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Fu H, Rong J, Chen Z, Zhou J, Collier T, Liang SH. Positron Emission Tomography (PET) Imaging Tracers for Serotonin Receptors. J Med Chem 2022; 65:10755-10808. [PMID: 35939391 DOI: 10.1021/acs.jmedchem.2c00633] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Serotonin (5-hydroxytryptamine, 5-HT) and 5-HT receptors (5-HTRs) have crucial roles in various neuropsychiatric disorders and neurodegenerative diseases, making them attractive diagnostic and therapeutic targets. Positron emission tomography (PET) is a noninvasive nuclear molecular imaging technique and is an essential tool in clinical diagnosis and drug discovery. In this context, numerous PET ligands have been developed for "visualizing" 5-HTRs in the brain and translated into human use to study disease mechanisms and/or support drug development. Herein, we present a comprehensive repertoire of 5-HTR PET ligands by focusing on their chemotypes and performance in PET imaging studies. Furthermore, this Perspective summarizes recent 5-HTR-focused drug discovery, including biased agonists and allosteric modulators, which would stimulate the development of more potent and subtype-selective 5-HTR PET ligands and thus further our understanding of 5-HTR biology.
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Affiliation(s)
- Hualong Fu
- Key Laboratory of Radiopharmaceuticals, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing 100875, China
| | - Jian Rong
- Division of Nuclear Medicine and Molecular Imaging, Massachusetts General Hospital, Boston, Massachusetts 02114, United States.,Department of Radiology, Harvard Medical School, Boston, Massachusetts 02115, United States
| | - Zhen Chen
- Jiangsu Co-Innovation Center of Efficient Processing and Utilization of Forest Resources, International Innovation Center for Forest Chemicals and Materials, College of Chemical Engineering, Nanjing Forestry University, Nanjing, Jiangsu 210037, China
| | - Jingyin Zhou
- Key Laboratory of Radiopharmaceuticals, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing 100875, China
| | - Thomas Collier
- Division of Nuclear Medicine and Molecular Imaging, Massachusetts General Hospital, Boston, Massachusetts 02114, United States.,Department of Radiology, Harvard Medical School, Boston, Massachusetts 02115, United States
| | - Steven H Liang
- Division of Nuclear Medicine and Molecular Imaging, Massachusetts General Hospital, Boston, Massachusetts 02114, United States.,Department of Radiology, Harvard Medical School, Boston, Massachusetts 02115, United States
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2
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Gamma camera imaging in psychiatric disorders. Nucl Med Mol Imaging 2022. [DOI: 10.1016/b978-0-12-822960-6.00222-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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3
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Opposite alterations of 5-HT 2A receptor brain density in subjects with schizophrenia: relevance of radiotracers pharmacological profile. Transl Psychiatry 2021; 11:302. [PMID: 34016955 PMCID: PMC8137947 DOI: 10.1038/s41398-021-01430-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/01/2020] [Revised: 04/26/2021] [Accepted: 05/05/2021] [Indexed: 02/04/2023] Open
Abstract
The status of serotonin 5-HT2A receptors (5-HT2ARs) in schizophrenia has been controversial. In vivo positron emission tomography neuroimaging and in vitro post-mortem binding studies have reported conflicting results about 5-HT2AR density. Radiotracers bind different receptor conformations depending on their agonist, antagonist or inverse agonist properties. This study investigates 5-HT2AR density in the post-mortem prefrontal cortex from subjects with schizophrenia and controls using three radiotracers with a different pharmacological profile. The specific binding parameters of the inverse agonist [18F]altanserin, the agonist [3H]lysergic acid diethylamide (LSD) and the antagonist [3H]MDL100907 to brain cortex membranes from 20 subjects with schizophrenia and 20 individually matched controls were evaluated under similar methodological conditions. Ten schizophrenia subjects were antipsychotic-free at death. Saturation curve analyses were performed by non-linear regression to obtain a maximal density of binding sites (Bmax) and the affinity of the respective radiotracers (Kd). In schizophrenia subjects, 5-HT2AR density was decreased when quantified by [18F]altanserin binding, whereas increased when evaluated by [3H]LSD binding. However, [3H]MDL100907 binding was unaltered. A slight loss of affinity (higher Kd) was observed exclusively in [3H]LSD binding. The findings were more evident in antipsychotic-free subjects than in antipsychotic-treated subjects. In conclusion, a higher proportion of the 5-HT2AR-active functional conformation, which is rather identified by agonist radiotracers, was observed in schizophrenia patients. A consequent reduction of the inactive 5-HT2AR conformation, which is preferentially identified by inverse agonist radiotracers, was also obtained. Antagonist radiotracers do not distinguish between molecular conformations of the receptor, and accordingly, the absence of changes was shown. These results are compatible with the proposed increased functional activity of brain cortical 5-HT2ARs in schizophrenia.
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Matheson GJ, Plavén-Sigray P, Louzolo A, Borg J, Farde L, Petrovic P, Cervenka S. Dopamine D1 receptor availability is not associated with delusional ideation measures of psychosis proneness. Schizophr Res 2020; 222:175-184. [PMID: 32616361 DOI: 10.1016/j.schres.2020.06.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/28/2020] [Revised: 05/25/2020] [Accepted: 06/01/2020] [Indexed: 10/24/2022]
Abstract
The dopamine D1 receptor (D1R) is thought to play a role in psychosis and schizophrenia, however positron emission tomography studies comparing patients and controls have been inconsistent. To circumvent some of the limitations of clinical studies, such as antipsychotic exposure, an alternative approach is to examine subclinical psychotic symptoms within the general population, i.e. psychosis proneness traits. In this study, we investigated whether D1R availability is associated with delusional ideation in healthy controls, in four experiments, using [11C]SCH23390 PET (n = 76) and psychometric questionnaires (n = 217). We performed exploratory analyses, direct self-replication, and confirmatory analyses using Bayesian statistical modelling. Collectively, we found strong evidence that there is little to no linear association between delusional ideation and D1R. If hypothesised changes in D1R in drug-naive psychosis patients can be confirmed, our results suggest that they may either occur at disease onset, or that they are associated with specific aspects of psychosis other than delusional ideation.
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Affiliation(s)
- Granville J Matheson
- Department of Clinical Neuroscience, Center for Psychiatry Research, Karolinska Institutet and Stockholm County Council, SE-171 76 Stockholm, Sweden.
| | - Pontus Plavén-Sigray
- Department of Clinical Neuroscience, Center for Psychiatry Research, Karolinska Institutet and Stockholm County Council, SE-171 76 Stockholm, Sweden
| | - Anaïs Louzolo
- Department of Clinical Neuroscience, Karolinska Institutet, SE-171 76 Stockholm, Sweden
| | - Jacqueline Borg
- Department of Clinical Neuroscience, Center for Psychiatry Research, Karolinska Institutet and Stockholm County Council, SE-171 76 Stockholm, Sweden
| | - Lars Farde
- Department of Clinical Neuroscience, Center for Psychiatry Research, Karolinska Institutet and Stockholm County Council, SE-171 76 Stockholm, Sweden; PET Science Centre, Precision Medicine and Genomics, IMED Biotech Unit, AstraZeneca, Karolinska Institutet, Sweden
| | - Predrag Petrovic
- Department of Clinical Neuroscience, Karolinska Institutet, SE-171 76 Stockholm, Sweden
| | - Simon Cervenka
- Department of Clinical Neuroscience, Center for Psychiatry Research, Karolinska Institutet and Stockholm County Council, SE-171 76 Stockholm, Sweden
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5
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Stenkrona P, Matheson GJ, Halldin C, Cervenka S, Farde L. D1-Dopamine Receptor Availability in First-Episode Neuroleptic Naive Psychosis Patients. Int J Neuropsychopharmacol 2019; 22:415-425. [PMID: 30958880 PMCID: PMC6600463 DOI: 10.1093/ijnp/pyz017] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/10/2019] [Revised: 03/12/2019] [Accepted: 04/05/2019] [Indexed: 01/02/2023] Open
Abstract
BACKGROUND Positron emission tomography studies examining differences in D1-dopamine receptor binding between control subjects and patients with schizophrenia have been inconsistent, reporting higher, lower, and no difference in the frontal cortex. Exposure to antipsychotic medication has been suggested to be a likely source of this heterogeneity, and thus there is a need for studies of patients at early stages of the disorder who have not been exposed to such drugs. METHODS Here, we compared 17 healthy control subjects and 18 first-episode neuroleptic naive patients with schizophrenia or schizophreniform psychosis using positron emission tomography and the D1-dopamine receptor radioligand [11C]SCH23390. RESULTS We observed a statistically significant difference in the dorsolateral prefrontal cortex. Contrary to our expectations, patients had less D1-dopamine receptor availability with a moderate effect size. In a Bayesian analysis, we show that the data are over 50 times more likely to have occurred under the decrease as opposed to the increase hypothesis. This effect was not global, as our analysis showed that the null hypothesis was preferred over either hypothesis in the striatum. CONCLUSIONS This investigation represents the largest single sample of neuroleptic-naive patients examined for D1-dopamine receptor availability using PET and suggests a reduction of prefrontal D1-dopamine receptor density in the pathophysiology of schizophrenia. However, further work will be required to reach a consensus.
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Affiliation(s)
- Per Stenkrona
- Department of Clinical Neuroscience, Centre for Psychiatry Research, Karolinska Institutet and Stockholm County Council, Stockholm, Sweden,Correspondence: Per Stenkrona, MD, Karolinska Institutet, Department of Clinical Neuroscience Karolinska University Hospital, R5:02 SE-171 76 Stockholm, Sweden ()
| | - Granville J Matheson
- Department of Clinical Neuroscience, Centre for Psychiatry Research, Karolinska Institutet and Stockholm County Council, Stockholm, Sweden
| | - Christer Halldin
- Department of Clinical Neuroscience, Centre for Psychiatry Research, Karolinska Institutet and Stockholm County Council, Stockholm, Sweden
| | - Simon Cervenka
- Department of Clinical Neuroscience, Centre for Psychiatry Research, Karolinska Institutet and Stockholm County Council, Stockholm, Sweden
| | - Lars Farde
- Department of Clinical Neuroscience, Centre for Psychiatry Research, Karolinska Institutet and Stockholm County Council, Stockholm, Sweden,PET Science Centre, Precision Medicine, R&D Oncology, AstraZeneca, Karolinska Institutet, Sweden
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6
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Abstract
The dopamine (DA) system is considered to be centrally involved in the pathophysiology of several major psychiatric disorders. Using positron emission tomography (PET), aberrations in dopamine D2/D3-receptors (D2-R) levels and uptake of the DA precursor FDOPA have been shown for schizophrenia, substance abuse and depression. Radioligands for the dopamine D1-receptor (D1-R) have been available for more than three decades, however this receptor subtype has received much less attention in psychiatry research. Here, studies investigating D1-R in psychiatric patients in comparison to healthy control subjects are summarized. Although small sample sizes, medication effects and heterogeneous methods of quantification limit the conclusions that can be drawn, the data is suggestive of higher levels of cortical D1-R in drug naïve patients with psychosis, and lower D1-R in patients with affective disorders. Data sharing and reanalysis using harmonized methodology are important next steps towards clarifying the role of D1-R in these disorders.
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Affiliation(s)
- Simon Cervenka
- Department of Clinical Neuroscience, Center for Psychiatry Research, Karolinska Institutet and Stockholm County Council, SE-171 76 Stockholm, Sweden.
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7
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Mach RH. Small Molecule Receptor Ligands for PET Studies of the Central Nervous System-Focus on G Protein Coupled Receptors. Semin Nucl Med 2017; 47:524-535. [PMID: 28826524 DOI: 10.1053/j.semnuclmed.2017.05.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
G protein-coupled receptors (GPRCs) are a class of proteins that are expressed in high abundance and are responsible for numerous signal transduction pathways in the central nervous system. Consequently, alterations in GPRC function have been associated with a wide variety of neurologic and neuropsychiatric disorders. The development of PET probes for imaging GPRCs has served as a major emphasis of PET radiotracer development and PET imaging studies over the past 30 years. In this review, a basic description of the biology of G proteins and GPRCs is provided. This includes recent evidence of the existence of dimeric and multimeric species of GPRCs that have been termed "receptor mosaics," with an emphasis on the different GPRCs that form complexes with the dopamine D2 receptor. An overview of the different PET radiotracers for imaging the component GPRC within these different multimeric complexes of the D2 receptor is also provided.
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Affiliation(s)
- Robert H Mach
- Department of Radiology, Perelman School Medicine, University of Pennsylvania, Philadelphia, PA.
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Perkovic MN, Erjavec GN, Strac DS, Uzun S, Kozumplik O, Pivac N. Theranostic Biomarkers for Schizophrenia. Int J Mol Sci 2017; 18:E733. [PMID: 28358316 PMCID: PMC5412319 DOI: 10.3390/ijms18040733] [Citation(s) in RCA: 59] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2017] [Revised: 03/23/2017] [Accepted: 03/27/2017] [Indexed: 12/14/2022] Open
Abstract
Schizophrenia is a highly heritable, chronic, severe, disabling neurodevelopmental brain disorder with a heterogeneous genetic and neurobiological background, which is still poorly understood. To allow better diagnostic procedures and therapeutic strategies in schizophrenia patients, use of easy accessible biomarkers is suggested. The most frequently used biomarkers in schizophrenia are those associated with the neuroimmune and neuroendocrine system, metabolism, different neurotransmitter systems and neurotrophic factors. However, there are still no validated and reliable biomarkers in clinical use for schizophrenia. This review will address potential biomarkers in schizophrenia. It will discuss biomarkers in schizophrenia and propose the use of specific blood-based panels that will include a set of markers associated with immune processes, metabolic disorders, and neuroendocrine/neurotrophin/neurotransmitter alterations. The combination of different markers, or complex multi-marker panels, might help in the discrimination of patients with different underlying pathologies and in the better classification of the more homogenous groups. Therefore, the development of the diagnostic, prognostic and theranostic biomarkers is an urgent and an unmet need in psychiatry, with the aim of improving diagnosis, therapy monitoring, prediction of treatment outcome and focus on the personal medicine approach in order to improve the quality of life in patients with schizophrenia and decrease health costs worldwide.
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Affiliation(s)
| | | | - Dubravka Svob Strac
- Rudjer Boskovic Institute, Division of Molecular Medicine, 10000 Zagreb, Croatia.
| | - Suzana Uzun
- Clinic for Psychiatry Vrapce, 10090 Zagreb, Croatia.
| | | | - Nela Pivac
- Rudjer Boskovic Institute, Division of Molecular Medicine, 10000 Zagreb, Croatia.
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Dean B, Copolov D, Scarr E. Understanding the pathophysiology of schizophrenia: Contributions from the Melbourne Psychiatric Brain Bank. Schizophr Res 2016; 177:108-114. [PMID: 27184458 DOI: 10.1016/j.schres.2016.04.037] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/02/2016] [Revised: 04/20/2016] [Accepted: 04/23/2016] [Indexed: 11/24/2022]
Abstract
The Melbourne Psychiatric Brain Bank came into existence 25years ago. This review focusses on lines of research that have used tissue from the Brain Bank over periods of time. Hence there is a discussion on the significance of changes in levels of serotonin 2A receptors in the cortex of patients with schizophrenia and the relevance of such changes with regards to the pathophysiology of the disorder. The extensive contribution made by studies using tissue from the Melbourne Psychiatric Brain Bank to understanding the role of muscarinic receptors in the pathophysiology and treatment of schizophrenia is summarised. Finally, findings using brain bank tissue and "omics" technologies are reviewed. In each case, findings using tissue from the Melbourne Psychiatric Brain Bank is placed in context with research carried out on human postmortem CNS in schizophrenia and with findings in other lines of research that can help explain the causes or consequences of changes in CNS molecular cytoarchitecture. This timely review of data from the Melbourne Psychiatric Brain Bank reinforces the challenges faced in trying to increase our understanding of the molecular pathophysiology of schizophrenia. Continuing to increase our understanding of the disorder is important as a precursor to identifying new drug targets that can be exploited to improve the treatment of a disorder where treatment resistance remains a significant problem (Millan et al., 2016).
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Affiliation(s)
- Brian Dean
- The Molecular Psychiatry Laboratory, The Florey Institute for Neuroscience and Mental Health, Parkville, Victoria, Australia.
| | - David Copolov
- Office of the Vice-Chancellor and President, Monash University, Clayton, Victoria, Australia
| | - Elizabeth Scarr
- The Molecular Psychiatry Laboratory, The Florey Institute for Neuroscience and Mental Health, Parkville, Victoria, Australia
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10
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Nikolaus S, Müller HW, Hautzel H. Different patterns of 5-HT receptor and transporter dysfunction in neuropsychiatric disorders--a comparative analysis of in vivo imaging findings. Rev Neurosci 2016; 27:27-59. [PMID: 26376220 DOI: 10.1515/revneuro-2015-0014] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2015] [Accepted: 08/05/2015] [Indexed: 11/15/2022]
Abstract
Impairment of serotonin receptor and transporter function is increasingly recognized to play a major role in the pathophysiology of neuropsychiatric diseases including anxiety disorder (AD), major depressive disorder (MDD), bipolar disorder (BD) and schizophrenia (SZ). We conducted a PubMed search, which provided a total of 136 in vivo studies with PET and SPECT, in which 5-HT synthesis, 5-HT transporter binding, 5-HT1 receptor binding or 5-HT2 receptor binding in patients with the primary diagnosis of acute AD, MDD, BD or SZ was compared to healthy individuals. A retrospective analysis revealed that AD, MDD, BD 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 receptor binding sites.
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Švob Štrac D, Pivac N, Mück-Šeler D. The serotonergic system and cognitive function. Transl Neurosci 2016; 7:35-49. [PMID: 28123820 PMCID: PMC5017596 DOI: 10.1515/tnsci-2016-0007] [Citation(s) in RCA: 143] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2015] [Accepted: 04/22/2016] [Indexed: 01/23/2023] Open
Abstract
Symptoms of cognitive dysfunction like memory loss, poor concentration, impaired learning and executive functions are characteristic features of both schizophrenia and Alzheimer’s disease (AD). The neurobiological mechanisms underlying cognition in healthy subjects and neuropsychiatric patients are not completely understood. Studies have focused on serotonin (5-hydroxytryptamine, 5-HT) as one of the possible cognitionrelated biomarkers. The aim of this review is to provide a summary of the current literature on the role of the serotonergic (5-HTergic) system in cognitive function, particularly in AD and schizophrenia. The role of the 5-HTergic system in cognition is modulated by the activity and function of 5-HT receptors (5-HTR) classified into seven groups, which differ in structure, action, and localization. Many 5-HTR are located in the regions linked to various cognitive processes. Preclinical studies using animal models of learning and memory, as well as clinical in vivo (neuroimaging) and in vitro (post-mortem) studies in humans have shown that alterations in 5-HTR activity influence cognitive performance. The current evidence implies that reduced 5-HT neurotransmission negatively influences cognitive functions and that normalization of 5-HT activity may have beneficial effects, suggesting that 5-HT and 5-HTR represent important pharmacological targets for cognition enhancement and restoration of impaired cognitive performance in neuropsychiatric disorders.
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Affiliation(s)
| | - Nela Pivac
- Division of Molecular Medicine, Ruđer Bošković Institute, Zagreb, Croatia
| | - Dorotea Mück-Šeler
- Division of Molecular Medicine, Ruđer Bošković Institute, Zagreb, Croatia
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12
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Selvaraj S, Arnone D, Cappai A, Howes O. Alterations in the serotonin system in schizophrenia: a systematic review and meta-analysis of postmortem and molecular imaging studies. Neurosci Biobehav Rev 2014; 45:233-45. [PMID: 24971825 DOI: 10.1016/j.neubiorev.2014.06.005] [Citation(s) in RCA: 140] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2013] [Revised: 05/13/2014] [Accepted: 06/16/2014] [Indexed: 02/04/2023]
Abstract
Serotonergic dysfunction is thought to contribute to the pathophysiology of schizophrenia but the evidence has not been systematically synthesised before. We therefore systematically reviewed postmortem and in vivo molecular imaging studies of serotonin function in schizophrenia. We identified fifty relevant studies investigating eight different serotonin receptor systems in a total of 684 patients and 675 controls. Meta-analysis of postmortem studies found an elevation in prefrontal 5-HT1A receptors with a moderate to large effect size (N=8, 85 patients and 94 controls, SMD=0.60; CI: 0.17-1.03; p=0.007) and a reduction with a large effect size in prefrontal 5-HT2A receptors (N=8, 168 patients and 163 controls, SMD=-0.73; CI: -1.33, -0.12; p=0.019) in schizophrenia vs healthy controls. The evidence for alterations in serotonin transporter availability or other serotonin receptors (5-HT1B; 5-HT1D; 5-HT3; 5-HT4; 5-HT7) is limited. There are fewer studies investigating 5-HT receptors in schizophrenia with neuroimaging. Findings indicated possible 5-HT alterations at psychosis onset, although due to the limited number it was not possible to combine studies in a meta-analysis. Further in vivo studies, particularly in drug naive patients using radiotracers that can index high affinity states, will help determine if the postmortem findings are primary or secondary to other factors.
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Affiliation(s)
- Sudhakar Selvaraj
- Medical Research Council, Clinical Sciences Centre, Institute of Clinical Sciences, Hammersmith Hospital Campus, Imperial College London, London W12 0NN, UK; Department of Psychiatry and Behavioural Sciences, The University of Texas Health Science Centre at Houston, Houston, TX, USA.
| | - Danilo Arnone
- Centre for Affective Disorders, Institute of Psychiatry, King's College London, London SE5 8AF, UK
| | - Alessandra Cappai
- Medical Research Council, Clinical Sciences Centre, Institute of Clinical Sciences, Hammersmith Hospital Campus, Imperial College London, London W12 0NN, UK; Forensic Outreach Service & Inreach Team HMP Wandsworth, South West London & St George's NHS Mental Health Trust, Springfield Hospital, Glenburnie Road, London SW17 7DJ, UK
| | - Oliver Howes
- Medical Research Council, Clinical Sciences Centre, Institute of Clinical Sciences, Hammersmith Hospital Campus, Imperial College London, London W12 0NN, UK; Department of Psychosis Studies, Institute of Psychiatry, King's College London, London SE5 8AF, 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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Abstract
One of the oldest models of schizophrenia is based on the effects of serotonergic hallucinogens such as mescaline, psilocybin, and (+)-lysergic acid diethylamide (LSD), which act through the serotonin 5-HT(2A) receptor. These compounds produce a 'model psychosis' in normal individuals that resembles at least some of the positive symptoms of schizophrenia. Based on these similarities, and because evidence has emerged that the serotonergic system plays a role in the pathogenesis of schizophrenia in some patients, animal models relevant to schizophrenia have been developed based on hallucinogen effects. Here we review the behavioural effects of hallucinogens in four of those models, the receptor and neurochemical mechanisms for the effects and their translational relevance. Despite the difficulty of modelling hallucinogen effects in nonverbal species, animal models of schizophrenia based on hallucinogens have yielded important insights into the linkage between 5-HT and schizophrenia and have helped to identify receptor targets and interactions that could be exploited in the development of new therapeutic agents.
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Wyss C, Hitz K, Hengartner MP, Theodoridou A, Obermann C, Uhl I, Roser P, Grünblatt E, Seifritz E, Juckel G, Kawohl W. The loudness dependence of auditory evoked potentials (LDAEP) as an indicator of serotonergic dysfunction in patients with predominant schizophrenic negative symptoms. PLoS One 2013; 8:e68650. [PMID: 23874705 PMCID: PMC3709903 DOI: 10.1371/journal.pone.0068650] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2013] [Accepted: 05/31/2013] [Indexed: 11/18/2022] Open
Abstract
Besides the influence of dopaminergic neurotransmission on negative symptoms in schizophrenia, there is evidence that alterations of serotonin (5-HT) system functioning also play a crucial role in the pathophysiology of these disabling symptoms. From post mortem and genetic studies on patients with negative symptoms a 5-HT dysfunction is documented. In addition atypical neuroleptics and some antidepressants improve negative symptoms via serotonergic action. So far no research has been done to directly clarify the association between the serotonergic functioning and the extent of negative symptoms. Therefore, we examined the status of brain 5-HT level in negative symptoms in schizophrenia by means of the loudness dependence of auditory evoked potentials (LDAEP). The LDAEP provides a well established and non-invasive in vivo marker of the central 5-HT activity. We investigated 13 patients with schizophrenia with predominant negative symptoms treated with atypical neuroleptics and 13 healthy age and gender matched controls with a 32-channel EEG. The LDAEP of the N1/P2 component was evaluated by dipole source analysis and single electrode estimation at Cz. Psychopathological parameters, nicotine use and medication were assessed to control for additional influencing factors. Schizophrenic patients showed significantly higher LDAEP in both hemispheres than controls. Furthermore, the LDAEP in the right hemisphere in patients was related to higher scores in scales assessing negative symptoms. A relationship with positive symptoms was not found. These data might suggest a diminished central serotonergic neurotransmission in patients with predominant negative symptoms.
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Affiliation(s)
- Christine Wyss
- Department of Psychiatry, Psychotherapy and Psychosomatics, Psychiatric University Hospital Zurich, Zurich, Switzerland
| | - Konrad Hitz
- Department of Psychiatry, Psychotherapy and Psychosomatics, Psychiatric University Hospital Zurich, Zurich, Switzerland
| | - Michael P. Hengartner
- Department of Psychiatry, Psychotherapy and Psychosomatics, Psychiatric University Hospital Zurich, Zurich, Switzerland
| | - Anastasia Theodoridou
- Department of Psychiatry, Psychotherapy and Psychosomatics, Psychiatric University Hospital Zurich, Zurich, Switzerland
| | - Caitriona Obermann
- Department of Psychiatry, Psychotherapy and Psychosomatics, Psychiatric University Hospital Zurich, Zurich, Switzerland
| | - Idun Uhl
- Department of Psychiatry, Ruhr University Bochum, LWL University Hospital, Bochum, Germany
| | - Patrik Roser
- Department of Psychiatry, Ruhr University Bochum, LWL University Hospital, Bochum, Germany
| | - Edna Grünblatt
- Department of Child and Adolescent Psychiatry, University of Zurich, Zurich, Switzerland
| | - Erich Seifritz
- Department of Psychiatry, Psychotherapy and Psychosomatics, Psychiatric University Hospital Zurich, Zurich, Switzerland
| | - Georg Juckel
- Department of Psychiatry, Ruhr University Bochum, LWL University Hospital, Bochum, Germany
| | - Wolfram Kawohl
- Department of Psychiatry, Psychotherapy and Psychosomatics, Psychiatric University Hospital Zurich, Zurich, Switzerland
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Delille HK, Mezler M, Marek GJ. The two faces of the pharmacological interaction of mGlu2 and 5-HT₂A - relevance of receptor heterocomplexes and interaction through functional brain pathways. Neuropharmacology 2013; 70:296-305. [PMID: 23466331 DOI: 10.1016/j.neuropharm.2013.02.005] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2012] [Revised: 02/01/2013] [Accepted: 02/04/2013] [Indexed: 11/28/2022]
Abstract
Important functional interactions between the metabotropic glutamate 2 (mGlu2) and 5-hydroxytryptamine2A (5-HT₂A) neurotransmitter receptors have been established based on electrophysiological, biochemical and behavioral evidence. Over the last several years, dimerization between 5-HT₂A and mGlu2 receptors has been proposed to account for the functional cross-talk between these two receptors in the prefrontal cortex. The pros and cons for the existence of a heteromeric complex between 5-HT₂A and mGlu2 receptors will be reviewed here. First, the fundamental criteria needing to establish evidence for heteromeric complexes will be reviewed. Then, the in vitro evidence for and against heteromeric complexes between 5-HT₂A and mGlu2 receptors will be discussed in regard to physical and functional interactions. Finally, the data with native in situ mGlu2 and 5-HT₂A receptors will be discussed with respect to whether heteromeric complexes or a simple functional interaction between two distinct GPCRs based on brain network activity is the more simple explanation for a range of in vivo data.
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Affiliation(s)
- Hannah K Delille
- Abbott Diagnostics Division, Max-Planck-Ring 2, 65205 Wiesbaden, Germany
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Evaluation of dopamine D₂/D₃ and serotonin 5-HT₂A receptor occupancy for a novel antipsychotic, lurasidone, in conscious common marmosets using small-animal positron emission tomography. Psychopharmacology (Berl) 2013; 225:329-39. [PMID: 22868411 DOI: 10.1007/s00213-012-2815-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/02/2012] [Accepted: 07/17/2012] [Indexed: 12/13/2022]
Abstract
RATIONALE Lurasidone is a novel antipsychotic drug with potent binding affinity for dopamine D(2) and serotonin (5-hydroxytryptamine, 5-HT)(2A), 5-HT(7), and 5-HT(1A) receptors. Previous pharmacological studies have revealed that lurasidone exhibits a preferable profile (potent antipsychotic activity and lower incidence of catalepsy) to other antipsychotic drugs, although the contribution of receptor subtypes to this profile remains unclear. OBJECTIVES To compare target engagements of lurasidone with those of an atypical antipsychotic, olanzapine, we performed evaluation of dopamine D(2)/D(3) and serotonin 5-HT(2A) receptor occupancy in vivo by positron emission tomography (PET) with conscious common marmosets. METHODS We measured brain receptor occupancies in conscious common marmosets after oral administrations of lurasidone or olanzapine by PET with [(11)C]raclopride and [(11)C]R-(+)-α-(2,3-dimethoxyphenyl)-1-[2-(4-fluorophenylethyl)]-4-piperidine methanol (MDL 100907) for D(2)/D(3) and 5-HT(2A) receptors, respectively. RESULTS Increases in brain D(2)/D(3) receptor occupancies of both lurasidone and olanzapine, which reached >80 % at maximum, were observed in the striatum with significant correlations to plasma drug levels. However, lurasidone showed lower 5-HT(2A) receptor occupancy in the frontal cortex within the same dose range, while olanzapine showed broadly comparable 5-HT(2A) and D(2)/D(3) receptor occupancies. CONCLUSIONS Compared with olanzapine, lurasidone preferentially binds to D(2)/D(3) receptors rather than 5-HT(2A) receptors in common marmosets. These results suggest that the contribution of in vivo 5-HT(2A) receptor blocking activity to the pharmacological profile of lurasidone might differ from olanzapine in terms of the low risk of extrapyramidal syndrome and efficacy against negative symptoms.
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Howes OD, Fusar-Poli P, Bloomfield M, Selvaraj S, McGuire P. From the prodrome to chronic schizophrenia: the neurobiology underlying psychotic symptoms and cognitive impairments. Curr Pharm Des 2012; 18:459-65. [PMID: 22239576 DOI: 10.2174/138161212799316217] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2011] [Accepted: 10/18/2011] [Indexed: 11/22/2022]
Abstract
Schizophrenia is a chronic psychotic disorder that remains a considerable cause of global disease burden. Cognitive impairments are common and contribute significantly to the morbidity of the disorder. Over the last two decades or so molecular imaging studies have refined understanding of the pathophysiology underlying the development of psychosis and cognitive impairments. Firstly they have consistently implicated presynaptic dopaminergic dysfunction in the disorder, finding that dopamine synthesis capacity, dopamine release and baseline dopamine levels are increased in the illness. Secondly recent findings show that dopamine synthesis capacity is elevated in those that go on to develop psychosis in the following year, but not in those that do not, and appears to increase further with the development of psychosis. Thirdly evidence links greater dopamine synthesis capacity to poorer cognitive performance and altered frontal cortical function measured using functional imaging during cognitive tasks. Finally they have provided data on the nature of other neurofunctional alterations in the disorder, in particular in the serotonergic system and neuroinflammation. We review these findings and discuss their implications for understanding the neurobiology of psychosis and cognitive impairments in schizophrenia.
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Affiliation(s)
- O D Howes
- Psychiatric Imaging Group Cyclotron Building Hammersmith Hospital, London W12 0NN, UK.
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Abi-Dargham A, Xu X, Thompson JL, Gil R, Kegeles LS, Urban N, Narendran R, Hwang DR, Laruelle M, Slifstein M. Increased prefrontal cortical D₁ receptors in drug naive patients with schizophrenia: a PET study with [¹¹C]NNC112. J Psychopharmacol 2012; 26:794-805. [PMID: 21768159 DOI: 10.1177/0269881111409265] [Citation(s) in RCA: 103] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
D₁ receptors are the main mediators of dopamine transmission in the cortex and subserve cognitive functions that are affected in patients with schizophrenia. Prior imaging studies have suggested abnormalities in the expression of these receptors in schizophrenia, but no conclusive picture has emerged yet. One source of discrepancy may have been prior antipsychotic exposure. We used positron emission tomography (PET) and a D1 radiotracer, [¹¹C]NNC112, in drug naïve (DN, n = 12) and drug free (DF, n = 13) patients with schizophrenia and 40 healthy control subjects (HC, n = 40 total, n = 24 per comparison group) matched for age, gender, ethnicity, parental socioeconomic status and cigarette smoking. We measured the binding potential BPP, corrected for partial volume effects. The outcome measure was obtained in cortical and striatal subregions outlined on coregistered individual MRIs. Partial volume effect corrected BPP measures were significantly higher in DN vs controls in cortical regions. No such increases were found in the DF versus controls comparison. Furthermore, in the DF group, DF interval correlated positively with cortical BPP. We conclude that upregulation of D1 receptors in schizophrenia is related to the illness itself and may be corrected and normalized by chronic antipsychotic treatment.
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Affiliation(s)
- Anissa Abi-Dargham
- Department of Psychiatry, Columbia University College of Physicians and Surgeons, New York, NY 10032, USA.
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Newberg AB, Moss AS, Monti DA, Alavi A. Positron emission tomography in psychiatric disorders. Ann N Y Acad Sci 2011; 1228:E13-25. [DOI: 10.1111/j.1749-6632.2011.06162.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Ebdrup BH, Rasmussen H, Arnt J, Glenthøj B. Serotonin 2A receptor antagonists for treatment of schizophrenia. Expert Opin Investig Drugs 2011; 20:1211-23. [PMID: 21740279 DOI: 10.1517/13543784.2011.601738] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
INTRODUCTION All approved antipsychotic drugs share an affinity for the dopamine 2 (D(2)) receptor; however, these drugs only partially ameliorate the symptoms of schizophrenia. It is, therefore, of paramount importance to identify new treatment strategies for schizophrenia. AREAS COVERED Preclinical, clinical and post-mortem studies of the serotonin 5-HT(2A) system in schizophrenia are reviewed. The implications of a combined D(2) and 5-HT(2A) receptor blockade, which is obtained by several current antipsychotic drugs, are discussed, and the rationale for the development of more selective 5-HT(2A) receptor antagonists is evaluated. Moreover, the investigational pipeline of major pharmaceutical companies is examined and an Internet search conducted to identify other pharmaceutical companies investigating 5-HT(2A) receptor antagonists for the treatment of schizophrenia. EXPERT OPINION 5-HT(2A) receptor antagonists appear to assume an intermediate position by being marginally superior to placebo but inferior to conventional antipsychotic drugs. Three previous 5-HT(2A) receptor antagonists have been discontinued after Phase II or III trials, and available Phase IIa data on the remaining 5-HT(2A) receptor antagonist will need substantial additional validation to be approved as a new treatment strategy against schizophrenia.
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Affiliation(s)
- Bjørn H Ebdrup
- Center for Neuropsychiatric Schizophrenia Research, Copenhagen University Hospital Glostrup, Faculty of Health Sciences, Psychiatric Center Glostrup, Nordre Ringvej 29, DK-2600 Glostrup, Denmark
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Paterson LM, Kornum BR, Nutt DJ, Pike VW, Knudsen GM. 5-HT radioligands for human brain imaging with PET and SPECT. Med Res Rev 2011; 33:54-111. [PMID: 21674551 DOI: 10.1002/med.20245] [Citation(s) in RCA: 119] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The serotonergic system plays a key modulatory role in the brain and is the target for many drug treatments for brain disorders either through reuptake blockade or via interactions at the 14 subtypes of 5-HT receptors. This review provides the history and current status of radioligands used for positron emission tomography (PET) and single photon emission computerized tomography (SPECT) imaging of human brain serotonin (5-HT) receptors, the 5-HT transporter (SERT), and 5-HT synthesis rate. Currently available radioligands for in vivo brain imaging of the 5-HT system in humans include antagonists for the 5-HT(1A), 5-HT(1B), 5-HT(2A), and 5-HT(4) receptors, and for SERT. Here we describe the evolution of these radioligands, along with the attempts made to develop radioligands for additional serotonergic targets. We describe the properties needed for a radioligand to become successful and the main caveats. The success of a PET or SPECT radioligand can ultimately be assessed by its frequency of use, its utility in humans, and the number of research sites using it relative to its invention date, and so these aspects are also covered. In conclusion, the development of PET and SPECT radioligands to image serotonergic targets is of high interest, and successful evaluation in humans is leading to invaluable insight into normal and abnormal brain function, emphasizing the need for continued development of both SPECT and PET radioligands for human brain imaging.
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Affiliation(s)
- Louise M Paterson
- Neuropsychopharmacology Unit, Division of Experimental Medicine, Imperial College London, Burlington Danes Building, Du Cane Road, London, United Kingdom
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Rasmussen H, Ebdrup BH, Erritzoe D, Aggernaes B, Oranje B, Kalbitzer J, Pinborg LH, Baaré WFC, Svarer C, Lublin H, Knudsen GM, Glenthoj B. Serotonin2A receptor blockade and clinical effect in first-episode schizophrenia patients treated with quetiapine. Psychopharmacology (Berl) 2011; 213:583-92. [PMID: 20614105 DOI: 10.1007/s00213-010-1941-5] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/19/2010] [Accepted: 06/24/2010] [Indexed: 10/19/2022]
Abstract
RATIONALE We have previously reported decreased frontal cortical serotonin2A receptor binding in 30 antipsychotic naïve first-episode schizophrenic patients and a relationship between this binding and positive psychotic symptoms. Until now, no longitudinal studies of serotonin2A receptor in first-episode antipsychotic-naïve schizophrenia patients have reported on the relationship between serotonin2A receptor occupancy and treatment effect after sustained treatment with a specific atypical antipsychotic compound. OBJECTIVES Here, we measured serotonin2A receptor occupancy with [(18)F]altanserin PET in 15 first-episode antipsychotic-naïve schizophrenia patients before and after 6 months of quetiapine treatment. Moreover, we investigated possible relationships between clinical efficacy, oral dose, and plasma levels of quetiapine RESULTS Significant nonlinear relationships were found between serotonin2A receptor occupancy, quetiapine dose, and plasma concentration. There was a modest effect on positive symptoms up until a serotonin2A receptor occupancy level of approximately 60%. A receptor occupancy level between 60% and 70% appeared to exert the optimal serotonin2A receptor related treatment effect on positive symptoms whereas no additional serotonin2A receptor associated treatment effect was obtained above a receptor occupancy of 70%. CONCLUSIONS Taken together, the data point to a therapeutic role of the serotonin2A receptor in the treatment of subgroups of patients with schizophrenia. Specifically, the study indicates a serotonin2A receptor associated therapeutic window on positive symptoms in responding patients in the range between 60% and 70% occupancy in antipsychotic-naïve first-episode schizophrenia. We speculate that non-responding patients need higher dopamine D(2) receptor blockade. Future studies with concurrent measurement of interactions with the dopamine system are, however, warranted to clarify this.
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Affiliation(s)
- Hans Rasmussen
- Center for Neuropsychiatric Schizophrenia Research, Faculty of Health Sciences, Copenhagen University Hospital Glostrup, Copenhagen, Denmark.
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Kosaka J, Takahashi H, Ito H, Takano A, Fujimura Y, Matsumoto R, Nozaki S, Yasuno F, Okubo Y, Kishimoto T, Suhara T. Decreased binding of [11C]NNC112 and [11C]SCH23390 in patients with chronic schizophrenia. Life Sci 2010; 86:814-8. [PMID: 20361984 DOI: 10.1016/j.lfs.2010.03.018] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2009] [Revised: 02/11/2010] [Accepted: 03/20/2010] [Indexed: 10/19/2022]
Abstract
AIMS Abnormality of cognitive function in schizophrenia has been suggested to be related to dopamine D1 receptor. However, the results of previous positron emission tomography (PET) studies of dopamine D1 receptor in schizophrenia were not consistent. MAIN METHODS In this study, six patients with schizophrenia in severe residual phase with chronic antipsychotic treatment and twelve healthy age-matched controls participated. Two different radioligands, [11C]NNC112 and [11C]SCH23390, for dopamine D1 receptor were used on the same subjects. Binding of the ligands was measured by PET, and statistical analysis was performed using one-way analysis of covariate (ANCOVA) with age as covariate. KEY FINDINGS Good correlations between binding potential values (BP(ND)) and age were observed in all regions of interest (ROIs) with both ligands. ANCOVA with age as covariate of BP(ND) values of all ROIs revealed that the patient group showed significantly lower BP(ND) value compared with the control group in both ligands. SIGNIFICANCE In patients with chronic schizophrenia in severe residual phase with chronic antipsychotic treatment, the binding potential values of both ligands were significantly lower in the striatum and cortical regions than those of healthy controls.
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Affiliation(s)
- Jun Kosaka
- Molecular Neuroimaging Group, Molecular Imaging Center, National Institute of Radiological Sciences, Inage-ku, Chiba, Japan
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Quednow BB, Geyer MA, Halberstadt AL. Serotonin and Schizophrenia. ACTA ACUST UNITED AC 2010. [DOI: 10.1016/s1569-7339(10)70102-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/29/2023]
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Abstract
Recent advances in the development and applications of neurochemical brain imaging methods have improved the ability to study the neurochemistry of the living brain in normal processes as well as psychiatric disorders. In particular, positron emission tomography (PET) and single photon emission computed tomography (SPECT) have been used to determine neurochemical substrates of schizophrenia and to uncover the mechanism of action of antipsychotic medications. The growing availability of radiotracers for monoaminergic neurotransmitter synthesis, transporters and receptors, has enabled the evaluation of hypotheses regarding neurotransmitter function in schizophrenia derived from preclinical and clinical observations. This chapter reviews the studies using neurochemical brain imaging methods for (1) detection of abnormalities in indices of dopamine and serotonin transmission in patients with schizophrenia compared to controls, (2) development of new tools to study other neurotransmitters systems, such as gamma-aminobutyric acid (GABA) and glutamate, and (3) characterization of target occupancy by antipsychotic drugs, as well as its relationship to efficacy and side effects. As more imaging tools become available, this knowledge will expand and will lead to better detection of disease, as well as better therapeutic approaches.
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Affiliation(s)
- Nina Urban
- Department of Psychiatry, New York State Psychiatric Institute, Columbia University, New York, NY 10032, USA.
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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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Schmaljohann J, Becherer A, Kletter K, Gündisch D. Radiosynthesis and in vitro evaluation of the 5HT2 receptor ligand [N-11C-methyl]-1-[2,5-dimethoxy-4-iodophenyl]-2-methylaminopropane for PET. RADIOCHIM ACTA 2009. [DOI: 10.1524/ract.92.4.345.35592] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Abstract
In vivo labelling of serotonergic receptors (5HT) could be a useful tool for understanding the physiological and pathophysiological role of neurodegenerative disorders. 1-[2,5-Dimethoxy-4-iodophenyl]-2-aminopropane (DOI), a well known agonist with high affinity to 5HT2 receptors, was labelled with C-11 for PET. Here we report the evaluation of the mono-methylated and dimethylated analogs of DOI for PET. The syntheses of [N-11C-methyl]-DOI ([11C]MDOI) and [N-11C-dimethyl]-DOI ([11C]DMDOI) were optimized resulting in radiochemical yields of up to 43%, allowing efficient production for clinical use. High affinities for the 5HT2A and 5HT2C receptors with a slight preference for 5HT2A were found for MDOI, similar to the highly potent hallucinogen DOI.
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Evidence for altered post-receptor modulation of the serotonin 2a receptor in schizophrenia. Schizophr Res 2008; 104:185-97. [PMID: 18693083 DOI: 10.1016/j.schres.2008.06.011] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/19/2007] [Revised: 06/11/2008] [Accepted: 06/15/2008] [Indexed: 11/23/2022]
Abstract
We have shown a decrease in cortical serotonin(2A) receptors using tissue sections, but not with washed membranes, from the same cohort of subjects. These discrepant findings led us to determine if we could obtain similar results using samples from the same tissue block. Our studies used single-point saturation analyses to estimate the total number of [(3)H]ketanserin binding sites in tissue sections, crude homogenate, membrane-enriched and cytosol-enriched tissue samples from Brodmann's area 9. There were significant decreases in the levels of [(3)H]ketanserin binding using tissue sections (mean+/-SD: 38+/-16 vs. 56+/-16 fmol/mg ETE; p=0.008) and crude tissue homogenates (131+/-53 vs. 168+/-38 fmol/mg protein; p<0.05) from subjects with schizophrenia compared to that in controls. By contrast, there was no significant difference in radioligand binding to the membrane-enriched (155+/-95 vs. 145+/-48 fmol/mg protein; p=0.72) or cytosol-enriched (8.6+/-14 vs. 7.5+/-10 mol/mg protein; p=0.85) tissue fraction. Significantly, adding 10(-5) M risperidone or chlorpromazine, as surrogates for residual antipsychotic drugs in the CNS, to crude homogenate from control subjects did not alter [(3)H]ketanserin binding. Our data therefore is consistent with the hypothesis that apparent decreases in serotonin(2A) receptors in schizophrenia are due to altered levels of a regulatory factor(s) that modulates the binding of ligands to the serotonin(2A) receptor and that separating the membrane and cytosol removes this regulatory control.
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Hurlemann R, Matusch A, Kuhn KU, Berning J, Elmenhorst D, Winz O, Kolsch H, Zilles K, Wagner M, Maier W, Bauer A. 5-HT2A receptor density is decreased in the at-risk mental state. Psychopharmacology (Berl) 2008; 195:579-90. [PMID: 17899021 DOI: 10.1007/s00213-007-0921-x] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/09/2007] [Accepted: 08/14/2007] [Indexed: 10/22/2022]
Abstract
RATIONALE Current perspectives on the pathophysiology of schizophrenia direct attention to serotonergic (serotonin, 5-HT) dysregulation in the prodrome or at-risk mental state (ARMS). OBJECTIVE To study the cerebral 5-HT(2A) receptor (5-HT(2A)R) in the ARMS with [(18)F]altanserin positron emission tomography (PET) and a bolus-infusion paradigm. MATERIALS AND METHODS We quantified the spatial distribution of 5-HT(2A)R binding potential (BP(1)') in never-medicated subjects assigned to early (n = 6) and late (n = 8) prodromal states of schizophrenia relative to healthy controls (n = 21). Five single nucleotide polymorphisms (SNPs) in the 5-HT(2A)R-encoding gene (HTR2A; 13q14-21) were genotyped to control for a potential bias in BP(1)' due to between-group differences in genotype distributions. RESULTS Group comparisons of partial-volume corrected PET data by statistical parametric mapping and confirmatory volume of interest analysis yielded a dissemination of BP(1)' decreases consistent with increasing levels of risk. An additional decrease in caudate BP(1)' was present in subjects who subsequently converted to first-episode psychosis (n = 5), but absent in non-converters (n = 9). Between-group differences were not confounded by a differential distribution of SNP genotypes. CONCLUSION These results suggest a progressive reduction of cortical 5-HT(2A)R density as a surrogate biological measure of increased risk for schizophrenia, irrespective of conversion. Progressive reductions of subcortical 5-HT(2A)R density could provide an indicator of illness activity and help to predict imminent conversion to schizophrenia. Moreover, our findings substantiate the rationale for establishing a phase-specific psychopharmacological intervention in the ARMS that addresses the serotonergic component of vulnerability to schizophrenia.
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Affiliation(s)
- René Hurlemann
- Brain Imaging Center West, Research Center Juelich, 52425, Juelich, Germany.
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Abstract
The use of molecular imaging techniques in the central nervous system (CNS) has a rich history. Most of the important developments in imaging-such as computed tomography, magnetic resonance imaging, single photon emission computed tomography, and positron emission tomography-began with neuropsychiatric applications. These techniques and modalities were then found to be useful for imaging other organs involved with various disease processes. Molecular imaging of the CNS has enabled scientists and researchers to understand better the basic biology of brain function and the way in which various disease processes affect the brain. Unlike other organs, the brain is not easily accessible, and it has a highly selective barrier at the endothelial cell level known as the blood-brain barrier. Furthermore, the brain is the most complex cellular network known to exist. Various neurotransmitters act in either an excitatory or an inhibitory fashion on adjacent neurons through a multitude of mechanisms. The various neuronal systems and the myriad of neurotransmitter systems become altered in many diseases. Some of the most devastating diseases, including Alzheimer disease, Parkinson disease, brain tumors, psychiatric disease, and numerous degenerative neurologic diseases, affect only the brain. Molecular neuroimaging will be critical to the future understanding and treatment of these diseases. Molecular neuroimaging of the brain shows tremendous promise for clinical application. In this article, the current state and clinical applications of molecular neuroimaging will be reviewed.
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Affiliation(s)
- Dima A Hammoud
- Department of Radiology, Johns Hopkins University School of Medicine, 1550 Orleans St, CRB-2, Room 492, Baltimore, MD 21231, USA
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Abstract
The ability of SPECT and PET to image specific biomolecules in the living brain provides a unique tool for clinical researchers. It is therefore not surprising that the use of neuroreceptor-imaging techniques has become more widespread over the past decade. This article reviews the application of these techniques to the study of schizophrenia. The design of neuroreceptor-imaging studies performed in the field of schizophrenia research can be broadly divided into two categories: (1) studies of pathophysiology and (2) studies of pharmacology. The former examines neuroreceptor and neurotransmitter parameters in individuals with schizophrenia compared to control subjects in order to provide a better understanding of the disease process. Studies of pharmacology seek to elucidate the mechanism of action for the treatments utilized in schizophrenia. This review will consider both studies of pathophysiology and pharmacology, with a discussion of the application of these techniques to drug development.
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Affiliation(s)
- W Gordon Frankle
- Department of Psychiatry, University of Pittsburgh, Pittsburgh, PA 15213, USA.
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Reimold M, Solbach C, Noda S, Schaefer JE, Bartels M, Beneke M, Machulla HJ, Bares R, Glaser T, Wormstall H. Occupancy of dopamine D(1), D (2) and serotonin (2A) receptors in schizophrenic patients treated with flupentixol in comparison with risperidone and haloperidol. Psychopharmacology (Berl) 2007; 190:241-9. [PMID: 17111172 DOI: 10.1007/s00213-006-0611-0] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/17/2006] [Accepted: 10/10/2006] [Indexed: 10/23/2022]
Abstract
RATIONALE Flupentixol (FLX) has been used as a neuroleptic for nearly 4 decades. In vitro data show comparable affinity to dopamine D(2), D(1) and 5-HT(2A) receptors and recently, FLX showed to be not inferior to risperidone in schizophrenic patients with predominant negative symptomatology, which was implicated with flupentixol's interaction with 5-HT(2A) and/or D(1) receptors. OBJECTIVES To assess in vivo receptor occupancy (RO) in patients clinically treated with FLX (n = 13, 5.7 +/- 1.4 mg/day) in comparison with risperidone (RIS, n = 11, 3.6 +/- 1.3 mg/day) and haloperidol (HAL, n = 11, 8.5 +/- 5.5 mg/day). MATERIALS AND METHODS Each patient underwent two PET scans with 3-N-[(11)C]methylspiperone (target: frontal 5-HT(2A)), [(11)C]SCH23390 (striatal D(1)) or [(11)C]raclopride (striatal D(2)). RO was calculated as the percentage reduction of specific binding in comparison with healthy controls. RESULTS D(2)-RO under FLX was between 50% and 70%, indicating an ED(50) of about 0.7 ng/ml serum. 5-HT(2A) and D(1)-RO was 20 +/- 10% and 20 +/- 5% (mean, SEM). Under HAL, D(1)-RO was 14 +/- 6% and under RIS not significantly different from zero. CONCLUSIONS We were able to demonstrate a moderate 5-HT(2A) and D(1) occupancy under clinically relevant doses of flupentixol, albeit lower than expected from in vitro data and clearly below saturation. Therefore, if flupentixol's efficacy on negative symptoms is based on its interaction with 5-HT(2A) and/or D(1) receptors, it should be highly dependent on serum concentration and thus on dosage and metabolism. However, these data suggest that mechanisms other than D(1) or 5-HT(2A) antagonism may contribute to flupentixol's efficacy on negative symptoms.
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Affiliation(s)
- M Reimold
- Department of Nuclear Medicine/PET Center, University of Tuebingen, Tuebingen, Germany.
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36
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Abi-Dargham A. Alterations of serotonin transmission in schizophrenia. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2007; 78:133-64. [PMID: 17349860 DOI: 10.1016/s0074-7742(06)78005-9] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
A role for serotonin alterations in the pathophysiology of schizophrenia has long been suspected because of the psychotogenic effects of serotonergic agonists and the therapeutic effects of 5-HT(2) antagonism. This chapter is a review of the evidence derived from pharmacological studies, postmortem, and imaging studies that have assessed the role of serotonin transmission in schizophrenia. While a clear picture of specific serotonergic alterations in schizophrenia has not emerged despite much research, this review reinforces a modulatory role of serotonergic agents on dopamine transmission in schizophrenia, which may contribute to the therapeutic effects of atypical antipsychotics.
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Affiliation(s)
- Anissa Abi-Dargham
- Department of Psychiatry, Columbia College of Physicians and Surgeons, New York State Psychiatric Institute, Columbia University, New York 10032, USA
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37
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Takano A, Suhara T. [PET (positron emission tomography) research on schizophrenia]. Nihon Yakurigaku Zasshi 2006; 128:177-83. [PMID: 16971782 DOI: 10.1254/fpj.128.177] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
MESH Headings
- Antipsychotic Agents/administration & dosage
- Antipsychotic Agents/pharmacology
- Brain/metabolism
- Brain/physiopathology
- Corpus Striatum
- Dopamine/metabolism
- Humans
- Neural Conduction
- Positron-Emission Tomography
- Receptor, Serotonin, 5-HT1A/metabolism
- Receptor, Serotonin, 5-HT1A/physiology
- Receptor, Serotonin, 5-HT2A/metabolism
- Receptor, Serotonin, 5-HT2A/physiology
- Receptors, Dopamine D1/metabolism
- Receptors, Dopamine D1/physiology
- Receptors, Dopamine D2/metabolism
- Receptors, Dopamine D2/physiology
- Schizophrenia/diagnostic imaging
- Schizophrenia/metabolism
- Schizophrenia/physiopathology
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Hodé Y, Reimold M, Demazières A, Reischl G, Bayle F, Nuss P, Hameg A, Dib M, Macher JP. A positron emission tomography (PET) study of cerebral dopamine D2 and serotonine 5-HT2A receptor occupancy in patients treated with cyamemazine (Tercian). Psychopharmacology (Berl) 2005; 180:377-84. [PMID: 15948013 DOI: 10.1007/s00213-005-2172-z] [Citation(s) in RCA: 168] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/06/2004] [Accepted: 12/07/2004] [Indexed: 01/23/2023]
Abstract
RATIONALE Cyamemazine (Tercian) is an antipsychotic drug with anxiolytic properties. Recently, an in vitro study showed that cyamemazine possesses high affinity for serotonin 5-HT(2A) receptors, which was fourfold higher than its affinity for dopamine D(2) receptors (Hameg et al. 2003). OBJECTIVES The aim of this study is to confirm these previous data in vivo in patients treated with clinically relevant doses of Tercian. METHODS Eight patients received 37.5, 75, 150 or 300 mg/day of Tercian depending on their symptomatology. Dopamine D(2) and serotonin 5-HT(2A) receptor occupancies (RO) were assessed at steady-state plasma levels of cyamemazine with positron emission tomography (PET), using [(11)C]raclopride and [(11)C]N-methyl-spiperone, respectively. The effective plasma level of the drug leading to 50% of receptor occupancy was estimated by fitting RO with plasma levels of cyamemazine at the time of the PET scan. RESULTS Cyamemazine induced near saturation of 5-HT(2A) receptors (RO=62.1-98.2%) in the frontal cortex even at low plasma levels of the drug. On the contrary, occupancy of striatal D(2) receptors increased with plasma levels, and no saturation was obtained even at high plasma levels (RO=25.2-74.9%). The effective plasma level of cyamemazine leading to 50% of D(2) receptor occupancy was fourfold higher than that for 5-HT(2A) receptors. Accordingly, individual 5-HT(2A)/D(2) RO ratios ranged from 1.26 to 2.68. No patients presented relevant increased prolactin levels, and only mild extrapyramidal side effects were noticed on Simpson and Angus Scale. CONCLUSION This in vivo binding study conducted in patients confirms previous in vitro findings indicating that cyamemazine has a higher affinity for serotonin 5-HT(2A) receptors compared to dopamine D(2) receptors. In the dose range 37.5-300 mg, levels of dopamine D(2) occupancy remained below the level for motor side effects observed with typical antipsychotics and is likely to explain the low propensity of the drug to induce extrapyramidal side effects.
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Affiliation(s)
- Y Hodé
- FORENAP Research Institute For Neuroscience, Pharmacology and Psychiatry, 68250 Rouffach, France.
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39
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Frankle WG, Slifstein M, Talbot PS, Laruelle M. Neuroreceptor Imaging in Psychiatry: Theory and Applications. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2005; 67:385-440. [PMID: 16291028 DOI: 10.1016/s0074-7742(05)67011-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- W Gordon Frankle
- Departments of Psychiatry, Columbia University College of Physicians and Surgeons and New York State Psychiatric Institute, New York, New York 10032, USA
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40
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Blanckaert P, Burvenich I, Staelens L, Dierckx RA, Slegers G. Synthesis, radiosynthesis and in vivo evaluation in mice of [123I]-(4-fluorophenyl) {1-[2-(4-iodophenyl)ethyl]piperidin-4-yl}methanone for visualization of the 5-HT2A receptor with SPECT. Appl Radiat Isot 2004; 62:737-43. [PMID: 15763480 DOI: 10.1016/j.apradiso.2004.10.008] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2004] [Revised: 10/07/2004] [Accepted: 10/29/2004] [Indexed: 11/24/2022]
Abstract
This work reports the synthesis, radiolabelling and preliminary in vivo evaluation of [(123)I]-(4-fluorophenyl){1-[2-(4-iodophenyl)ethyl]piperidin-4-yl}methanone. The tributylstannylprecursor was synthesized with a yield of 30%. Radiolabelling was performed using an electrophilic iododestannylation. Tracer yield was 80%, radiochemical purity was >95% and specific activity was at least 55 Ci/micromol. Log P was 1.5. The tracer showed uptake in mice brain (2.72% ID/g tissue at 5 min p.i.) and therefore will be evaluated further by regional brain biodistribution and displacement studies in rabbits.
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Affiliation(s)
- P Blanckaert
- Laboratory for Radiopharmacy, Ghent University, Harelbekestraat 72, B-9000 Gent, Belgium.
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41
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Abstract
Factors that place constraints on radio-chemists who are seeking to design and develop radiopharmaceuticals for PET imaging studies include the short half-lives of 11C and 18F, minimum radiochemical yield and specific activity requirements, and high radiation fields that are associated with multi-Curie quantities of PET radionuclides. Nevertheless, during the past 20 years, considerable progress has been made in the development and application of a variety of PET radiotracers for a range of imaging studies in human subjects. We have highlighted a few areas of radiochemistry that focused on PET radiotracers that are described in this issue. Although the number of PET radiotracers synthesized is in the hundreds [6], much work remains to develop specific and useful PET radiotracers for a host of new and exciting noninvasive imaging applications.
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Affiliation(s)
- N Scott Mason
- Positron Emission Tomography Facility, Department of Radiology, University of Pittsburgh, B-938, UPMC Presbyterian, 200 Lothrop Street, Pittsburgh, PA 15213-2582, USA.
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42
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Erritzoe D, Talbot P, Frankle WG, Abi-Dargham A. Positron emission tomography and single photon emission CT molecular imaging in schizophrenia. Neuroimaging Clin N Am 2003; 13:817-32. [PMID: 15024964 DOI: 10.1016/s1052-5149(03)00089-3] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We reviewed findings from PET and SPECT studies that have contributed to our understanding of the pathophysiology and treatment of schizophrenia. The most robust set of findings pertains to imaging of presynaptic dopaminergic function in the striatum. The results of these studies have been consistent in showing that schizophrenia, at least during episodes of illness exacerbation, is associated with increased activity of DA neurons; this increased presynaptic activity is associated with positive symptoms and good therapeutic response. Studies of cortical DA function are less numerous and less consistent. In the future, technical advances in PET instrumentation and radioligand development should contribute to a clarification of the role of prefrontal DA in the cognitive impairment that is presented by these patients. An important drawback of the literature in this field is the generally low number of subjects that are included in studies (typically less than 20 per group). Small samples are necessitated by the cost of these investigations, but also, in some instances, to the difficulty in recruiting appropriate clinical subjects (such as drug-free patients who have schizophrenia). In conditions that are characterized by marked heterogeneity, such as major depressive disorders, this factor is bound to yield divergent results across studies. Another source of discrepancy is the variety of technical approaches to data acquisition and analysis. For example, analytical methods range from "empirical" or "semiquantitative" (typically a region of interest to a region of reference ratio measured at one time point) to model-based methods that use an arterial input function. The limitations that are associated with empirical analytical methods might account for artifactual results, especially when the effect size of the between-group difference and the number of subjects are small [149]. In addressing these limitations it will be important to increase the availability of these techniques beyond a few academic centers, to promote multi-center studies in well-characterized populations, and to standardize analytical methods. Until recently, SPECT was the only widely available technique, and SPECT studies have provided a substantial contribution to this field. With the current increase in PET camera availability, the development of [18F]-based molecular imaging probes will provide unique opportunities for further dissemination of these techniques. The article reviewed seminal findings obtained with PET and SPECT molecular imaging of schizophrenia. These techniques do not play a major role in the diagnosis and treatment of this disorder, remain essentially research tools. The results that have been produced by this field to date suggest that PET will significantly contribute to unraveling the biologic bases of psychiatric disorders and may contribute to their clinical management. Moreover, it is foreseeable that PET will become increasingly involved in the development of new psychiatric medications. Expanding the availability of PET and the current radiopharmaceutical portfolio will be critical for these predictions to become reality.
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Affiliation(s)
- David Erritzoe
- Department of Psychiatry, Columbia University College of Physicians and Surgeons, New York State Psychiatric Institute, 1051 Riverside Drive, Unit 31, New York, NY 10032, USA
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43
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Meltzer HY, Li Z, Kaneda Y, Ichikawa J. Serotonin receptors: their key role in drugs to treat schizophrenia. Prog Neuropsychopharmacol Biol Psychiatry 2003; 27:1159-72. [PMID: 14642974 DOI: 10.1016/j.pnpbp.2003.09.010] [Citation(s) in RCA: 590] [Impact Index Per Article: 28.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Serotonin (5-HT)-receptor-based mechanisms have been postulated to play a critical role in the action of the new generation of antipsychotic drugs (APDs) that are usually referred to as atypical APDs because of their ability to achieve an antipsychotic effect with lower rates of extrapyramidal side effects (EPS) compared to first-generation APDs such as haloperidol. Specifically, it has been proposed by Meltzer et al. [J. Pharmacol. Exp. Ther. 251 (1989) 238] that potent 5-HT2A receptor antagonism together with weak dopamine (DA) D2 receptor antagonism are the principal pharmacologic features that differentiate clozapine and other apparent atypical APDs from first-generation typical APD. This hypothesis is consistent with the atypical features of quetiapine, olanzapine, risperidone, and ziprasidone, which are the most common treatments for schizophrenia in the United States and many other countries, as well as a large number of compounds in various stages of development. Subsequent research showed that 5-HT1A agonism may be an important consequence of 5-HT2A antagonism and that substitution of 5-HT1A agonism for 5-HT2A antagonism may also produce an atypical APD drug when coupled with weak D2 antagonism. Aripiprazole, the most recently introduced atypical APD, and a D2 receptor partial agonist, may also owe some of its atypical properties to its net effect of weak D2 antagonism, 5-HT2A antagonism and 5-HT1A agonism [Eur. J. Pharmacol. 441 (2002) 137]. By contrast, the alternative "fast-off" hypothesis of Kapur and Seeman [Am. J. Psychiatry 158 (2001) 360] applies only to clozapine and quetiapine and is inconsistent with the "slow" off rate of most atypical APDs, including olanzapine, risperidone and ziprasidone. 5-HT2A and 5-HT1A receptors located on glutamatergic pyramidal neurons in the cortex and hippocampus, 5-HT2A receptors on the cell bodies of DA neurons in the ventral tegmentum and substantia nigra and GABAergic interneurons in the cortex and hippocampus, and 5-HT1A receptors in the raphe nuclei are likely to be important sites of action of the atypical APDs. At the same time, evidence has accumulated for the important modulatory role of 5-HT2C and 5-HT6 receptors for some of the effects of some of the current APDs. Thus, 5-HT has joined DA as a critical target for developing effective APDs and led to the search for novel drugs with complex pharmacology, ending the exclusive search for single-receptor targets, e.g., the D3 or D4 receptor, and drugs that are selective for them.
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Affiliation(s)
- Herbert Y Meltzer
- Department of Psychiatry, Division of Psychopharmacology, Vanderbilt University School of Medicine, Suite 306, 1601 23rd Avenue, Nashville, TN 37212, USA.
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Abstract
A large body of evidence shows that there is a change in the density of cortical serotonin2A receptors (5HT2AR) in post-mortem CNS from subjects with schizophrenia. Furthermore, some antipsychotic drugs have also been shown to cause a decrease in the density of 5HT2AR in the rat CNS. Thus, it appeared possible that changes in this receptor in human post-mortem CNS simply reflected an antipsychotic drug effect. However, a great deal of research on the 5HT2AR and schizophrenia now suggests that the changes in this receptor are complex and may be involved in both the pathology of the disorder and the effects of some antipsychotic drugs. Moreover, recent advances in basic research on the role of the 5HT2AR in the CNS add further support to the hypothesis that the receptor could be involved in the pathology of the illness. In particular, an argument will be developed that the changes in the 5HT2AR in schizophrenia are reflective of a real or perceived change in serotonergic tone and that this forms an important part of the pathology of the illness.
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Affiliation(s)
- Brian Dean
- The Rebecca L. Cooper Research Laboratories, The Mental Health Research Institute of Victoria, Parkville, Victoria, Australia.
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45
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Abstract
Molecular imaging, the study of receptors, transporters and enzymes, as well as other cellular processes, has grown in recent years to be one of the most active neuroimaging areas. The application of single photon emission tomography (SPECT) and positron emission tomography (PET) techniques to the study of psychiatric illness has lead to increased understanding of disease processes as well as validated, in vivo, theories of illness etiology. Within the field of psychiatry these techniques have been applied most widely to the study of schizophrenia. Studies within schizophrenia are largely limited to either the dopamine or serotonin system. This is due in large part to the availability of suitable radiotracers as well as the current theories on the etiology of the illness. Two basic study designs are used when studying schizophrenia using molecular imaging and make up the majority of studies reviewed in this manuscript. The first type, termed "clinical studies," compares the findings from PET and SPECT studies in those with schizophrenia to normal controls in an attempt to understand the pathophysiology of the illness. The second study design, termed "occupancy studies," uses these techniques to enhance the understanding of the mechanism of action of the medications used in treating this illness. This review will focus on the findings of molecular imaging studies in schizophrenia, focusing, for the most part, on the serotonin and dopamine systems. Emphasis will be placed on how these findings and techniques are currently being used to inform the development of novel treatments for schizophrenia.
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Affiliation(s)
- W Gordon Frankle
- Department of Psychiatry, Columbia University College of Physicians and Surgeons and New York State Psychiatric Institute, New York 10032, USA.
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Yamamoto M, Suhara T, Okubo Y, Ichimiya T, Sudo Y, Inoue M, Takano A, Yasuno F, Yoshikawa K, Tanada S. Age-related decline of serotonin transporters in living human brain of healthy males. Life Sci 2002; 71:751-7. [PMID: 12074934 DOI: 10.1016/s0024-3205(02)01745-9] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
There is growing interest in serotonin transporter (5-HTT) function in the human brain, since alteration in 5-HTT has been suggested in a variety of neurophychiatric disorders. Age-related decline in postsynaptic 5-HT receptors has been demonstrated in postmortem human studies and in vivo imaging studies, and has been assumed to be related to changes in mental function in the normal aging process. However, few studies have investigated the aging effect on 5-HTT in human brain in vivo, since the availability of suitable ligands has been limited. To investigate the aging effect on 5-HTT in living human brain, we performed positron emission tomography (PET) scans with a selective ligand for 5-HTT, [11C](+)McN5652. We examined 28 healthy male volunteers aged between 20 and 79 years. The uptake was quantified in the thalamus and midbrain by graphical analysis with the cerebellum as a reference tissue, and binding potential (BP) was used for the index of 5-HTT binding. There was a significant age-related decline in BP in the thalamus and midbrain. The decline in [11C](+)McN5652 binding was 9.6% per decade in the thalamus and 10.5% per decade in the midbrain.
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Affiliation(s)
- Masahiro Yamamoto
- Brain Imaging Project, National Institute of Radiological Sciences, Chiba, Japan
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47
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Eastwood SL, Burnet PW, Gittins R, Baker K, Harrison PJ. Expression of serotonin 5-HT(2A) receptors in the human cerebellum and alterations in schizophrenia. Synapse 2001; 42:104-14. [PMID: 11574947 DOI: 10.1002/syn.1106] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The occurrence of human cerebellar serotonin 5-HT(2A) receptors (5-HT(2A)R) is equivocal and their status in schizophrenia unknown. Using a range of techniques, we investigated cerebellar 5-HT(2A)R expression in 16 healthy subjects and 16 subjects with schizophrenia. Immunocytochemistry with a monoclonal antibody showed labelling of Purkinje cell bodies and dendrites, as well as putative astrocytes. Western blots showed a major band at approximately 45 kDa. Receptor autoradiography and homogenate binding with [(3)H]ketanserin revealed cerebellar 5-HT(2A)R binding sites present at levels approximately a third of that in prefrontal cortex. 5-HT(2A)R mRNA was detected by reverse transcriptase-polymerase chain reaction, with higher relative levels in men than women. Several aspects of 5-HT(2A)R expression were altered in schizophrenia. 5-HT(2A)R immunoreactivity in Purkinje cells was partially redistributed from soma to dendrites and was increased in white matter. 5-HT(2A)R mRNA was decreased in the male patients. 5-HT(2A)R measured by dot blots and [(3)H]ketanserin binding (B(max) and K(d)) were not significantly altered in schizophrenia. These data show that 5-HT(2A)R gene products (mRNA, protein, binding sites) are expressed in the human cerebellum at nonnegligible levels; this bears upon 5-HT(2A)R imaging studies which use the cerebellum as a reference region. 5-HT(2A)R expression is altered in schizophrenia; the shift of 5-HT(2A)R from soma to dendrites is noteworthy since atypical antipsychotics have the opposite effect. Finally, the results emphasise that expression of a receptor gene is a mutifaceted process. Measurement of multiple parameters is necessary to give a clear picture of the normal situation and to show the profile of alterations in a disease.
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Affiliation(s)
- S L Eastwood
- University Department of Psychiatry, Warneford Hospital, Oxford, UK
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Brown JS. A novel mechanism to explain protein abnormalities in schizophrenia based on the flavivirus resistance gene. Mol Psychiatry 2001; 6:701-11. [PMID: 11673799 DOI: 10.1038/sj.mp.4000890] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/08/2000] [Revised: 01/23/2001] [Accepted: 01/25/2001] [Indexed: 11/09/2022]
Abstract
The geographical distribution of schizophrenia was previously shown to correlate with the global distribution of tick-borne flaviviruses. The correlation suggests a natural resistance gene to flaviviruses could be involved in schizophrenia. The flavivirus resistance gene, Flv, a gene found in wild mice and certain in-bred strains, confers resistance to flaviviruses through the interaction of cellular proteins with the flaviviral 3' untranslated regions (UTRs). Although the sequence and product of Flv are unknown, translation elongation factor alpha-1 (EF-1) is a protein known to interact with the 3' UTR flavivirus RNA, forming some complexes with long half-lives that inhibit RNA growth. A study was performed to assess the homology between flaviviral UTRs, subunits of EF-1, and selected proteins reported as abnormal in schizophrenia. The UTRs of four flaviviruses with wide geographical and phylogenic distribution were manually translated. Using the National Biomedical Research Foundation protein databank, the amino acid sequences were correlated with the amino acid sequences of selected proteins. The amino acid sequences of the EF-1 subunits were then correlated with the same proteins. Similar amino acid correlations between the proteins, EF-1 subunits and viral UTRs suggest that translational pathophysiology resulting from the product of Flv can be postulated as the cause of protein abnormalities observed in schizophrenia.
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Affiliation(s)
- J S Brown
- Mental Health Service Line, McGuire Veterans Administration Medical Center, 1201 Broad Rock Blvd, Richmond, VA 23249, USA.
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Hartvig P, Bergström M, Långström B. Use of positron emission tomography in analysing receptor function in vivo. Toxicol Lett 2001; 120:243-51. [PMID: 11323182 DOI: 10.1016/s0378-4274(01)00300-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The non-invasive radiotracer technique positron emission tomography (PET) may provide valuable information in the toxicokinetic-toxicodynamic evaluation of endogenous or toxic environmental compounds. Assessment of mechanism of action of toxins is often difficult to validate. In this respect, PET may offer advantages since it can quantify not only the distribution and kinetics of the radiolabelled toxin in the body, but also the altered rates of physiological or biochemical processes induced by the toxin. It is even possible to validate the body distribution and tissue accumulation of the toxic compound in primates, since linear kinetics can be assumed after administration of the radiolabelled compound in minute amounts without any toxic or physiological effects. Quantitative estimates can be derived with accuracy and high precision. Using a multi-tracer protocol, it is often possible to illuminate both the kinetics and the dynamics of a toxic compound. Long-term effects of different toxins on dopamine receptor function have been evaluated with PET as well as the influence of Parkinson disease medication on pre- and postsynaptic dopaminergic receptor function over the course of the disease. In conclusion, PET may provide very informative insight into complex receptor interactions of both toxic compounds and drugs under development.
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Affiliation(s)
- P Hartvig
- Uppsala University PET Centre, University Hospital, 751 85, Uppsala, Sweden.
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