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Gopinath K, Maltbie E, Urushino N, Kempf D, Howell L. Ketamine-induced changes in connectivity of functional brain networks in awake female nonhuman primates: a translational functional imaging model. Psychopharmacology (Berl) 2016; 233:3673-3684. [PMID: 27530989 DOI: 10.1007/s00213-016-4401-z] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/03/2016] [Accepted: 07/28/2016] [Indexed: 12/13/2022]
Abstract
RATIONALE There is a significant interest in the NMDA-receptor antagonist ketamine due to its efficacy in treating depressive disorders and its induction of psychotic-like symptoms that make it a useful tool for modeling psychosis. Pharmacological MRI in awake nonhuman primates provides a highly translational model for studying the brain network dynamics involved in producing these drug effects. OBJECTIVE The present study evaluated ketamine-induced changes in functional connectivity (FC) in awake rhesus monkeys. The effects of ketamine after pretreatment with the antipsychotic drug risperidone were also examined. METHODS Functional MRI scans were conducted in four awake adult female rhesus monkeys during sub-anesthetic i.v. infusions of ketamine (0.345 mg/kg bolus followed by 0.256 mg kg-1 h-1 constant infusion) with and without risperidone pretreatment (0.06 mg/kg). A 10-min window of stable BOLD signal was used to compare FC between baseline and drug conditions. FC was assessed in specific regions of interest using seed-based cross-correlation analysis. RESULTS Ketamine infusion induced extensive changes in FC. In particular, FC to the dorsolateral prefrontal cortex (dlPFC) was increased in several cortical and subcortical regions. Pretreatment with risperidone largely attenuated ketamine-induced changes in FC. CONCLUSIONS The results are highly consistent with similar human imaging studies showing ketamine-induced changes in FC, as well as a significant attenuation of these changes when ketamine infusion is preceded by pretreatment with risperidone. The extensive increases shown in FC to the dlPFC are consistent with the idea that disinhibition of the dlPFC may be a key driver of the antidepressant and psychotomimetic effects of ketamine.
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Affiliation(s)
- Kaundinya Gopinath
- Department of Radiology and Imaging Sciences, Emory University, Atlanta, GA, 30329, USA.,Yerkes National Primate Research Center, Emory University, 954 Gatewood Rd NE, Atlanta, GA, 30329, USA
| | - Eric Maltbie
- Yerkes National Primate Research Center, Emory University, 954 Gatewood Rd NE, Atlanta, GA, 30329, USA
| | - Naoko Urushino
- Yerkes National Primate Research Center, Emory University, 954 Gatewood Rd NE, Atlanta, GA, 30329, USA.,Dainippon Sumitomo Pharma, Co. Ltd., Osaka, Japan
| | - Doty Kempf
- Yerkes National Primate Research Center, Emory University, 954 Gatewood Rd NE, Atlanta, GA, 30329, USA
| | - Leonard Howell
- Yerkes National Primate Research Center, Emory University, 954 Gatewood Rd NE, Atlanta, GA, 30329, USA. .,Department of Psychiatry and Behavioral Sciences, Emory University, Atlanta, GA, 30329, USA.
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De Rossi P, Chiapponi C, Spalletta G. Brain Functional Effects of Psychopharmacological Treatments in Schizophrenia: A Network-based Functional Perspective Beyond Neurotransmitter Systems. Curr Neuropharmacol 2016; 13:435-44. [PMID: 26412063 PMCID: PMC4790396 DOI: 10.2174/1570159x13666150507223542] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Psychopharmacological treatments for schizophrenia have always been a matter of debate and a very important issue in public health given the chronic, relapsing and disabling nature of the disorder. A thorough understanding of the pros and cons of currently available pharmacological treatments for schizophrenia is critical to better capture the features of treatment-refractory clinical pictures and plan the developing of new treatment strategies. This review focuses on brain functional changes induced by antipsychotic drugs as assessed by modern functional neuroimaging techniques (i.e. fMRI, PET, SPECT, MRI spectroscopy). The most important papers on this topic are reviewed in order to draw an ideal map of the main functional changes occurring in the brain during antipsychotic treatment. This supports the hypothesis that a network-based perspective and a functional connectivity approach are needed to fill the currently existing gap of knowledge in the field of psychotropic drugs and their mechanisms of action beyond neurotransmitter systems.
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Affiliation(s)
| | | | - Gianfranco Spalletta
- Neuropsychiatry Laboratory, Department of Clinical and Behavioural Neurology, IRCCS Santa Lucia Foundation, Via Ardeatina, 306, 00179 Rome, Italy.
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3
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Wulff S, Pinborg LH, Svarer C, Jensen LT, Nielsen MØ, Allerup P, Bak N, Rasmussen H, Frandsen E, Rostrup E, Glenthøj BY. Striatal D(2/3) Binding Potential Values in Drug-Naïve First-Episode Schizophrenia Patients Correlate With Treatment Outcome. Schizophr Bull 2015; 41:1143-52. [PMID: 25698711 PMCID: PMC4535636 DOI: 10.1093/schbul/sbu220] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
One of best validated findings in schizophrenia research is the association between blockade of dopamine D2 receptors and the effects of antipsychotics on positive psychotic symptoms. The aim of the present study was to examine correlations between baseline striatal D(2/3) receptor binding potential (BP(p)) values and treatment outcome in a cohort of antipsychotic-naïve first-episode schizophrenia patients. Additionally, we wished to investigate associations between striatal dopamine D(2/3) receptor blockade and alterations of negative symptoms as well as functioning and subjective well-being. Twenty-eight antipsychotic-naïve schizophrenia patients and 26 controls were included in the study. Single-photon emission computed tomography (SPECT) with [(123)I]iodobenzamide ([(123)I]-IBZM) was used to examine striatal D(2/3) receptor BP(p). Patients were examined before and after 6 weeks of treatment with the D(2/3) receptor antagonist amisulpride. There was a significant negative correlation between striatal D(2/3) receptor BP(p) at baseline and improvement of positive symptoms in the total group of patients. Comparing patients responding to treatment to nonresponders further showed significantly lower baseline BP(p) in the responders. At follow-up, the patients demonstrated a negative correlation between the blockade and functioning, whereas no associations between blockade and negative symptoms or subjective well-being were observed. The results show an association between striatal BP(p) of dopamine D(2/3) receptors in antipsychotic-naïve first-episode patients with schizophrenia and treatment response. Patients with a low BP(p) have a better treatment response than patients with a high BP(p). The results further suggest that functioning may decline at high levels of dopamine receptor blockade.
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Affiliation(s)
- Sanne Wulff
- Center for Neuropsychiatric Schizophrenia Research (CNSR) and Center for Clinical Intervention and Neuropsychiatric Schizophrenia Research (CINS), Psychiatric Center Glostrup, University of Copenhagen, Copenhagen, Denmark; Department of Clinical Medicine, Faculty of Health and Medical Sciences University of Copenhagen, Denmark;
| | - Lars Hageman Pinborg
- Neurobiology Research Unit (NRU), Rigshospitalet, University of Copenhagen, Denmark
| | - Claus Svarer
- Neurobiology Research Unit (NRU), Rigshospitalet, University of Copenhagen, Denmark
| | - Lars Thorbjørn Jensen
- Department of Clinical Physiology and Nuclear Medicine, Herlev Hospital, University of Copenhagen, Denmark
| | - Mette Ødegaard Nielsen
- Center for Neuropsychiatric Schizophrenia Research (CNSR) and,Center for Clinical Intervention and Neuropsychiatric Schizophrenia Research (CINS), Psychiatric Center Glostrup, University of Copenhagen, Copenhagen, Denmark
| | - Peter Allerup
- Department of Education, Centre for Research in Compulsory Schooling, Aarhus University, Denmark
| | - Nikolaj Bak
- Center for Neuropsychiatric Schizophrenia Research (CNSR) and,Center for Clinical Intervention and Neuropsychiatric Schizophrenia Research (CINS), Psychiatric Center Glostrup, University of Copenhagen, Copenhagen, Denmark
| | - Hans Rasmussen
- Center for Neuropsychiatric Schizophrenia Research (CNSR) and,Center for Clinical Intervention and Neuropsychiatric Schizophrenia Research (CINS), Psychiatric Center Glostrup, University of Copenhagen, Copenhagen, Denmark
| | - Erik Frandsen
- Department of Diagnostics, Functional Imaging Unit and Section of Clinical Physiology and Nuclear Medicine, Glostrup Hospital, University of Copenhagen, Denmark
| | - Egill Rostrup
- Department of Diagnostics, Functional Imaging Unit and Section of Clinical Physiology and Nuclear Medicine, Glostrup Hospital, University of Copenhagen, Denmark
| | - Birte Yding Glenthøj
- Center for Neuropsychiatric Schizophrenia Research (CNSR) and,Center for Clinical Intervention and Neuropsychiatric Schizophrenia Research (CINS), Psychiatric Center Glostrup, University of Copenhagen, Copenhagen, Denmark;,Department of Clinical Medicine, Faculty of Health and Medical Sciences University of Copenhagen, Denmark
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4
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Zhang Y, Liu F, Zhang X, Xu T, Quan W, Wang H, Shi J, Dai Z, Wu B, Wu Q. Recognition and identification of active components from Radix Bupleuri using human neuroblastoma SH-SY5Y cells. Biomed Chromatogr 2015; 30:440-6. [DOI: 10.1002/bmc.3567] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2015] [Revised: 06/26/2015] [Accepted: 07/10/2015] [Indexed: 11/05/2022]
Affiliation(s)
- Yan Zhang
- Xian Mental Health Center; Xian Shaanxi China
- The Affiliated Mental Health Center of Xi'an School of Medicine; Xian Shaanxi China
| | - Feihu Liu
- Xian Mental Health Center; Xian Shaanxi China
- The Affiliated Mental Health Center of Xi'an School of Medicine; Xian Shaanxi China
| | - Xiaohong Zhang
- Xian Mental Health Center; Xian Shaanxi China
- The Affiliated Mental Health Center of Xi'an School of Medicine; Xian Shaanxi China
| | - Tanghui Xu
- The Affiliated No. 1 hospital of Xi'an School of Medicine; Xian Shaanxi China
| | - Wei Quan
- Xian Mental Health Center; Xian Shaanxi China
- The Affiliated Mental Health Center of Xi'an School of Medicine; Xian Shaanxi China
| | - Hui Wang
- Xian Mental Health Center; Xian Shaanxi China
- The Affiliated Mental Health Center of Xi'an School of Medicine; Xian Shaanxi China
| | - Jianguo Shi
- Xian Mental Health Center; Xian Shaanxi China
- The Affiliated Mental Health Center of Xi'an School of Medicine; Xian Shaanxi China
| | - Zunxiao Dai
- Xian Mental Health Center; Xian Shaanxi China
- The Affiliated Mental Health Center of Xi'an School of Medicine; Xian Shaanxi China
| | - Bin Wu
- Xian Mental Health Center; Xian Shaanxi China
- The Affiliated Mental Health Center of Xi'an School of Medicine; Xian Shaanxi China
| | - Qiangju Wu
- Xian Mental Health Center; Xian Shaanxi China
- The Affiliated Mental Health Center of Xi'an School of Medicine; Xian Shaanxi China
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5
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Bonoldi I, Howes OD. Presynaptic dopaminergic function: implications for understanding treatment response in psychosis. CNS Drugs 2014; 28:649-63. [PMID: 24919790 DOI: 10.1007/s40263-014-0177-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
All current antipsychotic drugs block dopamine (DA) receptors, but the nature of the DA dysfunction in schizophrenia has not been clear. However, consistent evidence now shows that presynaptic dopaminergic function is altered in schizophrenia, specifically in terms of increased DA synthesis capacity, baseline synaptic DA levels, and DA release. Furthermore, presynaptic dopaminergic function is already elevated in prodromal patients who later developed the disorder. Currently available antipsychotics act on postsynaptic receptors, not targeting presynaptic DA abnormalities. This has implications for understanding response and developing new treatments. The lack of normalization of the abnormal presynaptic function could explain why discontinuation is likely to lead to relapse, because the major dopaminergic function persists, meaning that once treatment stops there is nothing to oppose the dysregulated dopamine function reinstating symptoms. Furthermore, it suggests that drugs that target presynaptic dopaminergic function may constitute new treatment possibilities for schizophrenic patients, in particular, for those in whom antipsychotics are poorly effective. In addition, the longitudinal changes with the onset of psychosis indicate the potential to target a defined dynamic neurochemical abnormality to prevent the onset of psychosis.
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Affiliation(s)
- I Bonoldi
- Department of Psychosis Studies, Institute of Psychiatry, King's College of London, De Crespigny Park 16, London, SE5 8AF, UK,
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6
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Castellano O, Arji M, Sancho C, Carro J, Riolobos AS, Molina V, Gómez-Nieto R, de Anchieta de Castro E Horta J, Herrero-Turrión MJ, López DE. Chronic administration of risperidone in a rat model of schizophrenia: a behavioural, morphological and molecular study. Behav Brain Res 2013; 242:178-90. [PMID: 23291154 DOI: 10.1016/j.bbr.2012.12.036] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2012] [Revised: 12/18/2012] [Accepted: 12/22/2012] [Indexed: 01/04/2023]
Abstract
In the present work we analyzed the effect of the chronic administration of risperidone (2mg/kg over 65 days) on behavioural, morphological and molecular aspects in an experimental model of schizophrenia obtained by bilateral injection of ibotenic acid into the ventral hippocampus of new-born rats. Our results show that during their adult lives the animals with hippocampal lesions exhibit different alterations, mainly at behavioural level and in the gene expression of dopamine D(2) and 5-HT(2A) receptors. However, at morphological level the study performed on the prefrontal cortex did not reveal any alterations in either the thickness or the number of cells immunoreactive for c-Fos, GFAP, CBP or PV. Overall, risperidone administration elicited a trend towards the recovery of the values previously altered by the hippocampal lesion, approaching the values seen in the animals without lesions. It may be concluded that the administration of risperidone in the schizophrenia model employed helps to improve the altered functions, with no significant negative effects.
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MESH Headings
- Age Factors
- Animals
- Animals, Newborn
- Antipsychotic Agents/administration & dosage
- Avoidance Learning/drug effects
- Avoidance Learning/physiology
- Behavior, Animal/drug effects
- Brain/metabolism
- Brain/pathology
- CREB-Binding Protein/metabolism
- Cell Count
- Disease Models, Animal
- Drug Administration Schedule
- Excitatory Amino Acid Agonists/toxicity
- Exploratory Behavior/drug effects
- Exploratory Behavior/physiology
- Female
- Gene Expression Regulation/drug effects
- Glial Fibrillary Acidic Protein/metabolism
- Grooming/drug effects
- Hippocampus/drug effects
- Hippocampus/physiology
- Ibotenic Acid/toxicity
- Male
- Parvalbumins/metabolism
- Proto-Oncogene Proteins c-fos/metabolism
- Rats
- Rats, Wistar
- Receptor, Serotonin, 5-HT2A/genetics
- Receptor, Serotonin, 5-HT2A/metabolism
- Receptors, Dopamine D2/genetics
- Receptors, Dopamine D2/metabolism
- Risperidone/administration & dosage
- Schizophrenia/chemically induced
- Schizophrenia/drug therapy
- Schizophrenia/physiopathology
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Affiliation(s)
- O Castellano
- Institute for Neuroscience of Castilla y León, Salamanca, Spain; Department of Cell Biology and Pathology, University of Salamanca, Salamanca, Spain.
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7
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Dopaminergic genes influence early response to atypical antipsychotics in patients with first presentation of psychosis. J Clin Psychopharmacol 2012; 32:566-9. [PMID: 22760349 DOI: 10.1097/jcp.0b013e31825ec2cb] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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8
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Corripio I, Ferreira A, Portella MJ, Pérez V, Escartí MJ, Del Valle Camacho M, Sauras RB, Alonso A, Grasa EM, Carrió I, Catafau AM, Alvarez E. The role of striatal dopamine D2 receptors in the occurrence of extrapyramidal side effects: iodine-123-iodobenzamide single photon emission computed tomography study. Psychiatry Res 2012; 201:73-7. [PMID: 22281201 DOI: 10.1016/j.pscychresns.2011.02.004] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/04/2010] [Revised: 01/04/2011] [Accepted: 02/06/2011] [Indexed: 10/14/2022]
Abstract
Levels above 75% of striatal dopamine 2 receptor occupancy (D2RO) have been associated with extrapyramidal symptoms (EPS). The aim of the present study is to investigate the relationship between D2RO and EPS in a sample of psychotic patients in current treatment with both typical and atypical antipsychotics. Brain iodine-123-iodobenzamide single photon emission computed tomography ((123)I-IBZM SPECT) was performed in 81 patients taking stable doses of haloperidol, risperidone, olanzapine, quetiapine, clozapine or ziprasidone. First, the degree of D2RO and Positive and Negative Syndrome Scale (PANSS) scores was compared between the group of patients who presented EPS and the group free of EPS. Afterwards, these variables were compared among the different antipsychotic medications. The group with EPS presented means of D2RO significantly higher than the group free of EPS. Significant differences in D2RO were found in clozapine, quetiapine and ziprasidone groups compared with the haloperidol group. No differences were observed between either olanzapine or risperidone and haloperidol. No quetiapine- or clozapine-treated patients developed EPS. Haloperidol and risperidone demonstrated a relationship between striatal D2RO and EPS. The findings suggest that higher D2RO is related to appearance of EPS. Occupancy in the group with EPS was in agreement with previous studies that suggested a high degree of D2RO is necessary for the occurrence of EPS.
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Affiliation(s)
- Iluminada Corripio
- Department of Psychiatry, Universitat Autònoma de Barcelona, Barcelona, Spain
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9
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Abstract
This review summarizes the current state of knowledge regarding the proposed mechanisms by which antipsychotic agents reduce the symptoms of schizophrenia while giving rise to adverse side effects. The first part summarizes the contribution of neuroimaging studies to our understanding of the neurochemical substrates of schizophrenia, putting emphasis on direct evidence suggestive of a presynaptic rather than a postsynaptic dysregulation of dopaminergic neurotransmission in this disorder. The second part addresses the role of D(2) and non-D(2) receptor blockade in the treatment of schizophrenia and highlights a preponderant role of D(2) receptors in the mechanism of antipsychotic action. Neuroimaging studies have defined a narrow, but optimal, therapeutic window of 65-78 % D(2) receptor blockade within which most antipsychotics achieve optimal clinical efficacy with minimal side effects. Some antipsychotics though do not conform to that therapeutic window, notably clozapine. The reasons for its unexcelled clinical efficacy despite subthreshold levels of D(2) blockade are unclear and current theories on clozapine's mechanisms of action are discussed, including transiency of its D(2) receptor blocking effects or preferential blockade of limbic D(2) receptors. Evidence is also highlighted to consider the use of extended antipsychotic dosing to achieve transiency of D(2) blockade as a way to optimize functional outcomes in patients. We also present some critical clinical considerations regarding the mechanisms linking dopamine disturbance to the expression of psychosis and its blockade to the progressive resolution of psychosis, keeping in perspective the speed and onset of antipsychotic action. Finally, we discuss potential novel therapeutic strategies for schizophrenia.
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Affiliation(s)
- Nathalie Ginovart
- Department of Psychiatry, University of Geneva, Geneva, Switzerland.
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Stone JM, Raffin M, Morrison P, McGuire PK. Review: The biological basis of antipsychotic response in schizophrenia. J Psychopharmacol 2010; 24:953-64. [PMID: 19939865 DOI: 10.1177/0269881109106959] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Schizophrenia is a severe mental illness affecting approximately 1% of the population worldwide. Antipsychotic drugs are effective in symptom control in up to two-thirds of patients, but in at least one-third of patients the response is poor. The reason for this is not clear, but one possibility is that good and poor responders have different neurochemical pathologies, and may therefore benefit from different treatment approaches. In this selective review we summarise research findings investigating the biological differences between patients with schizophrenia who show a good or a poor response to treatment with antipsychotic drugs.
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Affiliation(s)
- James M Stone
- Institute of Psychiatry, King's College London, London SE5 8AF, UK.
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11
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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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Howes OD, Egerton A, Allan V, McGuire P, Stokes P, Kapur S. Mechanisms underlying psychosis and antipsychotic treatment response in schizophrenia: insights from PET and SPECT imaging. Curr Pharm Des 2009; 15:2550-9. [PMID: 19689327 DOI: 10.2174/138161209788957528] [Citation(s) in RCA: 160] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Molecular imaging studies have generated important in vivo insights into the etiology of schizophrenia and treatment response. This article first reviews the PET and SPECT evidence implicating dopaminergic dysfunction, especially presynaptic dysregulation, as a mechanism for psychosis. Second, it summarises the neurochemical imaging studies of antipsychotic action, focussing on D2/3 receptors. These studies show that all currently licensed antipsychotic drugs block striatal D2/3 receptors in vivo- a site downstream of the likely principal dopaminergic pathophysiology in schizophrenia- and that D2/3 occupancy above a threshold is required for antipsychotic treatment response. However, adverse events, such as extra-pyramidal side-effects or hyperprolactinemia, become much more likely at higher occupancy levels, which indicates there is an optimal 'therapeutic window' for D2/3 occupancy, and questions the use of high doses of antipsychotic treatment in clinical practice and trials. Adequate D2/3 blockade by antipsychotic drugs is necessary but not always sufficient for antipsychotic response. Molecular imaging studies of clozapine, the one antipsychotic licensed for treatment resistant schizophrenia, have provided insights into the mechanisms underlying its unique efficacy. To link this pharmacology to the phenomenology of the illness, we discuss the role of dopamine in motivational salience and show how i) psychosis could be viewed as a process of aberrant salience, and ii) antipsychotics might provide symptomatic relief by blocking this aberrant salience. Finally, we discuss the implications of these PET and SPECT findings for new avenues of drug development.
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Affiliation(s)
- O D Howes
- PET Psychiatry-MRC Clinical Sciences Centre, Imperial College Hammersmith Campus, Hammersmith Hospital, London, UK.
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13
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Abstract
The dopamine hypothesis of schizophrenia has been one of the most enduring ideas in psychiatry. Initially, the emphasis was on a role of hyperdopaminergia in the etiology of schizophrenia (version I), but it was subsequently reconceptualized to specify subcortical hyperdopaminergia with prefrontal hypodopaminergia (version II). However, these hypotheses focused too narrowly on dopamine itself, conflated psychosis and schizophrenia, and predated advances in the genetics, molecular biology, and imaging research in schizophrenia. Since version II, there have been over 6700 articles about dopamine and schizophrenia. We selectively review these data to provide an overview of the 5 critical streams of new evidence: neurochemical imaging studies, genetic evidence, findings on environmental risk factors, research into the extended phenotype, and animal studies. We synthesize this evidence into a new dopamine hypothesis of schizophrenia-version III: the final common pathway. This hypothesis seeks to be comprehensive in providing a framework that links risk factors, including pregnancy and obstetric complications, stress and trauma, drug use, and genes, to increased presynaptic striatal dopaminergic function. It explains how a complex array of pathological, positron emission tomography, magnetic resonance imaging, and other findings, such as frontotemporal structural and functional abnormalities and cognitive impairments, may converge neurochemically to cause psychosis through aberrant salience and lead to a diagnosis of schizophrenia. The hypothesis has one major implication for treatment approaches. Current treatments are acting downstream of the critical neurotransmitter abnormality. Future drug development and research into etiopathogenesis should focus on identifying and manipulating the upstream factors that converge on the dopaminergic funnel point.
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Affiliation(s)
- Oliver D. Howes
- Positron Emission Tomography (PET) Psychiatry Group, Medical Research Council (MRC) Clinical Sciences Centre, Faculty of Medicine, Imperial College London, Hammersmith Hospital Campus, London W12 0NN, UK,Institute of Psychiatry, King's College London, London SE5 8AF, UK
| | - Shitij Kapur
- Positron Emission Tomography (PET) Psychiatry Group, Medical Research Council (MRC) Clinical Sciences Centre, Faculty of Medicine, Imperial College London, Hammersmith Hospital Campus, London W12 0NN, UK,To whom correspondence should be addressed; PO Box 053, Institute of Psychiatry, King's College London, De Crespigny Park, London, SE5 8AF, UK; tel: +44-20-7848-0593, fax: +44-20-7848-0287, e-mail:
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Catafau AM, Suarez M, Bullich S, Llop J, Nucci G, Gunn RN, Brittain C, Laruelle M. Within-subject comparison of striatal D2 receptor occupancy measurements using [123I]IBZM SPECT and [11C]Raclopride PET. Neuroimage 2009; 46:447-58. [PMID: 19233294 DOI: 10.1016/j.neuroimage.2009.02.005] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2008] [Revised: 01/23/2009] [Accepted: 02/03/2009] [Indexed: 11/30/2022] Open
Abstract
Antipsychotic-induced D2 receptor occupancy values tend to be lower when measured with [(123)I]IBZM SPECT than with [(11)C]Raclopride PET. To clarify this issue, D2 receptor occupancy was measured in the same subjects using both techniques. Twenty patients with schizophrenia on monotherapy with risperidone (n=7; 3-9 mg/d), olanzapine (n=5; 5-20 mg/d) or clozapine (n=8; 150-450 mg/d) at stable doses, and ten healthy volunteers (HV) underwent both a [(123)I]IBZM SPECT and a [(11)C]Raclopride PET examinations in random order on different days within a week. Patients with schizophrenia were scanned at a fixed interval after last dose administration. Quantification of receptor availability was performed using the most conventional methods from the literature: the tissue ratio derived specific uptake ratios (SUR) were used for SPECT, and simplified reference tissue model (SRTM) derived binding potentials (BP(ND)) for PET. Analysis was performed using both occipital cortex and cerebellum as reference regions for both modalities. Striatal D2 receptor occupancy was measured as the percentage reduction of [(123)I]IBZM SUR or [(11)C]Raclopride BP(ND) compared to the population average measured in HV using the same modality. Occupancy values measured by SPECT were lower than those measured with PET, by 12.4% and 13.8% when occipital cortex and cerebellum were used as reference regions. This difference should be taken in consideration when interpreting reported antipsychotic striatal D2 receptor occupancy values from the literature.
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