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Fukuyama K, Motomura E, Okada M. A Novel Gliotransmitter, L-β-Aminoisobutyric Acid, Contributes to Pathophysiology of Clinical Efficacies and Adverse Reactions of Clozapine. Biomolecules 2023; 13:1288. [PMID: 37759688 PMCID: PMC10526296 DOI: 10.3390/biom13091288] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2023] [Revised: 08/18/2023] [Accepted: 08/22/2023] [Indexed: 09/29/2023] Open
Abstract
Clozapine is listed as one of the most effective antipsychotics and has been approved for treating treatment-resistant schizophrenia (TRS); however, several type A and B adverse reactions, including weight gain, metabolic complications, cardiotoxicity, convulsions, and discontinuation syndromes, exist. The critical mechanisms of clinical efficacy for schizophrenia, TRS, and adverse reactions of clozapine have not been elucidated. Recently, the GABA isomer L-β-aminoisobutyric acid (L-BAIBA), a protective myokine in the peripheral organs, was identified as a candidate novel transmission modulator in the central nervous system (CNS). L-BAIBA activates adenosine monophosphate-activated protein kinase (AMPK) signalling in both the peripheral organs and CNS. Activated AMPK signalling in peripheral organs is an established major target for treating insulin-resistant diabetes, whereas activated AMPK signalling in the hypothalamus contributes to the pathophysiology of weight gain and metabolic disturbances. Clozapine increases L-BAIBA synthesis in the hypothalamus. In addition, the various functions of L-BAIBA in the CNS have recently been elucidated, including as an activator of GABA-B and group-III metabotropic glutamate (III-mGlu) receptors. Considering the expressions of GABA-B and III-mGlu receptors (localised in the presynaptic regions), the activation of GABA-B and III-mGlu receptors can explain the distinct therapeutic advantages of clozapine in schizophrenia or TRS associated with N-methyl-D-aspartate (NMDA) receptor disturbance compared with other atypical antipsychotics via the inhibition of the persistent tonic hyperactivation of thalamocortical glutamatergic transmission in the prefrontal cortex. L-BAIBA has also been identified as a gliotransmitter, and a detailed exploration of the function of L-BAIBA in tripartite synaptic transmission can further elucidate the pathophysiology of effectiveness for treating TRS and/or specific adverse reactions of clozapine.
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Affiliation(s)
| | | | - Motohiro Okada
- Department of Neuropsychiatry, Division of Neuroscience, Graduate School of Medicine, Mie University, Tsu 514-8507, Japan; (K.F.); (E.M.)
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2
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Hsiao YC, Lee MY, Chan MH, Chen HH. NMDA Receptor Glycine Binding Site Modulators for Prevention and Treatment of Ketamine Use Disorder. Pharmaceuticals (Basel) 2023; 16:812. [PMID: 37375760 DOI: 10.3390/ph16060812] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2023] [Revised: 05/26/2023] [Accepted: 05/26/2023] [Indexed: 06/29/2023] Open
Abstract
Ketamine offers a fast-acting approach to relieving treatment-resistant depression, but its abuse potential is an issue of concern. As ketamine is a noncompetitive N-methyl-D-aspartate receptor (NMDAR) ion channel blocker, modulation of NMDAR might be an effective strategy to counteract the abuse liability of ketamine and even to treat ketamine use disorder. This study evaluated whether NMDAR modulators that act on glycine binding sites can decrease motivation to obtain ketamine and reduce reinstatement to ketamine-seeking behavior. Two NMDAR modulators, D-serine and sarcosine were examined. Male Sprague-Dawley rats underwent training to acquire the ability to self-administer ketamine. The motivation to self-administer ketamine or sucrose pellets was examined under a progressive ratio (PR) schedule. The reinstatement of ketamine-seeking and sucrose pellet-seeking behaviors were assessed after extinction. The results showed that both D-serine and sarcosine significantly decreased the breakpoints for ketamine and prevented reinstatement of ketamine seeking. However, these modulators did not alter motivated behavior for sucrose pellets, the ability of the cue and sucrose pellets to reinstate sucrose-seeking behavior or spontaneous locomotor activity. These findings indicate that two NMDAR modulators can specifically reduce the measures of motivation and relapse for ketamine in rats, suggesting that targeting the glycine binding site of the NMDAR is a promising approach for preventing and treating ketamine use disorder.
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Affiliation(s)
- Yu-Chin Hsiao
- Center for Neuropsychiatric Research, National Health Research Institutes, 35 Keyan Road, Zhunan, Miaoli County 35053, Taiwan
| | - Mei-Yi Lee
- Center for Neuropsychiatric Research, National Health Research Institutes, 35 Keyan Road, Zhunan, Miaoli County 35053, Taiwan
| | - Ming-Huan Chan
- Institute of Neuroscience, National Chengchi University, 64, Sec. 2, ZhiNan Road, Wenshan District, Taipei City 11605, Taiwan
- Research Center for Mind, Brain, and Learning, National Chengchi University, 64, Sec. 2, ZhiNan Road, Wenshan District, Taipei City 11605, Taiwan
| | - Hwei-Hsien Chen
- Center for Neuropsychiatric Research, National Health Research Institutes, 35 Keyan Road, Zhunan, Miaoli County 35053, Taiwan
- Institute of Neuroscience, National Chengchi University, 64, Sec. 2, ZhiNan Road, Wenshan District, Taipei City 11605, Taiwan
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de Bartolomeis A, Manchia M, Marmo F, Vellucci L, Iasevoli F, Barone A. Glycine Signaling in the Framework of Dopamine-Glutamate Interaction and Postsynaptic Density. Implications for Treatment-Resistant Schizophrenia. Front Psychiatry 2020; 11:369. [PMID: 32477178 PMCID: PMC7240307 DOI: 10.3389/fpsyt.2020.00369] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/22/2020] [Accepted: 04/14/2020] [Indexed: 12/14/2022] Open
Abstract
Treatment-resistant schizophrenia (TRS) or suboptimal response to antipsychotics affects almost 30% of schizophrenia (SCZ) patients, and it is a relevant clinical issue with significant impact on the functional outcome and on the global burden of disease. Among putative novel treatments, glycine-centered therapeutics (i.e. sarcosine, glycine itself, D-Serine, and bitopertin) have been proposed, based on a strong preclinical rationale with, however, mixed clinical results. Therefore, a better appraisal of glycine interaction with the other major players of SCZ pathophysiology and specifically in the framework of dopamine - glutamate interactions is warranted. New methodological approaches at cutting edge of technology and drug discovery have been applied to study the role of glycine in glutamate signaling, both at presynaptic and post-synaptic level and have been instrumental for unveiling the role of glycine in dopamine-glutamate interaction. Glycine is a non-essential amino acid that plays a critical role in both inhibitory and excitatory neurotransmission. In caudal areas of central nervous system (CNS), such as spinal cord and brainstem, glycine acts as a powerful inhibitory neurotransmitter through binding to its receptor, i.e. the Glycine Receptor (GlyR). However, glycine also works as a co-agonist of the N-Methyl-D-Aspartate receptor (NMDAR) in excitatory glutamatergic neurotransmission. Glycine concentration in the synaptic cleft is finely tuned by glycine transporters, i.e. GlyT1 and GlyT2, that regulate the neurotransmitter's reuptake, with the first considered a highly potential target for psychosis therapy. Reciprocal regulation of dopamine and glycine in forebrain, glycine modulation of glutamate, glycine signaling interaction with postsynaptic density proteins at glutamatergic synapse, and human genetics of glycinergic pathways in SCZ are tackled in order to highlight the exploitation of this neurotransmitters and related molecules in SCZ and TRS.
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Affiliation(s)
- Andrea de Bartolomeis
- Laboratory of Molecular Psychiatry and Translational Psychiatry, Unit of Treatment Resistant Psychosis, Section of Psychiatry, Department of Neuroscience, Reproductive Science and Odontostomatology, University School of Medicine of Napoli Federico II, Naples, Italy
| | - Mirko Manchia
- Section of Psychiatry, Department of Medical Science and Public Health, University of Cagliari, Cagliari, Italy.,Department of Pharmacology, Dalhousie University, Halifax, NS, Canada
| | - Federica Marmo
- Laboratory of Molecular Psychiatry and Translational Psychiatry, Unit of Treatment Resistant Psychosis, Section of Psychiatry, Department of Neuroscience, Reproductive Science and Odontostomatology, University School of Medicine of Napoli Federico II, Naples, Italy
| | - Licia Vellucci
- Laboratory of Molecular Psychiatry and Translational Psychiatry, Unit of Treatment Resistant Psychosis, Section of Psychiatry, Department of Neuroscience, Reproductive Science and Odontostomatology, University School of Medicine of Napoli Federico II, Naples, Italy
| | - Felice Iasevoli
- Laboratory of Molecular Psychiatry and Translational Psychiatry, Unit of Treatment Resistant Psychosis, Section of Psychiatry, Department of Neuroscience, Reproductive Science and Odontostomatology, University School of Medicine of Napoli Federico II, Naples, Italy
| | - Annarita Barone
- Laboratory of Molecular Psychiatry and Translational Psychiatry, Unit of Treatment Resistant Psychosis, Section of Psychiatry, Department of Neuroscience, Reproductive Science and Odontostomatology, University School of Medicine of Napoli Federico II, Naples, Italy
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Jankowska A, Satała G, Partyka A, Wesołowska A, Bojarski AJ, Pawłowski M, Chłoń-Rzepa G. Discovery and Development of Non-Dopaminergic Agents for the Treatment of Schizophrenia: Overview of the Preclinical and Early Clinical Studies. Curr Med Chem 2019; 26:4885-4913. [PMID: 31291870 DOI: 10.2174/0929867326666190710172002] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2019] [Revised: 06/11/2019] [Accepted: 06/14/2019] [Indexed: 02/05/2023]
Abstract
Schizophrenia is a chronic psychiatric disorder that affects about 1 in 100 people around the world and results in persistent emotional and cognitive impairments. Untreated schizophrenia leads to deterioration in quality of life and premature death. Although the clinical efficacy of dopamine D2 receptor antagonists against positive symptoms of schizophrenia supports the dopamine hypothesis of the disease, the resistance of negative and cognitive symptoms to these drugs implicates other systems in its pathophysiology. Many studies suggest that abnormalities in glutamate homeostasis may contribute to all three groups of schizophrenia symptoms. Scientific considerations also include disorders of gamma-aminobutyric acid-ergic and serotonergic neurotransmissions as well as the role of the immune system. The purpose of this review is to update the most recent reports on the discovery and development of non-dopaminergic agents that may reduce positive, negative, and cognitive symptoms of schizophrenia, and may be alternative to currently used antipsychotics. This review collects the chemical structures of representative compounds targeting metabotropic glutamate receptor, gamma-aminobutyric acid type A receptor, alpha 7 nicotinic acetylcholine receptor, glycine transporter type 1 and glycogen synthase kinase 3 as well as results of in vitro and in vivo studies indicating their efficacy in schizophrenia. Results of clinical trials assessing the safety and efficacy of the tested compounds have also been presented. Finally, attention has been paid to multifunctional ligands with serotonin receptor affinity or phosphodiesterase inhibitory activity as novel strategies in the search for dedicated medicines for patients with schizophrenia.
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Affiliation(s)
- Agnieszka Jankowska
- Department of Medicinal Chemistry, Jagiellonian University Medical College, 9 Medyczna Street, 30-688 Krakow, Poland
| | - Grzegorz Satała
- Department of Medicinal Chemistry, Institute of Pharmacology, Polish Academy of Sciences, 12 Smetna Street, 31-343 Krakow, Poland
| | - Anna Partyka
- Department of Clinical Pharmacy, Jagiellonian University Medical College, 9 Medyczna Street, 30-688 Krakow, Poland
| | - Anna Wesołowska
- Department of Clinical Pharmacy, Jagiellonian University Medical College, 9 Medyczna Street, 30-688 Krakow, Poland
| | - Andrzej J Bojarski
- Department of Medicinal Chemistry, Institute of Pharmacology, Polish Academy of Sciences, 12 Smetna Street, 31-343 Krakow, Poland
| | - Maciej Pawłowski
- Department of Medicinal Chemistry, Jagiellonian University Medical College, 9 Medyczna Street, 30-688 Krakow, Poland
| | - Grażyna Chłoń-Rzepa
- Department of Medicinal Chemistry, Jagiellonian University Medical College, 9 Medyczna Street, 30-688 Krakow, Poland
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Pei JC, Hung WL, Lin BX, Shih MH, Lu LY, Luo DZ, Tai HC, Studer V, Min MY, Lai WS. Therapeutic potential and underlying mechanism of sarcosine (N-methylglycine) in N-methyl-D-aspartate (NMDA) receptor hypofunction models of schizophrenia. J Psychopharmacol 2019; 33:1288-1302. [PMID: 31294644 DOI: 10.1177/0269881119856558] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
BACKGROUND Compelling animal and clinical studies support the N-methyl-D-aspartate receptor (NMDAR) hypofunction hypothesis of schizophrenia and suggest promising pharmacological agents to ameliorate negative and cognitive symptoms of schizophrenia, including sarcosine, a glycine transporter-1 inhibitor. AIMS AND METHODS It is imperative to evaluate the therapeutic potential of sarcosine in animal models, which provide indispensable tools for testing drug effects in detail and elucidating the underlying mechanisms. In this study, a series of seven experiments was conducted to investigate the effect of sarcosine in ameliorating behavioral deficits and the underlying mechanism in pharmacological (i.e., MK-801-induced) and genetic (i.e., serine racemase-null mutant (SR-/-) mice) NMDAR hypofunction models. RESULTS In Experiment 1, the acute administration of 500/1000 mg/kg sarcosine (i.p.) had no adverse effects on motor function and serum biochemical responses. In Experiments 2-4, sarcosine significantly alleviated MK-801-induced (0.2 mg/kg) brain abnormalities and behavioral deficits in MK-801-induced and SR-/- mouse models. In Experiment 5, the injection of sarcosine enhanced CSF levels of glycine and serine in rat brain. In Experiments 6-7, we show for the first time that sarcosine facilitated NMDAR-mediated hippocampal field excitatory postsynaptic potentials and influenced the movement of surface NMDARs at extrasynaptic sites. CONCLUSIONS Sarcosine effectively regulated the surface trafficking of NMDARs, NMDAR-evoked electrophysiological activity, brain glycine levels and MK-801-induced abnormalities in the brain, which contributed to the amelioration of behavioral deficits in mouse models of NMDAR hypofunction.
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Affiliation(s)
- Ju-Chun Pei
- Department of Psychology, National Taiwan University, Taipei, Taiwan
| | - Wei-Li Hung
- Department of Psychology, National Taiwan University, Taipei, Taiwan
| | - Bei-Xuan Lin
- Institute of Zoology, National Taiwan University, Taipei, Taiwan
| | - Min-Han Shih
- Department of Chemistry, National Taiwan University, Taipei, Taiwan
| | - Liang-Yin Lu
- Department of Psychology, National Taiwan University, Taipei, Taiwan
| | - Da-Zhong Luo
- Department of Psychology, National Taiwan University, Taipei, Taiwan
| | - Hwan-Ching Tai
- Department of Chemistry, National Taiwan University, Taipei, Taiwan
| | - Vincent Studer
- Interdisciplinary Institute for Neuroscience, University of Bordeaux, Bordeaux, France.,French National Center for Scientific Research (CNRS), Bordeaux, France
| | - Ming-Yuan Min
- Institute of Zoology, National Taiwan University, Taipei, Taiwan.,Graduate Institute of Brain and Mind Sciences, National Taiwan University, Taipei, Taiwan.,Neurobiology and Cognitive Science Center, National Taiwan University, Taipei, Taiwan
| | - Wen-Sung Lai
- Department of Psychology, National Taiwan University, Taipei, Taiwan.,Graduate Institute of Brain and Mind Sciences, National Taiwan University, Taipei, Taiwan.,Neurobiology and Cognitive Science Center, National Taiwan University, Taipei, Taiwan
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6
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Lin CH, Lane HY. Early Identification and Intervention of Schizophrenia: Insight From Hypotheses of Glutamate Dysfunction and Oxidative Stress. Front Psychiatry 2019; 10:93. [PMID: 30873052 PMCID: PMC6400883 DOI: 10.3389/fpsyt.2019.00093] [Citation(s) in RCA: 44] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/09/2018] [Accepted: 02/08/2019] [Indexed: 12/22/2022] Open
Abstract
Schizophrenia is a severe mental disorder which leads to functional deterioration. Early detection and intervention are vital for better prognosis. However, the diagnosis of schizophrenia still depends on clinical observation to date. Without reliable biomarkers, schizophrenia is difficult to detect in its early phase. Further, there is no approved medication for prodromal schizophrenia because current antipsychotics fail to show satisfactory efficacy and safety. Therefore, to develop an effective early diagnostic and therapeutic approach for schizophrenia, especially in its prodromal phase, is crucial. Glutamate signaling dysfunction and dysregulation of oxidative stress have been considered to play important roles in schizophrenic prodrome. The N-methyl-D-aspartate receptor (NMDAR) is one of three types of ionotropic glutamate receptors. In this article, we reviewed literature regarding NMDAR hypofunction, oxidative stress, and the linkage between both in prodromal schizophrenia. The efficacy of NMDAR enhancers such as D-amino acid oxidase inhibitor was addressed. Finally, we highlighted potential biomarkers related to NMDAR and oxidative stress regulation, and therefore suggested the strategies of early detection and intervention of prodromal schizophrenia. Future larger-scale studies combining biomarkers and novel drug development for early psychosis are warranted.
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Affiliation(s)
- Chieh-Hsin Lin
- Department of Psychiatry, Kaohsiung Chang Gung Memorial Hospital, Chang Gung University College of Medicine, Kaohsiung, Taiwan
- School of Medicine, Chang Gung University, Taoyuan, Taiwan
- Graduate Institute of Biomedical Sciences, China Medical University, Taichung, Taiwan
| | - Hsien-Yuan Lane
- Graduate Institute of Biomedical Sciences, China Medical University, Taichung, Taiwan
- Department of Psychiatry and Brain Disease Research Center, China Medical University Hospital, Taichung, Taiwan
- Department of Psychology, College of Medical and Health Sciences, Asia University, Taichung, Taiwan
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7
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Ketamine and pharmacological imaging: use of functional magnetic resonance imaging to evaluate mechanisms of action. Behav Pharmacol 2018; 28:610-622. [PMID: 29049083 DOI: 10.1097/fbp.0000000000000354] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Ketamine has been used as a pharmacological model for schizophrenia as subanesthetic infusions have been shown to produce temporary schizophrenia-like symptoms in healthy humans. More recently, ketamine has emerged as a potential treatment for multiple psychiatric disorders, including treatment-resistant depression and suicidal ideation. However, the mechanisms underlying both the psychotomimetic and the therapeutic effects of ketamine remain poorly understood. This review provides an overview of what is known of the neural mechanisms underlying the effects of ketamine and details what functional MRI studies have yielded at a systems level focused on brain circuitry. Multiple analytic approaches show that ketamine exerts robust and consistent effects at the whole-brain level. These effects are highly conserved across human and nonhuman primates, validating the use of nonhuman primate models for further investigations with ketamine. Regional analysis of brain functional connectivity suggests that the therapeutic potential of ketamine may be derived from a strengthening of executive control circuitry, making it an intriguing candidate for the treatment of drug abuse. There are still important questions about the mechanism of action and the therapeutic potential of ketamine that can be addressed using appropriate functional neuroimaging techniques.
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8
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Lin JC, Chan MH, Lee MY, Chen YC, Chen HH. N,N-dimethylglycine differentially modulates psychotomimetic and antidepressant-like effects of ketamine in mice. Prog Neuropsychopharmacol Biol Psychiatry 2016; 71:7-13. [PMID: 27296677 DOI: 10.1016/j.pnpbp.2016.06.002] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/28/2016] [Revised: 06/04/2016] [Accepted: 06/09/2016] [Indexed: 01/22/2023]
Abstract
Ketamine, a dissociative anesthetic, produces rapid and sustained antidepressant effects at subanesthtic doses. However, it still inevitably induces psychotomimetic side effects. N,N-dimethylglycine (DMG) is a derivative of the amino acid glycine and is used as a dietary supplement. Recently, DMG has been found acting at glycine binding site of the N-methyl-d-aspartate receptor (NMDAR). As blockade of NMDARs is one of the main mechanisms responsible for the action of ketamine on central nervous system, DMG might modulate the behavioral responses to ketamine. The present study determined the effects of DMG on the ketamine-induced psychotomimetic, anesthetic and antidepressant-like effects in mice. DMG pretreatment reversed the ketamine-induced locomotor hyperactivity and impairment in the rotarod performance, novel location and novel object recognition tests, and prepulse inhibition. In addition, DMG alone exhibited antidepressant-like effects in the forced swim test and produced additive effects when combined with ketamine. However, DMG did not affect ketamine-induced anesthesia. These results reveal that DMG could antagonize ketamine's psychotomimetic effects, yet produce additive antidepressant-like effects with ketamine, suggesting that DMG might have antipsychotic potential and be suitable as an add-on therapy to ketamine for patients with treatment-resistant depression.
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Affiliation(s)
- Jen-Cheng Lin
- Graduate Institute of Medical Sciences, National Defense Medical Center, Taipei, Taiwan
| | - Ming-Huan Chan
- Institute of Neuroscience, National Chengchi University, 64, Sec. 2, Zhinan Road, Wenshan District, Taipei 11605, Taiwan; Research Center for Mind, Brain, and Learning, National Chengchi University, 64, Sec. 2, Zhinan Road, Wenshan District, Taipei 11605, Taiwan
| | - Mei-Yi Lee
- Department of Pharmacology and Toxicology, Tzu Chi University, 701, Section 3, Chung-Yang Road, Hualien 97004, Taiwan
| | - Yi-Chyan Chen
- Graduate Institute of Medical Sciences, National Defense Medical Center, Taipei, Taiwan; School of Medicine, Tzu Chi University, 701, Section 3, Chung-Yang Road, Hualien 97004, Taiwan; Department of Psychiatry, Taipei Tzu Chi Hospital, Buddhist Tzu Chi Medical Foundation, New Taipei City, Taiwan.
| | - Hwei-Hsien Chen
- Graduate Institute of Medical Sciences, National Defense Medical Center, Taipei, Taiwan; Institute of Neuroscience, National Chengchi University, 64, Sec. 2, Zhinan Road, Wenshan District, Taipei 11605, Taiwan; Department of Pharmacology and Toxicology, Tzu Chi University, 701, Section 3, Chung-Yang Road, Hualien 97004, Taiwan; Center for Neuropsychiatric Research, National Health Research Institutes, 35 Keyan Road, Zhunan, Miaoli County 35053, Taiwan.
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9
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Betaine enhances antidepressant-like, but blocks psychotomimetic effects of ketamine in mice. Psychopharmacology (Berl) 2016; 233:3223-35. [PMID: 27363702 DOI: 10.1007/s00213-016-4359-x] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/14/2015] [Accepted: 06/13/2016] [Indexed: 01/26/2023]
Abstract
Ketamine is emerging as a new hope against depression, but ketamine-associated psychotomimetic effects limit its clinical use. An adjunct therapy along with ketamine to alleviate its adverse effects and even potentiate the antidepressant effects might be an alternative strategy. Betaine, a methyl derivative of glycine and a dietary supplement, has been shown to have antidepressant-like effects and to act like a partial agonist at the glycine site of N-methyl-D-aspartate receptors (NMDARs). Accordingly, betaine might have potential to be an adjunct to ketamine treatment for depression. The antidepressant-like effects of ketamine and betaine were evaluated by forced swimming test and novelty suppressed feeding test in mice. Both betaine and ketamine produced antidepressant-like effects. Furthermore, we determined the effects of betaine on ketamine-induced antidepressant-like and psychotomimetic behaviors, motor incoordination, hyperlocomotor activity, and anesthesia. The antidepressant-like responses to betaine combined with ketamine were stronger than their individual effects. In contrast, ketamine-induced impairments in prepulse inhibition, novel object recognition test, social interaction, and rotarod test were remarkably attenuated, whereas ketamine-induced hyperlocomotion and loss of righting reflex were not affected by betaine. These findings revealed that betaine could enhance the antidepressant-like effects, yet block the psychotomimetic effects of ketamine, suggesting that betaine can be considered as an add-on therapy to ketamine for treatment-resistant depression and suitable for the treatment of depressive symptoms in patients with schizophrenia.
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10
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Zhao J, Tao H, Xian W, Cai Y, Cheng W, Yin M, Liang G, Li K, Cui L, Zhao B. A Highly Selective Inhibitor of Glycine Transporter-1 Elevates the Threshold for Maximal Electroshock-Induced Tonic Seizure in Mice. Biol Pharm Bull 2016; 39:174-80. [DOI: 10.1248/bpb.b15-00501] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- Jianghao Zhao
- Institute of Neurology, Affiliated Hospital of Guangdong Medical University
- Guangdong Key Laboratory of Age-Related Cardiac and Cerebral Diseases, Affiliated Hospital of Guangdong Medical University
| | - Hua Tao
- Institute of Neurology, Affiliated Hospital of Guangdong Medical University
| | - Wenchuan Xian
- Institute of Neurology, Affiliated Hospital of Guangdong Medical University
| | - Yujie Cai
- Guangdong Key Laboratory of Age-Related Cardiac and Cerebral Diseases, Affiliated Hospital of Guangdong Medical University
| | - Wanwen Cheng
- Institute of Neurology, Affiliated Hospital of Guangdong Medical University
| | - Mingkang Yin
- Institute of Neurology, Affiliated Hospital of Guangdong Medical University
| | - Guocong Liang
- Institute of Neurology, Affiliated Hospital of Guangdong Medical University
| | - Keshen Li
- Guangdong Key Laboratory of Age-Related Cardiac and Cerebral Diseases, Affiliated Hospital of Guangdong Medical University
| | - Lili Cui
- Guangdong Key Laboratory of Age-Related Cardiac and Cerebral Diseases, Affiliated Hospital of Guangdong Medical University
| | - Bin Zhao
- Guangdong Key Laboratory of Age-Related Cardiac and Cerebral Diseases, Affiliated Hospital of Guangdong Medical University
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11
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Castner SA, Murthy NV, Ridler K, Herdon H, Roberts BM, Weinzimmer DP, Huang Y, Zheng MQ, Rabiner EA, Gunn RN, Carson RE, Williams GV, Laruelle M. Relationship between glycine transporter 1 inhibition as measured with positron emission tomography and changes in cognitive performances in nonhuman primates. Neuropsychopharmacology 2014; 39:2742-9. [PMID: 24487737 PMCID: PMC4200505 DOI: 10.1038/npp.2014.4] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/27/2012] [Revised: 11/04/2013] [Accepted: 12/13/2013] [Indexed: 01/22/2023]
Abstract
Several lines of evidence suggest that schizophrenia is associated with deficits in glutamatergic transmission at the N-methyl-d-aspartate (NMDA) receptors. Glycine is a NMDA receptor co-agonist, and extracellular levels of glycine are regulated in the forebrain by the glycine type-1 transporters (GlyT-1). GlyT-1 inhibitors elevate extracellular glycine and thus potentiate NMDA transmission. This mechanism represents a promising new avenue for the treatment of schizophrenia. Here, the recently introduced positron emission tomography radiotracer [11C]GSK931145 was used to quantify the relationship between occupancy of GlyT-1 by a GlyT-1 inhibitor, Org 25935, and its impact on spatial working memory performances in rhesus monkeys. The effect of Org 25935 on working memory was assessed both in control conditions and during a state of relative NMDA hypofunction induced by ketamine administration, at a dose selected for each animal to reduce task performance by about 50%. Under control conditions, Org 25935 had no effect on working memory at GlyT-1 occupancies lower than 75% and significantly impaired working memory at occupancies higher than 75%. Under ketamine conditions, Org 25935 reversed the deficit in working memory induced by ketamine and did so optimally in the 40-70% GlyT-1 occupancy range. The results confirm the efficacy of this mechanism to correct working memory deficits associated with NMDA hypofunction. These data also suggest the existence of an inverted-U dose-response curve in the potential therapeutic effect of this class of compounds.
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Affiliation(s)
- S A Castner
- Department of Psychiatry, Yale University School of Medicine, New Haven, CT, USA
| | - N V Murthy
- Neurosciences Centre for Excellence in Drug Discovery, GlaxoSmithKline, Harlow, UK
| | - K Ridler
- Clinical Imaging Centre, GlaxoSmithKline, Hammersmith Hospital–Imperial College, London, UK
| | - H Herdon
- Neurosciences Centre for Excellence in Drug Discovery, GlaxoSmithKline, Harlow, UK
| | - B M Roberts
- Department of Psychiatry, Yale University School of Medicine, New Haven, CT, USA
| | - D P Weinzimmer
- Department of Radiology, Yale University School of Medicine, New Haven, CT, USA
| | - Y Huang
- Department of Radiology, Yale University School of Medicine, New Haven, CT, USA
| | - M Q Zheng
- Department of Radiology, Yale University School of Medicine, New Haven, CT, USA
| | - E A Rabiner
- Clinical Imaging Centre, GlaxoSmithKline, Hammersmith Hospital–Imperial College, London, UK
| | - R N Gunn
- Clinical Imaging Centre, GlaxoSmithKline, Hammersmith Hospital–Imperial College, London, UK
| | - R E Carson
- Department of Radiology, Yale University School of Medicine, New Haven, CT, USA
| | - G V Williams
- Department of Psychiatry, Yale University School of Medicine, New Haven, CT, USA
| | - M Laruelle
- Department of Psychiatry, Yale University School of Medicine, New Haven, CT, USA,Neurosciences Centre for Excellence in Drug Discovery, GlaxoSmithKline, Harlow, UK,Department of Radiology, Yale University School of Medicine, New Haven, CT, USA,UCB Pharma, Braine-l'Alleud, Brussels, Belgium,UCB Pharma, Chemin du Foriest, Braine-l'Alleud 1420, Belgium, Tel: +1 914 316 0923, Fax: +322 386 2550, E-mail:
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Subanesthetic ketamine treatment promotes abnormal interactions between neural subsystems and alters the properties of functional brain networks. Neuropsychopharmacology 2014; 39:1786-98. [PMID: 24492765 PMCID: PMC4023152 DOI: 10.1038/npp.2014.26] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/05/2013] [Revised: 01/23/2014] [Accepted: 01/23/2014] [Indexed: 01/07/2023]
Abstract
Acute treatment with subanesthetic ketamine, a non-competitive N-methyl-D-aspartic acid (NMDA) receptor antagonist, is widely utilized as a translational model for schizophrenia. However, how acute NMDA receptor blockade impacts on brain functioning at a systems level, to elicit translationally relevant symptomatology and behavioral deficits, has not yet been determined. Here, for the first time, we apply established and recently validated topological measures from network science to brain imaging data gained from ketamine-treated mice to elucidate how acute NMDA receptor blockade impacts on the properties of functional brain networks. We show that the effects of acute ketamine treatment on the global properties of these networks are divergent from those widely reported in schizophrenia. Where acute NMDA receptor blockade promotes hyperconnectivity in functional brain networks, pronounced dysconnectivity is found in schizophrenia. We also show that acute ketamine treatment increases the connectivity and importance of prefrontal and thalamic brain regions in brain networks, a finding also divergent to alterations seen in schizophrenia. In addition, we characterize how ketamine impacts on bipartite functional interactions between neural subsystems. A key feature includes the enhancement of prefrontal cortex (PFC)-neuromodulatory subsystem connectivity in ketamine-treated animals, a finding consistent with the known effects of ketamine on PFC neurotransmitter levels. Overall, our data suggest that, at a systems level, acute ketamine-induced alterations in brain network connectivity do not parallel those seen in chronic schizophrenia. Hence, the mechanisms through which acute ketamine treatment induces translationally relevant symptomatology may differ from those in chronic schizophrenia. Future effort should therefore be dedicated to resolve the conflicting observations between this putative translational model and schizophrenia.
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Glycine transporters as novel therapeutic targets in schizophrenia, alcohol dependence and pain. Nat Rev Drug Discov 2014; 12:866-85. [PMID: 24172334 DOI: 10.1038/nrd3893] [Citation(s) in RCA: 154] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Glycine transporters are endogenous regulators of the dual functions of glycine, which acts as a classical inhibitory neurotransmitter at glycinergic synapses and as a modulator of neuronal excitation mediated by NMDA (N-methyl-D-aspartate) receptors at glutamatergic synapses. The two major subtypes of glycine transporters, GlyT1 and GlyT2, have been linked to the pathogenesis and/or treatment of central and peripheral nervous system disorders, including schizophrenia and related affective and cognitive disturbances, alcohol dependence, pain, epilepsy, breathing disorders and startle disease (also known as hyperekplexia). This Review examines the rationale for the therapeutic potential of GlyT1 and GlyT2 inhibition, and surveys the latest advances in the biology of glycine reuptake and transport as well as the drug discovery and clinical development of compounds that block glycine transporters.
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Atypical antipsychotic olanzapine reversed deficit on prepulse inhibition of the acoustic startle reflex produced by microinjection of dizocilpine (MK-801) into the inferior colliculus in rats. Behav Brain Res 2013; 257:77-82. [DOI: 10.1016/j.bbr.2013.09.018] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2013] [Revised: 09/03/2013] [Accepted: 09/07/2013] [Indexed: 12/15/2022]
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Mouri A, Nagai T, Ibi D, Yamada K. Animal models of schizophrenia for molecular and pharmacological intervention and potential candidate molecules. Neurobiol Dis 2013; 53:61-74. [DOI: 10.1016/j.nbd.2012.10.025] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2012] [Revised: 10/23/2012] [Accepted: 10/28/2012] [Indexed: 12/22/2022] Open
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Chan MH, Chung SS, Stoker AK, Markou A, Chen HH. Sarcosine attenuates toluene-induced motor incoordination, memory impairment, and hypothermia but not brain stimulation reward enhancement in mice. Toxicol Appl Pharmacol 2012; 265:158-65. [PMID: 23067721 DOI: 10.1016/j.taap.2012.10.004] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2012] [Revised: 10/03/2012] [Accepted: 10/05/2012] [Indexed: 12/22/2022]
Abstract
Toluene, a widely used and commonly abused organic solvent, produces various behavioral disturbances, including motor incoordination and cognitive impairment. Toluene alters the function of a large number of receptors and ion channels. Blockade of N-methyl-d-aspartate (NMDA) receptors has been suggested to play a critical role in toluene-induced behavioral manifestations. The present study determined the effects of various toluene doses on motor coordination, recognition memory, body temperature, and intracranial self-stimulation (ICSS) thresholds in mice. Additionally, the effects of sarcosine on the behavioral and physiological effects induced by toluene were evaluated. Sarcosine may reverse toluene-induced behavioral manifestations by acting as an NMDA receptor co-agonist and by inhibiting the effects of the type I glycine transporter (GlyT1). Mice were treated with toluene alone or combined with sarcosine pretreatment and assessed for rotarod performance, object recognition memory, rectal temperature, and ICSS thresholds. Toluene dose-dependently induced motor incoordination, recognition memory impairment, and hypothermia and lowered ICSS thresholds. Sarcosine pretreatment reversed toluene-induced changes in rotarod performance, novel object recognition, and rectal temperature but not ICSS thresholds. These findings suggest that the sarcosine-induced potentiation of NMDA receptors may reverse motor incoordination, memory impairment, and hypothermia but not the enhancement of brain stimulation reward function associated with toluene exposure. Sarcosine may be a promising compound to prevent acute toluene intoxications by occupational or intentional exposure.
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Affiliation(s)
- Ming-Huan Chan
- Department of Pharmacology and Toxicology, Tzu Chi University, Hualien, Taiwan
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Characterization of the neuropsychological phenotype of glycine N-methyltransferase-/- mice and evaluation of its responses to clozapine and sarcosine treatments. Eur Neuropsychopharmacol 2012; 22:596-606. [PMID: 22264868 DOI: 10.1016/j.euroneuro.2011.12.007] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/17/2011] [Revised: 11/29/2011] [Accepted: 12/16/2011] [Indexed: 02/06/2023]
Abstract
Glycine N-methyltransferase (GNMT) affects cellular methylation capacity through regulating the ratio between S-adenosylmethionine (SAM) and S-adenosylhomocysteine (SAH). The product of its enzymatic reaction-sarcosine has antipsychotic effect in patients with schizophrenia. In this study, through RT-PCR and immunohistochemical staining, we demonstrated that GNMT expressed in various neurons located in the cerebral cortex, hippocampus, substantia nigra and cerebellum. Compared to the wild-type mice, Gnmt-/- mice had significantly lower level of sarcosine in the cerebral cortex. Real-time PCR identified genes involved in the methionine metabolism (Dnmt1 and Dnmt3a), ErbB (Nrg1 and ErbB4) and mTOR (Akt2, S6, S6k1 and S6k2) signaling pathways were dysregulated significantly in the cortex of Gnmt-/- mice. Acoustic startle reflex test demonstrated that Gnmt-/- mice had significantly lower level of prepulse inhibition and the deficit was ameliorated through clozapine or sarcosine treatment. Furthermore, liver-specific-human-GNMT transgenic with Gnmt-/- (Tg-GNMT/Gnmt-/-) mice were used to rule out that the phenotype was due to abnormal liver function. In summary, the neuropsychological abnormalities found in Gnmt-/- mice may represent an endophenotype of schizophrenia. GNMT plays an important role in maintaining normal physiological function of brain and Tg-GNMT/Gnmt-/- mice are useful models for development of therapeutics for patients with schizophrenia.
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Targeting glutamate system for novel antipsychotic approaches: Relevance for residual psychotic symptoms and treatment resistant schizophrenia. Eur J Pharmacol 2012; 682:1-11. [DOI: 10.1016/j.ejphar.2012.02.033] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2011] [Revised: 02/08/2012] [Accepted: 02/15/2012] [Indexed: 01/04/2023]
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Páleníček T, Fujáková M, Brunovský M, Balíková M, Horáček J, Gorman I, Tylš F, Tišlerová B, Soš P, Bubeníková-Valešová V, Höschl C, Krajča V. Electroencephalographic spectral and coherence analysis of ketamine in rats: correlation with behavioral effects and pharmacokinetics. Neuropsychobiology 2011; 63:202-18. [PMID: 21422767 DOI: 10.1159/000321803] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/26/2010] [Accepted: 09/27/2010] [Indexed: 11/19/2022]
Abstract
AIMS This study was designed to evaluate the changes in EEG power spectra and EEG coherence in a ketamine model of psychosis in rats. Analyses of behavioral measurements--locomotion and sensorimotor gating--and the pharmacokinetics of ketamine and norketamine were also conducted. METHODS Ketamine and norketamine levels in rat sera and brains were analyzed by gas chromatography-mass spectrometry after ketamine 30 mg/kg (i.p.). Ketamine 9 and 30 mg/kg (i.p.) were used in the behavioral and EEG experiments. Locomotor effects in an open field test and deficits in prepulse inhibition of acoustic startle reaction (PPI ASR) were evaluated in the behavioral experiments. EEG signals were simultaneously recorded from 12 implanted active electrodes; subsequently, an EEG power spectral and coherence analysis was performed. RESULTS Ketamine had a rapid penetration into the brain; the peak concentrations of the drug were reached within 15 min after administration. Ketamine induced marked hyperlocomotion and deficits in the PPI ASR. EEG spectral analysis mainly showed increases in EEG power as well as coherence. These were most robust at 10-15 min after the administration and influenced all parts of the spectrum with ketamine 30 mg/kg. CONCLUSIONS Ketamine at behaviorally active doses induces a robust increase in EEG power spectra and coherence. The maximum levels of change correlated with the kinetics of ketamine.
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Nikiforuk A, Kos T, Rafa D, Behl B, Bespalov A, Popik P. Blockade of glycine transporter 1 by SSR-504734 promotes cognitive flexibility in glycine/NMDA receptor-dependent manner. Neuropharmacology 2011; 61:262-7. [DOI: 10.1016/j.neuropharm.2011.04.010] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2010] [Revised: 04/05/2011] [Accepted: 04/08/2011] [Indexed: 10/18/2022]
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Singer P, Boison D, Möhler H, Feldon J, Yee BK. Modulation of sensorimotor gating in prepulse inhibition by conditional brain glycine transporter 1 deletion in mice. Eur Neuropsychopharmacol 2011; 21:401-13. [PMID: 20647165 PMCID: PMC2980791 DOI: 10.1016/j.euroneuro.2010.06.014] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/20/2009] [Revised: 06/21/2010] [Accepted: 06/23/2010] [Indexed: 01/07/2023]
Abstract
Inhibition of glycine transporter 1 (GlyT1) augments N-methyl-D-aspartate receptor (NMDAR)-mediated transmission and represents a potential antipsychotic drug target according to the NMDAR hypofunction hypothesis of schizophrenia. Preclinical evaluation of GlyT1 inhibiting drugs using the prepulse inhibition (PPI) test, however, has yielded mixed outcomes. Here, we tested for the first time the impact of two conditional knockouts of GlyT1 on PPI expression. Complete deletion of GlyT1 in the cerebral cortices confers resistance to PPI disruption induced by the NMDAR blocker MK-801 (0.2mg/kg, i.p.) without affecting PPI expression in unchallenged conditions. In contrast, restricting GlyT1 deletion to neurons in forebrain including the striatum significantly attenuated PPI, and the animals remained sensitive to the PPI-disruptive effect of MK-801 at the same dose. These results demonstrate in mice that depending on the regional and/or cell-type specificity, deletion of the GlyT1 gene could yield divergent effects on PPI.
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Affiliation(s)
- Philipp Singer
- Laboratory of Behavioural Neurobiology, Federal Institute of Technology Zurich, Schorenstrasse 16, CH-8603 Schwerzenbach, Switzerland
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Möhler H, Boison D, Singer P, Feldon J, Pauly-Evers M, Yee BK. Glycine transporter 1 as a potential therapeutic target for schizophrenia-related symptoms: evidence from genetically modified mouse models and pharmacological inhibition. Biochem Pharmacol 2011; 81:1065-77. [PMID: 21333635 DOI: 10.1016/j.bcp.2011.02.003] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2010] [Revised: 02/09/2011] [Accepted: 02/09/2011] [Indexed: 12/18/2022]
Abstract
Schizophrenia is characterized by positive symptoms such as hallucinations, negative symptoms such as blunted affect, and symptoms of cognitive deficiency such as deficits in working memory and selective attention. N-methyl-d-aspartate receptor (NMDAR) hypofunction has been implicated in all three pathophysiological aspects of the disease. Due to the severe side effects of direct NMDAR agonists, targeting the modulatory co-agonist glycine-B site of the NMDAR is considered to be a promising strategy to ameliorate NMDAR hypofunction. To assess the antipsychotic and pro-cognitive potential of this approach, we examine the strategies designed to enhance glycine-B site occupancy through glycine transporter 1 (GlyT1) blockade. Among the existing transgenic mouse models with GlyT1 deficits, the one specifically targeting forebrain neuronal GlyT1 has yielded the most promising data on cognitive enhancement. Parallel advances in the pharmacology of GlyT1 inhibition point not only to an enhancement of attention, learning and memory but also include suggestions of mood enhancing effects that might be valuable for treating negative symptoms. Thus, interventions at GlyT1 are highly effective in modifying multiple brain functions, and dissection of their respective mechanisms is expected to further maximize their therapeutic potential for human mental diseases.
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Affiliation(s)
- Hanns Möhler
- Institute of Pharmacology, University and ETH Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland.
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Nakato K, Harada K, Tobe T, Yamaji T, Takakura S. [Stimulating glutamatergic neurons as a potential novel therapeutic avenue for schizophrenia]. Nihon Yakurigaku Zasshi 2010; 136:128-32. [PMID: 20838012 DOI: 10.1254/fpj.136.128] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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Chen HH, Stoker A, Markou A. The glutamatergic compounds sarcosine and N-acetylcysteine ameliorate prepulse inhibition deficits in metabotropic glutamate 5 receptor knockout mice. Psychopharmacology (Berl) 2010; 209:343-50. [PMID: 20217053 PMCID: PMC2855017 DOI: 10.1007/s00213-010-1802-2] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/23/2009] [Accepted: 02/11/2010] [Indexed: 11/11/2022]
Abstract
RATIONALE Mice lacking metabotropic glutamate receptors 5 (mGluR5) exhibit reduced glutamatergic function and behavioral abnormalities, including deficits in prepulse inhibition (PPI) of the startle response that may be relevant to schizophrenia. Thus, these mice are an animal model that may be used for preclinical evaluation of potentially new classes of antipsychotic compounds. Recent clinical studies have suggested several compounds that modulate glutamatergic transmission through distinct mechanisms, such as potentiation of the N-methyl-D: -aspartate (NMDA) receptor glycine site, activation of group II mGluR, and activation of glutamate-cysteine antiporters, as being efficacious in the treatment of schizophrenia. OBJECTIVES The aim of this work is to evaluate the effects of sarcosine (a selective inhibitor of the glycine transporter 1 [GlyT1]), LY379268 (a group II mGluR agonist), and N-acetylcysteine (a cysteine prodrug that indirectly activates cystine-glutamate antiporters to increase glutamate levels in the extrasynaptic space) on PPI deficits in mGluR5 knockout mice. RESULTS Sarcosine and N-acetylcysteine, but not LY379268, ameliorated PPI deficits in mGluR5 knockout mice. The ability of N-acetylcysteine to restore PPI deficits was not blocked by the group II mGluR antagonist LY341495, indicating that the effects of N-acetylcysteine were not attributable to activation of group II mGluRs by glutamate. CONCLUSIONS These findings provide evidence that the interactions between mGluR5 and NMDA receptors are involved in the regulation of PPI and suggest that activation of glutamate receptors, other than group II receptors, by increased endogenous glutamate transmission, may ameliorate the behavioral abnormalities associated with mGluR5 deficiency.
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Affiliation(s)
- Hwei-Hsien Chen
- Institute of Pharmacology and Toxicology, Tzu Chi University, 701, Section 3, Chung-Yang Road, Hualien, 970, Taiwan.
| | - Astrid Stoker
- Department of Psychiatry, School of Medicine, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0603 USA ,Department of Psychopharmacology, Utrecht Institute of Pharmaceutical Science, University of Utrecht, Utrecht, The Netherlands
| | - Athina Markou
- Department of Psychiatry, School of Medicine, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0603 USA
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