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O'Neill JR, Jameson A, McLean SL, Dixon M, Cardno AG, Lawrence C. A proposal for reducing maximum target doses of drugs for psychosis: Reviewing dose-response literature. J Psychopharmacol 2024; 38:344-352. [PMID: 38494791 DOI: 10.1177/02698811241239543] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 03/19/2024]
Abstract
BACKGROUND Presently, there is limited guidance on the maximal dosing of psychosis drugs that is based on effectiveness rather than safety or toxicity. Current maximum dosing recommendations may far exceed the necessary degree of dopamine D2 receptor blockade required to treat psychosis. This may lead to excess harm through cognitive impairment and side effects. AIMS This analysis aimed to establish guidance for prescribers by optimally dosing drugs for psychosis based on efficacy and benefit. METHODS We used data from two dose-response meta-analyses and reviewed seven of the most prescribed drugs for psychosis in the UK. Where data were not available, we used appropriate comparison techniques based on D2 receptor occupancy to extrapolate our recommendations. RESULTS We found that the likely threshold dose for achieving remission of psychotic symptoms was often significantly below the currently licensed dose for these drugs. We therefore recommend that clinicians are cautious about exceeding our recommended doses. Individual factors, however, should be accounted for. We outline potentially relevant factors including age, ethnicity, sex, smoking status and pharmacogenetics. Additionally, we recommend therapeutic drug monitoring as a tool to determine individual pharmacokinetic variation. CONCLUSIONS In summary, we propose a new set of maximum target doses for psychosis drugs based on efficacy. Further research through randomised controlled trials should be undertaken to evaluate the effect of reducing doses from current licensing maximums or from doses that are above our recommendations. However, dose reductions should be implemented in a manner that accounts for and reduces the effects of drug withdrawal.
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Affiliation(s)
- James R O'Neill
- Faculty of Medicine and Health, University of Leeds, Leeds, UK
- South West Yorkshire Partnership NHS Foundation Trust, Wakefield, UK
- Leeds and York Partnership NHS Foundation Trust, Leeds, UK
| | - Adam Jameson
- School of Pharmacy and Medical Sciences, University of Bradford, Bradford, UK
- Wolfson Centre for Applied Health Research, Bradford, UK
- Bradford District Care NHS Foundation Trust, Shipley, UK
| | - Samantha L McLean
- School of Pharmacy and Medical Sciences, University of Bradford, Bradford, UK
- Wolfson Centre for Applied Health Research, Bradford, UK
| | - Michael Dixon
- Leeds and York Partnership NHS Foundation Trust, Leeds, UK
| | | | - Christopher Lawrence
- Southern Health NHS Foundation Trust, Southampton, UK
- University of Southampton, Southampton, UK
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de Bartolomeis A, Ciccarelli M, De Simone G, Mazza B, Barone A, Vellucci L. Canonical and Non-Canonical Antipsychotics' Dopamine-Related Mechanisms of Present and Next Generation Molecules: A Systematic Review on Translational Highlights for Treatment Response and Treatment-Resistant Schizophrenia. Int J Mol Sci 2023; 24:ijms24065945. [PMID: 36983018 PMCID: PMC10051989 DOI: 10.3390/ijms24065945] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2023] [Revised: 03/15/2023] [Accepted: 03/17/2023] [Indexed: 03/30/2023] Open
Abstract
Schizophrenia is a severe psychiatric illness affecting almost 25 million people worldwide and is conceptualized as a disorder of synaptic plasticity and brain connectivity. Antipsychotics are the primary pharmacological treatment after more than sixty years after their introduction in therapy. Two findings hold true for all presently available antipsychotics. First, all antipsychotics occupy the dopamine D2 receptor (D2R) as an antagonist or partial agonist, even if with different affinity; second, D2R occupancy is the necessary and probably the sufficient mechanism for antipsychotic effect despite the complexity of antipsychotics' receptor profile. D2R occupancy is followed by coincident or divergent intracellular mechanisms, implying the contribution of cAMP regulation, β-arrestin recruitment, and phospholipase A activation, to quote some of the mechanisms considered canonical. However, in recent years, novel mechanisms related to dopamine function beyond or together with D2R occupancy have emerged. Among these potentially non-canonical mechanisms, the role of Na2+ channels at the dopamine at the presynaptic site, dopamine transporter (DAT) involvement as the main regulator of dopamine concentration at synaptic clefts, and the putative role of antipsychotics as chaperones for intracellular D2R sequestration, should be included. These mechanisms expand the fundamental role of dopamine in schizophrenia therapy and may have relevance to considering putatively new strategies for treatment-resistant schizophrenia (TRS), an extremely severe condition epidemiologically relevant and affecting almost 30% of schizophrenia patients. Here, we performed a critical evaluation of the role of antipsychotics in synaptic plasticity, focusing on their canonical and non-canonical mechanisms of action relevant to the treatment of schizophrenia and their subsequent implication for the pathophysiology and potential therapy of TRS.
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Affiliation(s)
- Andrea de Bartolomeis
- Section of Psychiatry, Laboratory of Translational and Molecular Psychiatry and Unit of Treatment-Resistant Psychosis, Department of Neuroscience, Reproductive Sciences and Dentistry, University Medical School of Naples "Federico II", 80131 Naples, Italy
| | - Mariateresa Ciccarelli
- Section of Psychiatry, Laboratory of Translational and Molecular Psychiatry and Unit of Treatment-Resistant Psychosis, Department of Neuroscience, Reproductive Sciences and Dentistry, University Medical School of Naples "Federico II", 80131 Naples, Italy
| | - Giuseppe De Simone
- Section of Psychiatry, Laboratory of Translational and Molecular Psychiatry and Unit of Treatment-Resistant Psychosis, Department of Neuroscience, Reproductive Sciences and Dentistry, University Medical School of Naples "Federico II", 80131 Naples, Italy
| | - Benedetta Mazza
- Section of Psychiatry, Laboratory of Translational and Molecular Psychiatry and Unit of Treatment-Resistant Psychosis, Department of Neuroscience, Reproductive Sciences and Dentistry, University Medical School of Naples "Federico II", 80131 Naples, Italy
| | - Annarita Barone
- Section of Psychiatry, Laboratory of Translational and Molecular Psychiatry and Unit of Treatment-Resistant Psychosis, Department of Neuroscience, Reproductive Sciences and Dentistry, University Medical School of Naples "Federico II", 80131 Naples, Italy
| | - Licia Vellucci
- Section of Psychiatry, Laboratory of Translational and Molecular Psychiatry and Unit of Treatment-Resistant Psychosis, Department of Neuroscience, Reproductive Sciences and Dentistry, University Medical School of Naples "Federico II", 80131 Naples, Italy
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3
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de Bartolomeis A, Vellucci L, Barone A, Manchia M, De Luca V, Iasevoli F, Correll CU. Clozapine's multiple cellular mechanisms: What do we know after more than fifty years? A systematic review and critical assessment of translational mechanisms relevant for innovative strategies in treatment-resistant schizophrenia. Pharmacol Ther 2022; 236:108236. [PMID: 35764175 DOI: 10.1016/j.pharmthera.2022.108236] [Citation(s) in RCA: 20] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2022] [Revised: 06/21/2022] [Accepted: 06/21/2022] [Indexed: 12/21/2022]
Abstract
Almost fifty years after its first introduction into clinical care, clozapine remains the only evidence-based pharmacological option for treatment-resistant schizophrenia (TRS), which affects approximately 30% of patients with schizophrenia. Despite the long-time experience with clozapine, the specific mechanism of action (MOA) responsible for its superior efficacy among antipsychotics is still elusive, both at the receptor and intracellular signaling level. This systematic review is aimed at critically assessing the role and specific relevance of clozapine's multimodal actions, dissecting those mechanisms that under a translational perspective could shed light on molecular targets worth to be considered for further innovative antipsychotic development. In vivo and in vitro preclinical findings, supported by innovative techniques and methods, together with pharmacogenomic and in vivo functional studies, point to multiple and possibly overlapping MOAs. To better explore this crucial issue, the specific affinity for 5-HT2R, D1R, α2c, and muscarinic receptors, the relatively low occupancy at dopamine D2R, the interaction with receptor dimers, as well as the potential confounder effects resulting in biased ligand action, and lastly, the role of the moiety responsible for lipophilic and alkaline features of clozapine are highlighted. Finally, the role of transcription and protein changes at the synaptic level, and the possibility that clozapine can directly impact synaptic architecture are addressed. Although clozapine's exact MOAs that contribute to its unique efficacy and some of its severe adverse effects have not been fully understood, relevant information can be gleaned from recent mechanistic understandings that may help design much needed additional therapeutic strategies for TRS.
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Affiliation(s)
- Andrea de Bartolomeis
- Section of Psychiatry, Laboratory of Translational and Molecular Psychiatry and Unit of Treatment Resistant Psychosis, Department of Neuroscience, Reproductive Science and Dentistry, University Medical School of Naples "Federico II", Naples, Italy.
| | - Licia Vellucci
- Section of Psychiatry, Laboratory of Translational and Molecular Psychiatry and Unit of Treatment Resistant Psychosis, Department of Neuroscience, Reproductive Science and Dentistry, University Medical School of Naples "Federico II", Naples, Italy
| | - Annarita Barone
- Section of Psychiatry, Laboratory of Translational and Molecular Psychiatry and Unit of Treatment Resistant Psychosis, Department of Neuroscience, Reproductive Science and Dentistry, University Medical School of Naples "Federico II", Naples, Italy
| | - Mirko Manchia
- Section of Psychiatry, Department of Medical Sciences and Public Health, University of Cagliari, Cagliari, Italy; Department of Pharmacology, Dalhousie University, Halifax, Nova Scotia, Canada
| | | | - Felice Iasevoli
- Section of Psychiatry, Laboratory of Translational and Molecular Psychiatry and Unit of Treatment Resistant Psychosis, Department of Neuroscience, Reproductive Science and Dentistry, University Medical School of Naples "Federico II", Naples, Italy
| | - Christoph U Correll
- The Zucker Hillside Hospital, Department of Psychiatry, Northwell Health, Glen Oaks, NY, USA; Donald and Barbara Zucker School of Medicine at Hofstra/Northwell, Department of Psychiatry and Molecular Medicine, Hempstead, NY, USA; Charité Universitätsmedizin Berlin, Department of Child and Adolescent Psychiatry, Berlin, Germany
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Zeng F, Fan Y, Brown RW, Drew Gill W, Price JB, Jones TC, Zhu MY. Effects of Manipulation of Noradrenergic Activities on the Expression of Dopaminergic Phenotypes in Aged Rat Brains. ASN Neuro 2021; 13:17590914211055064. [PMID: 34812056 PMCID: PMC8613899 DOI: 10.1177/17590914211055064] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
This study investigated the effects of the pharmacological manipulation of noradrenergic activities on dopaminergic phenotypes in aged rats. Results showed that the administration of L-threo-3,4-dihydroxyphenylserine (L-DOPS) for 21 days significantly increased the expression of tyrosine hydroxylase (TH) and dopamine transporter (DAT) in the striatum and substantia nigra (SN) of 23-month-old rats. Furthermore, this treatment significantly increased norepinephrine/DA concentrations in the striatum and caused a deficit of sensorimotor gating as measured by prepulse inhibition (PPI). Next, old rats were injected with the α2-adrenoceptor antagonist 2-methoxy idazoxan or β2-adrenoceptor agonist salmeterol for 21 days. Both drugs produced similar changes of TH and DAT in the striatum and SN. Moreover, treatments with L-DOPS, 2-methoxy idazoxan, or salmeterol significantly increased the protein levels of phosphorylated Akt in rat striatum and SN. However, although a combination of 2-methoxy idazoxan and salmeterol resulted in a deficit of PPI in these rats, the administration of 2-methoxy idazoxan alone showed an opposite behavioral change. The in vitro experiments revealed that treatments with norepinephrine markedly increased mRNAs and proteins of ATF2 and CBP/p300 and reduced mRNA and proteins of HDAC2 and HDAC5 in MN9D cells. A ChIP assay showed that norepinephrine significantly increased CBP/p300 binding or reduced HDAC2 and HDAC5 binding on the TH promoter. The present results indicate that facilitating noradrenergic activity in the brain can improve the functions of dopaminergic neurons in aged animals. While this improvement may have biochemically therapeutic indication for the status involving the degeneration of dopaminergic neurons, it may not definitely include behavioral improvements, as indicated by using 2-methoxy idazoxan only.
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Affiliation(s)
- Fei Zeng
- Department of Neurology, Renmin Hospital of the Wuhan University, China.,Departments of Biomedical Sciences, Quillen College of Medicine, 4154East Tennessee State University, USA
| | - Yan Fan
- Departments of Biomedical Sciences, Quillen College of Medicine, 4154East Tennessee State University, USA.,Department of Biochemistry, Nantong University College of Medicine, China
| | - Russell W Brown
- Departments of Biomedical Sciences, Quillen College of Medicine, 4154East Tennessee State University, USA
| | - Wesley Drew Gill
- Departments of Biomedical Sciences, Quillen College of Medicine, 4154East Tennessee State University, USA
| | - Jennifer B Price
- Department of Biological Sciences, College of Arts and Sciences, 4154East Tennessee State University, USA
| | - Thomas C Jones
- Department of Biological Sciences, College of Arts and Sciences, 4154East Tennessee State University, USA
| | - Meng-Yang Zhu
- Departments of Biomedical Sciences, Quillen College of Medicine, 4154East Tennessee State University, USA
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5
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Miller LJ, Marco EJ, Chu RC, Camarata S. Editorial: Sensory Processing Across the Lifespan: A 25-Year Initiative to Understand Neurophysiology, Behaviors, and Treatment Effectiveness for Sensory Processing. Front Integr Neurosci 2021; 15:652218. [PMID: 33897385 PMCID: PMC8063042 DOI: 10.3389/fnint.2021.652218] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Key Words] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2021] [Accepted: 02/24/2021] [Indexed: 11/13/2022] Open
Affiliation(s)
- Lucy Jane Miller
- Department of Pediatrics (Emeritus), University of Colorado, Denver, CO, United States.,Sensory Therapies and Research Institute for Sensory Processing Disorder, Centennial, CO, United States
| | - Elysa J Marco
- Cortica (United States), San Diego, CA, United States
| | - Robyn C Chu
- Radiology & Biomedical Imaging, University of California San Francisco, San Francisco, CA, United States.,Growing Healthy Children Therapy Services, Rescue, CA, United States
| | - Stephen Camarata
- School of Medicine, Vanderbilt University, Nashville, TN, United States
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6
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Ballesteros A, Sánchez-Torres AM, López-Ilundain JM, Cabrera B, Lobo A, González-Pinto AM, Díaz-Caneja C, Corripio I, Vieta E, de la Serna E, Bobes J, Usall J, Contreras F, Lorente-Omeñaca R, Mezquida G, Bernardo M, Cuesta MJ. Is cognitive impairment associated with antipsychotic dose and anticholinergic equivalent loads in first-episode psychosis? Psychol Med 2018; 48:2247-2256. [PMID: 29331153 DOI: 10.1017/s0033291717003774] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
BACKGROUND Cognitive deficits are a core feature of early stages in schizophrenia. However, the extent to which antipsychotic (AP) have a deleterious effect on cognitive performance remains under debate. We aim to investigate whether anticholinergic loadings and dose of AP drugs in first episode of psychosis (FEP) in advanced phase of remission are associated with cognitive impairment and the differences between premorbid intellectual quotient (IQ) subgroups. METHODS Two hundred and sixty-six patients participated. The primary outcomes were cognitive dimensions, dopaminergic/anticholinergic load of AP [in chlorpromazine equivalents (Eq-CPZ) and the Anticholinergic Risk Scale (ARS), respectively]. RESULTS Impairments in processing speed, verbal memory and global cognition were significantly associated with high Eq-CPZ and verbal impairment with high ARS score. Moreover, this effect was higher in the low IQ subgroup. CONCLUSIONS Clinicians should be aware of the potential cognitive impairment associated with AP in advanced remission FEP, particularly in lower premorbid IQ patients.
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Affiliation(s)
| | | | | | - Bibiana Cabrera
- Barcelona Clínic Schizophrenia Unit,Neuroscience Institute,Hospital Clínic de Barcelona,Barcelona,Spain
| | - Antonio Lobo
- Department of Medicine and Psychiatry,University of Zaragoza. Aragon Institute for Health Research (IIS Aragon),Zaragoza,Spain
| | | | | | - Iluminada Corripio
- Network Centre for Biomedical Research in Mental Health (CIBERSAM),Madrid,Spain
| | - Eduard Vieta
- Network Centre for Biomedical Research in Mental Health (CIBERSAM),Madrid,Spain
| | - Elena de la Serna
- Network Centre for Biomedical Research in Mental Health (CIBERSAM),Madrid,Spain
| | - Julio Bobes
- Network Centre for Biomedical Research in Mental Health (CIBERSAM),Madrid,Spain
| | - Judith Usall
- Network Centre for Biomedical Research in Mental Health (CIBERSAM),Madrid,Spain
| | - Fernando Contreras
- Network Centre for Biomedical Research in Mental Health (CIBERSAM),Madrid,Spain
| | | | - Gisela Mezquida
- Barcelona Clínic Schizophrenia Unit,Neuroscience Institute,Hospital Clínic de Barcelona,Barcelona,Spain
| | - Miguel Bernardo
- Barcelona Clínic Schizophrenia Unit,Neuroscience Institute,Hospital Clínic de Barcelona,Barcelona,Spain
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7
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Kononoff Vanhanen J, Nuutinen S, Tuominen M, Panula P. Histamine H3 Receptor Regulates Sensorimotor Gating and Dopaminergic Signaling in the Striatum. ACTA ACUST UNITED AC 2016; 357:264-72. [DOI: 10.1124/jpet.115.230771] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2015] [Accepted: 03/03/2016] [Indexed: 01/29/2023]
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8
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O'Connor WT, O'Shea SD. Clozapine and GABA transmission in schizophrenia disease models. Pharmacol Ther 2015; 150:47-80. [DOI: 10.1016/j.pharmthera.2015.01.005] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2015] [Accepted: 01/06/2015] [Indexed: 11/30/2022]
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Meclizine enhancement of sensorimotor gating in healthy male subjects with high startle responses and low prepulse inhibition. Neuropsychopharmacology 2014; 39:651-9. [PMID: 24045586 PMCID: PMC3895242 DOI: 10.1038/npp.2013.248] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/23/2013] [Revised: 09/09/2013] [Accepted: 09/11/2013] [Indexed: 11/08/2022]
Abstract
Histamine H1 receptor systems have been shown in animal studies to have important roles in the reversal of sensorimotor gating deficits, as measured by prepulse inhibition (PPI). H1-antagonist treatment attenuates the PPI impairments caused by either blockade of NMDA glutamate receptors or facilitation of dopamine transmission. The current experiment brought the investigation of H1 effects on sensorimotor gating to human studies. The effects of the histamine H1 antagonist meclizine on the startle response and PPI were investigated in healthy male subjects with high baseline startle responses and low PPI levels. Meclizine was administered to participants (n=24) using a within-subjects design with each participant receiving 0, 12.5, and 25 mg of meclizine in a counterbalanced order. Startle response, PPI, heart rate response, galvanic skin response, and changes in self-report ratings of alertness levels and affective states (arousal and valence) were assessed. When compared with the control (placebo) condition, the two doses of meclizine analyzed (12.5 and 25 mg) produced significant increases in PPI without affecting the magnitude of the startle response or other physiological variables. Meclizine also caused a significant increase in overall self-reported arousal levels, which was not correlated with the observed increase in PPI. These results are in agreement with previous reports in the animal literature and suggest that H1 antagonists may have beneficial effects in the treatment of subjects with compromised sensorimotor gating and enhanced motor responses to sensory stimuli.
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Differential effects of the antidepressant mirtazapine on amphetamine- and dizocilpine-induced PPI deficits. Pharmacol Biochem Behav 2012; 102:82-7. [PMID: 22469866 DOI: 10.1016/j.pbb.2012.03.010] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/18/2011] [Revised: 03/09/2012] [Accepted: 03/17/2012] [Indexed: 11/21/2022]
Abstract
Prepulse inhibition (PPI) refers to the decrease in motor startle response to salient sensory stimuli (pulses) when they are closely preceded in time by another more modest sensory stimulus (prepulse). PPI deficits can be induced by stimulation of dopamine receptors (e.g., amphetamine or apomorphine) or blockade of NMDA glutamate receptors (e.g., dizocilpine or PCP). Previously we found that antagonists of α(2)-noradrenergic and H(1)-histaminergic receptors significantly attenuate PPI impairments caused by amphetamine or dizocilpine. In the current study we assessed the effects of the antidepressant mirtazapine, which has combined antagonist effects at α(2)-noradrenergic, H(1)-histaminergic and 5-HT serotonergic receptors, on amphetamine- and dizocilpine-induced PPI deficits. In Experiment 1, rats were tested for PPI of the startle response to a tactile air-puff stimulus after auditory prepulses of three different intensities. Drug treatments consisted of combinations of amphetamine (0 and 1mg/kg) and mirtazapine (0, 0.5, 1, 2, and 5mg/kg), with all rats receiving all drug doses and combinations with different counterbalanced orders. In Experiment 2, a different group of rats was tested with drug treatments consisting of combinations of dizocilpine (0 and 0.05 mg/kg) and mirtazapine (0, 0.5, 1, 2, and 5 mg/kg). In Experiment 1 amphetamine (1 mg/kg) significantly reduced PPI whereas mirtazapine caused the opposite effect, with the highest dose of mirtazapine (5 mg/kg) effectively reversing the amphetamine-induced PPI deficit. In Experiment 2 dizocilpine (0.05 mg/kg) significantly reduced PPI, but mirtazapine did not have a significant effect on the inhibition of the startle response. These results indicate that the potential beneficial effects of combined α-adrenergic, 5-HT, and H(1) receptor blockade in counteracting PPI deficits may be associated to cases of sensorimotor gating disorders mediated by dopamine, but not necessarily to NMDA glutamate-induced PPI impairments.
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Humbert-Claude M, Davenas E, Gbahou F, Vincent L, Arrang JM. Involvement of histamine receptors in the atypical antipsychotic profile of clozapine: a reassessment in vitro and in vivo. Psychopharmacology (Berl) 2012; 220:225-41. [PMID: 21912901 DOI: 10.1007/s00213-011-2471-5] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/06/2011] [Accepted: 08/24/2011] [Indexed: 12/11/2022]
Abstract
RATIONALE The basis of the unique clinical profile of the antipsychotic clozapine is not yet elucidated. Brain histamine receptors may play a role in schizophrenia and its treatment, but their involvement in the profile of clozapine remained unknown. OBJECTIVES We explored the properties of clozapine and its two metabolites, N-desmethylclozapine (NDMC) and clozapine N-oxide, at the four human histaminergic receptors. We compared their active concentrations with their blood concentrations in patients treated by clozapine. We investigated the changes in receptor densities induced in rat brain by repeated administration of a therapeutic dose of clozapine. RESULTS Clozapine and NDMC behaved as very potent, and partial, H(1)-receptor inverse agonists, weak, and full, H(2)-receptor inverse agonists, moderate, and protean, H(3)-receptor agonists, and moderate, and partial, H(4)-receptor agonists. Taking into account their micromolar mean blood concentrations found in 75 treated patients, and assuming that they are enriched in human brain as they are in rat brain, a full occupation of H(1)-, H(3)-, and H(4)-receptors, and a partial occupation of H(2) receptors, is expected. In agreement, repeated administration of clozapine at a therapeutic dose (20 mg/kg/day for 20 days) induced an up-regulation of H(1)- and H(2)-receptors in rat brain. CONCLUSIONS Clozapine and its active metabolite NDMC interact with the four human histamine receptors at clinically relevant concentrations. This interaction may substantiate, at least in part, the atypical antipsychotic profile of clozapine, as well as its central and peripheral side effects such as sedation and weight gain.
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Affiliation(s)
- Marie Humbert-Claude
- Laboratoire de Neurobiologie et Pharmacologie Moléculaire, Centre de Psychiatrie et Neurosciences (CPN, U 894), INSERM, 2 ter rue d'Alésia, 75014 Paris, France
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12
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The α₂-adrenergic antagonist idazoxan counteracts prepulse inhibition deficits caused by amphetamine or dizocilpine in rats. Psychopharmacology (Berl) 2012; 219:99-108. [PMID: 21710169 DOI: 10.1007/s00213-011-2377-2] [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: 07/26/2010] [Accepted: 06/08/2011] [Indexed: 10/18/2022]
Abstract
RATIONALE Prepulse inhibition (PPI) is the reduction in startle response magnitude when intense stimuli are closely preceded by other weak stimuli. Animal models used to investigate sensorimotor gating deficits include both the stimulation of dopamine receptors (e.g., amphetamine or apomorphine) and the blockade of NMDA-glutamate receptors (e.g., dizocilpine or phencyclidine). OBJECTIVES We assessed the effects of idazoxan (an α(2)-adrenergic antagonist) on amphetamine- and dizocilpine-induced PPI disruptions in adult female Sprague-Dawley rats. METHODS In experiment 1, rats were tested for PPI in a bimodal paradigm with an acoustic prepulse and a tactile startle stimulus. Interactions of amphetamine (1 mg/kg) and idazoxan (0.5, 1, and 2 mg/kg) were assessed, with all rats receiving all drug doses in a counterbalanced order. In experiment 2, dizocilpine (0.05 mg/kg) and idazoxan (0.5, 1, and 2 mg/kg) interactions were analyzed. RESULTS Amphetamine (1 mg/kg) caused a significant reduction in PPI. Both the 1- and 2-mg/kg doses of idazoxan significantly counteracted this effect. Dizocilpine (.05 mg/kg) effectively inhibited PPI, and the 2-mg/kg idazoxan dose significantly counteracted this impairment. CONCLUSIONS These results suggest that the effectiveness of atypical antipsychotics such as clozapine in counteracting sensorimotor gating deficits reported in previous studies (e.g., Swerdlow and Geyer, Pharmacol Biochem Behav 44:741-744, 1993; Bakshi et al., J Pharmacol Exp Ther 271:787-794, 1994) may be related to their α(2)-antagonist effects, which may be a critical mechanism of the therapeutic effects of atypical antipsychotics in schizophrenia.
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Abstract
The treatment options for Alzheimer's type dementia are limited to the use of acetyl-cholinesterase inhibitors, along with memantine in some cases, and offer variable success in the treatment of cognitive impairment and to improve or stabilize activities of daily living, behavioral abnormalities, and impairment of global function. This review examines dimebolin, a nonselective antihistamine drug that has been used in Russia in the past for its antihistamine effect and has now generated considerable interest in the treatment of Alzheimer's type dementia, following results in the initial trials (Doody et al., 2008) and is currently under further evaluation. This article considers various theories proposed to explain its effect in the treatment of dementia. The results from further trials will help to clarify the future of dimebolin as a potential treatment for chronic neurodegenerative disorders that include dementia that affects 25 million people worldwide.
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Affiliation(s)
- Deepak Sachdeva
- Moor Side Unit, Trafford General Hospital, Urmston, Manchester, UK
| | - Alistair Burns
- Psychiatry Research Group, University of Manchester, Manchester, UK
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PPI deficit induced by amphetamine is attenuated by the histamine H1 antagonist pyrilamine, but is exacerbated by the serotonin 5-HT2 antagonist ketanserin. Psychopharmacology (Berl) 2010; 212:551-8. [PMID: 20811878 DOI: 10.1007/s00213-010-2005-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/05/2010] [Accepted: 07/26/2010] [Indexed: 10/19/2022]
Abstract
RATIONALE Prepulse inhibition (PPI) of the startle response is a classic model of sensorimotor gating. Robust PPI impairments can be induced by dopamine agonists such as the indirect agonist amphetamine. The antipsychotic clozapine can attenuate PPI impairment induced by dopamine agonists. Clozapine is a complex drug with antagonistic effects on a variety of receptors, including serotonin and histamine. The relative contribution of its component actions to its efficacy is still unclear. OBJECTIVES To better characterize the role of histamine and serotonin receptors in the modulation of PPI in rats, we studied the effects of the H(1) histamine antagonist pyrilamine (10, 20, and 40 mg/kg) on amphetamine-induced (1 mg/kg) PPI deficits (Experiment 1); and the interaction of pyrilamine (20 mg/kg) with the 5-HT(2) antagonist ketanserin (1 and 2 mg/kg) on the amphetamine-induced PPI disruption (Experiment 2). METHODS Tactile startle stimuli consisted of 30 PSI air-puffs. Three acoustic prepulse intensity levels were used: 68, 71, and 77 dB, presented on a 65-dB background noise. In both experiments, all animals received all drug doses and combinations with different counterbalanced orders. RESULTS Pyrilamine (20 mg/kg) was effective in counteracting the PPI impairment caused by amphetamine administration, whereas ketanserin exacerbated the amphetamine-induced PPI deficit. CONCLUSIONS Based on its ability to reverse amphetamine-induced PPI deficits, blockade of histamine H(1) receptors seems to contribute to the therapeutic effect of the antipsychotic clozapine. Serotonin 5-HT(2)-receptor blockade, though, does not appear to contribute to this effect, and may in fact detract from it.
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Abstract
Converging data from multiple lines of research provide growing understanding of the pharmacological basis of the efficacy and tolerability of antipsychotic agents. This review highlights some of the drawbacks of the current practice of classifying antipsychotic agents into first- and second-generation agents, and argues that much of what is known about an antipsychotic agent in terms of its efficacy and tolerability can be predicted from its binding affinity at different receptors. This makes a case for a new system of classification that reflects the receptor binding affinity profiles of individual antipsychotic agents. In its quest to make a compelling case, the review provides detailed explanations for the pharmacological basis of antipsychotic efficacy, antipsychotic-induced weight gain and diabetes mellitus, cognitive effects and other adverse effects.
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Affiliation(s)
- Ripu D Jindal
- Department of Psychiatry, University of Ottawa School of Medicine, Ottawa, Ontario, Canada.
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Swerdlow NR, Weber M, Qu Y, Light GA, Braff DL. Realistic expectations of prepulse inhibition in translational models for schizophrenia research. Psychopharmacology (Berl) 2008; 199:331-88. [PMID: 18568339 PMCID: PMC2771731 DOI: 10.1007/s00213-008-1072-4] [Citation(s) in RCA: 421] [Impact Index Per Article: 26.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/17/2007] [Accepted: 01/03/2008] [Indexed: 12/16/2022]
Abstract
INTRODUCTION Under specific conditions, a weak lead stimulus, or "prepulse", can inhibit the startling effects of a subsequent intense abrupt stimulus. This startle-inhibiting effect of the prepulse, termed "prepulse inhibition" (PPI), is widely used in translational models to understand the biology of brainbased inhibitory mechanisms and their deficiency in neuropsychiatric disorders. In 1981, four published reports with "prepulse inhibition" as an index term were listed on Medline; over the past 5 years, new published Medline reports with "prepulse inhibition" as an index term have appeared at a rate exceeding once every 2.7 days (n=678). Most of these reports focus on the use of PPI in translational models of impaired sensorimotor gating in schizophrenia. This rapid expansion and broad application of PPI as a tool for understanding schizophrenia has, at times, outpaced critical thinking and falsifiable hypotheses about the relative strengths vs. limitations of this measure. OBJECTIVES This review enumerates the realistic expectations for PPI in translational models for schizophrenia research, and provides cautionary notes for the future applications of this important research tool. CONCLUSION In humans, PPI is not "diagnostic"; levels of PPI do not predict clinical course, specific symptoms, or individual medication responses. In preclinical studies, PPI is valuable for evaluating models or model organisms relevant to schizophrenia, "mapping" neural substrates of deficient PPI in schizophrenia, and advancing the discovery and development of novel therapeutics. Across species, PPI is a reliable, robust quantitative phenotype that is useful for probing the neurobiology and genetics of gating deficits in schizophrenia.
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Affiliation(s)
- Neal R Swerdlow
- Department of Psychiatry, UCSD School of Medicine, La Jolla, CA, 92093-0804, USA,
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Jia F, Mobarakeh JI, Dai H, Kato M, Xu A, Okuda T, Sakurai E, Okamura N, Takahashi K, Yanai K. Blocking Histamine H1 Improves Learning and Mnemonic Dysfunction in Mice With Social Isolation Plus Repeated Methamphetamine Injection. J Pharmacol Sci 2008; 107:167-74. [DOI: 10.1254/jphs.fp0072424] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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