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Chen L, Liu L, Ge Z, Yang X, Yang P, Li L. Perceptual spatial position induces the attentional enhancement of prepulse inhibition and its neural mechanism. Hear Res 2022; 420:108511. [DOI: 10.1016/j.heares.2022.108511] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/04/2021] [Revised: 04/14/2022] [Accepted: 04/23/2022] [Indexed: 11/04/2022]
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Thomson AM. Circuits and Synapses: Hypothesis, Observation, Controversy and Serendipity - An Opinion Piece. Front Neural Circuits 2021; 15:732315. [PMID: 34602985 PMCID: PMC8482872 DOI: 10.3389/fncir.2021.732315] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2021] [Accepted: 08/11/2021] [Indexed: 11/29/2022] Open
Abstract
More than a century of dedicated research has resulted in what we now know, and what we think we know, about synapses and neural circuits. This piece asks to what extent some of the major advances - both theoretical and practical - have resulted from carefully considered theory, or experimental design: endeavors that aim to address a question, or to refute an existing hypothesis. It also, however, addresses the important part that serendipity and chance have played. There are cases where hypothesis driven research has resulted in important progress. There are also examples where a hypothesis, a model, or even an experimental approach - particularly one that seems to provide welcome simplification - has become so popular that it becomes dogma and stifles advance in other directions. The nervous system rejoices in complexity, which should neither be ignored, nor run from. The emergence of testable "rules" that can simplify our understanding of neuronal circuits has required the collection of large amounts of data that were difficult to obtain. And although those collecting these data have been criticized for not advancing hypotheses while they were "collecting butterflies," the beauty of the butterflies always enticed us toward further exploration.
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Affiliation(s)
- Alex M. Thomson
- Department of Pharmacology, UCL School of Pharmacy, London, United Kingdom
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Sherwood MW, Oliet SHR, Panatier A. NMDARs, Coincidence Detectors of Astrocytic and Neuronal Activities. Int J Mol Sci 2021; 22:7258. [PMID: 34298875 PMCID: PMC8307462 DOI: 10.3390/ijms22147258] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2021] [Revised: 06/30/2021] [Accepted: 06/30/2021] [Indexed: 12/18/2022] Open
Abstract
Synaptic plasticity is an extensively studied cellular correlate of learning and memory in which NMDARs play a starring role. One of the most interesting features of NMDARs is their ability to act as a co-incident detector. It is unique amongst neurotransmitter receptors in this respect. Co-incident detection is possible because the opening of NMDARs requires membrane depolarisation and the binding of glutamate. Opening of NMDARs also requires a co-agonist. Although the dynamic regulation of glutamate and membrane depolarization have been well studied in coincident detection, the role of the co-agonist site is unexplored. It turns out that non-neuronal glial cells, astrocytes, regulate co-agonist availability, giving them the ability to influence synaptic plasticity. The unique morphology and spatial arrangement of astrocytes at the synaptic level affords them the capacity to sample and integrate information originating from unrelated synapses, regardless of any pre-synaptic and post-synaptic commonality. As astrocytes are classically considered slow responders, their influence at the synapse is widely recognized as modulatory. The aim herein is to reconsider the potential of astrocytes to participate directly in ongoing synaptic NMDAR activity and co-incident detection.
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Affiliation(s)
- Mark W. Sherwood
- University of Bordeaux, INSERM, Neurocentre Magendie, U1215, F-3300 Bordeaux, France;
| | | | - Aude Panatier
- University of Bordeaux, INSERM, Neurocentre Magendie, U1215, F-3300 Bordeaux, France;
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Meng Q, Ding Y, Chen L, Li L. The medial agranular cortex mediates attentional enhancement of prepulse inhibition of the startle reflex. Behav Brain Res 2020; 383:112511. [DOI: 10.1016/j.bbr.2020.112511] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2019] [Revised: 01/15/2020] [Accepted: 01/24/2020] [Indexed: 12/12/2022]
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Yao L, Wang Z, Deng D, Yan R, Ju J, Zhou Q. The impact of D-cycloserine and sarcosine on in vivo frontal neural activity in a schizophrenia-like model. BMC Psychiatry 2019; 19:314. [PMID: 31653237 PMCID: PMC6814999 DOI: 10.1186/s12888-019-2306-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/17/2019] [Accepted: 09/30/2019] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND N-methyl-D-aspartate receptor (NMDAR) hypofunction has been proposed to underlie the pathogenesis of schizophrenia. Specifically, reduced function of NMDARs leads to altered balance between excitation and inhibition which further drives neural network malfunctions. Clinical studies suggested that NMDAR modulators (glycine, D-serine, D-cycloserine and glycine transporter inhibitors) may be beneficial in treating schizophrenia patients. Preclinical evidence also suggested that these NMDAR modulators may enhance synaptic NMDAR function and synaptic plasticity in brain slices. However, an important issue that has not been addressed is whether these NMDAR modulators modulate neural activity/spiking in vivo. METHODS By using in vivo calcium imaging and single unit recording, we tested the effect of D-cycloserine, sarcosine (glycine transporter 1 inhibitor) and glycine, on schizophrenia-like model mice. RESULTS In vivo neural activity is significantly higher in the schizophrenia-like model mice, compared to control mice. D-cycloserine and sarcosine showed no significant effect on neural activity in the schizophrenia-like model mice. Glycine induced a large reduction in movement in home cage and reduced in vivo brain activity in control mice which prevented further analysis of its effect in schizophrenia-like model mice. CONCLUSIONS We conclude that there is no significant impact of the tested NMDAR modulators on neural spiking in the schizophrenia-like model mice.
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Affiliation(s)
- Lulu Yao
- 0000 0001 2256 9319grid.11135.37School of Chemical Biology and Biotechnology, Peking University Shenzhen Graduate School, Shenzhen, 518055 China
| | - Zongliang Wang
- 0000 0001 2256 9319grid.11135.37School of Chemical Biology and Biotechnology, Peking University Shenzhen Graduate School, Shenzhen, 518055 China
| | - Di Deng
- 0000 0001 2256 9319grid.11135.37School of Chemical Biology and Biotechnology, Peking University Shenzhen Graduate School, Shenzhen, 518055 China
| | - Rongzhen Yan
- 0000 0001 2256 9319grid.11135.37School of Chemical Biology and Biotechnology, Peking University Shenzhen Graduate School, Shenzhen, 518055 China
| | - Jun Ju
- 0000 0001 2256 9319grid.11135.37School of Chemical Biology and Biotechnology, Peking University Shenzhen Graduate School, Shenzhen, 518055 China
| | - Qiang Zhou
- School of Chemical Biology and Biotechnology, Peking University Shenzhen Graduate School, Shenzhen, 518055, China. .,State Key Laboratory of Chemical Oncogenomics, Key Laboratory of Chemical Genomics, Peking University Shenzhen Graduate School, Shenzhen, 518055, China.
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Destreel G, Seutin V, Engel D. Subsaturation of the N-methyl-D-aspartate receptor glycine site allows the regulation of bursting activity in juvenile rat nigral dopamine neurons. Eur J Neurosci 2019; 50:3454-3471. [PMID: 31206829 DOI: 10.1111/ejn.14491] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2019] [Revised: 05/23/2019] [Accepted: 06/10/2019] [Indexed: 01/09/2023]
Abstract
The activation of N-methyl-D-aspartate receptors (NMDARs) in substantia nigra pars compacta (SNc) dopamine (DA) cells is central to generate the bursting activity, a phasic signal linked to DA-related behaviours via the change in postsynaptic DA release. NMDARs are recruited during excitatory synaptic transmission by glutamate release, but the glycine site level of occupancy of these receptors during basal action potential-dependent activity is not known for SNc DA neurons. We explored NMDAR-dependent signals during exogenous applications of co-agonists in midbrain slices from juvenile rats. We found that both glycine and D-serine strengthened the NMDAR-dependent component of excitatory postsynaptic currents (EPSCs) in a concentration-dependent manner. EPSCs were also increased by endogenous glycine via the blockade of the glycine transport. The glycine site of NMDARs contributing to synaptic transmission is therefore subsaturated. The behaviourally relevant burst firing was more sensitive to exogenous D-serine and endogenous glycine than to exogenous glycine. The mechanisms regulating the availability of the co-agonists exert consequently a critical influence on the excitability of DA neurons via NMDARs. The modulation of the phasic firing in DA neurons by ambient NMDAR co-agonists may be important for nigral information processing and downstream motor-related behaviour.
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Affiliation(s)
- Geoffrey Destreel
- GIGA-Neurosciences, Neurophysiology Group, University of Liege, Liege, Belgium
| | - Vincent Seutin
- GIGA-Neurosciences, Neurophysiology Group, University of Liege, Liege, Belgium
| | - Dominique Engel
- GIGA-Neurosciences, Neurophysiology Group, University of Liege, Liege, Belgium
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Insights on current and novel antipsychotic mechanisms from the MAM model of schizophrenia. Neuropharmacology 2019; 163:107632. [PMID: 31077730 DOI: 10.1016/j.neuropharm.2019.05.009] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2018] [Revised: 04/25/2019] [Accepted: 05/07/2019] [Indexed: 12/18/2022]
Abstract
Current antipsychotic drugs (APDs) act on D2 receptors, and preclinical studies demonstrate that repeated D2 antagonist administration downregulates spontaneously active DA neurons by producing overexcitation-induced inactivation of firing (depolarization block). Animal models of schizophrenia based on the gestational MAM administration produces offspring with adult phenotypes consistent with schizophrenia, including ventral hippocampal hyperactivity and a DA neuron overactivity. The MAM model reveals that APDs act differently in a hyperdopamineregic system compared to a normal one, including rapid onset of depolarization block in response to acute D2 antagonist administration and downregulation of DA neuron population activity following acute and repeated D2 partial agonist administration, none of which are observed in normal rats. Novel target compounds have been developed based on the theory that glutamatergic dysfunction is central to schizophrenia pathology. Despite showing promise in preclinical research, none of the novel drugs succeeded in clinical trials. However, preclinical research is generally performed in normal, drug-naïve rats, whereas models with disease-relevant pathology and prior APD exposure may improve the predictive validity of preclinical research. Indeed, in MAM rats, chronic D2 antagonist treatment leads to persistent DA supersensitivity that interferes with the response to drugs that target upstream pathology. Moreover, MAM rats revealed that the peri-pubertal period is a stress-sensitive window that can be targeted to prevent the development of MAM pathology in adulthood. Neurodevelopmental models, such as the MAM model, can thus be used to test potential pharmacotherapies that may be able to treat schizophrenia in early stages of the disease. This article is part of the issue entitled 'Special Issue on Antipsychotics'.
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Altered mRNA expressions for N-methyl-D-aspartate receptor-related genes in WBC of patients with major depressive disorder. J Affect Disord 2019; 245:1119-1125. [PMID: 30699855 DOI: 10.1016/j.jad.2018.12.016] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/31/2018] [Revised: 11/27/2018] [Accepted: 12/08/2018] [Indexed: 01/06/2023]
Abstract
OBJECTIVE Major depressive disorder (MDD) is a complex mental disorder. The lack of well-established biomarkers hinders its diagnosis, treatment, and new-drug development. N-methyl-D-aspartate receptor (NMDAR) dysfunction has been implicated in the pathogenesis of MDD. This study examined whether expressions of the NMDAR-related genes are characteristic of MDD. METHODS Expressions of NMDAR-related genes including SRR, SHMT2, PSAT1, GCAT, GAD1, SLC1A4, NRG1 and COMT in peripheral WBCs of 110 patients with MDD (25 drug-naïve, 21 drug-free, and 64 medicated patients) and 125 healthy individuals were measured using quantitative PCR. RESULTS The mRNA expression levels of SRR, PSAT1, GCAT, GAD1, NRG1 and COMT were significantly different among the four groups (all p < 0.05). For drug-naïve patients, the ΔΔCT values of SRR, PSAT1, GCAT, GAD1, and NRG1 mRNA expressions were significantly different from those in healthy individuals (all p < 0.05). The ROC analysis of the ΔΔCT values of the target genes for differentiating drug-naïve patients from healthy controls showed an excellent sensitivity (0.960) and modest specificity (0.640) (AUC = 0.889). Drug-free and medicated patients obtained less favorable AUC values while compared to healthy controls. The results for the age- and sex-matched cohort were similar to those of the unmatched cohort. CONCLUSIONS This is the first study demonstrating that the peripheral mRNA expression levels of NMDAR-related genes may be altered in patients with MDD, especially drug-naïve individuals. The finding supports the NMDAR hypothesis of depression. Whether mRNA expresssion of NMDAR-related genes could serve as a potential biomarker of MDD deserves further investigations.
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Chi-Castañeda D, Ortega A. Glial Cells in the Genesis and Regulation of Circadian Rhythms. Front Physiol 2018; 9:88. [PMID: 29483880 PMCID: PMC5816069 DOI: 10.3389/fphys.2018.00088] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2017] [Accepted: 01/26/2018] [Indexed: 12/26/2022] Open
Abstract
Circadian rhythms are biological oscillations with a period of ~24 h. These rhythms are orchestrated by a circadian timekeeper in the suprachiasmatic nucleus of the hypothalamus, the circadian "master clock," which exactly adjusts clock outputs to solar time via photic synchronization. At the molecular level, circadian rhythms are generated by the interaction of positive and negative feedback loops of transcriptional and translational processes of the so-called "clock genes." A large number of clock genes encode numerous proteins that regulate their own transcription and that of other genes, collectively known as "clock-controlled genes." In addition to the sleep/wake cycle, many cellular processes are regulated by circadian rhythms, including synaptic plasticity in which an exquisite interplay between neurons and glial cells takes place. In particular, there is compelling evidence suggesting that glial cells participate in and regulate synaptic plasticity in a circadian fashion, possibly representing the missing cellular and physiological link between circadian rhythms with learning and cognition processes. Here we review recent studies in support of this hypothesis, focusing on the interplay between glial cells, synaptic plasticity, and circadian rhythmogenesis.
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Affiliation(s)
- Donají Chi-Castañeda
- Laboratorio de Neurotoxicología, Departamento de Toxicología, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Ciudad de Mexico, Mexico.,Soluciones para un México Verde S.A. de C.V., Ciudad de Mexico, Mexico
| | - Arturo Ortega
- Laboratorio de Neurotoxicología, Departamento de Toxicología, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Ciudad de Mexico, Mexico
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Astrocytes as Pharmacological Targets in the Treatment of Schizophrenia. HANDBOOK OF BEHAVIORAL NEUROSCIENCE 2016. [DOI: 10.1016/b978-0-12-800981-9.00025-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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Yagi H, Nagano T, Xie MJ, Ikeda H, Kuroda K, Komada M, Iguchi T, Tariqur RM, Morikubo S, Noguchi K, Murase K, Okabe M, Sato M. Filamin A-interacting protein (FILIP) is a region-specific modulator of myosin 2b and controls spine morphology and NMDA receptor accumulation. Sci Rep 2014; 4:6353. [PMID: 25220605 PMCID: PMC4163676 DOI: 10.1038/srep06353] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2014] [Accepted: 08/26/2014] [Indexed: 12/14/2022] Open
Abstract
Learning and memory depend on morphological and functional changes to neural spines. Non-muscle myosin 2b regulates actin dynamics downstream of long-term potentiation induction. However, the mechanism by which myosin 2b is regulated in the spine has not been fully elucidated. Here, we show that filamin A-interacting protein (FILIP) is involved in the control of neural spine morphology and is limitedly expressed in the brain. FILIP bound near the ATPase domain of non-muscle myosin heavy chain IIb, an essential component of myosin 2b, and modified the function of myosin 2b by interfering with its actin-binding activity. In addition, FILIP altered the subcellular distribution of myosin 2b in spines. Moreover, subunits of the NMDA receptor were differently distributed in FILIP-expressing neurons, and excitation propagation was altered in FILIP-knockout mice. These results indicate that FILIP is a novel, region-specific modulator of myosin 2b.
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Affiliation(s)
- Hideshi Yagi
- 1] Division of Cell Biology and Neuroscience, Department of Morphological and Physiological Sciences, Faculty of Medical Sciences, University of Fukui, Fukui 910-1193, Japan [2] Research and Education Program for Life Science, University of Fukui, Fukui 910-8507, Japan [3] Department of Anatomy and Neuroscience, Hyogo College of Medicine, Hyogo 663-8501, Japan
| | - Takashi Nagano
- Division of Cell Biology and Neuroscience, Department of Morphological and Physiological Sciences, Faculty of Medical Sciences, University of Fukui, Fukui 910-1193, Japan
| | - Min-Jue Xie
- 1] Division of Cell Biology and Neuroscience, Department of Morphological and Physiological Sciences, Faculty of Medical Sciences, University of Fukui, Fukui 910-1193, Japan [2] Research and Education Program for Life Science, University of Fukui, Fukui 910-8507, Japan
| | - Hiroshi Ikeda
- 1] Research and Education Program for Life Science, University of Fukui, Fukui 910-8507, Japan [2] Department of Human and Artificial Intelligence Systems, Faculty of Engineering, University of Fukui, Fukui 910-8507, Japan
| | - Kazuki Kuroda
- 1] Division of Cell Biology and Neuroscience, Department of Morphological and Physiological Sciences, Faculty of Medical Sciences, University of Fukui, Fukui 910-1193, Japan [2] Research and Education Program for Life Science, University of Fukui, Fukui 910-8507, Japan
| | - Munekazu Komada
- 1] Division of Cell Biology and Neuroscience, Department of Morphological and Physiological Sciences, Faculty of Medical Sciences, University of Fukui, Fukui 910-1193, Japan [2] Research and Education Program for Life Science, University of Fukui, Fukui 910-8507, Japan
| | - Tokuichi Iguchi
- 1] Division of Cell Biology and Neuroscience, Department of Morphological and Physiological Sciences, Faculty of Medical Sciences, University of Fukui, Fukui 910-1193, Japan [2] Research and Education Program for Life Science, University of Fukui, Fukui 910-8507, Japan [3] Department of Anatomy and Neuroscience, Graduate School of Medicine, Osaka University, Osaka 565-0871, Japan
| | - Rahman M Tariqur
- Division of Cell Biology and Neuroscience, Department of Morphological and Physiological Sciences, Faculty of Medical Sciences, University of Fukui, Fukui 910-1193, Japan
| | - Soichi Morikubo
- 1] Division of Cell Biology and Neuroscience, Department of Morphological and Physiological Sciences, Faculty of Medical Sciences, University of Fukui, Fukui 910-1193, Japan [2] Division of Ophthalmology, Department of Sensory and Locomotor Medicine, Faculty of Medical Sciences, University of Fukui, Fukui 910-1193, Japan
| | - Koichi Noguchi
- Department of Anatomy and Neuroscience, Hyogo College of Medicine, Hyogo 663-8501, Japan
| | - Kazuyuki Murase
- 1] Research and Education Program for Life Science, University of Fukui, Fukui 910-8507, Japan [2] Department of Human and Artificial Intelligence Systems, Faculty of Engineering, University of Fukui, Fukui 910-8507, Japan
| | - Masaru Okabe
- Department of Experimental Genome Research, Genome Information Research Center, Osaka University, Osaka 565-0871, Japan
| | - Makoto Sato
- 1] Division of Cell Biology and Neuroscience, Department of Morphological and Physiological Sciences, Faculty of Medical Sciences, University of Fukui, Fukui 910-1193, Japan [2] Research and Education Program for Life Science, University of Fukui, Fukui 910-8507, Japan [3] Research Center for Child Mental Development, University of Fukui, Fukui 910-1193, Japan [4] United Graduate School of Child Development, Osaka University, Kanazawa University, Hamamatsu University School of Medicine, Chiba University and University of Fukui, Osaka 565-0871, Japan [5] Department of Anatomy and Neuroscience, Graduate School of Medicine, Osaka University, Osaka 565-0871, Japan
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Glycine modulates membrane potential, cell volume, and phagocytosis in murine microglia. Amino Acids 2014; 46:1907-17. [PMID: 24760586 DOI: 10.1007/s00726-014-1745-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2013] [Accepted: 04/05/2014] [Indexed: 12/19/2022]
Abstract
Phagocytes form engulfment pseudopodia at the contact area with their target particle by a process resembling cell volume (CV) regulatory mechanisms. We evaluated whether the osmoregulatory active neutral amino acid glycine, which contributes to CV regulation via activation of sodium-dependent neutral amino acid transporters (SNATs) improves phagocytosis in isotonic and hypertonic conditions in the murine microglial cell line BV-2 and primary microglial cells (pMG). In BV-2 cells and pMG, RT-PCR analysis revealed expression of SNATs (Slc38a1, Slc38a2), but not of GlyRs (Glra1-4). In BV-2 cells, glycine (5 mM) led to a rapid Na(+)-dependent depolarization of membrane potential (V mem). Furthermore, glycine increased CV by about 9%. Visualizing of phagocytosis of polystyrene microspheres by scanning electron microscopy revealed that glycine (1 mM) increased the number of BV-2 cells containing at least one microsphere by about 13%. Glycine-dependent increase in phagocytosis was suppressed by the SNAT inhibitor α-(methylamino)isobutyric acid (MeAIB), by replacing extracellular Na(+) with choline, and under hypertonic conditions, but not by the GlyR antagonist strychnine or the GlyR agonist taurine. Interestingly, hypertonicity-induced suppression of phagocytosis was rescued by glycine. These findings demonstrate that glycine increases phagocytosis in iso- and hypertonic conditions by activation of SNATs.
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Cho T, Ryu JK, Taghibiglou C, Ge Y, Chan AW, Liu L, Lu J, McLarnon JG, Wang YT. Long-term potentiation promotes proliferation/survival and neuronal differentiation of neural stem/progenitor cells. PLoS One 2013; 8:e76860. [PMID: 24146937 PMCID: PMC3798289 DOI: 10.1371/journal.pone.0076860] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2013] [Accepted: 08/28/2013] [Indexed: 11/19/2022] Open
Abstract
Neural stem cell (NSC) replacement therapy is considered a promising cell replacement therapy for various neurodegenerative diseases. However, the low rate of NSC survival and neurogenesis currently limits its clinical potential. Here, we examined if hippocampal long-term potentiation (LTP), one of the most well characterized forms of synaptic plasticity, promotes neurogenesis by facilitating proliferation/survival and neuronal differentiation of NSCs. We found that the induction of hippocampal LTP significantly facilitates proliferation/survival and neuronal differentiation of both endogenous neural progenitor cells (NPCs) and exogenously transplanted NSCs in the hippocampus in rats. These effects were eliminated by preventing LTP induction by pharmacological blockade of the N-methyl-D-aspartate glutamate receptor (NMDAR) via systemic application of the receptor antagonist, 3-[(R)-2-carboxypiperazin-4-yl]-propyl-1-phosphonic acid (CPP). Moreover, using a NPC-neuron co-culture system, we were able to demonstrate that the LTP-promoted NPC neurogenesis is at least in part mediated by a LTP-increased neuronal release of brain-derived neurotrophic factor (BDNF) and its consequent activation of tropomysosin receptor kinase B (TrkB) receptors on NSCs. Our results indicate that LTP promotes the neurogenesis of both endogenous and exogenously transplanted NSCs in the brain. The study suggests that pre-conditioning of the host brain receiving area with a LTP-inducing deep brain stimulation protocol prior to NSC transplantation may increase the likelihood of success of using NSC transplantation as an effective cell therapy for various neurodegenerative diseases.
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Affiliation(s)
- Taesup Cho
- Brain Research Centre and Department of Medicine, University of British Columbia, Vancouver, Canada
| | - Jae K. Ryu
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, Canada
| | - Changiz Taghibiglou
- Brain Research Centre and Department of Medicine, University of British Columbia, Vancouver, Canada
| | - Yuan Ge
- Brain Research Centre and Department of Medicine, University of British Columbia, Vancouver, Canada
| | - Allen W. Chan
- Brain Research Centre and Department of Medicine, University of British Columbia, Vancouver, Canada
| | - Lidong Liu
- Brain Research Centre and Department of Medicine, University of British Columbia, Vancouver, Canada
| | - Jie Lu
- Brain Research Centre and Department of Medicine, University of British Columbia, Vancouver, Canada
| | - James G. McLarnon
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, Canada
| | - Yu Tian Wang
- Brain Research Centre and Department of Medicine, University of British Columbia, Vancouver, Canada
- Translational Medicine Research Center, China Medical University Hospital and Graduate Institute of Immunology, China Medical University, Taichung, Taiwan, Republic of China
- * E-mail:
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Otte DM, Barcena de Arellano ML, Bilkei-Gorzo A, Albayram Ö, Imbeault S, Jeung H, Alferink J, Zimmer A. Effects of Chronic D-Serine Elevation on Animal Models of Depression and Anxiety-Related Behavior. PLoS One 2013; 8:e67131. [PMID: 23805296 PMCID: PMC3689701 DOI: 10.1371/journal.pone.0067131] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2012] [Accepted: 05/15/2013] [Indexed: 12/17/2022] Open
Abstract
NMDA receptors are activated after binding of the agonist glutamate to the NR2 subunit along with a co-agonist, either L-glycine or D-serine, to the NR1 subunit. There is substantial evidence to suggest that D-serine is the most relevant co-agonist in forebrain regions and that alterations in D-serine levels contribute to psychiatric disorders. D-serine is produced through isomerization of L-serine by serine racemase (Srr), either in neurons or in astrocytes. It is released by astrocytes by an activity-dependent mechanism involving secretory vesicles. In the present study we generated transgenic mice (SrrTg) expressing serine racemase under a human GFAP promoter. These mice were biochemically and behaviorally analyzed using paradigms of anxiety, depression and cognition. Furthermore, we investigated the behavioral effects of long-term administration of D-serine added to the drinking water. Elevated brain D-serine levels in SrrTg mice resulted in specific behavioral phenotypes in the forced swim, novelty suppression of feeding and olfactory bulbectomy paradigms that are indicative of a reduced proneness towards depression-related behavior. Chronic dietary D-serine supplement mimics the depression-related behavioral phenotype observed in SrrTg mice. Our results suggest that D-serine supplementation may improve mood disorders.
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Affiliation(s)
- David-Marian Otte
- Institute of Molecular Psychiatry, University of Bonn, Bonn, Germany
| | | | | | - Önder Albayram
- Institute of Molecular Psychiatry, University of Bonn, Bonn, Germany
| | - Sophie Imbeault
- Institute of Molecular Psychiatry, University of Bonn, Bonn, Germany
| | - Haang Jeung
- Department of Psychiatry, University of Bonn, Bonn, Germany
| | - Judith Alferink
- Institute of Molecular Psychiatry, University of Bonn, Bonn, Germany
- Department of Psychiatry, University of Bonn, Bonn, Germany
| | - Andreas Zimmer
- Institute of Molecular Psychiatry, University of Bonn, Bonn, Germany
- * E-mail:
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15
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Weilinger NL, Maslieieva V, Bialecki J, Sridharan SS, Tang PL, Thompson RJ. Ionotropic receptors and ion channels in ischemic neuronal death and dysfunction. Acta Pharmacol Sin 2013; 34:39-48. [PMID: 22864302 DOI: 10.1038/aps.2012.95] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Loss of energy supply to neurons during stroke induces a rapid loss of membrane potential that is called the anoxic depolarization. Anoxic depolarizations result in tremendous physiological stress on the neurons because of the dysregulation of ionic fluxes and the loss of ATP to drive ion pumps that maintain electrochemical gradients. In this review, we present an overview of some of the ionotropic receptors and ion channels that are thought to contribute to the anoxic depolarization of neurons and subsequently, to cell death. The ionotropic receptors for glutamate and ATP that function as ligand-gated cation channels are critical in the death and dysfunction of neurons. Interestingly, two of these receptors (P2X7 and NMDAR) have been shown to couple to the pannexin-1 (Panx1) ion channel. We also discuss the important roles of transient receptor potential (TRP) channels and acid-sensing ion channels (ASICs) in responses to ischemia. The central challenge that emerges from our current understanding of the anoxic depolarization is the need to elucidate the mechanistic and temporal interrelations of these ion channels to fully appreciate their impact on neurons during stroke.
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Collingridge GL, Volianskis A, Bannister N, France G, Hanna L, Mercier M, Tidball P, Fang G, Irvine MW, Costa BM, Monaghan DT, Bortolotto ZA, Molnár E, Lodge D, Jane DE. The NMDA receptor as a target for cognitive enhancement. Neuropharmacology 2012; 64:13-26. [PMID: 22796429 DOI: 10.1016/j.neuropharm.2012.06.051] [Citation(s) in RCA: 175] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2012] [Revised: 06/22/2012] [Accepted: 06/24/2012] [Indexed: 12/31/2022]
Abstract
NMDA receptors (NMDARs) play an important role in neural plasticity including long-term potentiation and long-term depression, which are likely to explain their importance for learning and memory. Cognitive decline is a major problem facing an ageing human population, so much so that its reversal has become an important goal for scientific research and pharmaceutical development. Enhancement of NMDAR function is a core strategy toward this goal. In this review we indicate some of the major ways of potentiating NMDAR function by both direct and indirect modulation. There is good evidence that both positive and negative modulation can enhance function suggesting that a subtle approach correcting imbalances in particular clinical situations will be required. Excessive activation and the resultant deleterious effects will need to be carefully avoided. Finally we describe some novel positive allosteric modulators of NMDARs, with some subunit selectivity, and show initial evidence of their ability to affect NMDAR mediated events. This article is part of a Special Issue entitled 'Cognitive Enhancers'.
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Affiliation(s)
- Graham L Collingridge
- MRC Centre for Synaptic Plasticity, School of Physiology and Pharmacology, University of Bristol, Bristol BS1 3NY, UK.
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17
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Wu PL, Lane HY, Tang HS, Tsai GE. Glutamate theory in developing novel pharmacotherapies for obsessive compulsive disorder: Focusing on N-methyl-D-aspartate signaling. Biomedicine (Taipei) 2012. [DOI: 10.1016/j.biomed.2012.04.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022] Open
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18
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Olischar M, Shany E, Aygün C, Azzopardi D, Hunt RW, Toet MC, Hamosh A, de Vries LS, Hellström-Westas L, Theda C. Amplitude-integrated electroencephalography in newborns with inborn errors of metabolism. Neonatology 2012; 102:203-11. [PMID: 22797054 DOI: 10.1159/000339567] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/22/2012] [Accepted: 05/17/2012] [Indexed: 12/13/2022]
Abstract
BACKGROUND The utility of amplitude-integrated electroencephalography (aEEG) monitoring has been established for patients with neonatal hypoxic-ischemic encephalopathy. OBJECTIVE To evaluate the role of aEEG in the diagnostic process and treatment of patients with encephalopathy due to inborn errors of metabolism. METHODS Cases collected through an international registry were divided into 5 groups of metabolic disorders. Common aEEG features were sought for each group. RESULTS In total, 21/30 (70%) cases had abnormal aEEG background patterns, 18/30 (60%) showed seizure activity. Patients with disorders of energy metabolism, hyperammonemia, and organic/amino acidopathies often showed marked aEEG depression with seizure activity. In contrast, aEEGs of patients with peroxisomal disorders did not show major background abnormalities but seizures were present in 5/6 subjects. We report two features of interest: firstly, two tracings displayed an unusual upward shift of the lower aEEG amplitude margin. Secondly, aEEGs of infants with non-ketotic hyperglycinemia showed a pattern we refer to as 'high-frequency burst-suppression pattern'. CONCLUSIONS aEEG in patients with inborn errors of metabolism frequently reveals abnormalities and assists clinicians in the clinical assessment, management and monitoring of these patients.
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Affiliation(s)
- Monika Olischar
- Department of Neonatology, University Children's Hospital Vienna, Vienna, Austria
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19
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Abstract
Prepulse inhibition (PPI) of startle is the suppression of the startle reflex when a weaker sensory stimulus (the prepulse) shortly precedes the startling stimulus. PPI can be attentionally enhanced in both humans and laboratory animals. This study investigated whether the following three forebrain structures, which are critical for initial cortical processing of auditory signals, auditory fear conditioning/memories, and spatial attention, respectively, play a role in the top-down modulation of PPI in rats: the primary auditory cortex (A1), lateral nucleus of the amygdala (LA), and posterior parietal cortex (PPC). The results show that, under the noise-masking condition, PPI was enhanced by fear conditioning of the prepulse in a prepulse-specific manner, and the conditioning-induced PPI enhancement was further increased by perceptual separation between the conditioned prepulse and the noise masker. Reversibly blocking glutamate receptors in the A1 with 2 mm kynurenic acid eliminated both the conditioning-induced and perceptual separation-induced PPI enhancements. Blocking the LA eliminated the conditioning-induced but not the perceptual separation-induced PPI enhancement, and blocking the PPC specifically eliminated the perceptual separation-induced PPI enhancement. The two types of PPI enhancements were also eliminated by the extinction manipulation. Thus, the top-down modulation of PPI is differentially organized and depends on operations of various forebrain structures. Due to the fine-tuned modulation by higher-order cognitive processes, functions of PPI can be more flexible to complex environments. The top-down enhancements of PPI in rats are also useful for modeling some mental disorders, such as schizophrenia, attention deficit/hyperactivity disorder, and posttraumatic stress disorder.
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Bakkar W, Ma CL, Pabba M, Khacho P, Zhang YL, Muller E, Martina M, Bergeron R. Chronically saturating levels of endogenous glycine disrupt glutamatergic neurotransmission and enhance synaptogenesis in the CA1 region of mouse hippocampus. Synapse 2011; 65:1181-95. [PMID: 21633974 DOI: 10.1002/syn.20956] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2011] [Accepted: 05/18/2011] [Indexed: 11/08/2022]
Abstract
Glycine serves a dual role in neurotransmission. It is the primary inhibitory neurotransmitter in the spinal cord and brain stem and is also an obligatory coagonist at the excitatory glutamate, N-methyl-D-aspartate receptor (NMDAR). Therefore, the postsynaptic action of glycine should be strongly regulated to maintain a balance between its inhibitory and excitatory inputs. The glycine concentration at the synapse is tightly regulated by two types of glycine transporters, GlyT1 and GlyT2, located on nerve terminals or astrocytes. Genetic studies demonstrated that homozygous (GlyT1-/-) newborn mice display severe sensorimotor deficits characterized by lethargy, hypotonia, and hyporesponsivity to tactile stimuli and ultimately die in their first postnatal day. These symptoms are similar to those associated with the human disease glycine encephalopathy in which there is a high level of glycine in cerebrospinal fluid of affected individuals. The purpose of this investigation is to determine the impact of chronically high concentrations of endogenous glycine on glutamatergic neurotransmission during postnatal development using an in vivo mouse model (GlyT1+/-). The results of our study indicate the following; that compared with wild-type mice, CA1 pyramidal neurons from mutants display significant disruptions in hippocampal glutamatergic neurotransmission, as suggested by a faster kinetic of NMDAR excitatory postsynaptic currents, a lower reduction of the amplitude of NMDAR excitatory postsynaptic currents by ifenprodil, no difference in protein expression for NR2A and NR2B but a higher protein expression for PSD-95, an increase in their number of synapses and finally, enhanced neuronal excitability.
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Affiliation(s)
- Wafae Bakkar
- Ottawa Hospital Research Institute, Ottawa, Ontario, Canada
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21
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Lin CH, Lane HY, Tsai GE. Glutamate signaling in the pathophysiology and therapy of schizophrenia. Pharmacol Biochem Behav 2011; 100:665-77. [PMID: 21463651 DOI: 10.1016/j.pbb.2011.03.023] [Citation(s) in RCA: 113] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/03/2010] [Revised: 03/14/2011] [Accepted: 03/28/2011] [Indexed: 11/26/2022]
Abstract
Glutamatergic neurotransmission, particularly through the N-methyl-d-aspartate (NMDA) receptor, has drawn attention for its role in the pathophysiology of schizophrenia. This paper reviews the neurodevelopmental origin and genetic susceptibility of schizophrenia relevant to NMDA neurotransmission, and discusses the relationship between NMDA hypofunction and different domains of symptom in schizophrenia as well as putative treatment modality for the disorder. A series of clinical trials and a meta-analysis which compared currently available NMDA-enhancing agents suggests that glycine, d-serine, and sarcosine are more efficacious than d-cycloserine in improving the overall psychopathology of schizophrenia without side effect or safety concern. In addition, enhancing glutamatergic neurotransmission via activating the AMPA receptor, metabotropic glutamate receptor or inhibition of d-amino acid oxidase (DAO) is also reviewed. More studies are needed to determine the NMDA vulnerability in schizophrenia and to confirm the long-term efficacy, functional outcome, and safety of these NMDA-enhancing agents in schizophrenic patients, particularly those with refractory negative and cognitive symptoms, or serious adverse effects while taking the existing antipsychotic agents.
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Affiliation(s)
- Chieh-Hsin Lin
- Department of Psychiatry, Chang Gung Memorial Hospital, Kaohsiung Medical Center, Chang Gung University College of Medicine, Kaohsiung, Taiwan
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22
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Coyle JT, Balu D, Benneyworth M, Basu A, Roseman A. Beyond the dopamine receptor: novel therapeutic targets for treating schizophrenia. DIALOGUES IN CLINICAL NEUROSCIENCE 2010. [PMID: 20954431 PMCID: PMC3181979 DOI: 10.31887/dcns.2010.12.3/jcoyle] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
All current drugs approved to treat schizophrenia appear to exert their antipsychotic effects through blocking the dopamine D2 receptor. Recent meta-analyses and comparative efficacy studies indicate marginal differences in efficacy of newer atypical antipsychotics and the older drugs, and little effects on negative and cognitive symptoms. This review integrates findings from postmortem, imaging, and drug-challenge studies to elucidate a corticolimbic “pathologic circuit” in schizophrenia that may be particularly relevant to the negative symptoms and cognitive impairments of schizophrenia. Potential sites for pharmacologic intervention targeting glutatatergic, GABAergic, and cholinergic neurotransmission to treat these symptoms of schizophrenia are discussed.
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Affiliation(s)
- Joseph T Coyle
- Department of Psychiatry, Harvard Medical School, McLean Hospital, Belmont, MA 02478, USA.
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24
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Labrie V, Roder JC. The involvement of the NMDA receptor D-serine/glycine site in the pathophysiology and treatment of schizophrenia. Neurosci Biobehav Rev 2009; 34:351-72. [PMID: 19695284 DOI: 10.1016/j.neubiorev.2009.08.002] [Citation(s) in RCA: 92] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2009] [Revised: 08/10/2009] [Accepted: 08/11/2009] [Indexed: 01/11/2023]
Abstract
Hypofunction of the N-methyl-D-aspartate receptor (NMDAR) has been implicated in the pathophysiology of schizophrenia. The NMDAR contains a D-serine/glycine site on the NR1 subunit that may be a promising therapeutic target for psychiatric illness. This review outlines the complex regulation of endogenous NMDAR D-serine/glycine site agonists and explores their contribution to schizophrenia pathogenesis and their potential clinical utility. Genetic studies have associated genes influencing NMDAR D-serine/glycine site activation with an increased susceptibility to schizophrenia. Postmortem studies have identified abnormalities in several transcripts affecting D-serine/glycine site activity, consistent with in vivo reports of alterations in levels of endogenous D-serine/glycine site agonists and antagonists. Genetically modified mice with aberrant NMDAR D-serine/glycine site function model certain features of the negative and cognitive symptoms of schizophrenia, and similar behavioral abnormalities have been observed in other candidate genes models. Compounds that directly activate the NMDAR D-serine/glycine site or inhibit glycine transport have demonstrated beneficial effects in preclinical models and clinical trials. Future pharmacological approaches for schizophrenia treatment may involve targeting enzymes that affect D-serine synthesis and metabolism.
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Affiliation(s)
- Viviane Labrie
- Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, ON M5G 1X5, Canada.
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25
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Inhibition of rat recombinant GluN1/GluN2A and GluN1/GluN2B NMDA receptors by ethanol at concentrations based on the US/UK drink-drive limit. Eur J Pharmacol 2009; 614:14-21. [DOI: 10.1016/j.ejphar.2009.04.034] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2009] [Revised: 04/07/2009] [Accepted: 04/20/2009] [Indexed: 11/20/2022]
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26
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Atkinson SE, Williams SR. Postnatal development of dendritic synaptic integration in rat neocortical pyramidal neurons. J Neurophysiol 2009; 102:735-51. [PMID: 19458150 DOI: 10.1152/jn.00083.2009] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The dendritic tree of layer 5 (L5) pyramidal neurons spans the neocortical layers, allowing the integration of intra- and extracortical synaptic inputs. Here we investigate the postnatal development of the integrative properties of rat L5 pyramidal neurons using simultaneous whole cell recording from the soma and distal apical dendrite. In young (P9-10) neurons, apical dendritic excitatory synaptic input powerfully drove action potential output by efficiently summating at the axonal site of action potential generation. In contrast, in mature (P25-29) neurons, apical dendritic excitatory input provided little direct depolarization at the site of action potential generation but was integrated locally in the apical dendritic tree leading to the generation of dendritic spikes. Consequently, over the first postnatal month the fraction of action potentials driven by apical dendritic spikes increased dramatically. This developmental remodeling of the integrative operations of L5 pyramidal neurons was controlled by a >10-fold increase in the density of apical dendritic Hyperpolarization-activated cyclic nucleotide (HCN)-gated channels found in cell-attached patches or by immunostaining for the HCN channel isoform HCN1. Thus an age-dependent increase in apical dendritic HCN channel density ensures that L5 pyramidal neurons develop from compact temporal integrators to compartmentalized integrators of basal and apical dendritic synaptic input.
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Affiliation(s)
- Susan E Atkinson
- Medical Research Council Laboratory of Molecular Biology, Cambridge CB2 0QH, United Kingdom
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27
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Li Y, Krupa B, Kang JS, Bolshakov VY, Liu G. Glycine site of NMDA receptor serves as a spatiotemporal detector of synaptic activity patterns. J Neurophysiol 2009; 102:578-89. [PMID: 19439669 DOI: 10.1152/jn.91342.2008] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Calcium influx associated with the opening of N-methyl-D-aspartate (NMDA) receptor channels is the major signal triggering synaptic and developmental plasticity. Controlling the NMDA receptor function is therefore critical for many functions of the brain. We explored the mechanisms of synaptic activation of the NMDAR glycine site by endogenous coagonist using whole cell voltage-clamp recordings from hippocampal neurons in mixed cultures, containing both neurons and glial cells, and, under more physiological conditions, in hippocampal slices. Here we show that the glycine site of the NMDA receptor at hippocampal synapses, both in culture and acute brain slices, is not saturated by the ambient coagonist concentration and is modulated through activity-dependent coagonist release. Augmentation of the NMDA receptor-mediated synaptic responses by local glutamate-induced coagonist release is spatially restricted and determined by spatiotemporal summation of synaptic events at neighboring synaptic inputs on a single dendritic branch. Therefore different spatiotemporal patterns of presynaptic activity could be translated into different levels of the NMDAR activation in specific afferent projections. These results suggest that the NMDA receptor glycine site may serve as a detector of the spatiotemporal characteristics of presynaptic activity patterns.
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Affiliation(s)
- Yan Li
- Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA, USA
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28
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Mao SC, Lin HC, Gean PW. Augmentation of Fear Extinction by Infusion of Glycine Transporter Blockers into the Amygdala. Mol Pharmacol 2009; 76:369-78. [DOI: 10.1124/mol.108.053728] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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29
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Coagonist release modulates NMDA receptor subtype contributions at synaptic inputs to retinal ganglion cells. J Neurosci 2009; 29:1469-79. [PMID: 19193893 DOI: 10.1523/jneurosci.4240-08.2009] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
NMDA receptors (NMDARs) are tetrameric protein complexes usually comprising two NR1 and two NR2 subunits. Different combinations of four potential NR2 subunits (NR2A-D) confer diversity in developmental expression, subsynaptic localization, and functional characteristics, including affinity for neurotransmitter. NR2B-containing NMDARs, for example, exhibit relatively high affinity both for glutamate and the coagonist glycine. Although multiple NMDAR subtypes can colocalize at individual synapses, particular subtypes often mediate inputs from distinct functional pathways. In retinal ganglion cells (RGCs), NMDARs contribute to synaptic responses elicited by light stimulus onset ("ON") and offset ("OFF"), but roles for particular NMDAR subtypes, and potential segregation between the ON and OFF pathways, have not been explored. Moreover, elements in the retinal circuitry release two different NMDAR coagonists, glycine and d-serine, but the effects of endogenous coagonist release on the relative contribution of different NMDAR subtypes are unclear. Here, we show that coagonist release within the retina modulates the relative contribution of different NMDARs in the ON pathway of the rat retina. By pharmacologically stimulating functional pathways independently in acute slices and recording synaptic responses in RGCs, we show that ON inputs, but not OFF inputs, are mediated in part by NMDARs exhibiting NR2B-like pharmacology. Furthermore, suppressing release of NMDAR coagonist reduces NMDAR activation at ON synapses and increases the relative contribution of these putative NR2B-containing receptors. These results demonstrate direct evidence for evoked coagonist release onto NMDARs and indicate that modulating coagonist release may regulate the relative activation of different NMDAR subtypes in the ON pathway.
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Mao SC, Lin HC, Gean PW. Augmentation of fear extinction by D-cycloserine is blocked by proteasome inhibitors. Neuropsychopharmacology 2008; 33:3085-95. [PMID: 18368037 DOI: 10.1038/npp.2008.30] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
D-Cycloserine (DCS) has been shown to facilitate extinction of conditioned fear in rats and to improve fear reduction of social phobia and fear of heights in human studies. Here, we investigate the mechanism of DCS effect by measuring internalized GluR1 and GluR2 using cell-surface biotinylation techniques. DCS selectively increased NMDA receptor-mediated synaptic response without affecting AMPA receptor-mediated synaptic response. Low-frequency stimulation (LFS) when applied in the presence of DCS induced GluR1 and GluR2 internalization in the amygdala slices. Proteasome inhibitors block DCS facilitation of LFS-induced depotentiation and a reduction in surface levels of GluR1 and GluR2. Furthermore, DCS in combination with LFS reduced cellular levels of PSD-95 and synapse-associated protein 97 (SAP97), which were also blocked by proteasome inhibitors. In the in vivo experiments, DCS-induced reduction of fear-potentiated startle and reversal of conditioning-induced increase in surface expression of GluR1 were blocked by proteasome inhibitors. DCS-treated rats fail to exhibit reinstatement after US-alone presentations. These results suggest that DCS facilitates receptor internalization in the presence of extinction training, resulting in augmented reduction of startle potentiation.
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Affiliation(s)
- Sheng-Chun Mao
- Institute of Basic Medical Sciences, National Cheng-Kung University, Tainan, Taiwan
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31
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Ahmed NAEH, Radwan NM, Ibrahim KM, Khedr ME, El Aziz MA, Khadrawy YA. Effect of Three Different Intensities of Infrared Laser Energy on the Levels of Amino Acid Neurotransmitters in the Cortex and Hippocampus of Rat Brain. Photomed Laser Surg 2008; 26:479-88. [DOI: 10.1089/pho.2007.2190] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Affiliation(s)
| | | | | | - Mona Emam Khedr
- Medical Physiology Department, National Research Center, Dokki, Giza, Egypt
| | - Mona A. El Aziz
- Department of Biotechnology, National Institute of Laser Enhanced Sciences, Cairo University, Cairo, Egypt
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Tsai GE, Lane HY, VanDenBerg CM, Liu YC, Tsai P, Jann MW. Disposition of D-Serine in Healthy Adults. J Clin Pharmacol 2008; 48:524-527. [DOI: 10.1177/0091270008314253] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/30/2023]
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Zhang LH, Gong N, Fei D, Xu L, Xu TL. Glycine uptake regulates hippocampal network activity via glycine receptor-mediated tonic inhibition. Neuropsychopharmacology 2008; 33:701-11. [PMID: 17522628 DOI: 10.1038/sj.npp.1301449] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Functional glycine receptors (GlyRs) are enriched in the hippocampus, but their role in hippocampal function remains unclear. Since the concentration of ambient glycine is determined by the presence of powerful glycine transporter (GlyT), we blocked the reuptake of glycine in hippocampal slices to examine the role of GlyRs. Antagonists of GlyT type 1 (GlyT1) but not that of GlyT type 2 (GlyT2) induced excitatory postsynaptic potential (EPSP)-spike depression, which was reversed by the specific GlyR antagonist strychnine. Moreover, endogenously elevating the glycine concentration with the GlyT1 antagonists facilitated NMDA receptor-dependent long-term potentiation induction, and elicited a strychnine-sensitive chloride current. In addition, impairment of glial function with fluoroacetate blocked the effect of GlyT1 antagonists on the EPSP-spike curve. Furthermore, pretreatment with sarcosine was effective in controlling pentylenetetrazol-induced seizures. These results indicate an essential role of GlyTs in fine-tuning tonic activation of GlyRs and suggest a potential role of GlyR-dependent EPSP-spike depression in hippocampal network stability.
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Affiliation(s)
- Long-Hua Zhang
- Institute of Neuroscience and Key Laboratory of Neurobiology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China
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Survey of ALS-associated factors potentially promoting Ca2+ overload of motor neurons. ACTA ACUST UNITED AC 2008; 8:260-5. [PMID: 17917848 DOI: 10.1080/17482960701523124] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The deleterious consequences of Ca(2+) overload are thought to be a probable cause of motoneuronal death in ALS, although the overloading mechanism is currently unclear. In this paper some ALS-linked factors are analysed with regard to their influence on Ca(2+ )influx into neurons. Intensive cortex activity can render motor neurons susceptible to stimulation of calcium-permeable glutamate NMDA-receptors; increase in CSF concentrations of glutamate, glycine, and norepinephrine supposedly can intensify these receptors' activity. Elevated CSF levels of GABA and reduced levels of serotonin can promote Ca(2+ )influx through glutamate AMPA-receptors and voltage-gated channels of L-, N-, and P-type. Additionally, brain ischaemia can contribute to Ca(2+ )overload of motor neurons. Thus, ALS is characterized by the unique combination of factors potentially able to promote the overload of motor neurons with calcium.
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Lane HY, Liu YC, Huang CL, Chang YC, Liau CH, Perng CH, Tsai GE. Sarcosine (N-methylglycine) treatment for acute schizophrenia: a randomized, double-blind study. Biol Psychiatry 2008; 63:9-12. [PMID: 17659263 DOI: 10.1016/j.biopsych.2007.04.038] [Citation(s) in RCA: 111] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/19/2006] [Revised: 04/22/2007] [Accepted: 04/27/2007] [Indexed: 11/30/2022]
Abstract
BACKGROUND Small molecules that enhance the N-methyl-D-aspartate (NMDA) neurotransmission have been shown to be beneficial as adjuvant therapy for schizophrenia. Among these compounds, sarcosine (a glycine transporter-I inhibitor), when added to an existing regimen of antipsychotic drugs, has shown its efficacy for both chronically stable and acutely ill patients. However, the efficacy of these agents as a primary antipsychotic agent has not yet been demonstrated. METHODS Twenty acutely symptomatic drug-free patients with schizophrenia were randomly assigned under double-blind conditions to receive a 6-week trial of 2 g or 1 g of sarcosine daily. RESULTS Overall, patients in the 2-g group were more likely to respond as defined by a 20% or more reduction of the Positive and Negative Syndrome Scale total score, particularly among antipsychotic-naïve patients. However, there was no significant between-group difference in the sarcosine dose x time interaction analysis. Both doses were well tolerated with minimal side effects. CONCLUSIONS Although patients receiving the 2-g daily dose were more likely to respond, it requires further clarification whether the effect is limited to the antipsychotic-naive population. Future placebo- or active-controlled, larger-sized studies are needed to fully assess sarcosine's effects.
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Affiliation(s)
- Hsien-Yuan Lane
- Department of Psychiatry, China Medical University and Hospital, Taichung, Taiwan
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36
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Chen PE, Geballe MT, Katz E, Erreger K, Livesey MR, O'Toole KK, Le P, Lee CJ, Snyder JP, Traynelis SF, Wyllie DJA. Modulation of glycine potency in rat recombinant NMDA receptors containing chimeric NR2A/2D subunits expressed in Xenopus laevis oocytes. J Physiol 2007; 586:227-45. [PMID: 17962328 DOI: 10.1113/jphysiol.2007.143172] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Heteromeric NMDARs are composed of coagonist glycine-binding NR1 subunits and glutamate-binding NR2 subunits. The majority of functional NMDARs in the mammalian central nervous system (CNS) contain two NR1 subunits and two NR2 subunits of which there are four types (A-D). We show that the potency of a variety of endogenous and synthetic glycine-site coagonists varies between recombinant NMDARs such that the highest potency is seen at NR2D-containing and the lowest at NR2A-containing NMDARs. This heterogeneity is specified by the particular NR2 subunit within the NMDAR complex since the glycine-binding NR1 subunit is common to all NMDARs investigated. To identify the molecular determinants responsible for this heterogeneity, we generated chimeric NR2A/2D subunits where we exchanged the S1 and S2 regions that form the ligand-binding domains and coexpressed these with NR1 subunits in Xenopus laevis oocytes. Glycine concentration-response curves for NMDARs containing NR2A subunits including the NR2D S1 region gave mean glycine EC(50) values similar to NR2A(WT)-containing NMDARs. However, receptors containing NR2A subunits including the NR2D S2 region or both NR2D S1 and S2 regions gave glycine potencies similar to those seen in NR2D(WT)-containing NMDARs. In particular, two residues in the S2 region of the NR2A subunit (Lys719 and Tyr735) when mutated to the corresponding residues found in the NR2D subunit influence glycine potency. We conclude that the variation in glycine potency is caused by interactions between the NR1 and NR2 ligand-binding domains that occur following agonist binding and which may be involved in the initial conformation changes that determine channel gating.
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Affiliation(s)
- Philip E Chen
- Centre for Neuroscience Research, Hugh Robson Building, University of Edinburgh, George Square, Edinburgh, UK
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Igartua I, Solís JM, Bustamante J. Glycine-induced long-term synaptic potentiation is mediated by the glycine transporter GLYT1. Neuropharmacology 2007; 52:1586-95. [PMID: 17462677 DOI: 10.1016/j.neuropharm.2007.03.003] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2006] [Revised: 02/13/2007] [Accepted: 03/05/2007] [Indexed: 11/29/2022]
Abstract
The negative symptoms of schizophrenia are reverted by treatment with glycine or other agonists of the glycine-B site which facilitate NMDA receptor function. On the other hand, there are experimental observations showing that exogenous application of glycine (0.5-10mM) results in a long-lasting potentiation of glutamatergic synaptic transmission (LTP-GLY). The characterization of the mechanisms underlying LTP-GLY could be useful to develop new therapies for schizophrenia. The main goal of this work is to deepen the understanding of this potentiation phenomenon. The present study demonstrates in rat hippocampal slices that superfusion of glycine 1mM during 30 min produces a potentiation of excitatory postsynaptic potentials in CA3-CA1 pathway lasting at least 1h. Glycine application does not modify neither presynaptic fiber volley nor paired-pulse facilitation of synaptic potentials. This LTP-GLY is independent of both strychnine-sensitive glycine receptors and nifedipine-sensitive calcium channels. Interestingly, LTP-GLY is not inhibited but strengthened by NMDA receptors antagonists such as AP-5 or MK-801. In contrast, LTP-GLY is partially or totally blocked with the antagonists of glycine transporter GLYT1, sarcosine or ALX-5407, respectively. These results indicate that LTP-GLY requires the activation of GLYT1, a glycine transporter co-localized and associated to NMDA receptors. In addition, the fact that NMDA receptor inhibition increases LTP-GLY magnitude, opens the possibility that these receptors could have a negative control on GLYT1 activity.
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Affiliation(s)
- Itziar Igartua
- Servicio de Neurobiología-Investigación, Hospital Ramón y Cajal, 28034 Madrid, Spain
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Lane HY, Huang CL, Wu PL, Liu YC, Chang YC, Lin PY, Chen PW, Tsai G. Glycine transporter I inhibitor, N-methylglycine (sarcosine), added to clozapine for the treatment of schizophrenia. Biol Psychiatry 2006; 60:645-9. [PMID: 16780811 DOI: 10.1016/j.biopsych.2006.04.005] [Citation(s) in RCA: 129] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/21/2005] [Revised: 03/13/2006] [Accepted: 04/07/2006] [Indexed: 10/24/2022]
Abstract
BACKGROUND Agonists at the N-methyl-D-aspartate (NMDA)-glycine site (D-serine, glycine, D-alanine and D-cycloserine) and glycine transporter-1 (GlyT-1) inhibitor (N-methylglycine, or called sarcosine) both improve the symptoms of stable chronic schizophrenia patients receiving concurrent antipsychotics. Previous studies, however, found no advantage of D-serine, glycine, or D-cycloserine added to clozapine. The present study aims to determine the effects of sarcosine adjuvant therapy for schizophrenic patients receiving clozapine treatment. METHODS Twenty schizophrenic inpatients enrolled in a 6-week double-blind, placebo-controlled trial of sarcosine (2 g/day) which was added to their stable doses of clozapine. Measures of clinical efficacy and side-effects were determined every other week. RESULTS Sarcosine produced no greater improvement when co-administered with clozapine than placebo plus clozapine at weeks 2, 4, and 6. Sarcosine was well tolerated and no significant side-effect was noted. CONCLUSIONS Unlike patients treated with other antipsychotics, patients who received clozapine treatment exhibit no improvement by adding sarcosine or agonists at the NMDA-glycine site. Clozapine possesses particular efficacy, possibly related to potentiation of NMDA-mediated neurotransmission. This may contribute to the clozapine's unique clinical efficacy and refractoriness to the addition of NMDA-enhancing agents.
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Affiliation(s)
- Hsien-Yuan Lane
- Department of Psychiatry, China Medical University and Hospital, Taichung, Taiwan
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39
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Miura K, Optican LM. Membrane channel properties of premotor excitatory burst neurons may underlie saccade slowing after lesions of omnipause neurons. J Comput Neurosci 2006; 20:25-41. [PMID: 16511656 DOI: 10.1007/s10827-006-4258-y] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2005] [Revised: 06/27/2005] [Accepted: 08/16/2005] [Indexed: 10/25/2022]
Abstract
Chemical lesions of the brain stem region containing glycinergic omnipause neurons (OPNs) cause saccade slowing with no change in latency. To explore the mechanisms responsible for this deficit, simulation studies were performed with a conductance-based model of premotor excitatory burst neurons (EBNs) that incorporated multiple membrane channels, including the T-type calcium channel. The peak speed of a normal saccade was determined by the T- and NMDA currents in EBNs after the OPNs shut off. After OPN lesions, the model made slow saccades, because the EBN activity was lower than normal due to a reduced T-current (caused by the loss of hyperpolarization), and a reduced NMDA current (caused by a reduced glycine concentration around the receptors). Thus, we propose that two biophysical mechanisms are responsible for saccade slowing after OPN lesions: reduced T-current and reduced NMDA current, both of which are caused by the loss of glycine from OPNs.
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Affiliation(s)
- Kenichiro Miura
- Department of Integrative Brain Science, Graduate School of Medicine, Kyoto University, Kyoto 606-8501, Japan
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Tsai GE, Yang P, Chang YC, Chong MY. D-alanine added to antipsychotics for the treatment of schizophrenia. Biol Psychiatry 2006; 59:230-4. [PMID: 16154544 DOI: 10.1016/j.biopsych.2005.06.032] [Citation(s) in RCA: 137] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/08/2005] [Revised: 06/02/2005] [Accepted: 06/27/2005] [Indexed: 11/15/2022]
Abstract
BACKGROUND Hypofunction of the N-methyl-d-aspartate (NMDA) subtype glutamate receptor had been implicated in the pathophysiology of schizophrenia. Treatment with D-serine, glycine, endogenous full agonists of the glycine site of the NMDA receptor (NMDA-glycine site), D-cycloserine, a partial agonist, or sarcosine, a glycine transporter-1 inhibitor, improves the symptoms of schizophrenia. D-alanine is another endogenous agonist of the NMDA-glycine site that might have beneficial effects on schizophrenia. METHODS Thirty-two schizophrenic patients enrolled in a 6-week double-blind, placebo-controlled trial of D-alanine (100 mg/kg/day), which was added to their stable antipsychotic regimens. Measures of clinical efficacy and side effects were determined every other week. RESULTS Patint who received D-alanine treatment revealed significant reductions in their Clinical Global Impression Scale and Positive and Negative Syndrome Scale (PANSS) total scores. The Scale for the Assessment of Negative Symptoms and PANSS subscores of positive and cognitive symptoms were improved. D-alanine was well tolerated, and no significant side effect was noted. CONCLUSIONS The significant improvement with the D-alanine further supports the hypothesis of hypofunction of NMDA neurotransmission in schizophrenia and strengthens the proof of the principle that NMDA-enhancing treatment is a promising approach for the pharmacotherapy of schizophrenia.
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Affiliation(s)
- Guochuan E Tsai
- Department of Psychiatry, Harbor-UCLA Medical Center, Torrance, California 90509, USA.
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Hayashi Y, Ishibashi H, Hashimoto K, Nakanishi H. Potentiation of the NMDA receptor-mediated responses through the activation of the glycine site by microglia secreting soluble factors. Glia 2006; 53:660-8. [PMID: 16498631 DOI: 10.1002/glia.20322] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
We have previously reported that both transferred microglia and microglia-conditioned medium (MCM) potentiated the N-methyl-D-aspatate (NMDA) receptor-mediated synaptic responses in cortical neurons. To elucidate the mechanism underlying the potentiation of NMDA receptor-mediated responses by microglia, we examined the effects of MCM on NMDA-induced inward currents in mechanically dissociated hippocampal CA1 neurons under whole-cell patch recordings. MCM potentiated the amplitude of NMDA-induced currents up to 10-fold in a dose-dependent manner, and this effect of MCM remained even after boiling or cutting off molecules with a molecular mass more than 3 kDa. In the presence of glycine with a concentration sufficient to saturate the NMDA receptor glycine site, MCM failed to further potentiate the NMDA-induced currents. The glycine site antagonist 5, 7-dichrolokynurenic acid, significantly inhibited the effects of MCM. The effect of MCM was still observed even after treatment with D-amino acid oxidase, a D-serine degrading enzyme. On the other hand, MCM had no significant effect on the voltage-dependent Mg(2+) blockade of NMDA receptors. Furthermore, MCM enhanced the formation of the long-term potentiation in the Schaffer collateral pathway-CA1 pyramidal cell synapses. Using a high performance liquid chromatography system, we found the levels of both glycine and L-serine in MCM to be significantly higher than those in the control medium. It was also noted that an increased glycine productivity of microglia was observed in the hippocampus in the acute phase of neuronal injury. These observations strongly suggest that glycine is a major causative molecule released from microglia that potentiates the NMDA-induced currents.
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MESH Headings
- Animals
- Animals, Newborn
- Cell Communication/drug effects
- Cell Communication/physiology
- Cells, Cultured
- Culture Media, Conditioned/pharmacology
- Dose-Response Relationship, Drug
- Excitatory Amino Acid Agonists/pharmacology
- Excitatory Amino Acid Antagonists/pharmacology
- Glutamic Acid/metabolism
- Glycine/metabolism
- Glycine/pharmacology
- Hippocampus/cytology
- Hippocampus/metabolism
- Long-Term Potentiation/drug effects
- Long-Term Potentiation/physiology
- Mice
- Mice, Inbred C57BL
- Microglia/drug effects
- Microglia/metabolism
- N-Methylaspartate/pharmacology
- Patch-Clamp Techniques
- Pyramidal Cells/drug effects
- Pyramidal Cells/metabolism
- Rats
- Rats, Wistar
- Receptors, Glycine/agonists
- Receptors, Glycine/antagonists & inhibitors
- Receptors, Glycine/metabolism
- Receptors, N-Methyl-D-Aspartate/drug effects
- Receptors, N-Methyl-D-Aspartate/metabolism
- Serine/antagonists & inhibitors
- Serine/metabolism
- Synaptic Transmission/drug effects
- Synaptic Transmission/physiology
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Affiliation(s)
- Yoshinori Hayashi
- Laboratory of Oral Aging Science, Faculty of Dental Sciences, Kyushu University, Fukuoka, Japan
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Bennett S, Gronier B. Modulation of striatal dopamine release in vitro by agonists of the glycineB site of NMDA receptors; interaction with antipsychotics. Eur J Pharmacol 2005; 527:52-9. [PMID: 16307739 DOI: 10.1016/j.ejphar.2005.10.015] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2005] [Revised: 09/23/2005] [Accepted: 10/05/2005] [Indexed: 11/19/2022]
Abstract
The N-methyl-D-aspartate (NMDA) glutamate receptor possesses an obligatory co-agonist site for D-serine and glycine, named the glycineB site. Several clinical trials indicate that glycineB agonists can improve negative and cognitive symptoms of schizophrenia when co-administered with antipsychotics. In the present study we have investigated the effects of glycineB agonists on the endogenous release of dopamine from preparations of rat striatal tissue prisms in static conditions. The glycineB agonists glycine (1 mM) and D-serine (10 microM), but not D-cycloserine (10 microM), substantially increased the spontaneous release of dopamine, but significantly reduced the release of dopamine evoked by NMDA. The effect of glycine on spontaneous release was abolished by the non-competitive NMDA antagonists 5R,10S-(+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d] cyclohepten-5,10-imine (MK-801, 10 microM) and ifenprodil (5 microM), but was only partially suppressed by the competitive antagonist 4-(3-phosphonopropyl)-piperazine-2-carboxylic acid (CPP, 10 microM). The selective inhibitor of the glial glycine transporter GlyT1 N[3-(4'-fluorophenyl)-3-(4'-phenylphenoxy)propyl]sarcosine (NFPS, 10 microM) significantly increased the release of dopamine in an MK-801-sensitive manner. Interestingly, haloperidol (1 microM), but not clozapine (10 microM), prevented the effects of glycine. This study shows that glycineB modulators can control dopamine release by interacting with a distinctive NMDA receptor subtype with which some typical antipsychotics can interfere.
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Affiliation(s)
- Stephen Bennett
- Leicester School of Pharmacy, De Montfort University, The Gateway, Leicester LE1 9BH, United Kingdom
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Fuchs SA, Berger R, Klomp LWJ, de Koning TJ. D-amino acids in the central nervous system in health and disease. Mol Genet Metab 2005; 85:168-80. [PMID: 15979028 DOI: 10.1016/j.ymgme.2005.03.003] [Citation(s) in RCA: 139] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/28/2005] [Revised: 03/05/2005] [Accepted: 03/09/2005] [Indexed: 11/13/2022]
Abstract
Recent evidence has shown that d-amino acids are present in animals and humans in high concentrations and fulfill specific biological functions. In the central nervous system, two d-amino acids, d-serine and d-aspartate, occur in considerable concentrations. d-Serine is synthesized and metabolized endogenously and the same might account for d-aspartate. d-Serine has been studied most extensively and was shown to play a role in excitatory amino acid metabolism, being a co-agonist of the N-methyl-d-aspartate (NMDA) receptor. Insight into d-serine metabolism is relevant for physiological NMDA receptor (NMDAr) activation and for all the disorders associated with an altered function of the NMDAr, such as schizophrenia, ischemia, epilepsy, and neurodegenerative disorders. d-Aspartate appears to play a role in development and endocrine function, but the precise function of d-aspartate and other d-amino acids in animals and humans requires further investigation. As d-amino acids play biological roles, alterations in the concentrations of d-amino acids might occur in some disorders and relate to the pathogenesis of these disorders. d-Amino acid concentrations may then not only help in the diagnostic process, but also provide novel therapeutic targets. Consequently, the presence and important roles of d-amino acids in higher organisms do not only challenge former theories on mammalian physiology, but also contribute to exciting new insights in human disease.
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Affiliation(s)
- Sabine A Fuchs
- Department of Metabolic and Endocrine Diseases, University Medical Center Utrecht, Utrecht, The Netherlands
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Panizzutti R, Rausch M, Zurbrügg S, Baumann D, Beckmann N, Rudin M. The pharmacological stimulation of NMDA receptors via co-agonist site: an fMRI study in the rat brain. Neurosci Lett 2005; 380:111-5. [PMID: 15854761 DOI: 10.1016/j.neulet.2005.01.062] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2004] [Revised: 01/09/2005] [Accepted: 01/10/2005] [Indexed: 10/25/2022]
Abstract
d-Serine has been proposed as an endogenous modulator at the co-agonist glycine-binding site of N-methyl-d-aspartate (NMDA) receptors. There is still some debate as to whether this site is saturated in vivo, but it seems likely that this depends on regional differences in local glycine or d-serine concentrations. In order to identify areas where the co-agonist site was not fully activated in vivo, we studied the effect of intraperitoneal d-serine administration in the rat brain using functional magnetic resonance imaging (fMRI). Using contrast agent injection, the variations in the relative cerebral blood volume (CBVrel) in several regions of interest were evaluated. d-Serine (50 mg/kg) elicited a significant statistical increase in the CBVrel in the hippocampus. This effect was inhibited by the specific full antagonist of the co-agonist glycine site L-701,324 indicating that the hippocampal activation occurred through the binding of the agonist d-serine to the glycine-binding site of NMDA receptors. This result demonstrates that in the hippocampus, the co-agonist sites of NMDA receptors are not endogenously saturated under our experimental conditions, suggesting an important role of d-serine in the modulation of receptor function in the hippocampus.
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Affiliation(s)
- Rogério Panizzutti
- Departamento de Anatomia, Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro, Av. Pau Brasil s/n, 21940-900 Rio de Janeiro, RJ, Brazil.
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Matsumoto M, Sasaki T, Nagashima H, Ahn ES, Young W, Kodama N. Effects of N-methyl-d-aspartate, glutamate, and glycine on the dorsal column axons of neonatal rat spinal cord: in vitro study. Neurol Med Chir (Tokyo) 2005; 45:73-80, discussion 81. [PMID: 15722604 DOI: 10.2176/nmc.45.73] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The effects of N-methyl-D-aspartate (NMDA), glutamate, and glycine on the developmental axons of the neonatal rat spinal cord were investigated. Isolated dorsal column preparations from postnatal day (PN) 0 to 14 Long-Evans hooded rats (n = 119) were used in vitro. Compound action potentials (CAPs) were recorded from the cuneate and gracile fasciculi with a glass micropipette electrode. NMDA (100 microM) significantly increased CAP amplitude in PN 0-6 cords by 21.5 +/- 9.2% (mean +/- standard error of the mean, p < 0.001, n = 8) and in PN 7-14 cords by 6.7 +/- 6.6% (p < 0.001, n = 10). NMDA (10 microM) significantly increased the CAP amplitude by 6.3 +/- 2.9% in PN 0-6 cords (p < 0.01, n = 10). The increase of CAP amplitude induced by NMDA (100 microM) in PN 0-6 cords was significantly greater than that in PN 7-14 cords (p < 0.005). Glutamate (100 microM) significantly increased the CAP amplitude by 8.8 +/- 8.1% in PN 0-6 cords (p < 0.001, n = 29) and 6.7 +/- 7.5% in PN 7-14 cords (p < 0.01, n = 14), and glutamate (10 microM) significantly increased by 6.3 +/- 2.9% in PN 0-6 cords (p < 0.01, n = 21). The amplitudes induced by glutamate (100 microM or 10 microM) did not significantly differ between PN 0-6 and PN 7-14 cords. Application of glycine (100 microM) did not significantly alter CAP amplitudes induced by NMDA (100 microM or 10 microM) and glutamate (100 microM or 10 microM). D(-)-2-amino-5-phosphonopentanoic acid (NMDA receptor antagonist) blocked the effects of NMDA and glutamate. These results suggest that NMDA receptor is present on afferent dorsal column axons and may modulate axonal excitability, especially during the 1st week after birth.
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Affiliation(s)
- Masato Matsumoto
- W.M. Keck Center for Collaborate Neuroscience, Rutgers-The State University of New Jersey, Piscataway, NJ, USA.
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Bergeron R, Coyle JT, Tsai G, Greene RW. NAAG reduces NMDA receptor current in CA1 hippocampal pyramidal neurons of acute slices and dissociated neurons. Neuropsychopharmacology 2005; 30:7-16. [PMID: 15354184 DOI: 10.1038/sj.npp.1300559] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
N-acetylaspartylglutamate (NAAG) is an abundant neuropeptide in the nervous system, yet its functions are not well understood. Pyramidal neurons of the CA1 sector of acutely prepared hippocampal slices were recorded using the whole-cell patch-clamp technique. At low concentrations (20 microM), NAAG reduced isolated N-methyl-D-aspartate receptor (NMDAR)-mediated synaptic currents or NMDA-induced currents. The NAAG-induced change in the NMDA concentration/response curve suggested that the antagonism was not competitive. However, the NAAG-induced change in the concentration/response curve for the NMDAR co-agonist, glycine, indicated that glycine can overcome the NAAG antagonism. The antagonism of the NMDAR induced by NAAG was still observed in the presence of LY-341495, a potent and selective mGluR3 antagonist. Moreover, in dissociated pyramidal neurons of the CA1 region, NAAG also reduced the NMDA current and this effect was reversed by glycine. These results suggest that NAAG reduces the NMDA currents in hippocampal CA1 pyramidal neurons.
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Huang H, Barakat L, Wang D, Bordey A. Bergmann glial GlyT1 mediates glycine uptake and release in mouse cerebellar slices. J Physiol 2004; 560:721-36. [PMID: 15331688 PMCID: PMC1665288 DOI: 10.1113/jphysiol.2004.067801] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Glycine is an inhibitory neurotransmitter and is critical for NMDA receptor activation. These roles are dependent on extracellular glycine levels, which are regulated by Na(+)/Cl(-)-dependent glycine transporters (GlyTs) in neurones and glia. The glial GlyT subtype GlyT1 is well located to activate NMDA receptors. However, glial GlyTs have not been studied in an intact system thus far. Whole-cell patch-clamp recordings were obtained from Bergmann glia in mice cerebellar slices to determine whether these glia express functional GlyT1 that can mediate both glycine uptake and efflux. In the presence of a glycine receptor blocker, glycine and a substrate agonist for GlyT1, sarcosine, induced voltage-dependent inward currents that were abolished by removing external Na(+), identifying them as transport currents. Inhibitors of glycine transport through GlyT1 (sarcosine and (N-[3-(4'-fluorophenyl)-3-(4'-phenylphenoxy)propyl]sarcosine (NFPS)) reduced glycine currents by approximately 85%, consistent with positive immunostaining for GlyT1 in Bergmann glia while inhibitors of glycine transport through GlyT2 (4-benzyloxy-3,5-dimethoxy-N-[1-(dimethylaminocyclopently)methyl]benzamide (ORG 25543) and amoxapine) or through systems A and ASC did not affect glycine transport currents. Following internal glycine perfusion during the recording, outward currents progressively developed at -50 mV and external glycine-induced uptake currents were reduced. Using paired recordings of a Bergmann glial cell and a granule cell in the whole cell and outside-out modes, respectively, depolarizations of Bergmann glia to +20 mV induced a 73% increase in the open probability of glycine receptor channels in membrane patches of granule cells. This increase was prevented when NFPS was included in the bath solution. Overall, these results demonstrate for the first time that Bergmann glia express functional GlyT1 that can work in reverse at near-physiological ionic and internal glycine conditions in brain slices. These glial GlyTs can probably mediate glycine efflux under conditions of metabolic impairments like ischaemia.
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Affiliation(s)
- Hao Huang
- Department of Neurosurgery, Yale University, 333 Cedar Street, New Haven, CT 06520-8082, USA
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48
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Alkondon M, Pereira EFR, Yu P, Arruda EZ, Almeida LEF, Guidetti P, Fawcett WP, Sapko MT, Randall WR, Schwarcz R, Tagle DA, Albuquerque EX. Targeted deletion of the kynurenine aminotransferase ii gene reveals a critical role of endogenous kynurenic acid in the regulation of synaptic transmission via alpha7 nicotinic receptors in the hippocampus. J Neurosci 2004; 24:4635-48. [PMID: 15140935 PMCID: PMC6729395 DOI: 10.1523/jneurosci.5631-03.2004] [Citation(s) in RCA: 115] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
It has been postulated that endogenous kynurenic acid (KYNA) modulates alpha7* nicotinic acetylcholine receptor (nAChR) and NMDA receptor activities in the brain.a To test this hypothesis, alpha7* nAChR and NMDA receptor functions were studied in mice with a targeted null mutation in the gene encoding kynurenine aminotransferase II (mKat-2-/- mice), an enzyme responsible for brain KYNA synthesis. At 21 postnatal days, mKat-2-/- mice had lower hippocampal KYNA levels and higher spontaneous locomotor activity than wild-type (WT) mice. At this age, alpha7* nAChR activity induced by exogenous application of agonists to CA1 stratum radiatum interneurons was approximately 65% higher in mKat-2-/- than WT mice. Binding studies indicated that the enhanced receptor activity may not have resulted from an increase in alpha7* nAChR number. In 21-d-old mKat-2-/- mice, endogenous alpha7* nAChR activity in the hippocampus was also increased, leading to an enhancement of GABAergic activity impinging onto CA1 pyramidal neurons that could be reduced significantly by acute exposure to KYNA (100 nM). The activities of GABA(A) and NMDA receptors in the interneurons and of alpha3beta4* nAChRs regulating glutamate release onto these neurons were comparable between mKat-2-/- and WT mice. By 60 d of age, KYNA levels and GABAergic transmission in the hippocampus and locomotor activity were similar between mKat-2-/- and WT mice. Our findings that alpha7* nAChRs are major targets for KYNA in the brain may provide insights into the pathophysiology of schizophrenia and Alzheimer's disease, disorders in which brain KYNA levels are increased and alpha7* nAChR functions are impaired.
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Affiliation(s)
- Manickavasagon Alkondon
- Department of Pharmacology and Experimental Therapeutics, University of Maryland School of Medicine, Baltimore, Maryland 21201, USA
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Wu SZ, Bodles AM, Porter MM, Griffin WST, Basile AS, Barger SW. Induction of serine racemase expression and D-serine release from microglia by amyloid beta-peptide. J Neuroinflammation 2004; 1:2. [PMID: 15285800 PMCID: PMC483052 DOI: 10.1186/1742-2094-1-2] [Citation(s) in RCA: 152] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2004] [Accepted: 04/20/2004] [Indexed: 11/17/2022] Open
Abstract
Background Roles for excitotoxicity and inflammation in Alzheimer's disease have been hypothesized. Proinflammatory stimuli, including amyloid β-peptide (Aβ), elicit a release of glutamate from microglia. We tested the possibility that a coagonist at the NMDA class of glutamate receptors, D-serine, could respond similarly. Methods Cultured microglial cells were exposed to Aβ. The culture medium was assayed for levels of D-serine by HPLC and for effects on calcium and survival on primary cultures of rat hippocampal neurons. Microglial cell lysates were examined for the levels of mRNA and protein for serine racemase, the enzyme that forms D-serine from L-serine. The racemase mRNA was also assayed in Alzheimer hippocampus and age-matched controls. A microglial cell line was transfected with a luciferase reporter construct driven by the putative regulatory region of human serine racemase. Results Conditioned medium from Aβ-treated microglia contained elevated levels of D-serine. Bioassays of hippocampal neurons with the microglia-conditioned medium indicated that Aβ elevated a NMDA receptor agonist that was sensitive to an antagonist of the D-serine/glycine site (5,7-dicholorokynurenic acid; DCKA) and to enzymatic degradation of D-amino acids by D-amino acid oxidase (DAAOx). In the microglia, Aβ elevated steady-state levels of dimeric serine racemase, the apparent active form of the enzyme. Promoter-reporter and mRNA analyses suggest that serine racemase is transcriptionally induced by Aβ. Finally, the levels of serine racemase mRNA were elevated in Alzheimer's disease hippocampus, relative to age-matched controls. Conclusions These data suggest that Aβ could contribute to neurodegeneration through stimulating microglia to release cooperative excitatory amino acids, including D-serine.
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Affiliation(s)
- Sheng-Zhou Wu
- Department of Neurobiology & Developmental Sciences, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA
| | - Angela M Bodles
- Department of Geriatrics, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA
| | - Mandy M Porter
- Department of Geriatrics, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA
| | - W Sue T Griffin
- Department of Neurobiology & Developmental Sciences, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA
- Department of Geriatrics, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA
- Geriatric Research Education and Clinical Center, Central Arkansas Veterans Healthcare System, Little Rock Arkansas, USA
| | | | - Steven W Barger
- Department of Neurobiology & Developmental Sciences, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA
- Department of Geriatrics, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA
- Geriatric Research Education and Clinical Center, Central Arkansas Veterans Healthcare System, Little Rock Arkansas, USA
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Tsai G, Lane HY, Yang P, Chong MY, Lange N. Glycine transporter I inhibitor, N-methylglycine (sarcosine), added to antipsychotics for the treatment of schizophrenia. Biol Psychiatry 2004; 55:452-6. [PMID: 15023571 DOI: 10.1016/j.biopsych.2003.09.012] [Citation(s) in RCA: 248] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/16/2003] [Revised: 09/05/2003] [Accepted: 09/24/2003] [Indexed: 11/28/2022]
Abstract
BACKGROUND Hypofunction of N-methyl-D-aspartate glutamate receptor had been implicated in the pathophysiology of schizophrenia. Treatment with D-serine or glycine, endogenous full agonists of the glycine site of N-methyl-D-aspartate receptor, or D-cycloserine, a partial agonist, improve the symptoms of schizophrenia. N-methylglycine (sarcosine) is an endogenous antagonist of glycine transporter-1, which potentiates glycine's action on N-methyl-D-aspartate glycine site and can have beneficial effects on schizophrenia. METHODS Thirty-eight schizophrenic patients were enrolled in a 6-week double-blind, placebo-controlled trial of sarcosine (2 g/d), which was added to their stable antipsychotic regimens. Twenty of them received risperidone. Measures of clinical efficacy and side effects were determined every other week. RESULTS Patient who received sarcosine treatment revealed significant improvements in their positive, negative, cognitive, and general psychiatric symptoms. Similar therapeutic effects were observed when only risperidone-treated patients were analyzed. Sarcosine was well-tolerated, and no significant side effect was noted. CONCLUSIONS Sarcosine treatment can benefit schizophrenic patients treated by antipsychotics including risperidone. The significant improvement with the sarcosine further supports the hypothesis of N-methyl-D-aspartate receptor hypofunction in schizophrenia. Glycine transporter-1 is a novel target for the pharmacotherapy to enhance N-methyl-D-aspartate function.
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Affiliation(s)
- Guochuan Tsai
- Laboratory of Molecular and Psychiatric Neuroscience (GT), McLean Hospital and Harvard Medical School, Boston, Massachusetts 02478, USA
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