department of Psychosis Studies, Institute of Psychiatry, Psychology and Neuroscience, King's College, London, England
- Psychosis Clinical Academic Group, South London and Maudsley National Health Service Foundation Trust, London, England
| | - Allan H Young
- Department of Psychological Medicine, Institute of Psychiatry, Psychology and Neuroscience, King's College, London, England
| | - Oliver D Howes
- Department of Psychosis Studies, Institute of Psychiatry, Psychology and Neuroscience, King's College, London, England
- Psychosis Clinical Academic Group, South London and Maudsley National Health Service Foundation Trust, London, England
- Medical Research Council London Institute of Medical Sciences, Imperial College, London, England
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6
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Piel M, Vernaleken I, Rösch F. Positron Emission Tomography in CNS Drug Discovery and Drug Monitoring. J Med Chem 2014; 57:9232-58. [DOI: 10.1021/jm5001858] [Citation(s) in RCA: 111] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Affiliation(s)
- Markus Piel
- Institute
of Nuclear Chemistry, Johannes Gutenberg-University, Fritz-Strassmann-Weg 2, D-55128 Mainz, Germany
| | - Ingo Vernaleken
- Department
of Psychiatry, Psychotherapy, and Psychosomatics, RWTH Aachen University, Pauwelsstraße 30, D-52074 Aachen, Germany
| | - Frank Rösch
- Institute
of Nuclear Chemistry, Johannes Gutenberg-University, Fritz-Strassmann-Weg 2, D-55128 Mainz, Germany
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Conway CR, Chibnall JT, Cumming P, Mintun MA, Gebara MAI, Perantie DC, Price JL, Cornell ME, McConathy JE, Gangwani S, Sheline YI. Antidepressant response to aripiprazole augmentation associated with enhanced FDOPA utilization in striatum: a preliminary PET study. Psychiatry Res 2014; 221:231-9. [PMID: 24468015 PMCID: PMC3982608 DOI: 10.1016/j.pscychresns.2014.01.003] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/13/2013] [Revised: 01/03/2014] [Accepted: 01/07/2014] [Indexed: 01/28/2023]
Abstract
Several double blind, prospective trials have demonstrated an antidepressant augmentation efficacy of aripiprazole in depressed patients unresponsive to standard antidepressant therapy. Although aripiprazole is now widely used for this indication, and much is known about its receptor-binding properties, the mechanism of its antidepressant augmentation remains ill-defined. In vivo animal studies and in vitro human studies using cloned dopamine dopamine D2 receptors suggest aripiprazole is a partial dopamine agonist; in this preliminary neuroimaging trial, we hypothesized that aripiprazole's antidepressant augmentation efficacy arises from dopamine partial agonist activity. To test this, we assessed the effects of aripiprazole augmentation on the cerebral utilization of 6-[(18)F]-fluoro-3,4-dihydroxy-l-phenylalanine (FDOPA) using positron emission tomography (PET). Fourteen depressed patients, who had failed 8 weeks of antidepressant therapy with selective serotonin reuptake inhibitors, underwent FDOPA PET scans before and after aripiprazole augmentation; 11 responded to augmentation. Whole brain, voxel-wise comparisons of pre- and post-aripiprazole scans revealed increased FDOPA trapping in the right medial caudate of augmentation responders. An exploratory analysis of depressive symptoms revealed that responders experienced large improvements only in putatively dopaminergic symptoms of lassitude and inability to feel. These preliminary findings suggest that augmentation of antidepressant response by aripiprazole may be associated with potentiation of dopaminergic activity.
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Affiliation(s)
- Charles R. Conway
- Washington University School of Medicine, Department of Psychiatry, 660 South Euclid, Campus Box 8134, St. Louis, MO 63110, USA,Saint Louis University School of Medicine, Department of Neurology & Psychiatry, 1438 South Grand Boulevard, St. Louis, MO 63104, USA,Corresponding author contact information: Address: Washington University Department of Psychiatry, 660 South Euclid, Campus Box 8134, St. Louis, MO 63110, Phone: 314-362-0038; Fax: 314-362-7017,
| | - John T. Chibnall
- Saint Louis University School of Medicine, Department of Neurology & Psychiatry, 1438 South Grand Boulevard, St. Louis, MO 63104, USA
| | - Paul Cumming
- Department of Nuclear Medicine, Friedrich-Alexander University, Erlangen/Nuremberg, Germany
| | - Mark A. Mintun
- Washington University School of Medicine, Departments of Radiology and Psychiatry, St. Louis, MO 63110, USA and Avid Radiopharmaceuticals, Philadelphia, PA 19104, USA
| | - Marie Anne I. Gebara
- Washington University School of Medicine, Department of Psychiatry, 660 South Euclid, Campus Box 8134, St. Louis, MO 63110, USA
| | - Dana C. Perantie
- Washington University School of Medicine, Department of Psychiatry, 660 South Euclid, Campus Box 8134, St. Louis, MO 63110, USA
| | - Joseph L. Price
- Washington University School of Medicine, Department of Anatomy and Neurobiology, St. Louis, MO 63110, USA
| | - Martha E. Cornell
- Washington University School of Medicine, Department of Psychiatry, 660 South Euclid, Campus Box 8134, St. Louis, MO 63110, USA
| | - Jonathan E. McConathy
- Washington University School of Medicine, Department of Radiology, Division of Nuclear Medicine, St. Louis, MO 63110, USA
| | - Sunil Gangwani
- Washington University School of Medicine, Department of Psychiatry, 660 South Euclid, Campus Box 8134, St. Louis, MO 63110, USA
| | - Yvette I. Sheline
- Washington University School of Medicine, Departments of Psychiatry, Neurology, and Radiology, St. Louis, MO 63110, USA
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Ito H, Takano H, Arakawa R, Takahashi H, Kodaka F, Takahata K, Nogami T, Suzuki M, Suhara T. Effects of dopamine D2 receptor partial agonist antipsychotic aripiprazole on dopamine synthesis in human brain measured by PET with L-[β-11C]DOPA. PLoS One 2012; 7:e46488. [PMID: 23029533 PMCID: PMC3460902 DOI: 10.1371/journal.pone.0046488] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2012] [Accepted: 09/05/2012] [Indexed: 12/15/2022] Open
Abstract
Dopamine D2 receptor partial agonist antipsychotic drugs can modulate dopaminergic neurotransmission as functional agonists or functional antagonists. The effects of antipsychotics on presynaptic dopaminergic functions, such as dopamine synthesis capacity, might also be related to their therapeutic efficacy. Positron emission tomography (PET) was used to examine the effects of the partial agonist antipsychotic drug aripiprazole on presynaptic dopamine synthesis in relation to dopamine D2 receptor occupancy and the resulting changes in dopamine synthesis capacity in healthy men. On separate days, PET studies with [11C]raclopride and L-[β-11C]DOPA were performed under resting condition and with single doses of aripiprazole given orally. Occupancy of dopamine D2 receptors corresponded to the doses of aripiprazole, but the changes in dopamine synthesis capacity were not significant, nor was the relation between dopamine D2 receptor occupancy and these changes. A significant negative correlation was observed between baseline dopamine synthesis capacity and changes in dopamine synthesis capacity by aripiprazole, indicating that this antipsychotic appears to stabilize dopamine synthesis capacity. The therapeutic effects of aripiprazole in schizophrenia might be related to such stabilizing effects on dopaminergic neurotransmission responsivity.
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Affiliation(s)
- Hiroshi Ito
- Molecular Imaging Center, National Institute of Radiological Sciences, Chiba, Japan.
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9
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Miyake N, Thompson J, Skinbjerg M, Abi-Dargham A. Presynaptic dopamine in schizophrenia. CNS Neurosci Ther 2010; 17:104-9. [PMID: 21199451 DOI: 10.1111/j.1755-5949.2010.00230.x] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Presynaptic dopamine (DA) transmission has been measured in schizophrenia using different paradigms aimed at providing estimates of the integrity or the activity of the presynaptic dopaminergic neuron. RESEARCHERS HAVE MEASURED: (1) DA synthesis capacity with [(18) F]DOPA, a measure of the activity of dopa decarboxylase, (2) DA release with studies measuring the impact of a DA releasing stimulant challenge on the binding of a D(2) receptor radiotracer, (3) D(2) baseline occupancy by DA, a measure of baseline intrasynaptic DA, assessed by the changes in binding of D(2) radiotracer induced by DA depletion, and (4) the DA and the vesicular monoamine transporters, to assess the integrity of presynaptic terminals. The relationship between DA release and D(2) receptor occupancy at baseline by DA has also been assessed in the same patients. Overall, these different imaging modalities have converged to show a dysregulation of presynaptic dopaminergic activity in schizophrenia, leading to excessive DA release in the striatum, particularly in the projection to the associative striatum, an area of integration between cognitive and limbic cortical inputs. Excessive striatal presynaptic DA is linked to the emergence of acute psychotic symptoms and to their response to treatment in schizophrenia. Understanding the etiology of this dysregulation and its consequences on the rest of the circuitry is important for future drug development.
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Affiliation(s)
- Nobumi Miyake
- Department of Psychiatry, Columbia University, New York State Psychiatric Institute, New York, NY, USA
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10
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Egerton A, Demjaha A, McGuire P, Mehta MA, Howes OD. The test-retest reliability of 18F-DOPA PET in assessing striatal and extrastriatal presynaptic dopaminergic function. Neuroimage 2009; 50:524-531. [PMID: 20034580 DOI: 10.1016/j.neuroimage.2009.12.058] [Citation(s) in RCA: 113] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2009] [Revised: 12/08/2009] [Accepted: 12/12/2009] [Indexed: 11/17/2022] Open
Abstract
Brain presynaptic dopaminergic function can be assessed using 18F-DOPA positron emission tomography (PET). Regional 18F-DOPA utilization may be used to index dopaminergic abnormalities over time or dopaminergic response to treatment in clinical populations. Such studies require prior knowledge of the stability of the 18F-DOPA signal in the brain regions of interest. Test-retest reliability was examined in eight healthy volunteers who each received two 18F-DOPA PET scans, approximately 2 years apart. 18F-DOPA utilization (k(i)(cer)) was determined using graphical analysis relative to a reference tissue input (Patlak and Blasberg, 1985). Reproducibility (measured as the within-subjects variation) and reliability (measured as intraclass correlation coefficients, ICCs) of 18F-DOPA k(i)(cer) were assessed in the structural and functional subdivisions of the striatum and select extrastriatal brain regions. Voxel-based median ICC maps were used to visualize the distribution of 18F-DOPA k(i)(cer) reliability across the brain. The caudate and putamen, and associative and sensorimotor, striatal subdivisions showed good reliability across the two scan sessions with bilateral ICCs ranging from 0.681 to 0.944. Reliability was generally lower in extrastriatal regions, with bilateral ICCs ranging from 0.235 in the amygdala to 0.894 in the thalamus. These data confirm the utility of 18F-DOPA PET in assessing dopaminergic function in the striatum and select extrastriatal areas but highlight the limitations in using this approach to measure dopaminergic function in low uptake extrastriatal brain areas. This information can be used to optimize the experimental design of future studies investigating changes in brain dopaminergic function with 18F-DOPA.
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Affiliation(s)
- Alice Egerton
- Psychiatric Imaging, Medical Research Council Clinical Sciences Centre, Imperial College London, Hammersmith Hospital, Du Cane Road, London W12 0NN, United Kingdom.,Division of Neurosciences & Mental Health, Imperial College London, United Kingdom.,Department of Psychological Medicine, Institute of Psychiatry, King's College London, London SE5 8AF, United Kingdom
| | - Arsime Demjaha
- Psychiatric Imaging, Medical Research Council Clinical Sciences Centre, Imperial College London, Hammersmith Hospital, Du Cane Road, London W12 0NN, United Kingdom.,Department of Psychological Medicine, Institute of Psychiatry, King's College London, London SE5 8AF, United Kingdom
| | - Philip McGuire
- Department of Psychological Medicine, Institute of Psychiatry, King's College London, London SE5 8AF, United Kingdom
| | - Mitul A Mehta
- Psychiatric Imaging, Medical Research Council Clinical Sciences Centre, Imperial College London, Hammersmith Hospital, Du Cane Road, London W12 0NN, United Kingdom.,Division of Neurosciences & Mental Health, Imperial College London, United Kingdom.,Department of Psychological Medicine, Institute of Psychiatry, King's College London, London SE5 8AF, United Kingdom
| | - Oliver D Howes
- Psychiatric Imaging, Medical Research Council Clinical Sciences Centre, Imperial College London, Hammersmith Hospital, Du Cane Road, London W12 0NN, United Kingdom.,Division of Neurosciences & Mental Health, Imperial College London, United Kingdom.,Department of Psychological Medicine, Institute of Psychiatry, King's College London, London SE5 8AF, United Kingdom
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11
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Effects of the antipsychotic risperidone on dopamine synthesis in human brain measured by positron emission tomography with L-[beta-11C]DOPA: a stabilizing effect for dopaminergic neurotransmission? J Neurosci 2009; 29:13730-4. [PMID: 19864585 DOI: 10.1523/jneurosci.4172-09.2009] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Effects of antipsychotic drugs have widely been considered to be mediated by blockade of postsynaptic dopamine D(2) receptors. Effects of antipsychotics on presynaptic functions of dopaminergic neurotransmission might also be related to therapeutic effects of antipsychotics. To investigate the effects of antipsychotics on presynaptic functions of dopaminergic neurotransmission in relation with occupancy of dopamine D(2) receptors, changes in dopamine synthesis capacity by antipsychotics and occupancy of dopamine D(2) receptors were measured by positron emission tomography (PET) in healthy men. PET studies using [(11)C]raclopride and L-[beta-(11)C]DOPA were performed under resting condition and oral administration of single dose of the antipsychotic drug risperidone on separate days. Although occupancy of dopamine D(2) receptors corresponding dose of risperidone was observed, the changes in dopamine synthesis capacity by the administration of risperidone were not significant, nor was the relation between the occupancy of dopamine D(2) receptors and these changes. A significant negative correlation was observed between the baseline dopamine synthesis capacity and the changes in dopamine synthesis capacity by risperidone, indicating that this antipsychotic can be assumed to stabilize the dopamine synthesis capacity. The therapeutic effects of risperidone in schizophrenia might be related to such stabilizing effects on dopaminergic neurotransmission responsivity.
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Guillin O, Abi-Dargham A, Laruelle M. Neurobiology of dopamine in schizophrenia. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2009; 78:1-39. [PMID: 17349856 DOI: 10.1016/s0074-7742(06)78001-1] [Citation(s) in RCA: 79] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
This chapter is an update on the dopamine (DA) imbalance in schizophrenia, including the evidence for subcortical hyperstimulation of D2 receptors underlying positive symptoms and cortical hypodopaminergia-mediating cognitive disturbances and negative symptoms. After a brief review of the anatomical neurocircuitry of this transmitter system as a background, we summarize the evidence for dopaminergic alterations deriving from pharmacological, postmortem, and imaging studies. This evidence supports a prominent role for D2 antagonism in the treatment of positive symptoms of schizophrenia and strongly suggests the need for alternative approaches to address the more challenging problem of negative symptoms and cognitive disturbances.
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Affiliation(s)
- Olivier Guillin
- Department of Psychiatry, Columbia College of Physicians and Surgeons, New York State Psychiatric Institute, Columbia University, New York 10032, USA
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Hadjiconstantinou M, Neff NH. Enhancing aromatic L-amino acid decarboxylase activity: implications for L-DOPA treatment in Parkinson's disease. CNS Neurosci Ther 2009; 14:340-51. [PMID: 19040557 DOI: 10.1111/j.1755-5949.2008.00058.x] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Aromatic L-amino acid decarboxylase (AAAD) is an essential enzyme for the formation of catecholamines, indolamines, and trace amines. Moreover, it is a required enzyme for converting L-DOPA to dopamine when treating patients with Parkinson's disease (PD). There is now substantial evidence that the activity of AAAD in striatum is regulated by activation and induction, and second messengers play a role. Enzyme activity can be modulated by drugs acting on a number of neurotransmitter receptors including dopamine (D1-4), glutamate (NMDA), serotonin (5-HT(1A), 5-HT(2A)) and nicotinic acetylcholine receptors. Generally, antagonists enhance AAAD activity; while, agonists may diminish it. Enhancement of AAAD activity is functional, as the formation of dopamine from exogenous L-DOPA mirrors activity. Following a lesion of nigrostriatal dopaminergic neurons, AAAD in striatum responds more robustly to pharmacological manipulations, and this is true for the decarboxylation of exogenous L-DOPA as well. We review the evidence for parallel modulation of AAAD activity and L-DOPA decarboxylation and propose that this knowledge can be exploited to optimize the formation of dopamine from exogenous L-DOPA. This information can be used as a blue print for the design of novel L-DOPA treatment adjuvants to benefit patients with PD.
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Affiliation(s)
- Maria Hadjiconstantinou
- Division of Molecular Neuropsychopharmacology, Department of Psychiatry, College of Medicine, Ohio State University, Columbus, OH 43210, USA
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Vernaleken I, Kumakura Y, Buchholz HG, Siessmeier T, Hilgers RD, Bartenstein P, Cumming P, Gründer G. Baseline [18F]-FDOPA kinetics are predictive of haloperidol-induced changes in dopamine turnover and cognitive performance: A positron emission tomography study in healthy subjects. Neuroimage 2008; 40:1222-31. [PMID: 18262797 DOI: 10.1016/j.neuroimage.2007.12.045] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2007] [Revised: 12/23/2007] [Accepted: 12/28/2007] [Indexed: 10/22/2022] Open
Abstract
The telencephalic dopamine innervations contribute to the modulation of cognitive processing. However, the relationship between cognitive effects of D(2/3)-receptor antagonism and dopamine transmission is not described in healthy subjects. We therefore tested effects of acute haloperidol (5 mg/d over 3 days) on continuous performance task (CPT) performance and 6-[(18)F]-fluoro-l-DOPA (FDOPA) PET parameters. Nine physically and mentally healthy male men performed two FDOPA-PET scans including arterial plasma withdrawal. Over 3 days before the second scan, all subjects were treated with 5 mg/d haloperidol orally. Using our novel steady-state analysis, we calculated the intrinsic rate of the cerebral FDOPA utilization (K), the turnover of [(18)F]fluorodopamine formed in brain (k(loss)) and the storage for FDOPA and its brain metabolites (V(d)). Furthermore, a ds-CPT and EPS-screening was performed before every PET scan. We found that FDOPA kinetics in those normal subjects with relatively high baseline K showed a more pronounced sensitivity to haloperidol treatment, manifesting in reduced storage capacity and elevated turnover of [(18)F]fluorodopamine, whereas subjects with lower K showed the opposite pattern of responses. Furthermore, low baseline K predicted improvements in the CPT task after haloperidol, whereas participants with higher baseline K showed a decline in cognitive performance. We conclude that the initial increase of [(18)F]fluorodopamine turnover after acute haloperidol challenge is associated with an over-stimulation in individuals with initially more pharmacologically responsive dopamine systems, but optimizes cognitive performance in those with lower normal FDOPA utilization at baseline. We hypothesize that these effects may be driven by D(1)-receptor mediated transmission during D(2) blockade.
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Affiliation(s)
- Ingo Vernaleken
- Department of Psychiatry and Psychotherapy, RWTH Aachen University, Pauwelsstrasse 30, 52074 Aachen, Germany.
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Abstract
The dopamine (DA) hypothesis of schizophrenia has evolved over the last decade from the stage of circumstantial evidence related to clinical observations and empirical validation from antipsychotic treatment to finally reach more direct testing and validation from imaging studies. These have provided much information that allows us at this point to assemble all the pieces and attempt to synthesize them and integrate them with the other neurotransmitter alterations observed in this illness. Although clearly not sufficient to explain the complexity of this disorder, the DA dysregulation offers a direct relationship to symptoms and to their treatment. We will review here its history, validation, and implications for treatment.
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Lind NM, Moustgaard A, Jelsing J, Vajta G, Cumming P, Hansen AK. The use of pigs in neuroscience: Modeling brain disorders. Neurosci Biobehav Rev 2007; 31:728-51. [PMID: 17445892 DOI: 10.1016/j.neubiorev.2007.02.003] [Citation(s) in RCA: 365] [Impact Index Per Article: 21.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2006] [Revised: 02/05/2007] [Accepted: 02/18/2007] [Indexed: 11/22/2022]
Abstract
The use of pigs in neuroscience research has increased in the past decade, which has seen broader recognition of the potential of pigs as an animal for experimental modeling of human brain disorders. The volume of available background data concerning pig brain anatomy and neurochemistry has increased considerably in recent years. The pig brain, which is gyrencephalic, resembles the human brain more in anatomy, growth and development than do the brains of commonly used small laboratory animals. The size of the pig brain permits the identification of cortical and subcortical structures by imaging techniques. Furthermore, the pig is an increasingly popular laboratory animal for transgenic manipulations of neural genes. The present paper focuses on evaluating the potential for modeling symptoms, phenomena or constructs of human brain diseases in pigs, the neuropsychiatric disorders in particular. Important practical and ethical aspects of the use of pigs as an experimental animal as pertaining to relevant in vivo experimental brain techniques are reviewed. Finally, current knowledge of aspects of behavioral processes including learning and memory are reviewed so as to complete the summary of the status of pigs as a species suitable for experimental models of diverse human brain disorders.
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Affiliation(s)
- Nanna Marie Lind
- Department of Experimental Medicine, University of Copenhagen, Panum Institute, Blegdamsvej 3B, Copenhagen N, Denmark.
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Bongiovanni R, Young D, Newbould E, Jaskiw GE. Increased striatal dopamine synthesis is associated with decreased tissue levels of tyrosine. Brain Res 2006; 1115:26-36. [PMID: 16934236 DOI: 10.1016/j.brainres.2006.07.074] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2006] [Revised: 07/20/2006] [Accepted: 07/24/2006] [Indexed: 10/24/2022]
Abstract
Tyrosine levels do not generally affect indices of dopamine (DA) synthesis or efflux under basal conditions, but can do so when DA synthesis is increased. One possibility is that a high rate of DA synthesis depletes the normally adequate pool of endogenous tyrosine. To study this, we administered drugs known to preferentially increase striatal DA synthesis and examined DOPA levels in striatal microdialysate during perfusion with NSD-1015. In additional groups, we also measured DA, tyrosine and large neutral amino acids in striatal microdialysate, as well as in tissue from striatum and medial prefrontal cortex (MPFC). gamma-butyrolactone (GBL) (750 mg/kg i.p.) increased DOPA levels in striatal microdialysate, increased tissue DA levels in the MPFC and striatum, but lowered tissue tyrosine levels only in striatum. In striatal microdialysate, GBL markedly lowered DA levels; tyrosine levels were only marginally lower. Haloperidol (HAL) (1.0 mg/kg s.c.)+/-amfonelic acid (AFA) (5 mg/kg i.p.) increased striatal DOPA accumulation, increased striatal DA efflux, lowered striatal tissue tyrosine levels, but did not affect microdialysate tyrosine levels. There were no consistent changes in levels of other large neutral amino acids. We conclude that increased tyrosine hydroxylation can significantly deplete the endogenous pool of tyrosine. Under such conditions, near normal extracellular tyrosine levels are maintained despite lower tissue levels. The data are consistent with a net transfer of tyrosine from non-DAergic cells to DA terminals in support of DA synthesis.
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Affiliation(s)
- Rodolfo Bongiovanni
- Psychiatry Service, Louis Stokes Department of Veterans Affairs Medical Center, Cleveland, OH 44141, USA
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Vernaleken I, Kumakura Y, Cumming P, Buchholz HG, Siessmeier T, Stoeter P, Müller MJ, Bartenstein P, Gründer G. Modulation of [18F]fluorodopa (FDOPA) kinetics in the brain of healthy volunteers after acute haloperidol challenge. Neuroimage 2006; 30:1332-9. [PMID: 16439159 DOI: 10.1016/j.neuroimage.2005.11.014] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2005] [Revised: 11/03/2005] [Accepted: 11/09/2005] [Indexed: 11/23/2022] Open
Abstract
In animal studies, acute antipsychotic treatment was shown to enhance striatal DOPA-decarboxylase (DDC) activity. However, this phenomenon has not been demonstrated in humans by positron emission tomography (PET). Therefore, we investigated acute haloperidol effects on DDC activity in humans using [18F]fluorodopa (FDOPA) PET. Nine healthy volunteers were scanned with FDOPA in drug-free baseline conditions and after 3 days of haloperidol treatment (5 mg/day). A continuous performance test (CPT) was administered in both conditions. The net blood-brain clearance of FDOPA (K(in)app) in striatum, mesencephalon, and medial prefrontal cortex was calculated by volume-of-interest analysis. The macroparameter K(in)app is a composite of several kinetic terms defining the distribution volume of FDOPA in brain (V(e)D) and the relative activity of DOPA decarboxylase (k3D). Therefore, compartmental kinetic analysis was used to identify the physiological basis of the observed changes in K(in)app period. The magnitude of K(in)app was significantly increased in the putamen (18%) and mesencephalon (36%). Furthermore, V(e)D in the brain was increased by 15%. Increments of k3(D) in the basal ganglia did not attain statistical significance. The significant worsening of CPT results did not correlate with changes in FDOPA utilization. The present PET results indicate potentiation of FDOPA utilization in human basal ganglia by acute haloperidol treatment, apparently due to increased availability throughout the brain. The stimulation of DDC cannot be excluded due to insufficient statistical power in the estimation of k3(D) changes.
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Affiliation(s)
- Ingo Vernaleken
- Department of Psychiatry and Psychotherapy, RWTH Aachen University, Aachen, Germany.
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Lyck L, Jelsing J, Jensen PS, Lambertsen KL, Pakkenberg B, Finsen B. Immunohistochemical visualization of neurons and specific glial cells for stereological application in the porcine neocortex. J Neurosci Methods 2005; 152:229-42. [PMID: 16269187 DOI: 10.1016/j.jneumeth.2005.09.009] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2005] [Revised: 09/06/2005] [Accepted: 09/08/2005] [Indexed: 01/23/2023]
Abstract
The pig is becoming an increasingly used non-primate model in basic experimental studies of human neurological diseases. In spite of the widespread use of immunohistochemistry and cell type specific markers, the application of immunohistochemistry in the pig brain has not been systematically described. Therefore, to facilitate future stereological studies of the neuronal and glial cell populations in experimental neurological diseases in the pig, we established a battery of immunohistochemical protocols for staining of perfusion fixed porcine brain tissue processed as free floating cryostat-, vibratome- or paraffin sections. Antibodies against NeuN, GFAP, S100-protein, MBP, CNPase, CD11b, CD68 (KP1), CD45 and Ki67 were evaluated, and all except CD68 and CD45 resulted in staining of high quality in either type of tissue. Each staining was evaluated with respect to specificity and sensitivity in identification of the individual cells, and for penetration of the staining and maintenance of section thickness above 25 microm, necessary for stereological cell counting. In the cases of NeuN, CNPase, CD11b and Ki67 the staining met the demands to be applicable in stereological analyses using the optical disector. In conclusion, all protocols will be applicable in studies of pathological and neurochemical changes in the porcine brain, and a few protocols applicable for stereology.
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Affiliation(s)
- Lise Lyck
- Medical Biotechnology Centre, University of Southern Denmark, Winsløwparken 25, 2nd floor, DK-5000 Odense C, and Research Laboratory for Stereology and Neuroscience, Bispebjerg University Hospital, Copenhagen, Denmark.
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Kumakura Y, Danielsen EH, Reilhac A, Gjedde A, Cumming P. Levodopa effect on [18F]fluorodopa influx to brain: normal volunteers and patients with Parkinson's disease. Acta Neurol Scand 2004; 110:188-95. [PMID: 15285777 DOI: 10.1111/j.1600-0404.2004.00299.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVES Levodopa is the immediate precursor of dopamine and the substrate for DOPA decarboxylase, an enzyme subject to regulation in living brain. To test whether this regulation changes in disease, we used Positron Emission Tomography (PET) with parametric mapping to measure the effect of levodopa on the net clearance of [(18)F]fluorodopa to brain (K, ml/g/min). METHODS Five patients with early Parkinson's disease with pause of medication for 3 days and six age-matched healthy volunteers were studied in a baseline condition and after levodopa challenge. RESULTS Levodopa (200 mg as Sinemet) increased the magnitude of the net clearance K in the left and right putamen of the healthy volunteers by 11% relative to the baseline condition. In contrast, resumption of medication with levodopa did not significantly alter the magnitude of K in putamen of the Parkinson's disease patients. Compartmental analysis was used to probe the physiological basis of the activation of K: levodopa treatment increased by 15% the apparent distribution volume of [(18)F]fluorodopa in cerebellum (, ml/g) of both patients and control subjects, without significantly altering the unidirectional blood-brain clearance (, ml/g/min) or the relative activity of DOPA decarboxylase (, min(-1)) in putamen. CONCLUSION We conclude that levodopa treatment increases the distribution volume of [(18)F]fluorodopa in brain, increasing its availability for utilization in dopamine terminals. We speculate that levodopa act as a direct beta-adrenergic agonist at receptors regulating the permeability of the blood-brain barrier to levodopa. However, the PET analytical method was without sufficient power to detect the consequent increase in magnitude of K in brain of only five Parkinson's disease subjects.
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Affiliation(s)
- Y Kumakura
- PET Centre, Aarhus University Hospitals and Centre for Functionally Integrated Neuroscience, Aarhus, Denmark
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Ikemoto K. Significance of human striatal D-neurons: implications in neuropsychiatric functions. Prog Neuropsychopharmacol Biol Psychiatry 2004; 28:429-34. [PMID: 15093949 DOI: 10.1016/j.pnpbp.2003.11.017] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 11/14/2003] [Indexed: 11/22/2022]
Abstract
The human striatum, especially its ventral part, the nucleus accumbens (Acc), contains numerous nonmonoaminergic aromatic L-amino acid decarboxylase (AADC) [=dopa decarboxylase (DDC)] neurons (D-neurons). AADC is the second-step synthesizing enzyme for monoamines and is also the rate-limiting enzyme of phenylethylamine (PEA) synthesis. D-neurons may participate in the manifestation of efficacy of pharmacotherapy for Parkinson's disease by taking up monoamine precursors including L-dopa or droxidopa (L-threo-DOPS) and by converting them to dopamine or noradrenaline, respectively. Although previous studies have shown that AADC activity was elevated in the striatum of drug-naive schizophrenia, the number of striatal D-neurons was reduced in autopsy brains of schizophrenia. It is unclear whether or not such reduction of striatal D-neurons implies downregulation. Possible pluripotentiality of D-neurons, including compensatory functions against aging and degeneration, was discussed based on recent published works.
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Affiliation(s)
- Keiko Ikemoto
- Clinical Research Institute, National Minami Hanamaki Hospital, 500 Suwa, Hanamaki, Iwate, 025-0033, Japan.
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Mamo D, Remington G, Nobrega J, Hussey D, Chirakal R, Wilson AA, Baker G, Houle S, Kapur S. Effect of acute antipsychotic administration on dopamine synthesis in rodents and human subjects using 6-[18F]-L-m-tyrosine. Synapse 2004; 52:153-62. [PMID: 15034921 DOI: 10.1002/syn.20016] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Clinical effects of antipsychotic drugs are thought to be mediated primarily through antagonism of the dopamine D2 receptors. Recent studies have demonstrated increased aromatic decarboxylase activity following acute administration of dopamine D2 receptor antagonists both in vivo and ex vivo. However, this effect has never been demonstrated in human subjects. We studied the effect of acute antipsychotic administration on dopamine synthesis in rodents and healthy human subjects using 6-[18F]-L-m-tyrosine. In rats, we studied the effect of a single subcutaneous injection of haloperidol and risperidone on dopamine synthesis using 6-[18F]-L-m-tyrosine. In our human study, six healthy volunteers underwent two 6-[18F]-L-m-tyrosine PET scans, before and after 3 mg risperidone to measure the rate of accumulation of radioactivity in the striatum as an index of dopamine synthesis. The striatal/cerebellar radioactivity count ratio and the ratio of dopamine metabolites to dopamine concentration was significantly higher in all rodent treatment groups compared to controls. In the PET study we found no significant change in the rate of uptake in the striatum. Our results suggest that 6-[18F]-L-m-tyrosine PET may not be a useful tool in the study of the effect of antipsychotics on dopamine synthesis in human subjects.
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Affiliation(s)
- David Mamo
- Department of Psychiatry, University of Toronto, Canada.
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Gründer G, Vernaleken I, Müller MJ, Davids E, Heydari N, Buchholz HG, Bartenstein P, Munk OL, Stoeter P, Wong DF, Gjedde A, Cumming P. Subchronic haloperidol downregulates dopamine synthesis capacity in the brain of schizophrenic patients in vivo. Neuropsychopharmacology 2003; 28:787-94. [PMID: 12655326 DOI: 10.1038/sj.npp.1300103] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The antipsychotic effect of neuroleptics cannot be attributed entirely to acute blockade of postsynaptic D(2)-like dopamine (DA) receptors, but may arise in conjunction with the delayed depolarization block of the presynaptic neurons and reduced DA synthesis capacity. Whereas the phenomenon of depolarization block is well established in animals, it is unknown if a similar phenomenon occurs in humans treated with neuroleptics. We hypothesized that haloperidol treatment should result in decreased DA synthesis capacity. We used 6-[(18)F]fluoro-L-dopa (FDOPA) and positron emission tomography (PET) in conjunction with compartmental modeling to measure the relative activity of DOPA decarboxylase (DDC) (k(D)(3), min(-1)) in the brain of nine unmedicated patients with schizophrenia, first in the untreated condition and again after treatment with haloperidol. Patients were administered psychometric rating scales at baseline and after treatment. Consistent with our hypothesis, there was a 25% decrease in the magnitude of k(D)(3) in both caudate and putamen following 5 weeks of haloperidol therapy. In addition, the magnitudes of k(D)(3) in cerebral cortex and thalamus were also decreased. Psychopathology as measured with standard rating scales improved significantly in all patients. The decrease of k(D)(3) in the thalamus was highly significantly correlated with the improvement of negative symptoms. Subchronic treatment with haloperidol decreased the activity of DDC in the brain of patients with schizophrenia. This observation is consistent with the hypothesis that the antipsychotic effect of chronic neuroleptic treatment is associated with a decrease in DA synthesis, reflecting a depolarization block of presynaptic DA neurons. We link an alteration in cerebral catecholamine metabolism in human brain with the therapeutic action of neuroleptic medication.
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