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Santoro V, Hou MD, Premoli I, Belardinelli P, Biondi A, Carobin A, Puledda F, Michalopoulou PG, Richardson MP, Rocchi L, Shergill SS. Investigating cortical excitability and inhibition in patients with schizophrenia: A TMS-EEG study. Brain Res Bull 2024; 212:110972. [PMID: 38710310 DOI: 10.1016/j.brainresbull.2024.110972] [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: 02/14/2024] [Revised: 04/24/2024] [Accepted: 04/30/2024] [Indexed: 05/08/2024]
Abstract
BACKGROUND Transcranial magnetic stimulation (TMS) combined with electromyography (EMG) has widely been used as a non-invasive brain stimulation tool to assess excitation/inhibition (E/I) balance. E/I imbalance is a putative mechanism underlying symptoms in patients with schizophrenia. Combined TMS-electroencephalography (TMS-EEG) provides a detailed examination of cortical excitability to assess the pathophysiology of schizophrenia. This study aimed to investigate differences in TMS-evoked potentials (TEPs), TMS-related spectral perturbations (TRSP) and intertrial coherence (ITC) between patients with schizophrenia and healthy controls. MATERIALS AND METHODS TMS was applied over the motor cortex during EEG recording. Differences in TEPs, TRSP and ITC between the patient and healthy subjects were analysed for all electrodes at each time point, by applying multiple independent sample t-tests with a cluster-based permutation analysis to correct for multiple comparisons. RESULTS Patients demonstrated significantly reduced amplitudes of early and late TEP components compared to healthy controls. Patients also showed a significant reduction of early delta (50-160 ms) and theta TRSP (30-250ms),followed by a reduction in alpha and beta suppression (220-560 ms; 190-420 ms). Patients showed a reduction of both early (50-110 ms) gamma increase and later (180-230 ms) gamma suppression. Finally, the ITC was significantly lower in patients in the alpha band, from 30 to 260 ms. CONCLUSION Our findings support the putative role of impaired GABA-receptor mediated inhibition in schizophrenia impacting excitatory neurotransmission. Further studies can usefully elucidate mechanisms underlying specific symptoms clusters using TMS-EEG biometrics.
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Affiliation(s)
- V Santoro
- Department of Basic and Clinical Neuroscience, Institute of Psychiatry, Psychology and Neuroscience (IoPPN), King's College London, London, United Kingdom; Headache Group, Wolfson SPaRC, Institute of Psychiatry Psychology and Neuroscience (IoPPN), King's College London, London, United Kingdom.
| | - M D Hou
- Department of Psychosis Studies, Institute of Psychiatry, Psychology and Neuroscience (IoPPN), King's College London, London, United Kingdom
| | - I Premoli
- Department of Basic and Clinical Neuroscience, Institute of Psychiatry, Psychology and Neuroscience (IoPPN), King's College London, London, United Kingdom
| | - P Belardinelli
- Cimec, Center for Mind/Brain Sciences, University of Trento, Trento, Italy
| | - A Biondi
- Department of Basic and Clinical Neuroscience, Institute of Psychiatry, Psychology and Neuroscience (IoPPN), King's College London, London, United Kingdom
| | - A Carobin
- Department of Basic and Clinical Neuroscience, Institute of Psychiatry, Psychology and Neuroscience (IoPPN), King's College London, London, United Kingdom
| | - F Puledda
- Headache Group, Wolfson SPaRC, Institute of Psychiatry Psychology and Neuroscience (IoPPN), King's College London, London, United Kingdom
| | - P G Michalopoulou
- Department of Psychosis Studies, Institute of Psychiatry, Psychology and Neuroscience (IoPPN), King's College London, London, United Kingdom
| | - M P Richardson
- Department of Basic and Clinical Neuroscience, Institute of Psychiatry, Psychology and Neuroscience (IoPPN), King's College London, London, United Kingdom
| | - L Rocchi
- Department of Basic and Clinical Neuroscience, Institute of Psychiatry, Psychology and Neuroscience (IoPPN), King's College London, London, United Kingdom; Department of Medical Sciences and Public Health, University of Cagliari, Cagliari, Italy; Department of Clinical and Movement Neurosciences, UCL Queen Square Institute of Neurology, University College London, London, United Kingdom
| | - S S Shergill
- Department of Psychosis Studies, Institute of Psychiatry, Psychology and Neuroscience (IoPPN), King's College London, London, United Kingdom; Kent and Medway Medical School, Canterbury CT2 7FS, United Kingdom; Kent and Medway NHS and Social Care Partnership Trust, Maidstone, ME7 4JL, United Kingdom
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2
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Synthesis and In Vitro Evaluation of Novel Dopamine Receptor D 2 3,4-dihydroquinolin-2(1 H)-one Derivatives Related to Aripiprazole. Biomolecules 2021; 11:biom11091262. [PMID: 34572475 PMCID: PMC8464836 DOI: 10.3390/biom11091262] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2021] [Revised: 08/19/2021] [Accepted: 08/20/2021] [Indexed: 12/28/2022] Open
Abstract
In this pilot study, a series of new 3,4-dihydroquinolin-2(1H)-one derivatives as potential dopamine receptor D2 (D2R) modulators were synthesized and evaluated in vitro. The preliminary structure-activity relationship disclosed that compound 5e exhibited the highest D2R affinity among the newly synthesized compounds. In addition, 5e showed a very low cytotoxic profile and a high probability to cross the blood-brain barrier, which is important considering the observed affinity. However, molecular modelling simulation revealed completely different binding mode of 5e compared to USC-D301, which might be the culprit of the reduced affinity of 5e toward D2R in comparison with USC-D301.
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Seeman MV. History of the dopamine hypothesis of antipsychotic action. World J Psychiatry 2021; 11:355-364. [PMID: 34327128 PMCID: PMC8311512 DOI: 10.5498/wjp.v11.i7.355] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/25/2021] [Revised: 04/22/2021] [Accepted: 06/22/2021] [Indexed: 02/06/2023] Open
Abstract
The dopamine hypothesis of how antipsychotic drugs exert their beneficial effect in psychotic illness has an interesting history that dates back to 1950. This hypothesis is not to be confused with the dopamine hypothesis of schizophrenia; the aim of the latter is to explain the etiology of schizophrenia. The present review does not deal with schizophrenia but, rather, with the historical development of our current understanding of the dopamine-associated actions of the drugs that reduce the symptoms of psychosis. This historical review begins with the serendipitous discovery of chlorpromazine, a drug synthesized around a chemical core that initially served to produce man-made dyes. This molecular core subsequently contributed to the chemistry of antihistamines. It was with the aim of producing a superior antihistamine that chlorpromazine was synthesized; instead, it revolutionized the treatment of psychosis. The first hypothesis of how this drug worked was that it induced hypothermia, a cooling of the body that led to a tranquilization of the mind. The new, at the time, discoveries of the presence of chemical transmitters in the brain soon steered investigations away from a temperature-related hypothesis toward questioning how this drug, and other drugs with similar properties and effects, modulated endogenous neurotransmission. As a result, over the years, researchers from around the world have begun to progressively learn what antipsychotic drugs do in the brain.
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Affiliation(s)
- Mary V Seeman
- Department of Psychiatry, University of Toronto, Toronto M5P 3L6, Ontario, Canada
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4
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Egerton A, Murphy A, Donocik J, Anton A, Barker GJ, Collier T, Deakin B, Drake R, Eliasson E, Emsley R, Gregory CJ, Griffiths K, Kapur S, Kassoumeri L, Knight L, Lambe EJB, Lawrie SM, Lees J, Lewis S, Lythgoe DJ, Matthews J, McGuire P, McNamee L, Semple S, Shaw AD, Singh KD, Stockton-Powdrell C, Talbot PS, Veronese M, Wagner E, Walters JTR, Williams SR, MacCabe JH, Howes OD. Dopamine and Glutamate in Antipsychotic-Responsive Compared With Antipsychotic-Nonresponsive Psychosis: A Multicenter Positron Emission Tomography and Magnetic Resonance Spectroscopy Study (STRATA). Schizophr Bull 2021; 47:505-516. [PMID: 32910150 PMCID: PMC7965076 DOI: 10.1093/schbul/sbaa128] [Citation(s) in RCA: 47] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The variability in the response to antipsychotic medication in schizophrenia may reflect between-patient differences in neurobiology. Recent cross-sectional neuroimaging studies suggest that a poorer therapeutic response is associated with relatively normal striatal dopamine synthesis capacity but elevated anterior cingulate cortex (ACC) glutamate levels. We sought to test whether these measures can differentiate patients with psychosis who are antipsychotic responsive from those who are antipsychotic nonresponsive in a multicenter cross-sectional study. 1H-magnetic resonance spectroscopy (1H-MRS) was used to measure glutamate levels (Glucorr) in the ACC and in the right striatum in 92 patients across 4 sites (48 responders [R] and 44 nonresponders [NR]). In 54 patients at 2 sites (25 R and 29 NR), we additionally acquired 3,4-dihydroxy-6-[18F]fluoro-l-phenylalanine (18F-DOPA) positron emission tomography (PET) to index striatal dopamine function (Kicer, min-1). The mean ACC Glucorr was higher in the NR than the R group after adjustment for age and sex (F1,80 = 4.27; P = .04). This was associated with an area under the curve for the group discrimination of 0.59. There were no group differences in striatal dopamine function or striatal Glucorr. The results provide partial further support for a role of ACC glutamate, but not striatal dopamine synthesis, in determining the nature of the response to antipsychotic medication. The low discriminative accuracy might be improved in groups with greater clinical separation or increased in future studies that focus on the antipsychotic response at an earlier stage of the disorder and integrate other candidate predictive biomarkers. Greater harmonization of multicenter PET and 1H-MRS may also improve sensitivity.
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Affiliation(s)
- Alice Egerton
- Department of Psychosis Studies, Institute of Psychiatry, Psychology & Neuroscience, King’s College London, London, UK
- NIHR Biomedical Research Centre at South London and Maudsley NHS Foundation Trust, London, UK
| | - Anna Murphy
- Division of Neuroscience and Experimental Psychology, School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK
| | - Jacek Donocik
- Department of Psychosis Studies, Institute of Psychiatry, Psychology & Neuroscience, King’s College London, London, UK
| | - Adriana Anton
- Division of Neuroscience and Experimental Psychology, School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK
- Academic Unit of Radiology, Medical School, Faculty of Medicine, Dentistry & Health, University of Sheffield, Sheffield, UK
| | - Gareth J Barker
- NIHR Biomedical Research Centre at South London and Maudsley NHS Foundation Trust, London, UK
- Department of Neuroimaging, Institute of Psychiatry, Psychology & Neuroscience, King’s College London, London, UK
| | - Tracy Collier
- Department of Psychosis Studies, Institute of Psychiatry, Psychology & Neuroscience, King’s College London, London, UK
- NIHR Biomedical Research Centre at South London and Maudsley NHS Foundation Trust, London, UK
| | - Bill Deakin
- Division of Neuroscience and Experimental Psychology, School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK
| | - Richard Drake
- Division of Psychology and Mental Health, School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK
| | - Emma Eliasson
- Division of Psychiatry, University of Edinburgh, Edinburgh, UK
| | - Richard Emsley
- NIHR Biomedical Research Centre at South London and Maudsley NHS Foundation Trust, London, UK
- Department of Biostatistics and Health Informatics, Institute of Psychiatry, Psychology & Neuroscience, King’s College London, London, UK
| | - Catherine J Gregory
- Division of Neuroscience and Experimental Psychology, School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK
| | - Kira Griffiths
- Department of Psychosis Studies, Institute of Psychiatry, Psychology & Neuroscience, King’s College London, London, UK
| | - Shitij Kapur
- Department of Psychosis Studies, Institute of Psychiatry, Psychology & Neuroscience, King’s College London, London, UK
- NIHR Biomedical Research Centre at South London and Maudsley NHS Foundation Trust, London, UK
- Faculty of Medicine, Dentistry and Health Sciences, University of Melbourne, Parkville, Victoria, Australia
| | - Laura Kassoumeri
- Department of Psychosis Studies, Institute of Psychiatry, Psychology & Neuroscience, King’s College London, London, UK
- NIHR Biomedical Research Centre at South London and Maudsley NHS Foundation Trust, London, UK
| | - Laura Knight
- CUBRIC, School of Psychology, College of Biomedical and Life Sciences, Cardiff University, Cardiff, UK
| | - Emily J B Lambe
- CUBRIC, School of Psychology, College of Biomedical and Life Sciences, Cardiff University, Cardiff, UK
| | | | - Jane Lees
- Division of Psychology and Mental Health, School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK
| | - Shôn Lewis
- Division of Psychology and Mental Health, School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK
| | - David J Lythgoe
- NIHR Biomedical Research Centre at South London and Maudsley NHS Foundation Trust, London, UK
- Department of Neuroimaging, Institute of Psychiatry, Psychology & Neuroscience, King’s College London, London, UK
| | - Julian Matthews
- Division of Neuroscience and Experimental Psychology, School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK
| | - Philip McGuire
- Department of Psychosis Studies, Institute of Psychiatry, Psychology & Neuroscience, King’s College London, London, UK
- NIHR Biomedical Research Centre at South London and Maudsley NHS Foundation Trust, London, UK
| | - Lily McNamee
- Division of Psychiatry, University of Edinburgh, Edinburgh, UK
| | - Scott Semple
- Centre for Cardiovascular Science, University of Edinburgh, Edinburgh, UK
| | - Alexander D Shaw
- CUBRIC, School of Psychology, College of Biomedical and Life Sciences, Cardiff University, Cardiff, UK
| | - Krish D Singh
- CUBRIC, School of Psychology, College of Biomedical and Life Sciences, Cardiff University, Cardiff, UK
| | - Charlotte Stockton-Powdrell
- Division of Psychology and Mental Health, School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK
| | - Peter S Talbot
- Division of Neuroscience and Experimental Psychology, School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK
| | - Mattia Veronese
- NIHR Biomedical Research Centre at South London and Maudsley NHS Foundation Trust, London, UK
- Department of Neuroimaging, Institute of Psychiatry, Psychology & Neuroscience, King’s College London, London, UK
| | - Ernest Wagner
- Division of Psychiatry, University of Edinburgh, Edinburgh, UK
| | - James T R Walters
- MRC Centre for Neuropsychiatric Genetics and Genomics, Division of Psychological Medicine and Clinical Neurosciences, School of Medicine, Cardiff University, Cardiff, UK
| | - Stephen R Williams
- Division of Informatics, Imaging and Data Sciences, University of Manchester, Manchester, UK
| | - James H MacCabe
- Department of Psychosis Studies, Institute of Psychiatry, Psychology & Neuroscience, King’s College London, London, UK
- NIHR Biomedical Research Centre at South London and Maudsley NHS Foundation Trust, London, UK
| | - Oliver D Howes
- Department of Psychosis Studies, Institute of Psychiatry, Psychology & Neuroscience, King’s College London, London, UK
- NIHR Biomedical Research Centre at South London and Maudsley NHS Foundation Trust, London, UK
- Psychiatric Imaging Group, MRC London Institute of Medical Sciences, Hammersmith Hospital, London, UK
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5
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Chestnykh DA, Amato D, Kornhuber J, Müller CP. Pharmacotherapy of schizophrenia: Mechanisms of antipsychotic accumulation, therapeutic action and failure. Behav Brain Res 2021; 403:113144. [PMID: 33515642 DOI: 10.1016/j.bbr.2021.113144] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2020] [Revised: 01/21/2021] [Accepted: 01/22/2021] [Indexed: 12/13/2022]
Abstract
Schizophrenia is a multi-dimensional disorder with a complex and mostly unknown etiology, leading to a severe decline in life quality. Antipsychotic drugs (APDs) remain beneficial interventions in the treatment of the disorder, but vary significantly in binding profile, clinical effects and adverse reactions. The present review summarizes the main principles of APD mechanisms of action with a particular focus on recent findings in APD accumulation and its role in the therapeutic efficacy and treatment failure. High and low doses of APDs were shown to be effective in different dimensions of antipsychotic-like behaviour in rodent models. Efficacy of the APDs correlates with high dopamine D2 receptor occupancy, which occurs quickly after drug administration. However, onset and peak of action are delayed up to several days or weeks. APD accumulation via acidic trapping in synaptic vesicles is considered to underlie the time course of APD action. Use-dependent exocytosis, co-release with dopamine and serotonin and inhibition of ion channels impact on the neuronal transmission and determine effects of APDs. Disruption in accumulating properties leads to diminished APD effects. In addition, long-term APD administration at therapeutic doses leads to treatment failure both in animal models and in humans. APD failure was associated with treatment induced neuroadaptations, including a decline in extracellular dopamine levels, dopamine transporter upregulation, and altered neuronal firing. However, enhanced synaptic vesicle release has also been reported. APD loss of efficacy may be reversed through inhibition of the dopamine transporter or switching the administration regimen from continuous to intermittent. Thus, manipulating the accumulation properties of APDs, changes in the administration regimen and doses, or co-administration with dopamine transporter inhibitors may be considered to yield benefits in the development of new effective strategies in the treatment of schizophrenia.
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Affiliation(s)
- Daria A Chestnykh
- Department of Psychiatry and Psychotherapy, University Clinic, Friedrich-Alexander-University Erlangen-Nuremberg, Schwabachanlage 6, 91054, Erlangen, Germany
| | - Davide Amato
- Department of Psychiatry and Psychotherapy, University Clinic, Friedrich-Alexander-University Erlangen-Nuremberg, Schwabachanlage 6, 91054, Erlangen, Germany; Department of Neuroscience, Medical University of South Carolina, Charleston, SC, USA
| | - Johannes Kornhuber
- Department of Psychiatry and Psychotherapy, University Clinic, Friedrich-Alexander-University Erlangen-Nuremberg, Schwabachanlage 6, 91054, Erlangen, Germany
| | - Christian P Müller
- Department of Psychiatry and Psychotherapy, University Clinic, Friedrich-Alexander-University Erlangen-Nuremberg, Schwabachanlage 6, 91054, Erlangen, Germany.
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6
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A dopaminergic mechanism of antipsychotic drug efficacy, failure, and failure reversal: the role of the dopamine transporter. Mol Psychiatry 2020; 25:2101-2118. [PMID: 30038229 PMCID: PMC7473845 DOI: 10.1038/s41380-018-0114-5] [Citation(s) in RCA: 37] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/23/2017] [Revised: 04/30/2018] [Accepted: 05/25/2018] [Indexed: 12/21/2022]
Abstract
Antipsychotic drugs are effective interventions in schizophrenia. However, the efficacy of these agents often decreases over time, which leads to treatment failure and symptom recurrence. We report that antipsychotic efficacy in rat models declines in concert with extracellular striatal dopamine levels rather than insufficient dopamine D2 receptor occupancy. Antipsychotic efficacy was associated with a suppression of dopamine transporter activity, which was reversed during failure. Antipsychotic failure coincided with reduced dopamine neuron firing, which was not observed during antipsychotic efficacy. Synaptic field responses in dopamine target areas declined during antipsychotic efficacy and showed potentiation during failure. Antipsychotics blocked synaptic vesicle release during efficacy but enhanced this release during failure. We found that the pharmacological inhibition of the dopamine transporter rescued antipsychotic drug treatment outcomes, supporting the hypothesis that the dopamine transporter is a main target of antipsychotic drugs and predicting that dopamine transporter blockers may be an adjunct treatment to reverse antipsychotic treatment failure.
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7
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Leung CCY, Gadelrab R, Ntephe CU, McGuire PK, Demjaha A. Clinical Course, Neurobiology and Therapeutic Approaches to Treatment Resistant Schizophrenia. Toward an Integrated View. Front Psychiatry 2019; 10:601. [PMID: 31551822 PMCID: PMC6735262 DOI: 10.3389/fpsyt.2019.00601] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/15/2018] [Accepted: 07/29/2019] [Indexed: 12/19/2022] Open
Abstract
Despite considerable psychotherapeutic advancement since the discovery of chlorpromazine, almost one third of patients with schizophrenia remain resistant to dopamine-blocking antipsychotics, and continue to be exposed to unwanted and often disabling side effects, but little if any clinical benefit. Even clozapine, the superior antipsychotic treatment, is ineffective in approximately half of these patients. Thus treatment resistant schizophrenia (TRS), continues to present a major therapeutic challenge to psychiatry. The main impediment to finding novel treatments is the lack of understanding of precise molecular mechanisms leading to TRS. Not only has the neurobiology been enigmatic for decades, but accurate and early detection of patients who are at risk of not responding to dopaminergic blockade remains elusive. Fortunately, recent work has started to unravel some of the neurobiological mechanisms underlying treatment resistance, providing long awaited answers, at least to some extent. Here we focus on the scientific advances in the field, from the clinical course of TRS to neurobiology and available treatment options. We specifically emphasize emerging evidence from TRS imaging and genetic literature that implicates dysregulation in several neurotransmitters, particularly dopamine and glutamate, and in addition genetic and neural alterations that concertedly may lead to the formation of TRS. Finally, we integrate available findings into a putative model of TRS, which may provide a platform for future studies in a bid to open the avenues for subsequent development of effective therapeutics.
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Affiliation(s)
- Cheryl Cheuk-Yan Leung
- Department of Old Age Psychiatry, Institute of Psychiatry, Psychology, and Neuroscience (IoPPN), King’s College London, London, United Kingdom
- South London and Maudsley NHS Foundation Trust, London, United Kingdom
| | - Romayne Gadelrab
- South London and Maudsley NHS Foundation Trust, London, United Kingdom
| | | | - Philip K. McGuire
- Department of Psychosis Studies, Institute of Psychiatry, Psychology, and Neuroscience (IoPPN), King’s College London, London, United Kingdom
- National Institute for Health Research (NIHR) Biomedical Research Centre (BRC), South London and Maudsley NHS Foundation Trust, London, United Kingdom
| | - Arsime Demjaha
- Department of Psychosis Studies, Institute of Psychiatry, Psychology, and Neuroscience (IoPPN), King’s College London, London, United Kingdom
- National Institute for Health Research (NIHR) Biomedical Research Centre (BRC), South London and Maudsley NHS Foundation Trust, London, United Kingdom
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8
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Nikolaus S, Mamlins E, Hautzel H, Müller HW. Acute anxiety disorder, major depressive disorder, bipolar disorder and schizophrenia are related to different patterns of nigrostriatal and mesolimbic dopamine dysfunction. Rev Neurosci 2019; 30:381-426. [PMID: 30269107 DOI: 10.1515/revneuro-2018-0037] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2018] [Accepted: 06/30/2018] [Indexed: 11/15/2022]
Abstract
Dopamine (DA) receptor and transporter dysfunctions play a major role in the pathophysiology of neuropsychiatric diseases including anxiety disorder (AD), major depressive disorder (MDD), bipolar disorder (BD) in the manic (BDman) or depressive (BDdep) state and schizophrenia (SZ). We performed a PUBMED search, which provided a total of 239 in vivo imaging studies with either positron emission tomography (PET) or single-proton emission computed tomography (SPECT). In these studies, DA transporter binding, D1 receptor (R) binding, D2R binding, DA synthesis and/or DA release in patients with the primary diagnosis of acute AD (n=310), MDD (n=754), BDman (n=15), BDdep (n=49) or SZ (n=1532) were compared to healthy individuals. A retrospective analysis revealed that AD, MDD, BDman, BDdep and SZ differed as to affected brain region(s), affected synaptic constituent(s) and extent as well as direction of dysfunction in terms of either sensitization or desensitization of transporter and/or receptor binding sites. In contrast to AD and SZ, in MDD, BDman and BDdep, neostriatal DA function was normal, whereas MDD, BDman, and BDdep were characterized by the increased availability of prefrontal and frontal DA. In contrast to AD, MDD, BDman and BDdep, DA function in SZ was impaired throughout the nigrostriatal and mesolimbocortical system with an increased availability of DA in the striatothalamocortical and a decreased availability in the mesolimbocortical pathway.
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Affiliation(s)
- Susanne Nikolaus
- Clinic of Nuclear Medicine, University Hospital Düsseldorf, Heinrich Heine University, Moorenstr. 5, D-40225 Düsseldorf, Germany
| | - Eduards Mamlins
- Clinic of Nuclear Medicine, University Hospital Düsseldorf, Heinrich Heine University, Moorenstr. 5, D-40225 Düsseldorf, Germany
| | - Hubertus Hautzel
- Clinic of Nuclear Medicine, University Hospital Düsseldorf, Heinrich Heine University, Moorenstr. 5, D-40225 Düsseldorf, Germany
| | - Hans-Wilhelm Müller
- Clinic of Nuclear Medicine, University Hospital Düsseldorf, Heinrich Heine University, Moorenstr. 5, D-40225 Düsseldorf, Germany
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Kaar SJ, Natesan S, McCutcheon R, Howes OD. Antipsychotics: Mechanisms underlying clinical response and side-effects and novel treatment approaches based on pathophysiology. Neuropharmacology 2019; 172:107704. [PMID: 31299229 DOI: 10.1016/j.neuropharm.2019.107704] [Citation(s) in RCA: 143] [Impact Index Per Article: 28.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2019] [Revised: 06/13/2019] [Accepted: 07/08/2019] [Indexed: 12/17/2022]
Abstract
Antipsychotic drugs are central to the treatment of schizophrenia and other psychotic disorders but are ineffective for some patients and associated with side-effects and nonadherence in others. We review the in vitro, pre-clinical, clinical and molecular imaging evidence on the mode of action of antipsychotics and their side-effects. This identifies the key role of striatal dopamine D2 receptor blockade for clinical response, but also for endocrine and motor side-effects, indicating a therapeutic window for D2 blockade. We consider how partial D2/3 receptor agonists fit within this framework, and the role of off-target effects of antipsychotics, particularly at serotonergic, histaminergic, cholinergic, and adrenergic receptors for efficacy and side-effects such as weight gain, sedation and dysphoria. We review the neurobiology of schizophrenia relevant to the mode of action of antipsychotics, and for the identification of new treatment targets. This shows elevated striatal dopamine synthesis and release capacity in dorsal regions of the striatum underlies the positive symptoms of psychosis and suggests reduced dopamine release in cortical regions contributes to cognitive and negative symptoms. Current drugs act downstream of the major dopamine abnormalities in schizophrenia, and potentially worsen cortical dopamine function. We consider new approaches including targeting dopamine synthesis and storage, autoreceptors, and trace amine receptors, and the cannabinoid, muscarinic, GABAergic and glutamatergic regulation of dopamine neurons, as well as post-synaptic modulation through phosphodiesterase inhibitors. Finally, we consider treatments for cognitive and negative symptoms such dopamine agonists, nicotinic agents and AMPA modulators before discussing immunological approaches which may be disease modifying. This article is part of the issue entitled 'Special Issue on Antipsychotics'.
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Affiliation(s)
- Stephen J Kaar
- Department of Psychosis Studies, 5th Floor, Institute of Psychiatry, Psychology & Neuroscience (IoPPN), King's College London, PO63 De Crespigny Park, London, SE5 8AF, United Kingdom.
| | - Sridhar Natesan
- Department of Psychosis Studies, 5th Floor, Institute of Psychiatry, Psychology & Neuroscience (IoPPN), King's College London, PO63 De Crespigny Park, London, SE5 8AF, United Kingdom
| | - Robert McCutcheon
- Department of Psychosis Studies, 5th Floor, Institute of Psychiatry, Psychology & Neuroscience (IoPPN), King's College London, PO63 De Crespigny Park, London, SE5 8AF, United Kingdom
| | - Oliver D Howes
- Department of Psychosis Studies, 5th Floor, Institute of Psychiatry, Psychology & Neuroscience (IoPPN), King's College London, PO63 De Crespigny Park, London, SE5 8AF, United Kingdom.
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10
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Jauhar S, Veronese M, Nour MM, Rogdaki M, Hathway P, Natesan S, Turkheimer F, Stone J, Egerton A, McGuire P, Kapur S, Howes OD. The Effects of Antipsychotic Treatment on Presynaptic Dopamine Synthesis Capacity in First-Episode Psychosis: A Positron Emission Tomography Study. Biol Psychiatry 2019; 85:79-87. [PMID: 30122287 PMCID: PMC6269123 DOI: 10.1016/j.biopsych.2018.07.003] [Citation(s) in RCA: 49] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/01/2018] [Revised: 07/02/2018] [Accepted: 07/03/2018] [Indexed: 10/28/2022]
Abstract
BACKGROUND Elevated striatal dopamine synthesis capacity has been implicated in the etiology and antipsychotic response in psychotic illness. The effects of antipsychotic medication on dopamine synthesis capacity are poorly understood, and no prospective studies have examined this question in a solely first-episode psychosis sample. Furthermore, it is unknown whether antipsychotic efficacy is linked to reductions in dopamine synthesis capacity. We conducted a prospective [18F]-dihydroxyphenyl-L-alanine positron emission tomography study in antipsychotic naïve/free people with first-episode psychosis commencing antipsychotic treatment. METHODS Dopamine synthesis capacity (indexed as influx rate constant) and clinical symptoms (measured using Positive and Negative Syndrome Scale) were measured before and after at least 5 weeks of antipsychotic treatment in people with first-episode psychosis. Data from a prior study indicated that a sample size of 13 would have >80% power to detect a statistically significant change in dopamine synthesis capacity at alpha = .05 (two tailed). RESULTS A total of 20 people took part in the study, 17 of whom were concordant with antipsychotic medication at therapeutic doses. There was no significant effect of treatment on dopamine synthesis capacity in the whole striatum (p = .47), thalamus, or midbrain, nor was there any significant relationship between change in dopamine synthesis capacity and change in positive (ρ = .35, p = .13), negative, or total psychotic symptoms. CONCLUSIONS Dopamine synthesis capacity is unaltered by antipsychotic treatment, and therapeutic effects are not mediated by changes in this aspect of dopaminergic function.
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Affiliation(s)
- Sameer Jauhar
- Department of Psychological Medicine, Institute of Psychiatry, Psychology and Neuroscience, King’s College London, London, United Kingdom,Early Intervention Psychosis Clinical Academic Group, South London and Maudsley NHS Trust, London, United Kingdom
| | - Mattia Veronese
- Centre for Neuroimaging Sciences, Institute of Psychiatry, Psychology and Neuroscience, King’s College London, London, United Kingdom
| | - Matthew M. Nour
- Psychosis Studies, Institute of Psychiatry, Psychology and Neuroscience, King’s College London, London, United Kingdom
| | - Maria Rogdaki
- Psychosis Studies, Institute of Psychiatry, Psychology and Neuroscience, King’s College London, London, United Kingdom,Psychiatric Imaging Group, MRC London Institute of Medical Sciences, Imperial College, Hammersmith Hospital, London, United Kingdom
| | - Pamela Hathway
- Psychosis Studies, Institute of Psychiatry, Psychology and Neuroscience, King’s College London, London, United Kingdom
| | - Sridhar Natesan
- Psychosis Studies, Institute of Psychiatry, Psychology and Neuroscience, King’s College London, London, United Kingdom
| | - Federico Turkheimer
- Centre for Neuroimaging Sciences, Institute of Psychiatry, Psychology and Neuroscience, King’s College London, London, United Kingdom
| | - James Stone
- Centre for Neuroimaging Sciences, Institute of Psychiatry, Psychology and Neuroscience, King’s College London, London, United Kingdom,Psychosis Studies, Institute of Psychiatry, Psychology and Neuroscience, King’s College London, London, United Kingdom
| | - Alice Egerton
- Psychosis Studies, Institute of Psychiatry, Psychology and Neuroscience, King’s College London, London, United Kingdom
| | - Philip McGuire
- Psychosis Studies, Institute of Psychiatry, Psychology and Neuroscience, King’s College London, London, United Kingdom,Early Intervention Psychosis Clinical Academic Group, South London and Maudsley NHS Trust, London, United Kingdom
| | - Shitij Kapur
- Faculty of Medicine, Dentistry and Health Sciences, University of Melbourne, Parkville, Victoria, Australia
| | - Oliver D. Howes
- Psychosis Studies, Institute of Psychiatry, Psychology and Neuroscience, King’s College London, London, United Kingdom,Psychiatric Imaging Group, MRC London Institute of Medical Sciences, Imperial College, Hammersmith Hospital, London, United Kingdom,Institute of Clinical Sciences, Faculty of Medicine, Imperial College, Hammersmith Hospital, London, United Kingdom,Address correspondence to Oliver Howes, Ph.D., Po 67 Psychosis Studies, Institute of Psychiatry, Psychology and Neuroscience, King’s College London, Camberwell, London SE5 8AF, UK.
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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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Amato D, Vernon AC, Papaleo F. Dopamine, the antipsychotic molecule: A perspective on mechanisms underlying antipsychotic response variability. Neurosci Biobehav Rev 2018; 85:146-159. [DOI: 10.1016/j.neubiorev.2017.09.027] [Citation(s) in RCA: 49] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2017] [Revised: 09/20/2017] [Accepted: 09/26/2017] [Indexed: 12/12/2022]
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Abstract
In a textbook of psychopharmacology published as recently as 1990, Hollister and Csernansky wrote about antipsychotics “It is most discouraging that more effective pharmacotherapy has not been developed. Present drugs have many deficiences: they are not curative; their ameliorative effects are often limited, many patients remain totally unresponsive; they are unpleasant to take so that many patients are less than fully compliant; they produce major side effects such as tardive dyskinesia whose full implications are still uncertain”.
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Abstract
BackgroundAn increased focus in research specific to first-episode schizophrenia has provided a rapidly growing body of evidence that can be directly translated to clinical practice.AimsTo provide clinical recommendations specific to effective pharmacotherapy of first-episode schizophrenia.MethodEvidence from clinical trials focused on the first-episode population is combined with data from other areas of investigation.ResultsIn first-episode psychosis, when to initiate treatment is not always clear, being intimately linked to challenges regarding early detection and diagnosis. There may be differences in antipsychotic dosing, patterns of response and sensitivity to side-effects. Adherence appears to be even more problematic at this stage.ConclusionsClinicians currently treating early psychosis have considerably more information to guide their decision-making. However, the speed at which the field is growing is a reminder totreatthis knowledge as a work in progress.
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Affiliation(s)
- Gary Remington
- Medical Assessment Program for Schizophrenia, Centre for Addiction and Mental Health, 250 College Street, Totonto, Ontario M5T 1R8, Canada.
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15
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Abstract
Most of the excitatory neurotransmission in the central nervous system (CNS) is mediated by the endogenous excitatory amino acids (EAAs) glutamate, aspartate and homocysteine. Most of the endogenous inhibitory neurotransmission is mediated by gamma-aminobutyric acid (GABA). EAAs modulate the firing of almost all neurons in the CNS, as excitatory neurotransmission can result in both neuronal inhibition and excitation. The glutamate system is the best characterised of the EAA systems (Box 1).
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Mouchlianitis E, Bloomfield MAP, Law V, Beck K, Selvaraj S, Rasquinha N, Waldman A, Turkheimer FE, Egerton A, Stone J, Howes OD. Treatment-Resistant Schizophrenia Patients Show Elevated Anterior Cingulate Cortex Glutamate Compared to Treatment-Responsive. Schizophr Bull 2016; 42:744-52. [PMID: 26683625 PMCID: PMC4838083 DOI: 10.1093/schbul/sbv151] [Citation(s) in RCA: 154] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
INTRODUCTION Resistance to antipsychotic treatment is a significant clinical problem in patients with schizophrenia with approximately 1 in 3 showing limited or no response to repeated treatments with antipsychotic medication. The neurobiological basis for treatment resistance is unknown but recent evidence implicates glutamatergic function in the anterior cingulate cortex. We examined glutamate levels of chronically ill treatment-resistant patients directly compared to treatment-responsive patients. METHODS We acquired proton magnetic resonance spectroscopy (1H-MRS) at 3 Tesla from 21 treatment-resistant and 20 treatment-responsive patients. All participants had a DSM-IV diagnosis of schizophrenia. Treatment-resistant patients were classified using the modified Kane criteria. The groups were matched for age, sex, smoking status, and illness duration. RESULTS Glutamate to creatine ratio levels were higher in treatment-resistant patients (Mean [SD] = 1.57 [0.24]) than in treatment-responsive patients (Mean[SD] = 1.38 [0.23]), (T[35] = 2.34, P = .025, 2-tailed), with a large effect size of d = 0.76. A model assuming 2 populations showed a 25% improvement in the fit of the Akaike weights (0.55) over a model assuming 1 population (0.44), producing group values almost identical to actual group means. DISCUSSION Increased anterior cingulate glutamate level is associated with treatment-resistant schizophrenia. This appears to be a stable neurobiological trait of treatment-resistant patients. We discuss possible explanations for glutamatergic dysfunction playing a significant role in resistance to conventional antipsychotic treatments, which are all dopamine-2 receptor blockers. Our findings suggest that glutamatergic treatments may be particularly effective in resistant patients and that 1H-MRS glutamate indices can potentially have clinical use.
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Affiliation(s)
- Elias Mouchlianitis
- Medical Research Council Clinical Sciences Centre, Psychiatric Imaging Group, Hammersmith Hospital, London, UK; Institute of Psychiatry Psychology and Neuroscience, Department of Psychosis Studies, King's College London, UK;
| | - Michael A. P. Bloomfield
- Medical Research Council Clinical Sciences Centre, Psychiatric Imaging Group, Hammersmith Hospital, London, UK;,University College London, Division of Psychiatry, London, UK
| | - Vincent Law
- Medical Research Council Clinical Sciences Centre, Psychiatric Imaging Group, Hammersmith Hospital, London, UK
| | - Katherine Beck
- Institute of Psychiatry Psychology and Neuroscience, Department of Psychosis Studies, King’s College London, UK
| | - Sudhakar Selvaraj
- Department of Psychiatry and Behavioral Sciences, University of Texas, Houston, TX
| | | | - Adam Waldman
- Division of Brain Sciences, Imperial College London, Hammersmith Hospital, London, UK
| | - Federico E. Turkheimer
- Institute of Psychiatry Psychology and Neuroscience, Department of Psychosis Studies, King’s College London, UK
| | - Alice Egerton
- Institute of Psychiatry Psychology and Neuroscience, Department of Psychosis Studies, King’s College London, UK
| | - James Stone
- Medical Research Council Clinical Sciences Centre, Psychiatric Imaging Group, Hammersmith Hospital, London, UK;,Institute of Psychiatry Psychology and Neuroscience, Department of Psychosis Studies, King’s College London, UK
| | - Oliver D. Howes
- Medical Research Council Clinical Sciences Centre, Psychiatric Imaging Group, Hammersmith Hospital, London, UK;,Institute of Psychiatry Psychology and Neuroscience, Department of Psychosis Studies, King’s College London, UK
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Wulff S, Pinborg LH, Svarer C, Jensen LT, Nielsen MØ, Allerup P, Bak N, Rasmussen H, Frandsen E, Rostrup E, Glenthøj BY. Striatal D(2/3) Binding Potential Values in Drug-Naïve First-Episode Schizophrenia Patients Correlate With Treatment Outcome. Schizophr Bull 2015; 41:1143-52. [PMID: 25698711 PMCID: PMC4535636 DOI: 10.1093/schbul/sbu220] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
One of best validated findings in schizophrenia research is the association between blockade of dopamine D2 receptors and the effects of antipsychotics on positive psychotic symptoms. The aim of the present study was to examine correlations between baseline striatal D(2/3) receptor binding potential (BP(p)) values and treatment outcome in a cohort of antipsychotic-naïve first-episode schizophrenia patients. Additionally, we wished to investigate associations between striatal dopamine D(2/3) receptor blockade and alterations of negative symptoms as well as functioning and subjective well-being. Twenty-eight antipsychotic-naïve schizophrenia patients and 26 controls were included in the study. Single-photon emission computed tomography (SPECT) with [(123)I]iodobenzamide ([(123)I]-IBZM) was used to examine striatal D(2/3) receptor BP(p). Patients were examined before and after 6 weeks of treatment with the D(2/3) receptor antagonist amisulpride. There was a significant negative correlation between striatal D(2/3) receptor BP(p) at baseline and improvement of positive symptoms in the total group of patients. Comparing patients responding to treatment to nonresponders further showed significantly lower baseline BP(p) in the responders. At follow-up, the patients demonstrated a negative correlation between the blockade and functioning, whereas no associations between blockade and negative symptoms or subjective well-being were observed. The results show an association between striatal BP(p) of dopamine D(2/3) receptors in antipsychotic-naïve first-episode patients with schizophrenia and treatment response. Patients with a low BP(p) have a better treatment response than patients with a high BP(p). The results further suggest that functioning may decline at high levels of dopamine receptor blockade.
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Affiliation(s)
- Sanne Wulff
- Center for Neuropsychiatric Schizophrenia Research (CNSR) and Center for Clinical Intervention and Neuropsychiatric Schizophrenia Research (CINS), Psychiatric Center Glostrup, University of Copenhagen, Copenhagen, Denmark; Department of Clinical Medicine, Faculty of Health and Medical Sciences University of Copenhagen, Denmark;
| | - Lars Hageman Pinborg
- Neurobiology Research Unit (NRU), Rigshospitalet, University of Copenhagen, Denmark
| | - Claus Svarer
- Neurobiology Research Unit (NRU), Rigshospitalet, University of Copenhagen, Denmark
| | - Lars Thorbjørn Jensen
- Department of Clinical Physiology and Nuclear Medicine, Herlev Hospital, University of Copenhagen, Denmark
| | - Mette Ødegaard Nielsen
- Center for Neuropsychiatric Schizophrenia Research (CNSR) and,Center for Clinical Intervention and Neuropsychiatric Schizophrenia Research (CINS), Psychiatric Center Glostrup, University of Copenhagen, Copenhagen, Denmark
| | - Peter Allerup
- Department of Education, Centre for Research in Compulsory Schooling, Aarhus University, Denmark
| | - Nikolaj Bak
- Center for Neuropsychiatric Schizophrenia Research (CNSR) and,Center for Clinical Intervention and Neuropsychiatric Schizophrenia Research (CINS), Psychiatric Center Glostrup, University of Copenhagen, Copenhagen, Denmark
| | - Hans Rasmussen
- Center for Neuropsychiatric Schizophrenia Research (CNSR) and,Center for Clinical Intervention and Neuropsychiatric Schizophrenia Research (CINS), Psychiatric Center Glostrup, University of Copenhagen, Copenhagen, Denmark
| | - Erik Frandsen
- Department of Diagnostics, Functional Imaging Unit and Section of Clinical Physiology and Nuclear Medicine, Glostrup Hospital, University of Copenhagen, Denmark
| | - Egill Rostrup
- Department of Diagnostics, Functional Imaging Unit and Section of Clinical Physiology and Nuclear Medicine, Glostrup Hospital, University of Copenhagen, Denmark
| | - Birte Yding Glenthøj
- Center for Neuropsychiatric Schizophrenia Research (CNSR) and,Center for Clinical Intervention and Neuropsychiatric Schizophrenia Research (CINS), Psychiatric Center Glostrup, University of Copenhagen, Copenhagen, Denmark;,Department of Clinical Medicine, Faculty of Health and Medical Sciences University of Copenhagen, Denmark
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Caravaggio F, Hahn M, Nakajima S, Gerretsen P, Remington G, Graff-Guerrero A. Reduced insulin-receptor mediated modulation of striatal dopamine release by basal insulin as a possible contributing factor to hyperdopaminergia in schizophrenia. Med Hypotheses 2015; 85:391-6. [PMID: 26118462 DOI: 10.1016/j.mehy.2015.06.011] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2015] [Revised: 05/22/2015] [Accepted: 06/17/2015] [Indexed: 12/23/2022]
Abstract
Schizophrenia is a severe and chronic neuropsychiatric disorder which affects 1% of the world population. Using the brain imaging technique positron emission tomography (PET) it has been demonstrated that persons with schizophrenia have greater dopamine transmission in the striatum compared to healthy controls. However, little progress has been made as to elucidating other biological mechanisms which may account for this hyperdopaminergic state in this disease. Studies in animals have demonstrated that insulin receptors are expressed on midbrain dopamine neurons, and that insulin from the periphery acts on these receptors to modify dopamine transmission in the striatum. This is pertinent given that several lines of evidence suggest that insulin receptor functioning may be abnormal in the brains of persons with schizophrenia. Post-mortem studies have shown that persons with schizophrenia have less than half the number of cortical insulin receptors compared to healthy persons. Moreover, these post-mortem findings are unlikely due to the effects of antipsychotic treatment; studies in cell lines and animals suggest antipsychotics enhance insulin receptor functioning. Further, hyperinsulinemia - even prior to antipsychotic use - seems to be related to less psychotic symptoms in patients with schizophrenia. Collectively, these data suggest that midbrain insulin receptor functioning may be abnormal in persons with schizophrenia, resulting in reduced insulin-mediated regulation of dopamine transmission in the striatum. Such a deficit may account for the hyperdopaminergic state observed in these patients and would help guide the development of novel treatment strategies. We hypothesize that, (i) insulin receptor expression and/or function is reduced in midbrain dopamine neurons in persons with schizophrenia, (ii) basal insulin should reduce dopaminergic transmission in the striatum via these receptors, and (iii) this modulation of dopaminergic transmission by basal insulin is reduced in the brains of persons with schizophrenia.
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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; Institute of Medical Science, University of Toronto, 2374 Medical Sciences Building, 1 King's College Circle, Toronto, Ontario M5S 1A8, Canada
| | - Margaret Hahn
- Institute of Medical Science, University of Toronto, 2374 Medical Sciences Building, 1 King's College Circle, Toronto, Ontario M5S 1A8, Canada; Department of Psychiatry, University of Toronto, 250 College Street, Toronto, Ontario M5T 1R8, Canada
| | - Shinichiro Nakajima
- Research Imaging Centre, Centre for Addiction and Mental Health, 250 College Street, Toronto, Ontario M5T 1R8, Canada; Department of Psychiatry, University of Toronto, 250 College Street, Toronto, Ontario M5T 1R8, Canada
| | - Philip Gerretsen
- Research Imaging Centre, Centre for Addiction and Mental Health, 250 College Street, Toronto, Ontario M5T 1R8, Canada; Institute of Medical Science, University of Toronto, 2374 Medical Sciences Building, 1 King's College Circle, Toronto, Ontario M5S 1A8, Canada; Department of Psychiatry, University of Toronto, 250 College Street, Toronto, Ontario M5T 1R8, Canada
| | - Gary Remington
- Research Imaging Centre, Centre for Addiction and Mental Health, 250 College Street, Toronto, Ontario M5T 1R8, Canada; Institute of Medical Science, University of Toronto, 2374 Medical Sciences Building, 1 King's College Circle, Toronto, Ontario M5S 1A8, Canada; Department of Psychiatry, University of Toronto, 250 College Street, Toronto, Ontario M5T 1R8, Canada
| | - Ariel Graff-Guerrero
- Research Imaging Centre, Centre for Addiction and Mental Health, 250 College Street, Toronto, Ontario M5T 1R8, Canada; Institute of Medical Science, University of Toronto, 2374 Medical Sciences Building, 1 King's College Circle, Toronto, Ontario M5S 1A8, Canada; Department of Psychiatry, University of Toronto, 250 College Street, Toronto, Ontario M5T 1R8, Canada.
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19
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Abstract
The glutamate and dopamine hypotheses are leading theories of the pathoaetiology of schizophrenia. Both were initially based on indirect evidence from pharmacological studies supported by post-mortem findings, but have since been substantially advanced by new lines of evidence from in vivo imaging studies. This review provides an update on the latest findings on dopamine and glutamate abnormalities in schizophrenia, focusing on in vivo neuroimaging studies in patients and clinical high-risk groups, and considers their implications for understanding the biology and treatment of schizophrenia. These findings have refined both the dopamine and glutamate hypotheses, enabling greater anatomical and functional specificity, and have been complemented by preclinical evidence showing how the risk factors for schizophrenia impact on the dopamine and glutamate systems. The implications of this new evidence for understanding the development and treatment of schizophrenia are considered, and the gaps in current knowledge highlighted. Finally, the evidence for an integrated model of the interactions between the glutamate and dopamine systems is reviewed, and future directions discussed.
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Affiliation(s)
- Oliver Howes
- Psychiatric Imaging, MRC Clinical Sciences Centre, Hammersmith Hospital, London, UK Institute of Psychiatry, King's College London, London, UK
| | - Rob McCutcheon
- Psychiatric Imaging, MRC Clinical Sciences Centre, Hammersmith Hospital, London, UK Institute of Psychiatry, King's College London, London, UK
| | - James Stone
- Psychiatric Imaging, MRC Clinical Sciences Centre, Hammersmith Hospital, London, UK Institute of Psychiatry, King's College London, London, UK
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Nikolaus S, Hautzel H, Müller HW. Neurochemical dysfunction in treated and nontreated schizophrenia - a retrospective analysis of in vivo imaging studies. Rev Neurosci 2014; 25:25-96. [PMID: 24486731 DOI: 10.1515/revneuro-2013-0063] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2013] [Accepted: 12/26/2013] [Indexed: 12/22/2022]
Abstract
To evaluate the contribution of individual synaptic constituents, all available in vivo imaging studies on schizophrenic patients were subjected to a retrospective analysis. For the pool of drug-naïve, drug-free, and acutely medicated patients, major findings were increases in neostriatal dopamine (DA) synthesis and release and decreases in neostriatal DA transporters and D1 receptors, neostriatal, thalamic, frontal, and parietal D2 receptors, mesencephalic/pontine and temporal 5-HT1A receptors, frontal and temporal HT2A and μ-amino butyric acid (GABA)A receptors. Based on the findings on drug-naïve and drug-free patients, it may be hypothesized that schizophrenia initially is characterized by an impaired mechanism of D2 autoreceptor and heteroreceptor sensitization leading to sensitization instead of desensitization in response to increased levels of neostriatal DA. Neuroleptic medication blocks neostriatal D2 autoreceptor and heteroreceptors, reducing neostriatal DA and disinhibiting DA action mediated by D2 heteroreceptor binding sites. Ultimately, this may result in a restitution of GABA function, leading to a recovery of inhibitory input to the target regions of the descending corticothalamostriatal efferents. Furthermore, a blockade of inhibitory and excitatory neocortical 5-HT function may be inferred, which is likely to reduce (excitatory) DAergic input to the mesolimbic target regions of corticothalamostriatal projections.
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Lau CI, Wang HC, Hsu JL, Liu ME. Does the dopamine hypothesis explain schizophrenia? Rev Neurosci 2013; 24:389-400. [PMID: 23843581 DOI: 10.1515/revneuro-2013-0011] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2013] [Accepted: 06/05/2013] [Indexed: 01/22/2023]
Abstract
The dopamine hypothesis has been the cornerstone in the research and clinical practice of schizophrenia. With the initial emphasis on the role of excessive dopamine, the hypothesis has evolved to a concept of combining prefrontal hypodopaminergia and striatal hyperdopaminergia, and subsequently to the present aberrant salience hypothesis. This article provides a brief overview of the development and evidence of the dopamine hypothesis. It will argue that the current model of aberrant salience explains psychosis in schizophrenia and provides a plausible linkage between the pharmacological and cognitive aspects of the disease. Despite the privileged role of dopamine hypothesis in psychosis, its pathophysiological rather than etiological basis, its limitations in defining symptoms other than psychosis, as well as the evidence of other neurotransmitters such as glutamate and adenosine, prompt us to a wider perspective of the disease. Finally, dopamine does explain the pathophysiology of schizophrenia, but not necessarily the cause per se. Rather, dopamine acts as the common final pathway of a wide variety of predisposing factors, either environmental, genetic, or both, that lead to the disease. Other neurotransmitters, such as glutamate and adenosine, may also collaborate with dopamine to give rise to the entire picture of schizophrenia.
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Dopamine D₂/₃ occupancy of ziprasidone across a day: a within-subject PET study. Psychopharmacology (Berl) 2013; 228:43-51. [PMID: 23417515 PMCID: PMC3679209 DOI: 10.1007/s00213-013-3012-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/09/2012] [Accepted: 01/24/2013] [Indexed: 10/27/2022]
Abstract
RATIONALE Ziprasidone is an atypical antipsychotic recommended to be administered twice daily. OBJECTIVES The purpose of this study was to investigate whether occupancy of the dopamine D2/3 receptors by ziprasidone is maintained across a day employing a within subject design. METHODS Positron emission tomography (PET) scans with [(11)C]-raclopride were performed in 12 patients with schizophrenia while treated with ziprasidone 60 mg twice daily. Each patient completed [(11)C]-raclopride PET scans at 5, 13 and 23 h after the last dose of ziprasidone. Dopamine D2/3 receptor occupancy was estimated with reference to binding potential data of 44 age- and sex-matched control subjects in the caudate, putamen and ventral striatum. RESULTS Eleven scans were available at each time point, and the mean occupancies at 5-, 13- and 23-h scans were 66, 39 and 2 % in the putamen; 62, 35 and -6 % in the caudate; and 68, 47 and 11 % in the ventral striatum, respectively. The time-course of receptor occupancy across the regions indicated an occupancy half-life of 8.3 h. The serum level of ziprasidone associated with 50 % D2/3 receptors occupancy was estimated to be 204 nmol/L (84 ng/ml). Prolactin levels were highest at 5-h post-dose and none showed hyperprolactinemia at 23-h scans. CONCLUSIONS The absence of ziprasidone striatal D2/3 receptor binding 23 h after taking 60 mg under steady-state conditions is consistent with its peripheral half-life. The results support our earlier report that ziprasidone 60 mg administered twice daily appears to be the minimal dose expected to achieve therapeutic central dopamine D2/3 receptor occupancy (i.e. 60 %). CLINICAL TRIALS REGISTRATION 24-Hour Time Course of Striatal Dopamine D2 Receptor Occupancy of Ziprasidone: A PET Study, www.clinicaltrials.gov/ct2/show/NCT00818298 , NCT00818298.
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Anterior cingulate glutamate levels related to clinical status following treatment in first-episode schizophrenia. Neuropsychopharmacology 2012; 37:2515-21. [PMID: 22763619 PMCID: PMC3442346 DOI: 10.1038/npp.2012.113] [Citation(s) in RCA: 140] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Many patients with schizophrenia show a limited symptomatic response to treatment with dopaminergic antipsychotics. This may reflect the additional involvement of non-dopaminergic neurochemical dysfunction in the pathophysiology of the disorder. We tested the hypothesis that brain glutamate levels would differ between patients with first-episode psychosis who were symptomatic compared with those with minimal symptoms following antipsychotic treatment. Proton magnetic resonance spectroscopy (1H-MRS) spectra were acquired at 3 Tesla in the anterior cingulate cortex and left thalamus in 15 patients with first-episode psychosis in symptomatic remission, and 17 patients with first-episode psychosis who were still symptomatic following at least one course of antipsychotic treatment. Metabolite levels were estimated in ratio to creatine (Cr) using LCModel. Levels of glutamate/Cr in the anterior cingulate cortex were significantly higher in patients who were still symptomatic than in those in remission (T(30)=3.02; P=0.005). Across the entire sample, higher levels of glutamate/Cr in the anterior cingulate cortex were associated with a greater severity of negative symptoms (r=0.42; P=0.017) and a lower level of global functioning (r=-0.47; P=0.007). These findings suggest that clinical status following antipsychotic treatment in schizophrenia is linked to glutamate dysfunction. Treatment with compounds acting on the glutamatergic system might therefore be beneficial in patients who respond poorly to dopaminergic antipsychotics.
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Corripio I, Ferreira A, Portella MJ, Pérez V, Escartí MJ, Del Valle Camacho M, Sauras RB, Alonso A, Grasa EM, Carrió I, Catafau AM, Alvarez E. The role of striatal dopamine D2 receptors in the occurrence of extrapyramidal side effects: iodine-123-iodobenzamide single photon emission computed tomography study. Psychiatry Res 2012; 201:73-7. [PMID: 22281201 DOI: 10.1016/j.pscychresns.2011.02.004] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/04/2010] [Revised: 01/04/2011] [Accepted: 02/06/2011] [Indexed: 10/14/2022]
Abstract
Levels above 75% of striatal dopamine 2 receptor occupancy (D2RO) have been associated with extrapyramidal symptoms (EPS). The aim of the present study is to investigate the relationship between D2RO and EPS in a sample of psychotic patients in current treatment with both typical and atypical antipsychotics. Brain iodine-123-iodobenzamide single photon emission computed tomography ((123)I-IBZM SPECT) was performed in 81 patients taking stable doses of haloperidol, risperidone, olanzapine, quetiapine, clozapine or ziprasidone. First, the degree of D2RO and Positive and Negative Syndrome Scale (PANSS) scores was compared between the group of patients who presented EPS and the group free of EPS. Afterwards, these variables were compared among the different antipsychotic medications. The group with EPS presented means of D2RO significantly higher than the group free of EPS. Significant differences in D2RO were found in clozapine, quetiapine and ziprasidone groups compared with the haloperidol group. No differences were observed between either olanzapine or risperidone and haloperidol. No quetiapine- or clozapine-treated patients developed EPS. Haloperidol and risperidone demonstrated a relationship between striatal D2RO and EPS. The findings suggest that higher D2RO is related to appearance of EPS. Occupancy in the group with EPS was in agreement with previous studies that suggested a high degree of D2RO is necessary for the occurrence of EPS.
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Affiliation(s)
- Iluminada Corripio
- Department of Psychiatry, Universitat Autònoma de Barcelona, Barcelona, Spain
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Miller R. Mechanisms of action of antipsychotic drugs of different classes, refractoriness to therapeutic effects of classical neuroleptics, and individual variation in sensitivity to their actions: Part I. Curr Neuropharmacol 2011; 7:302-14. [PMID: 20514210 PMCID: PMC2811864 DOI: 10.2174/157015909790031229] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2009] [Revised: 07/15/2009] [Accepted: 07/28/2009] [Indexed: 12/25/2022] Open
Abstract
Many issues remain unresolved about antipsychotic drugs. Their therapeutic potency scales with affinity for dopamine D2 receptors, but there are indications that they act indirectly, with dopamine D1 receptors (and others) as possible ultimate targets. Classical neuroleptic drugs disinhibit striatal cholinergic interneurones and increase acetyl choline release. Their effects may then depend on stimulation of muscarinic receptors on principle striatal neurones (M4 receptors, with reduction of cAMP formation, for therapeutic effects; M1 receptors for motor side effects). Many psychotic patients do not benefit from neuroleptic drugs, or develop resistance to them during prolonged treatment, but respond well to clozapine. For patients who do respond, there is a wide (>ten-fold) range in optimal doses. Refractoriness or low sensitivity to antipsychotic effects (and other pathologies) could then arise from low density of cholinergic interneurones. Clozapine probably owes its special actions to direct stimulation of M4 receptors, a mechanism available when indirect action is lost.
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Affiliation(s)
- R Miller
- Otago Centre for Theoretical Studies in Psychiatry and Neuroscience (OCTSPAN), Department of Anatomy and Structural Biology, School of Medical Sciences, University of Otago, P.O.Box 913, Dunedin, New Zealand.
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Stone JM, Raffin M, Morrison P, McGuire PK. Review: The biological basis of antipsychotic response in schizophrenia. J Psychopharmacol 2010; 24:953-64. [PMID: 19939865 DOI: 10.1177/0269881109106959] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Schizophrenia is a severe mental illness affecting approximately 1% of the population worldwide. Antipsychotic drugs are effective in symptom control in up to two-thirds of patients, but in at least one-third of patients the response is poor. The reason for this is not clear, but one possibility is that good and poor responders have different neurochemical pathologies, and may therefore benefit from different treatment approaches. In this selective review we summarise research findings investigating the biological differences between patients with schizophrenia who show a good or a poor response to treatment with antipsychotic drugs.
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Affiliation(s)
- James M Stone
- Institute of Psychiatry, King's College London, London SE5 8AF, UK.
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Giegling I, Drago A, Schäfer M, Möller HJ, Rujescu D, Serretti A. Interaction of haloperidol plasma level and antipsychotic effect in early phases of acute psychosis treatment. J Psychiatr Res 2010; 44:487-92. [PMID: 19962159 DOI: 10.1016/j.jpsychires.2009.11.004] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/05/2009] [Revised: 10/28/2009] [Accepted: 11/05/2009] [Indexed: 11/17/2022]
Abstract
The definition of the best combination of "when" and "how much" of haloperidol dosing during acute psychotic illness still represents a challenge. Randomized controlled trials can hardly account for the high variability of dose x timing of dose increase strategies that can be applied in everyday practice. We conducted an observational study in order to study and evaluate the naturalistic strategies of haloperidol oral administration in a sample of 101 acutely ill psychotic patients. Out of this sample, 82 patients had complete data on PANSS scores and 50 patients had data on the haloperidol plasma levels. In accordance with previous evidence, we found that improvement during the first two weeks of treatment was a significant predictor of response (t=6.94, p=2.11E-08). On this note, increasing the haloperidol doses over 6.64+/-2.08 mg/day on average from the second to the third week of treatment in those patients who did not respond to treatment during the first two weeks of treatment was of no use for further amelioration. This cutoff was associated with treatment efficacy but not with the incidence of side effects. In conclusion a moderate dose of haloperidol is suggested in the first two weeks, in case of non response a dose increase is of no further benefit. This finding could contribute to tailor more individualized treatment and highlights the need for early detection of non-responders.
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Affiliation(s)
- Ina Giegling
- Department of Psychiatry, Ludwig Maximilians University, Munich, Germany
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Blockade of [11C](+)-PHNO binding in human subjects by the dopamine D3 receptor antagonist ABT-925. Int J Neuropsychopharmacol 2010; 13:273-87. [PMID: 19751545 DOI: 10.1017/s1461145709990642] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Dopamine D3 receptors are preferentially localized in the limbic system and midbrain, and thus may be involved in the pathophysiology of neuropsychiatry disorders. [11C](+)-PHNO is the first preferential D3 receptor radioligand in humans, yet there are no blockade studies with a D3 receptor antagonist in humans. This study characterized the blockade of [11C](+)-PHNO binding by ABT-925, a D3 receptor antagonist, in healthy male subjects. Sixteen subjects underwent 2-3 positron emission tomography (PET) scans, at baseline and following one or two doses of ABT-925 ranging from 50 mg to 600 mg. Receptor occupancies were estimated for globus pallidus, substantia nigra, caudate, putamen, and ventral striatum. At the 600-mg dose (n=9), ABT-925 receptor occupancy (mean+/-s.d.) was higher in substantia nigra (75+/-10%) and globus pallidus (64+/-22%) than in ventral striatum (44+/-17%), caudate (40+/-18%) and putamen (38+/-17%) (ANOVA: F4,140=15.02, p<0.001). The fractions of [11C](+)-PHNO binding attributable to D3 receptors in D3 receptor-rich regions were 100% (substantia nigra) and 90% (globus pallidus), and in D2 receptor-rich regions were 55% (caudate) and 53% (putamen). The ED50 of ABT-925 was 4.37 microg/ml across regions. Our results demonstrate that [11C](+)-PHNO binding can be blocked by a D3 receptor antagonist and confirm preclinical findings that [11C](+)-PHNO signal in the substantia nigra and globus pallidus is mainly reflective of its binding to D3 receptors. Thus, [11C](+)-PHNO seems a suitable PET radiotracer to estimate D3 receptor occupancy in humans.
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Nikolaus S, Antke C, Müller HW. In vivo imaging of synaptic function in the central nervous system: II. Mental and affective disorders. Behav Brain Res 2009; 204:32-66. [DOI: 10.1016/j.bbr.2009.06.009] [Citation(s) in RCA: 91] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2009] [Revised: 05/27/2009] [Accepted: 06/02/2009] [Indexed: 10/20/2022]
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Thompson JL, Urban N, Abi-Dargham A. How have developments in molecular imaging techniques furthered schizophrenia research? ACTA ACUST UNITED AC 2009; 1:135-153. [PMID: 21243081 DOI: 10.2217/iim.09.22] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Molecular imaging techniques have led to significant advances in understanding the pathophysiology of schizophrenia and contributed to knowledge regarding potential mechanisms of action of the drugs used to treat this illness. The aim of this article is to provide a review of the major findings related to the application of molecular imaging techniques that have furthered schizophrenia research. This article focuses specifically on neuroreceptor imaging studies with PET and SPECT. After providing a brief overview of neuroreceptor imaging methodology, we consider relevant findings from studies of receptor availability, and dopamine synthesis and release. Results are discussed in the context of current hypotheses regarding neurochemical alterations in the illness. We then selectively review pharmacological occupancy studies and the role of neuroreceptor imaging in drug development for schizophrenia.
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Affiliation(s)
- Judy L Thompson
- Department of Psychiatry, Columbia University and New York State Psychiatric Institute, 1051 Riverside Drive, Unit 31, New York, NY 10032, USA
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Howes OD, Egerton A, Allan V, McGuire P, Stokes P, Kapur S. Mechanisms underlying psychosis and antipsychotic treatment response in schizophrenia: insights from PET and SPECT imaging. Curr Pharm Des 2009; 15:2550-9. [PMID: 19689327 DOI: 10.2174/138161209788957528] [Citation(s) in RCA: 160] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Molecular imaging studies have generated important in vivo insights into the etiology of schizophrenia and treatment response. This article first reviews the PET and SPECT evidence implicating dopaminergic dysfunction, especially presynaptic dysregulation, as a mechanism for psychosis. Second, it summarises the neurochemical imaging studies of antipsychotic action, focussing on D2/3 receptors. These studies show that all currently licensed antipsychotic drugs block striatal D2/3 receptors in vivo- a site downstream of the likely principal dopaminergic pathophysiology in schizophrenia- and that D2/3 occupancy above a threshold is required for antipsychotic treatment response. However, adverse events, such as extra-pyramidal side-effects or hyperprolactinemia, become much more likely at higher occupancy levels, which indicates there is an optimal 'therapeutic window' for D2/3 occupancy, and questions the use of high doses of antipsychotic treatment in clinical practice and trials. Adequate D2/3 blockade by antipsychotic drugs is necessary but not always sufficient for antipsychotic response. Molecular imaging studies of clozapine, the one antipsychotic licensed for treatment resistant schizophrenia, have provided insights into the mechanisms underlying its unique efficacy. To link this pharmacology to the phenomenology of the illness, we discuss the role of dopamine in motivational salience and show how i) psychosis could be viewed as a process of aberrant salience, and ii) antipsychotics might provide symptomatic relief by blocking this aberrant salience. Finally, we discuss the implications of these PET and SPECT findings for new avenues of drug development.
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Affiliation(s)
- O D Howes
- PET Psychiatry-MRC Clinical Sciences Centre, Imperial College Hammersmith Campus, Hammersmith Hospital, London, UK.
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Vernaleken I, Weibrich C, Siessmeier T, Buchholz HG, Rösch F, Heinz A, Cumming P, Stoeter P, Bartenstein P, Gründer G. Asymmetry in dopamine D(2/3) receptors of caudate nucleus is lost with age. Neuroimage 2006; 34:870-8. [PMID: 17174574 DOI: 10.1016/j.neuroimage.2006.10.013] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2006] [Revised: 10/11/2006] [Accepted: 10/13/2006] [Indexed: 11/25/2022] Open
Abstract
Molecular and functional imaging techniques reveal evidence for lateralization of human cerebral function. Based on animal data, we hypothesized that asymmetry in dopamine neurotransmission declines during normal aging. In order to test this hypothesis, we measured dopamine D2/3 receptor availability with [18F]desmethoxyfallypride-PET (DMFP) in putamen and caudate nucleus (NC) of 21 healthy, right-handed males (24-60 years; 35+/-10). For volumetric analysis, high-resolution T1-weighted MR-images were obtained in 18 of the PET-subjects in order to assess possible age-related decreases in NC and putamen volume. The calculated DMFP binding potentials (BP) showed a right-ward asymmetry in NC of young subjects that decreased with age (r = 0.577, p = 0.006; Pearson correlation; two-tailed). An age-independent analysis showed a right-ward asymmetry in NC of the whole subject group (left: 1.49+/-0.35; right: 1.65+/-0.43 [mean+/-S.D.]; p = 0.020). No such side lateralization or age-effects could be found in the putamen. Volumes tended to be asymmetric in the putamen (right: 4.85+/-0.56 cm3; left: 4.64+/-0.86 cm3 [mean+/-S.D.]; p = 0.063), but not in NC. The decline of putamen volume during aging was significant in the right putamen (r = -0.613; p = 0.007; Pearson correlation; two-tailed). There were no other significant correlations between striatal volumes and age or BP. Because ventral striatal dopamine neurotransmission is involved in cognitive processes, this loss of physiological asymmetry in NC dopamine transmission during aging might be involved in age-related declines of cognitive performance.
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Affiliation(s)
- Ingo Vernaleken
- Department of Psychiatry and Psychotherapy, RWTH Aachen University, Germany Pauwelsstrasse 30, 52074 Aachen, Germany.
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Catafau AM, Corripio I, Pérez V, Martin JC, Schotte A, Carrió I, Alvarez E. Dopamine D2 receptor occupancy by risperidone: implications for the timing and magnitude of clinical response. Psychiatry Res 2006; 148:175-83. [PMID: 17059881 DOI: 10.1016/j.pscychresns.2006.02.001] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/06/2005] [Accepted: 02/02/2006] [Indexed: 10/24/2022]
Abstract
The objective of the study is to investigate whether dopamine D2 receptor occupancy by risperidone and plasma levels over time can account for therapeutic efficacy and the latency period to response. Thirty-eight examinations with (123)I-IBZM single photon emission computed tomography were performed on 22 patients with schizophrenia, at diagnosis, 48 h after starting risperidone treatment and at a stable dose. Risperidone plasma levels were determined and psychopathologic evaluations (Brief Psychiatric Rating Scale, Positive and Negative Syndrome Scale) were carried out. No differences in the striatal/occipital (S/O) ratio or plasma levels were found between examinations at the 48-h time point and when a stable dose level had been established, so these parameters could not account for the latency period required for clinical response. D2 receptor occupancy at 48 h correlated positively with clinical improvement after 2 weeks of treatment. Therefore, if these results are confirmed, D2 receptor occupancy at the beginning of treatment with risperidone may be a predictor of subsequent clinical response.
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Affiliation(s)
- Ana M Catafau
- Department of Nuclear Medicine, St Pau Hospital, U.A.B. (Autónoma University from Barcelona), Barcelona, Spain
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Stone JM, Pilowsky LS. Antipsychotic drug action: targets for drug discovery with neurochemical imaging. Expert Rev Neurother 2006; 6:57-64. [PMID: 16466312 DOI: 10.1586/14737175.6.1.57] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Schizophrenia is a serious lifelong mental illness for which current treatments may only be partially effective. All antipsychotic medications available at present are thought to exert their main antipsychotic effect through antagonism of dopamine D2 receptors. Clozapine is the most effective antipsychotic drug currently available, but it can cause serious side effects, including agranulocytosis and diabetes. Pharmacologic factors that distinguish clozapine from other antipsychotic drugs have been studied to try to develop safer drugs with similar efficacy to clozapine. These have met with limited success. Neurochemical imaging techniques, such as positron emission tomography, single photon emission tomography and magnetic resonance spectroscopy, have been used to study antipsychotic drug action in living human subjects. These techniques shed a great deal of light on the mechanisms of antipsychotic action and have revealed a number of novel targets for future drug development in schizophrenia. Next-generation antipsychotic medications will aim to improve on the efficacy and tolerability of currently available medications. The authors believe that they are likely to achieve this through drug action at non-D2 sites. Future research and drug development, including the development of medications to prevent progression from the prepsychotic stage to schizophrenia, will rely heavily on neurochemical imaging methods at all stages in the drug-discovery pipeline.
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Affiliation(s)
- James M Stone
- Section of Neurochemical Imaging, Psychological Medicine, King's College London Institute of Psychiatry, London SE5 8AF, UK.
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Corripio I, Catafau AM, Perez V, Puigdemont D, Mena E, Aguilar Y, Carrió I, Alvarez E. Striatal dopaminergic D2 receptor occupancy and clinical efficacy in psychosis exacerbation: a 123I-IBZM study with ziprasidone and haloperidol. Prog Neuropsychopharmacol Biol Psychiatry 2005; 29:91-6. [PMID: 15610950 DOI: 10.1016/j.pnpbp.2004.10.010] [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] [Accepted: 10/15/2004] [Indexed: 10/26/2022]
Abstract
OBJECTIVE The aim of this study was to compare striatal dopaminergic D2 receptor occupancy (D2 RO) induced by ziprasidone and haloperidol and its relationship with clinical response and extrapyramidal side effects (EPS) in patients with acute psychosis exacerbation. METHOD Twenty patients hospitalized with an acute psychosis exacerbation were randomised in a single-blind study to receive either ziprasidone (80-120 mg/day) or haloperidol (5-20 mg/day) for more than 2 weeks. When stable doses were achieved, data on 123I-IBZM single-photon emission computed tomography (SPECT), as well as data on clinical efficacy (positive and negative symptoms scale [PANSS]) and EPS (Simpson Angus scale [SAS]), were compared between the two groups of patients. Clinical response was defined as a percentage of change of >30% in PANSS. Striatal D2 RO and clinical data were also compared between responders and nonresponders on each treatment group. RESULTS All patients on haloperidol and four patients on ziprasidone showed EPS. Mean D2 RO was significantly higher in the haloperidol (74.7+/-3.5) than in the ziprasidone (60.2+/-14.4) group (Mann Whitney U-test [M-W U-test] 8.50; p=0.002). Five patients were responders, and five were nonresponders on each group of treatment. Haloperidol responders and nonresponders did not differ in D2 RO, duration of treatment, doses or EPS. Ziprasidone responders were on higher doses than nonresponders and showed higher D2 RO although below 74%. A positive correlation of ziprasidone D2 RO was found with dose (r Spearman 0.87; p=0.001) and with SAS scores (r Spearman 0.88; p=0.001). CONCLUSIONS Ziprasidone induces lower D2 RO and EPS than haloperidol, which is consistent with an atypical antipsychotic profile. A direct relationship of ziprasidone D2 RO with dose, clinical efficacy and EPS has been found in this study. These data suggest that high ziprasidone doses might be more beneficial in patients with psychosis exacerbation and claim for caution regarding EPS appearance with such high dosages.
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Affiliation(s)
- Iluminada Corripio
- Department of Psychiatry, Hospital de la Sta. Creu i St. Pau, Autonomous University of Barcelona (UAB) [corrected] Sant Antoni Maria Claret 167 08025 Barcelona, Spain.
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Bressan RA, Pilowsky LS. [Glutamatergic hypothesis of schizophrenia]. REVISTA BRASILEIRA DE PSIQUIATRIA (SAO PAULO, BRAZIL : 1999) 2003; 25:177-83. [PMID: 12975693 DOI: 10.1590/s1516-44462003000300011] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Schizophrenia is a devastating psychiatric disorder whose pathophysiology has not been fully clarified yet. Although dopamine dysfunction in schizophrenia is unequivocal, there are many evidences suggesting the involvement of the glutamatergic system. This paper briefly describes some basic knowledge regarding the functioning of the glutamatergic receptors with emphasis on the N-methyl-D-aspartate (NMDA) receptors. Presents evidence for glutamatergic dysfunction in schizophrenia, more specifically NMDA receptor hypofunction. Finaly the paper discusses the interaction between the dopaminergic and the glutamatergic systems; in special how hyperdopaminergic state found in schizophrenia can be associated to glutamatergic dysfunctions.
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Affiliation(s)
- Rodrigo A Bressan
- Departamento de Psiquiatria, Universidade Federal de São Paulo (UNIFESP). São Paulo, SP, Brasil.
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Bressan RA, Costa DC, Jones HM, Ell PJ, Pilowsky LS. Typical antipsychotic drugs -- D(2) receptor occupancy and depressive symptoms in schizophrenia. Schizophr Res 2002; 56:31-6. [PMID: 12084417 DOI: 10.1016/s0920-9964(01)00185-2] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
We tested the hypothesis that the degree of striatal dopamine D(2) receptor blockade induced by typical antipsychotic treatment directly correlates with the presence and severity of depressive symptoms in schizophrenia. Clinical and [(123)I]-IBZM single-photon emission tomography (SPET) scan data obtained from 18 typical antipsychotic treated schizophrenic patients was analysed to evaluate the relationship between striatal D(2) receptor occupancy and the depressive subscale of the Brief Psychiatric Rating Scale (BPRS-D). Striatal D(2) receptor occupancy by typical antipsychotic drugs was significantly positively correlated with BPRS-D scores (r=0.52, p=0.025). This study suggests that high striatal dopamine D(2) blockade by typical antipsychotic drugs may contribute to the emergence of depressive symptoms in typical antipsychotic treated schizophrenic patients.
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Affiliation(s)
- Rodrigo A Bressan
- Institute of Psychiatry, De Crespigny Park, Denmark Hill, London SE5 8AF, UK.
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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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Abstract
The use of in vivo receptor imaging by positron emission tomography (PET) and single photon emission tomography (SPET) has permitted exploration of targets for antipsychotic drug action in living patients. Early PET and SPET studies focused on striatal D2 dopamine receptors. There is broad agreement that unwanted extrapyramidal (parkinsonian) side effects of antipsychotic drugs result from high striatal dopamine D2/D3 receptor blockade by these drugs. The dopamine hypothesis of antipsychotic drug action suggests that clinical response is directly related to the level of striatal D2/D3 receptor occupancy of antipsychotic drugs. This may be true for classical antipsychotic drugs, but recent evidence suggests that novel, atypical antipsychotic drugs produce efficacy in association with modest and transient striatal D2/D3 receptor occupancy levels. Furthermore, atypical antipsychotic drugs appear to show preferential occupancy of limbic cortical dopamine D2 receptors. Cortical dopamine D2/D2-like receptors may be a common site of action for all antipsychotic drugs. Data from receptor challenge paradigms has highlighted the need to explore the neurotransmitter systems involved in regulating or stabilising dopamine transmission, either via dopamine autoreceptors or non-dopaminergic pathways. These may be promising targets for drug development. In vivo PET and SPET imaging has produced unique data contributing to the design of better, less toxic drugs for schizophrenia.
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Affiliation(s)
- L S Pilowsky
- Institute of Nuclear Medicine, UCL, Middlesex Hospital, London.
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Bressan RA, Bigliani V, Pilowsky LS. Neuroimagem de receptores D2 de dopamina na esquizofrenia. BRAZILIAN JOURNAL OF PSYCHIATRY 2001. [DOI: 10.1590/s1516-44462001000500014] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Elkashef AM, Doudet D, Bryant T, Cohen RM, Li SH, Wyatt RJ. 6-(18)F-DOPA PET study in patients with schizophrenia. Positron emission tomography. Psychiatry Res 2000; 100:1-11. [PMID: 11090720 DOI: 10.1016/s0925-4927(00)00064-0] [Citation(s) in RCA: 81] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Presynaptic dopamine metabolism was studied in a group of patients with schizophrenia and in an age- and gender-matched normal control group using 6-[(18)F]fluoro-L-DOPA ((18)F-DOPA) and positron emission tomography (PET). Nineteen patients, nine drug-free, 10 on neuroleptics, and 13 normal control subjects underwent PET scans using (18)F-DOPA. The neuroleptic-treated patients were taking typical neuroleptics (N=4) or the atypical neuroleptic, clozapine (N=6). The ratio of specific/non-specific activity was calculated for eight cortical and subcortical regions of interest. Medication-free patients had a significant reduction in (18)F-DOPA uptake in the ventral striatum (P=0.04) and significantly increased uptake in the posterior cingulate (P=0.02) compared with normal control subjects. The 18F-DOPA PET technique proved to be useful and sensitive in detecting changes in dopamine metabolism in patients with schizophrenia in vivo. The results of this study provide evidence of an aberrant dopamine system in schizophrenia.
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Affiliation(s)
- A M Elkashef
- Clinical Trials Branch, DTRD/NIDA, NIH, 6001 Executive Blvd, Room 4123, MSC 551, Bethesda, MD, 20892-9551, USA.
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Kapur S. Receptor Occupancy by Antipsychotics — Concepts and Findings. NEUROTRANSMITTER RECEPTORS IN ACTIONS OF ANTIPSYCHOTIC MEDICATIONS 2000. [DOI: 10.1201/9781420041774.ch11] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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Makoff AJ, Graham JM, Arranz MJ, Forsyth J, Li T, Aitchison KJ, Shaikh S, Grünewald RA. Association study of dopamine receptor gene polymorphisms with drug-induced hallucinations in patients with idiopathic Parkinson's disease. PHARMACOGENETICS 2000; 10:43-8. [PMID: 10739171 DOI: 10.1097/00008571-200002000-00006] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Some patients with idiopathic Parkinson's disease experience hallucinations as a result of treatment with levodopa and dopamine agonists. There is evidence for some heterogeneity in these hallucinating patients based on duration of Parkinson's disease at onset of hallucinations. We compared the frequency of polymorphisms in the dopamine D2 and D3 receptor genes between patients with drug-induced hallucinations and non-hallucinating patients. Two polymorphisms close to DRD2 and one in DRD3 were studied. No association was found with the whole group of hallucinating patients and their controls. However, an association was found with late-onset hallucinations and the C allele of the TaqIA polymorphism, 10.5 kb 3' to DRD2. This polymorphism may be in linkage disequilibrium with a mutation in DRD2 or a nearby gene that predisposes to drug-induced hallucinations which occur later in the course of idiopathic Parkinson's disease.
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Affiliation(s)
- A J Makoff
- Department of Psychological Medicine, Institute of Psychiatry, London, UK.
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Bigliani V, Mulligan RS, Acton PD, Visvikis D, Ell PJ, Stephenson C, Kerwin RW, Pilowsky LS. In vivo occupancy of striatal and temporal cortical D2/D3 dopamine receptors by typical antipsychotic drugs. [123I]epidepride single photon emission tomography (SPET) study. Br J Psychiatry 1999; 175:231-8. [PMID: 10645324 DOI: 10.1192/bjp.175.3.231] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
BACKGROUND The dopamine hypothesis proposes that antipsychotic drugs act primarily through limbic cortical D2/D2-like dopamine receptor blockade. AIM To evaluate this hypothesis with the D2/D3-selective SPET probe [123I]-epidepride. METHOD [123I]-epidepride SPET scans were performed on 12 patients with schizophrenia treated with antipsychotics and II age-matched healthy controls. [123I]-epidepride 'specific binding' to D2/D3 dopamine receptors was estimated, and relative percentage D2/D3 receptor occupancy by typical antipsychotic drugs determined. RESULTS Mean (s.d.) daily dose was 669.12 (516.8) mg chlorpromazine equivalents. Mean percentage D2/D3 receptor occupancy was 81.6 (8.1) and 73.2 (13.9) in the temporal cortex and striatum respectively. CONCLUSIONS Typical antipsychotic drug treatment is associated with substantial temporal cortical D2/D3 receptor occupancy. The relationship between this and efficacy is poor in patients with treatment-resistant schizophrenia.
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Duncan GE, Sheitman BB, Lieberman JA. An integrated view of pathophysiological models of schizophrenia. BRAIN RESEARCH. BRAIN RESEARCH REVIEWS 1999; 29:250-64. [PMID: 10209235 DOI: 10.1016/s0165-0173(99)00002-8] [Citation(s) in RCA: 129] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Pathophysiological processes that underlie the profound neuropsychiatric disturbances in schizophrenia are poorly understood. However, the clinical course of the disease, and a number of clinical and basic science observations, provide direction for formulating pathophysiological models that could be empirically tested. For example, repeated psychostimulant administration to healthy subjects can induce psychotic symptoms, and acute stimulant challenge in schizophrenia patients can precipitate psychosis. Also, NMDA antagonists induce positive, negative, and cognitive schizophrenic-like symptoms in healthy volunteers and precipitate thought disorder and delusions in schizophrenia patients. These human studies provide support for the dopamine and NMDA receptor hypofunction hypotheses of schizophrenia. Well-documented effects of NMDA antagonists on dopamine systems provide a basis to integrate the dopamine and NMDA receptor hypofunction hypotheses. Furthermore, it has become apparent that prominent actions of antipsychotic drugs, especially those with 'atypical' properties, involve antagonism of behavioral, electrophysiological and brain metabolic effects produced by administration of NMDA receptor antagonists. A confluence of clinical and basic science data suggests that an early developmental insult, potentially involving reduced NMDA receptor function, could facilitate sensitization of dopamine systems, leading to the formal onset of schizophrenia in late adolescence and early adulthood. Although clearly speculative, this conceptual model is consistent with existing evidence and suggests lines of future experimental investigation.
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Affiliation(s)
- G E Duncan
- Department of Psychiatry, School of Medicine, University of North Carolina, Chapel Hill, NC 27599-7250, USA.
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Tracers. Clin Nucl Med 1998. [DOI: 10.1007/978-1-4899-3356-0_21] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Acton PD, Pilowsky LS, Costa DC, Ell PJ. Multivariate cluster analysis of dynamic iodine-123 iodobenzamide SPET dopamine D2 receptor images in schizophrenia. EUROPEAN JOURNAL OF NUCLEAR MEDICINE 1997; 24:111-8. [PMID: 9021106 DOI: 10.1007/bf02439541] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
This paper describes the application of a multivariate statistical technique to investigate striatal dopamine D2 receptor concentrations measured by iodine-123 iodobenzamide (123I-IBZM) single-photon emission tomography (SPET). This technique enables the automatic segmentation of dynamic nuclear medicine images based on the underlying time-activity curves present in the data. Once the time-activity curves have been extracted, each pixel can be mapped back on to the underlying distribution, considerably reducing image noise. Cluster analysis has been verified using computer simulations and phantom studies. The technique has been applied to SPET images of dopamine D2 receptors in a total of 20 healthy and 20 schizophrenic volunteers (22 male, 18 female), using the ligand 123I-IBZM. Following automatic image segmentation, the concentration of striatal dopamine D2 receptors shows a significant left-sided asymmetry in male schizophrenics compared with male controls. The mean left-minus-right laterality index for controls is -1.52 (95% CI -3.72-0.66) and for patients 4.04 (95% CI 1.07-7.01). Analysis of variance shows a case-by-sex-by-side interaction, with F=10.01, P=0. 005. We can now demonstrate that the previously observed male sex-specific D2 receptor asymmetry in schizophrenia, which had failed to attain statistical significance, is valid. Cluster analysis of dynamic nuclear medicine studies provides a powerful tool for automatic segmentation and noise reduction of the images, removing much of the subjectivity inherent in region-of-interest analysis. The observed striatal D2 asymmetry could reflect long hypothesized disruptions in dopamine-rich cortico-striatal-limbic circuits in schizophrenic males.
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Affiliation(s)
- P D Acton
- Institute of Nuclear Medicine, University College London Medical School, London, UK
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Busatto GF, Kerwin RW. Perspectives on the role of serotonergic mechanisms in the pharmacology of schizophrenia. J Psychopharmacol 1997; 11:3-12. [PMID: 9097883 DOI: 10.1177/026988119701100102] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
In recent years, a number of research findings has renewed interest in the possible role of serotonin (5-HT) in the pharmacology of schizophrenia. Atypical antipsychotics that potently block 5-HT receptors have been shown to be at least as effective as classical antipsychotics as well as producing fewer extrapyramidal side-effects. In addition, molecular biological studies have suggested that allelic variations of 5-HT receptor genes may affect both susceptibility to schizophrenia and clinical response to atypical antipsychotics. Building on these findings, this article proposes that 5-HT receptors are critical sites of antipsychotic action, and examines the implications of this to the treatment and pathophysiology of schizophrenia. Possible pharmacological mechanisms underlying the clinical efficacy of 5-HT blocking antipsychotics are discussed, and the potential of functional neuroimaging techniques to further elucidate these mechanisms is emphasized.
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Affiliation(s)
- G F Busatto
- Department of Psychological Medicine, Institute of Psychiatry, DeCrespigny Park, Denmark Hill, London, UK
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Mulcrone J, Kerwin RW. No difference in the expression of the D4 gene in post-mortem frontal cortex from controls and schizophrenics. Neurosci Lett 1996; 219:163-6. [PMID: 8971805 DOI: 10.1016/s0304-3940(96)13191-8] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The primary biochemical theory of schizophrenia has centered on the role of dopaminergic dysfunction in the illness. The D2 receptor has been primarily indicated however, some atypical neuroleptics may not act at D2. The D4 receptor has a high affinity for the atypical antipsychotic clozapine and is therefore a potential target for drug design. The role of D4 in the aetiology of schizophrenia has, however, been the subject of controversy. Using radioligand binding assays some researchers have detected an elevation of D4-like receptors in schizophrenic striatum whilst conversely other workers claim that D4 receptors are undetectable in this region. Analysis of receptor levels is difficult due to the lack of a ligand selective for D4. We have therefore examined D4 at the level of gene expression. D4 mRNA levels have been examined in post-mortem frontal cortex from nine controls and eight schizophrenics using a reverse transcription-polymerase chain reaction (RT-PCR) method. No significant difference in D4 mRNA levels was found between the two groups. This result does not support a major role for variability of D4 gene expression in the aetiology of schizophrenia.
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Affiliation(s)
- J Mulcrone
- Department of Psychological Medicine, Institute of Psychiatry, London, UK
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