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Kimble L, Twiddy JS, Berger JM, Forderhase AG, McCarty GS, Meitzen J, Sombers LA. Simultaneous, Real-Time Detection of Glutamate and Dopamine in Rat Striatum Using Fast-Scan Cyclic Voltammetry. ACS Sens 2023; 8:4091-4100. [PMID: 37962541 PMCID: PMC10683757 DOI: 10.1021/acssensors.3c01267] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2023] [Revised: 10/24/2023] [Accepted: 11/01/2023] [Indexed: 11/15/2023]
Abstract
Glutamate and dopamine (DA) represent two key contributors to striatal functioning, a region of the brain that is essential to motor coordination and motivated behavior. While electroanalytical techniques can be utilized for rapid, spatially resolved detection of DA in the interferent-rich brain environment, glutamate, a nonelectroactive analyte, cannot be directly detected using electroanalytical techniques. However, it can be probed using enzyme-based sensors, which generate an electroactive reporter in the presence of glutamate. The vast majority of glutamate biosensors have relied on amperometric sensing, which is an inherently nonselective detection technique. This approach necessitates the use of complex and performance-limiting modifications to ensure the desired single-analyte specificity. Here, we present a novel glutamate microbiosensor fabricated on a carbon-fiber microelectrode substrate and coupled with fast-scan cyclic voltammetry (FSCV) to enable the simultaneous quantification of glutamate and DA at single recording sites in the brain, which is impossible when using typical amperometric approaches. The glutamate microbiosensors were characterized for sensitivity, stability, and selectivity by using a voltammetric waveform optimized for the simultaneous detection of both species. The applicability of these sensors for the investigation of neural circuits was validated in the rat ventral striatum. Electrically evoked glutamate and DA release were recorded at single-micrometer-scale locations before and after pharmacological manipulation of glutamatergic signaling. Our novel glutamate microbiosensor advances the state of the art by providing a powerful tool for probing coordination between these two species in a way that has previously not been possible.
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Affiliation(s)
- Laney
C. Kimble
- Department
of Chemistry, Department of Biological Sciences, and Comparative Medicine Institute, North Carolina State University, Raleigh, North Carolina 27695, United States
| | - Jack S. Twiddy
- Department
of Chemistry, Department of Biological Sciences, and Comparative Medicine Institute, North Carolina State University, Raleigh, North Carolina 27695, United States
- Joint
Department of Biomedical Engineering, North
Carolina State University and University of North Carolina at Chapel
Hill, Raleigh, North Carolina 27695, United States
| | - Jenna M. Berger
- Department
of Chemistry, Department of Biological Sciences, and Comparative Medicine Institute, North Carolina State University, Raleigh, North Carolina 27695, United States
| | - Alexandra G. Forderhase
- Department
of Chemistry, Department of Biological Sciences, and Comparative Medicine Institute, North Carolina State University, Raleigh, North Carolina 27695, United States
| | - Gregory S. McCarty
- Department
of Chemistry, Department of Biological Sciences, and Comparative Medicine Institute, North Carolina State University, Raleigh, North Carolina 27695, United States
| | - John Meitzen
- Department
of Chemistry, Department of Biological Sciences, and Comparative Medicine Institute, North Carolina State University, Raleigh, North Carolina 27695, United States
| | - Leslie A. Sombers
- Department
of Chemistry, Department of Biological Sciences, and Comparative Medicine Institute, North Carolina State University, Raleigh, North Carolina 27695, United States
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2
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Custodio RJP, Hobloss Z, Myllys M, Hassan R, González D, Reinders J, Bornhorst J, Weishaupt AK, Seddek AL, Abbas T, Friebel A, Hoehme S, Getzmann S, Hengstler JG, van Thriel C, Ghallab A. Cognitive Functions, Neurotransmitter Alterations, and Hippocampal Microstructural Changes in Mice Caused by Feeding on Western Diet. Cells 2023; 12:2331. [PMID: 37759553 PMCID: PMC10529844 DOI: 10.3390/cells12182331] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2023] [Revised: 09/14/2023] [Accepted: 09/19/2023] [Indexed: 09/29/2023] Open
Abstract
Metabolic Dysfunction Associated Steatotic Liver Disease (MASLD) is the most common chronic liver disease in Western countries. It is becoming increasingly evident that peripheral organ-centered inflammatory diseases, including liver diseases, are linked with brain dysfunctions. Therefore, this study aims to unravel the effect of MASLD on brain histology, cognitive functions, and neurotransmitters. For this purpose, mice fed for 48 weeks on standard (SD) or Western diet (WD) were evaluated by behavioral tests, followed by sacrifice and analysis of the liver-brain axis including histopathology, immunohistochemistry, and biochemical analyses. Histological analysis of the liver showed features of Metabolic Dysfunction-Associated Steatohepatitis (MASH) in the WD-fed mice including lipid droplet accumulation, inflammation, and fibrosis. This was accompanied by an elevation of transaminase and alkaline phosphatase activities, increase in inflammatory cytokine and bile acid concentrations, as well as altered amino acid concentrations in the blood. Interestingly, compromised blood capillary morphology coupled with astrogliosis and microgliosis were observed in brain hippocampus of the WD mice, indicating neuroinflammation or a disrupted neurovascular unit. Moreover, attention was impaired in WD-fed mice along with the observations of impaired motor activity and balance, enhanced anxiety, and stereotyped head-twitch response (HTR) behaviors. Analysis of neurotransmitters and modulators including dopamine, serotonin, GABA, glutamate, and acetylcholine showed region-specific dysregulation in the brain of the WD-fed mice. In conclusion, the induction of MASH in mice is accompanied by the alteration of cellular morphology and neurotransmitter expression in the brain, associated with compromised cognitive functions.
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Affiliation(s)
- Raly James Perez Custodio
- Leibniz Research Centre for Working Environment and Human Factors at TU Dortmund (IfADo), Ardeystrasse 67, 44139 Dortmund, Germany; (R.J.P.C.); (Z.H.); (M.M.); (R.H.); (D.G.); (J.R.); (S.G.)
| | - Zaynab Hobloss
- Leibniz Research Centre for Working Environment and Human Factors at TU Dortmund (IfADo), Ardeystrasse 67, 44139 Dortmund, Germany; (R.J.P.C.); (Z.H.); (M.M.); (R.H.); (D.G.); (J.R.); (S.G.)
| | - Maiju Myllys
- Leibniz Research Centre for Working Environment and Human Factors at TU Dortmund (IfADo), Ardeystrasse 67, 44139 Dortmund, Germany; (R.J.P.C.); (Z.H.); (M.M.); (R.H.); (D.G.); (J.R.); (S.G.)
| | - Reham Hassan
- Leibniz Research Centre for Working Environment and Human Factors at TU Dortmund (IfADo), Ardeystrasse 67, 44139 Dortmund, Germany; (R.J.P.C.); (Z.H.); (M.M.); (R.H.); (D.G.); (J.R.); (S.G.)
- Department of Forensic Medicine and Toxicology, Faculty of Veterinary Medicine, South Valley University, Qena 83523, Egypt;
| | - Daniela González
- Leibniz Research Centre for Working Environment and Human Factors at TU Dortmund (IfADo), Ardeystrasse 67, 44139 Dortmund, Germany; (R.J.P.C.); (Z.H.); (M.M.); (R.H.); (D.G.); (J.R.); (S.G.)
| | - Jörg Reinders
- Leibniz Research Centre for Working Environment and Human Factors at TU Dortmund (IfADo), Ardeystrasse 67, 44139 Dortmund, Germany; (R.J.P.C.); (Z.H.); (M.M.); (R.H.); (D.G.); (J.R.); (S.G.)
| | - Julia Bornhorst
- Food Chemistry, Faculty of Mathematics and Natural Sciences, University of Wuppertal, Gaußstraße 20, 42119 Wuppertal, Germany; (J.B.); (A.-K.W.)
| | - Ann-Kathrin Weishaupt
- Food Chemistry, Faculty of Mathematics and Natural Sciences, University of Wuppertal, Gaußstraße 20, 42119 Wuppertal, Germany; (J.B.); (A.-K.W.)
| | - Abdel-latif Seddek
- Department of Forensic Medicine and Toxicology, Faculty of Veterinary Medicine, South Valley University, Qena 83523, Egypt;
| | - Tahany Abbas
- Histology Department, Faculty of Medicine, South Valley University, Qena 83523, Egypt;
| | - Adrian Friebel
- Institute of Computer Science & Saxonian Incubator for Clinical Research (SIKT), University of Leipzig, Haertelstraße 16-18, 04107 Leipzig, Germany; (A.F.); (S.H.)
| | - Stefan Hoehme
- Institute of Computer Science & Saxonian Incubator for Clinical Research (SIKT), University of Leipzig, Haertelstraße 16-18, 04107 Leipzig, Germany; (A.F.); (S.H.)
| | - Stephan Getzmann
- Leibniz Research Centre for Working Environment and Human Factors at TU Dortmund (IfADo), Ardeystrasse 67, 44139 Dortmund, Germany; (R.J.P.C.); (Z.H.); (M.M.); (R.H.); (D.G.); (J.R.); (S.G.)
| | - Jan G. Hengstler
- Leibniz Research Centre for Working Environment and Human Factors at TU Dortmund (IfADo), Ardeystrasse 67, 44139 Dortmund, Germany; (R.J.P.C.); (Z.H.); (M.M.); (R.H.); (D.G.); (J.R.); (S.G.)
| | - Christoph van Thriel
- Leibniz Research Centre for Working Environment and Human Factors at TU Dortmund (IfADo), Ardeystrasse 67, 44139 Dortmund, Germany; (R.J.P.C.); (Z.H.); (M.M.); (R.H.); (D.G.); (J.R.); (S.G.)
| | - Ahmed Ghallab
- Leibniz Research Centre for Working Environment and Human Factors at TU Dortmund (IfADo), Ardeystrasse 67, 44139 Dortmund, Germany; (R.J.P.C.); (Z.H.); (M.M.); (R.H.); (D.G.); (J.R.); (S.G.)
- Department of Forensic Medicine and Toxicology, Faculty of Veterinary Medicine, South Valley University, Qena 83523, Egypt;
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Singh D, Preetam Ambati A, Aich P. Sex and Time: Important Variables for Understanding the Impact of Constant Darkness on Behavior, Brain, and Physiology. Neuroscience 2023; 519:73-89. [PMID: 36966879 DOI: 10.1016/j.neuroscience.2023.03.016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2022] [Revised: 03/02/2023] [Accepted: 03/13/2023] [Indexed: 04/03/2023]
Abstract
The circadian clock can coordinate, regulate and predict physiology and behavior in response to the standard light-dark (LD: 12 h light and 12 h dark) cycle. If we alter the LD cycle by exposing mice to constant darkness (DD: 00 h light and 24 h dark), it can perturb behavior, the brain, and associated physiological parameters. The length of DD exposure and the sex of experimental animals are crucial variables that could alter the impact of DD on the brain, behavior, and physiology, which have not yet been explored. We exposed mice to DD for three and five weeks and studied their impact on (1) behavior, (2) hormones, (3) the prefrontal cortex, and (4) metabolites in male and female mice. We also studied the effect of three weeks of standard light-dark cycle restoration after five weeks of DD on the parameters mentioned above. We found that DD exposure was associated with anxiety-like behavior, increased corticosterone and pro-inflammatory cytokines (TNF-α, IL-6, and IL-1β), downregulated neurotrophins (BDNF and NGF), and altered metabolites profile in a duration of DD exposure and sex-dependent manner. Females showed a more robust adaptation than males under DD exposure. Three weeks of restoration was adequate to establish homeostasis in both sexes. To the best of our knowledge, this study is the first of its kind to look at how DD exposure impacts physiology and behavior as a function of sex- and time. These findings would have translational value and may help in establishing sex-specific interventions for addressing DD-related psychological issues.
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Affiliation(s)
- Dhyanendra Singh
- School of Biological Sciences, National Institute of Science Education and Research (NISER), HBNI, PO - Bhimpur-Padanpur, Jatni - 752050, Dist. -Khurda, Odisha, India; Centre for Interdisciplinary Science (CIS), National Institute of Science Education and Research (NISER), HBNI, PO - Bhimpur-Padanpur, Jatni - 752050, Dist. -Khurda, Odisha, India; Homi Bhabha National Institute, Training School Complex, Anushaktinagar, Mumbai 400094, India
| | - Abhilash Preetam Ambati
- School of Biological Sciences, National Institute of Science Education and Research (NISER), HBNI, PO - Bhimpur-Padanpur, Jatni - 752050, Dist. -Khurda, Odisha, India; Centre for Interdisciplinary Science (CIS), National Institute of Science Education and Research (NISER), HBNI, PO - Bhimpur-Padanpur, Jatni - 752050, Dist. -Khurda, Odisha, India
| | - Palok Aich
- School of Biological Sciences, National Institute of Science Education and Research (NISER), HBNI, PO - Bhimpur-Padanpur, Jatni - 752050, Dist. -Khurda, Odisha, India; Centre for Interdisciplinary Science (CIS), National Institute of Science Education and Research (NISER), HBNI, PO - Bhimpur-Padanpur, Jatni - 752050, Dist. -Khurda, Odisha, India; Homi Bhabha National Institute, Training School Complex, Anushaktinagar, Mumbai 400094, India.
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Channer B, Matt SM, Nickoloff-Bybel EA, Pappa V, Agarwal Y, Wickman J, Gaskill PJ. Dopamine, Immunity, and Disease. Pharmacol Rev 2023; 75:62-158. [PMID: 36757901 PMCID: PMC9832385 DOI: 10.1124/pharmrev.122.000618] [Citation(s) in RCA: 38] [Impact Index Per Article: 38.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2022] [Revised: 08/02/2022] [Accepted: 08/04/2022] [Indexed: 12/14/2022] Open
Abstract
The neurotransmitter dopamine is a key factor in central nervous system (CNS) function, regulating many processes including reward, movement, and cognition. Dopamine also regulates critical functions in peripheral organs, such as blood pressure, renal activity, and intestinal motility. Beyond these functions, a growing body of evidence indicates that dopamine is an important immunoregulatory factor. Most types of immune cells express dopamine receptors and other dopaminergic proteins, and many immune cells take up, produce, store, and/or release dopamine, suggesting that dopaminergic immunomodulation is important for immune function. Targeting these pathways could be a promising avenue for the treatment of inflammation and disease, but despite increasing research in this area, data on the specific effects of dopamine on many immune cells and disease processes remain inconsistent and poorly understood. Therefore, this review integrates the current knowledge of the role of dopamine in immune cell function and inflammatory signaling across systems. We also discuss the current understanding of dopaminergic regulation of immune signaling in the CNS and peripheral tissues, highlighting the role of dopaminergic immunomodulation in diseases such as Parkinson's disease, several neuropsychiatric conditions, neurologic human immunodeficiency virus, inflammatory bowel disease, rheumatoid arthritis, and others. Careful consideration is given to the influence of experimental design on results, and we note a number of areas in need of further research. Overall, this review integrates our knowledge of dopaminergic immunology at the cellular, tissue, and disease level and prompts the development of therapeutics and strategies targeted toward ameliorating disease through dopaminergic regulation of immunity. SIGNIFICANCE STATEMENT: Canonically, dopamine is recognized as a neurotransmitter involved in the regulation of movement, cognition, and reward. However, dopamine also acts as an immune modulator in the central nervous system and periphery. This review comprehensively assesses the current knowledge of dopaminergic immunomodulation and the role of dopamine in disease pathogenesis at the cellular and tissue level. This will provide broad access to this information across fields, identify areas in need of further investigation, and drive the development of dopaminergic therapeutic strategies.
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Affiliation(s)
- Breana Channer
- Department of Pharmacology and Physiology, Drexel University College of Medicine, Philadelphia, Pennsylvania (B.C., S.M.M., E.A.N-B., Y.A., J.W., P.J.G.); and The Children's Hospital of Philadelphia Research Institute, Philadelphia, Pennsylvania (V.P.)
| | - Stephanie M Matt
- Department of Pharmacology and Physiology, Drexel University College of Medicine, Philadelphia, Pennsylvania (B.C., S.M.M., E.A.N-B., Y.A., J.W., P.J.G.); and The Children's Hospital of Philadelphia Research Institute, Philadelphia, Pennsylvania (V.P.)
| | - Emily A Nickoloff-Bybel
- Department of Pharmacology and Physiology, Drexel University College of Medicine, Philadelphia, Pennsylvania (B.C., S.M.M., E.A.N-B., Y.A., J.W., P.J.G.); and The Children's Hospital of Philadelphia Research Institute, Philadelphia, Pennsylvania (V.P.)
| | - Vasiliki Pappa
- Department of Pharmacology and Physiology, Drexel University College of Medicine, Philadelphia, Pennsylvania (B.C., S.M.M., E.A.N-B., Y.A., J.W., P.J.G.); and The Children's Hospital of Philadelphia Research Institute, Philadelphia, Pennsylvania (V.P.)
| | - Yash Agarwal
- Department of Pharmacology and Physiology, Drexel University College of Medicine, Philadelphia, Pennsylvania (B.C., S.M.M., E.A.N-B., Y.A., J.W., P.J.G.); and The Children's Hospital of Philadelphia Research Institute, Philadelphia, Pennsylvania (V.P.)
| | - Jason Wickman
- Department of Pharmacology and Physiology, Drexel University College of Medicine, Philadelphia, Pennsylvania (B.C., S.M.M., E.A.N-B., Y.A., J.W., P.J.G.); and The Children's Hospital of Philadelphia Research Institute, Philadelphia, Pennsylvania (V.P.)
| | - Peter J Gaskill
- Department of Pharmacology and Physiology, Drexel University College of Medicine, Philadelphia, Pennsylvania (B.C., S.M.M., E.A.N-B., Y.A., J.W., P.J.G.); and The Children's Hospital of Philadelphia Research Institute, Philadelphia, Pennsylvania (V.P.)
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5
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Brak IV, Filimonova E, Zakhariya O, Khasanov R, Stepanyan I. Transcranial Current Stimulation as a Tool of Neuromodulation of Cognitive Functions in Parkinson’s Disease. Front Neurosci 2022; 16:781488. [PMID: 35903808 PMCID: PMC9314857 DOI: 10.3389/fnins.2022.781488] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2021] [Accepted: 04/28/2022] [Indexed: 11/13/2022] Open
Abstract
Decrease in cognitive function is one of the most common causes of poor life quality and early disability in patients with Parkinson’s disease (PD). Existing methods of treatment are aimed at both correction of motor and non-motor symptoms. Methods of adjuvant therapy (or complementary therapy) for maintaining cognitive functions in patients with PD are of interest. A promising subject of research in this regard is the method of transcranial electric current stimulation (tES). Here we reviewed the current understanding of the pathogenesis of cognitive impairment in PD and of the effects of transcranial direct current stimulation and transcranial alternating current stimulation on the cognitive function of patients with PD-MCI (Parkinson’s Disease–Mild Cognitive Impairment).
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Affiliation(s)
- Ivan V. Brak
- Laboratory of Comprehensive Problems of Risk Assessment to Population and Workers’ Health, Federal State Budgetary Scientific Institution “Izmerov Research Institute of Occupational Health”, Moscow, Russia
- “Engiwiki” Scientific and Engineering Projects Laboratory, Department of Information Technologies, Novosibirsk State University, Novosibirsk, Russia
- *Correspondence: Ivan V. Brak,
| | | | - Oleg Zakhariya
- Faculty of Philosophy, Lomonosov Moscow State University, Moscow, Russia
| | - Rustam Khasanov
- Faculty of Philosophy, Lomonosov Moscow State University, Moscow, Russia
- Independent Researcher, Novosibirsk, Russia
| | - Ivan Stepanyan
- Peoples’ Friendship University of Russia (RUDN University), Moscow, Russia
- Mechanical Engineering Research Institute of the Russian Academy of Sciences, Moscow, Russia
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Cosentino G, Todisco M, Blandini F. Noninvasive neuromodulation in Parkinson's disease: Neuroplasticity implication and therapeutic perspectives. HANDBOOK OF CLINICAL NEUROLOGY 2022; 184:185-198. [PMID: 35034733 DOI: 10.1016/b978-0-12-819410-2.00010-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Noninvasive brain stimulation techniques can be used to study in vivo the changes of cortical activity and plasticity in subjects with Parkinson's disease (PD). Also, an increasing number of studies have suggested a potential therapeutic effect of these techniques. High-frequency repetitive transcranial magnetic stimulation (rTMS) and anodal transcranial direct current stimulation (tDCS) represent the most used stimulation paradigms to treat motor and nonmotor symptoms of PD. Both techniques can enhance cortical activity, compensating for its reduction related to subcortical dysfunction in PD. However, the use of suboptimal stimulation parameters can lead to therapeutic failure. Clinical studies are warranted to clarify in PD the additional effects of these stimulation techniques on pharmacologic and neurorehabilitation treatments.
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Affiliation(s)
- Giuseppe Cosentino
- Translational Neurophysiology Research Unit, IRCCS Mondino Foundation, Pavia, Italy; Department of Brain and Behavioral Sciences, University of Pavia, Pavia, Italy
| | - Massimiliano Todisco
- Translational Neurophysiology Research Unit, IRCCS Mondino Foundation, Pavia, Italy; Department of Brain and Behavioral Sciences, University of Pavia, Pavia, Italy; Movement Disorders Research Center, IRCCS Mondino Foundation, Pavia, Italy.
| | - Fabio Blandini
- Department of Brain and Behavioral Sciences, University of Pavia, Pavia, Italy; Movement Disorders Research Center, IRCCS Mondino Foundation, Pavia, Italy
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Hur KH, Kim SE, Ma SX, Lee BR, Ko YH, Seo JY, Kim SK, Kim YJ, Sung SJ, Lee Y, Jung YH, Lee YS, Lee SY, Jang CG. Methoxphenidine (MXP) induced abnormalities: Addictive and schizophrenia-related behaviours based on an imbalance of neurochemicals in the brain. Br J Pharmacol 2021; 178:3869-3887. [PMID: 33987827 DOI: 10.1111/bph.15528] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2020] [Revised: 04/22/2021] [Accepted: 05/03/2021] [Indexed: 01/14/2023] Open
Abstract
BACKGROUND AND PURPOSE Methoxphenidine is a dissociative-based novel psychoactive designer drug. Although fatal accidents from methoxphenidine abuse have been reported, recreational use of the drug continues. We aim to provide scientific supportfor legal regulation of recreational abuse of methoxphenidine by demonstrating its the pharmacological action. EXPERIMENTAL APPROACH Addictive potential of methoxphenidine was examined using intravenous self-administration test with rats and conditioned place preference test with mice. Further, a series of behavioural tests (open field test, elevated plus maze test, novel object recognition test, social interaction test and tail suspension test) performed to assess whether methoxphenidine caused schizophrenia-related symptoms in mice. Additionally, neurotransmitter enzyme-linked immunosorbent assay and western blot were used to confirm methoxphenidine-induced neurochemical changes in specific brain regions related to abnormal behaviours. KEY RESULTS Methoxphenidine caused addictive behaviours via reinforcing and rewarding effects. Consistently, methoxphenidine induced over-activation of dopamine pathways in the nuclear accumbens, indicating activation of the brain reward circuit. Also, methoxphenidine caused all categories of schizophrenia-related symptoms, including positive symptoms (hyperactivity, impulsivity), negative symptoms (anxiety, social withdrawal, depression) and cognitive impairment. Consistently, methoxphenidine led to the disruption of the hippocampal-prefrontal cortex pathway that is considered to be pathological involved in schizophrenia. CONCLUSIONS AND IMPLICATIONS We demonastrate that methoxphenidine causes addictive and schizophrenia-like behaviours and induces neurochemical changes in brain regions associated with these behaviours. We propose that methoxphenidine could be used in developing useful animal disease models and that it also requires legal restrictions on its recreational use.
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Affiliation(s)
- Kwang-Hyun Hur
- Department of Pharmacology, School of Pharmacy, Sungkyunkwan University, Suwon, South Korea
| | - Seong-Eon Kim
- Department of Pharmacology, School of Pharmacy, Sungkyunkwan University, Suwon, South Korea
| | - Shi-Xun Ma
- Department of Pharmacology, School of Pharmacy, Sungkyunkwan University, Suwon, South Korea
| | - Bo-Ram Lee
- Department of Pharmacology, School of Pharmacy, Sungkyunkwan University, Suwon, South Korea
| | - Yong-Hyun Ko
- Department of Pharmacology, School of Pharmacy, Sungkyunkwan University, Suwon, South Korea
| | - Jee-Yeon Seo
- Department of Pharmacology, School of Pharmacy, Sungkyunkwan University, Suwon, South Korea
| | - Seon-Kyung Kim
- Department of Pharmacology, School of Pharmacy, Sungkyunkwan University, Suwon, South Korea
| | - Young-Jung Kim
- Department of Pharmacology, School of Pharmacy, Sungkyunkwan University, Suwon, South Korea
| | - Su-Jeong Sung
- Department of Pharmacology, School of Pharmacy, Sungkyunkwan University, Suwon, South Korea
| | - Youyoung Lee
- Department of Pharmacology, School of Pharmacy, Sungkyunkwan University, Suwon, South Korea
| | - Young Hoon Jung
- Organic and Medicinal Chemistry Laboratory, College of Pharmacy, Sungkyunkwan University, Suwon, South Korea
| | - Yong-Sup Lee
- Medicinal Chemistry Laboratory, Department of Pharmacy and Department of Life and Nanopharmaceutical Sciences, College of Pharmacy, Kyung Hee University, Seoul, South Korea
| | - Seok-Yong Lee
- Department of Pharmacology, School of Pharmacy, Sungkyunkwan University, Suwon, South Korea
| | - Choon-Gon Jang
- Department of Pharmacology, School of Pharmacy, Sungkyunkwan University, Suwon, South Korea
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Broeder S, Heremans E, Pinto Pereira M, Nackaerts E, Meesen R, Verheyden G, Nieuwboer A. Does transcranial direct current stimulation during writing alleviate upper limb freezing in people with Parkinson’s disease? A pilot study. Hum Mov Sci 2019; 65:S0167-9457(17)30936-3. [DOI: 10.1016/j.humov.2018.02.012] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2017] [Revised: 01/17/2018] [Accepted: 02/19/2018] [Indexed: 11/15/2022]
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9
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Broeder S, Nackaerts E, Heremans E, Vervoort G, Meesen R, Verheyden G, Nieuwboer A. Transcranial direct current stimulation in Parkinson's disease: Neurophysiological mechanisms and behavioral effects. Neurosci Biobehav Rev 2015; 57:105-17. [DOI: 10.1016/j.neubiorev.2015.08.010] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2015] [Revised: 07/16/2015] [Accepted: 08/17/2015] [Indexed: 10/23/2022]
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Prefrontal and Striatal Glutamate Differently Relate to Striatal Dopamine: Potential Regulatory Mechanisms of Striatal Presynaptic Dopamine Function? J Neurosci 2015; 35:9615-21. [PMID: 26134644 DOI: 10.1523/jneurosci.0329-15.2015] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
UNLABELLED Theoretical and animal work has proposed that prefrontal cortex (PFC) glutamate inhibits dopaminergic inputs to the ventral striatum (VS) indirectly, whereas direct VS glutamatergic afferents have been suggested to enhance dopaminergic inputs to the VS. In the present study, we aimed to investigate relationships of glutamate and dopamine measures in prefrontostriatal circuitries of healthy humans. We hypothesized that PFC and VS glutamate, as well as their balance, are differently associated with VS dopamine. Glutamate concentrations in the left lateral PFC and left striatum were assessed using 3-Tesla proton magnetic resonance spectroscopy. Striatal presynaptic dopamine synthesis capacity was measured by fluorine-18-l-dihydroxyphenylalanine (F-18-FDOPA) positron emission tomography. First, a negative relationship was observed between glutamate concentrations in lateral PFC and VS dopamine synthesis capacity (n = 28). Second, a positive relationship was revealed between striatal glutamate and VS dopamine synthesis capacity (n = 26). Additionally, the intraindividual difference between PFC and striatal glutamate concentrations correlated negatively with VS dopamine synthesis capacity (n = 24). The present results indicate an involvement of a balance in PFC and striatal glutamate in the regulation of VS dopamine synthesis capacity. This notion points toward a potential mechanism how VS presynaptic dopamine levels are kept in a fine-tuned range. A disruption of this mechanism may account for alterations in striatal dopamine turnover as observed in mental diseases (e.g., in schizophrenia). SIGNIFICANCE STATEMENT The present work demonstrates complementary relationships between prefrontal and striatal glutamate and ventral striatal presynaptic dopamine using human imaging measures: a negative correlation between prefrontal glutamate and presynaptic dopamine and a positive relationship between striatal glutamate and presynaptic dopamine are revealed. The results may reflect a regulatory role of prefrontal and striatal glutamate for ventral striatal presynaptic dopamine levels. Such glutamate-dopamine relationships improve our understanding of neurochemical interactions in prefrontostriatal circuits and have implications for the neurobiology of mental disease.
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11
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Valentino F, Cosentino G, Brighina F, Pozzi NG, Sandrini G, Fierro B, Savettieri G, D'Amelio M, Pacchetti C. Transcranial direct current stimulation for treatment of freezing of gait: A cross-over study. Mov Disord 2014; 29:1064-9. [DOI: 10.1002/mds.25897] [Citation(s) in RCA: 91] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2013] [Revised: 03/12/2014] [Accepted: 03/30/2014] [Indexed: 01/25/2023] Open
Affiliation(s)
- Francesca Valentino
- Dipartimento di Biomedicina Sperimentale e Neuroscienze Cliniche (BioNeC); Università degli Studi di Palermo; Italy
| | - Giuseppe Cosentino
- Dipartimento di Biomedicina Sperimentale e Neuroscienze Cliniche (BioNeC); Università degli Studi di Palermo; Italy
| | - Filippo Brighina
- Dipartimento di Biomedicina Sperimentale e Neuroscienze Cliniche (BioNeC); Università degli Studi di Palermo; Italy
| | | | - Giorgio Sandrini
- Fondazione Istituto Neurologico Nazionale ‘‘C. Mondino''; IRCCS Pavia Italy
- Department of Brain and Behaviour, University of Pavia, Italy
| | - Brigida Fierro
- Dipartimento di Biomedicina Sperimentale e Neuroscienze Cliniche (BioNeC); Università degli Studi di Palermo; Italy
| | - Giovanni Savettieri
- Dipartimento di Biomedicina Sperimentale e Neuroscienze Cliniche (BioNeC); Università degli Studi di Palermo; Italy
| | - Marco D'Amelio
- Dipartimento di Biomedicina Sperimentale e Neuroscienze Cliniche (BioNeC); Università degli Studi di Palermo; Italy
| | - Claudio Pacchetti
- Fondazione Istituto Neurologico Nazionale ‘‘C. Mondino''; IRCCS Pavia Italy
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12
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Combinational effects of ketamine and amphetamine on behaviors and neurotransmitter systems of mice. Neurotoxicology 2013; 37:136-43. [DOI: 10.1016/j.neuro.2013.04.014] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2012] [Revised: 04/16/2013] [Accepted: 04/25/2013] [Indexed: 11/19/2022]
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13
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Morales I, Sabate M, Rodriguez M. Striatal glutamate induces retrograde excitotoxicity and neuronal degeneration of intralaminar thalamic nuclei: their potential relevance for Parkinson's disease. Eur J Neurosci 2013; 38:2172-82. [DOI: 10.1111/ejn.12205] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2013] [Revised: 02/27/2013] [Accepted: 02/28/2013] [Indexed: 01/23/2023]
Affiliation(s)
| | - Magdalena Sabate
- Department of Pharmacology and Physical Medicine; Faculty of Medicine; University of La Laguna; Service of Rehabilitation HUC; La Laguna; Tenerife; Canary Islands; Spain
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14
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Izumi Y, Yamamoto N, Matsuo T, Wakita S, Takeuchi H, Kume T, Katsuki H, Sawada H, Akaike A. Vulnerability to glutamate toxicity of dopaminergic neurons is dependent on endogenous dopamine and MAPK activation. J Neurochem 2009; 110:745-55. [DOI: 10.1111/j.1471-4159.2009.06178.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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15
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Durand D, Pampillo M, Caruso C, Lasaga M. Role of metabotropic glutamate receptors in the control of neuroendocrine function. Neuropharmacology 2008; 55:577-83. [PMID: 18616955 DOI: 10.1016/j.neuropharm.2008.06.022] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2008] [Revised: 05/23/2008] [Accepted: 06/12/2008] [Indexed: 11/25/2022]
Abstract
Glutamate exerts its effects through binding and activation of two classes of specific receptors: ionotropic (iGluRs) and metabotropic (mGluRs). Group I mGluR includes mGluR1 and mGluR5 subtypes, group II includes mGluR2 and mGluR3 subtypes and group III includes the subtypes mGluR 4, 6, 7 and 8. Glutamate and its receptors are found in all key hypothalamic areas critically involved in reproduction and neuroendocrine function. To date, considerable data support an important role for iGluRs in the control of neuroendocrine function; however, the role of mGluRs as regulators of hypothalamic-pituitary function has not been clearly elucidated. mGluRs could be exerting a fine tune on the release of hypothalamic factors that regulate hormone release such as Substance P, GABA, alpha-MSH and CRH. Group II mGluR exert a direct inhibitory effect on anterior pituitary prolactin and GH secretion. Moreover, some group II mGluR agonists, like LY 354,740 and LY 379,268, can modulate PRL secretion from the anterior pituitary through their actions as dopamine receptor agonists. Evidence suggests a role for group III mGluR subtypes in stress-related behavioral disorders. Several reports indicate that selective ligands for mGluR subtypes have potential for the treatment of a wide variety of neurological and psychiatric disorders, including depression, anxiety disorders, schizophrenia, epilepsy and Alzheimer's disease among others. Since converging lines of evidence suggest a role for mGluRs subtypes in neuroendocrine regulation of hormone secretion, mGluRs neuroendocrine actions must be taken in consideration to insure proper treatment of these diseases. Moreover, discovery of selective agonists provides an opportunity to investigate the physiological role of mGluR subtypes and to directly test the neuroendocrine actions of mGluRs. Finally, mGluRs selective agonists may have an impact in the treatment of conditions involving chronic stress, such as depression and anxiety disorders, since they regulate neuroendocrine stress circuits involving the HPA axis and stress-sensitive hormones such as oxytocin and prolactin. This review aims to provide a survey of our current understanding of the effects of mGluR activation on neuroendocrine function.
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Affiliation(s)
- Daniela Durand
- Research Center in Reproduction, School of Medicine, University of Buenos Aires, Paraguay 2155, Piso 10, 1121 Buenos Aires, Argentina
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16
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Central neurophysiology and dopaminergic control of ejaculation. Neurosci Biobehav Rev 2008; 32:438-53. [DOI: 10.1016/j.neubiorev.2007.07.013] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2007] [Revised: 07/31/2007] [Accepted: 07/31/2007] [Indexed: 01/09/2023]
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17
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Dagher A, Nagano-Saito A. Functional and Anatomical Magnetic Resonance Imaging in Parkinson’s Disease. Mol Imaging Biol 2007; 9:234-42. [PMID: 17318668 DOI: 10.1007/s11307-007-0089-0] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
For the past 15 years, measurements of cerebral blood flow as an indicator of neuronal activity have been used to gain a better understanding of the neural basis of motor and cognitive deficits in Parkinson's disease. The initial studies, using positron emission tomography, yielded results in keeping with the hypothesis that symptoms result from excessive cortical inhibition from cortico-striatal loops. However, subsequent studies with functional magnetic resonance imaging (fMRI) have shown that specific aspects of the paradigms used, such as the need to pay attention to one's movements, have a significant impact on activation patterns, which may complicate the interpretation of results. Functional neuroimaging has also been used to investigate the causes of cognitive impairment in Parkinson's disease. While some studies implicate dopamine loss in striatum, more recent investigations using anatomical MRI to measure cortical atrophy suggest that some cognitive deficits are attributable to direct cortical involvement by the disease.
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Affiliation(s)
- Alain Dagher
- McConnell Brain Imaging Centre, Montreal Neurological Institute, McGill University, Montréal, Canada.
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18
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Parsons MP, Li S, Kirouac GJ. Functional and anatomical connection between the paraventricular nucleus of the thalamus and dopamine fibers of the nucleus accumbens. J Comp Neurol 2007; 500:1050-63. [PMID: 17183538 DOI: 10.1002/cne.21224] [Citation(s) in RCA: 109] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The shell of the nucleus accumbens (NacSh) receives a dense innervation from dopamine (DA) neurons in the ventral tegmental area (VTA) and from glutamate neurons in the paraventricular nucleus of the thalamus (PVT). The present study examined in urethane-anesthetized rats the effects of electrical stimulation of the PVT on DA levels in the NacSh as measured with amperometry and chronoamperometry. Stimulation of the PVT (40 Hz, 1.0 ms, 400 microA, 5 seconds) resulted in a brief increase in electrochemical currents detected in the NacSh. Inhibition of DA neurons in the VTA using lidocaine (4%, 500 nL) or intravenous apomorphine (0.15 mg/kg) decreased the resting voltammetric signal but had no effect on PVT-evoked responses. Blocking of ionotropic glutamate receptors in the NacSh with local administration of kynurenic acid attenuated the PVT-evoked responses. Anterograde tracing with biotinylated dextran amine demonstrated that PVT targets regions of very dense tyrosine hydroxylase fiber staining in the NacSh. Consistent with the projection pattern of the PVT to the NacSh, stimulation of the PVT evoked the largest oxidation current changes in the NacSh, whereas small or no changes were elicited in other areas of the striatum. This study suggests that glutamate release from PVT terminals can act on ionotropic glutamate receptors in the NacSh to induce DA efflux. Modulation of DA levels in the NacSh by the PVT may be linked to arousal-induced increases in DA tone and could be involved in the facilitation of specific behavioral patterns associated with arousal or stressful situations.
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Affiliation(s)
- Matthew P Parsons
- Division of Basic Medical Science, Faculty of Medicine, Memorial University of Newfoundland, St. John's, Newfoundland and Labrador, A1B 3V6, Canada
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19
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Izumi Y, Sawada H, Yamamoto N, Kume T, Katsuki H, Shimohama S, Akaike A. Novel neuroprotective mechanisms of pramipexole, an anti-Parkinson drug, against endogenous dopamine-mediated excitotoxicity. Eur J Pharmacol 2006; 557:132-40. [PMID: 17161393 DOI: 10.1016/j.ejphar.2006.11.011] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2006] [Revised: 11/01/2006] [Accepted: 11/06/2006] [Indexed: 11/30/2022]
Abstract
Parkinson disease is characterized by selective degeneration of mesencephalic dopaminergic neurons, and endogenous dopamine may play a pivotal role in the degenerative processes. Using primary cultured mesencephalic neurons, we found that glutamate, an excitotoxin, caused selective dopaminergic neuronal death depending on endogenous dopamine content. Pramipexole, a dopamine D2/D3 receptor agonist used clinically in the treatment of Parkinson disease, did not affect glutamate-induced calcium influx but blocked dopaminergic neuronal death induced by glutamate. Pramipexole reduced dopamine content but did not change the levels of total or phosphorylated tyrosine hydroxylase, a rate-limiting enzyme in dopamine synthesis. The neuroprotective effect of pramipexole was independent of dopamine receptor stimulation because it was not abrogated by domperidone, a dopamine D2-type receptor antagonist. Moreover, both active S(-)- and inactive R(+)-enantiomers of pramipexole as a dopamine D2-like receptor agonist equally suppressed dopaminergic neuronal death. These results suggest that pramipexole protects dopaminergic neurons from glutamate neurotoxicity by the reduction of intracellular dopamine content, independently of dopamine D2-like receptor activation.
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Affiliation(s)
- Yasuhiko Izumi
- Department of Pharmacology, Graduate School of Pharmaceutical Sciences, Kyoto University, 46-29 Yoshida-shimoadachi-cho, Sakyo-ku, Kyoto 606-8501, Japan
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20
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Ismayilova N, Verkhratsky A, Dascombe MJ. Changes in mGlu5 receptor expression in the basal ganglia of reserpinised rats. Eur J Pharmacol 2006; 545:134-41. [PMID: 16890937 DOI: 10.1016/j.ejphar.2006.06.076] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2006] [Revised: 06/26/2006] [Accepted: 06/28/2006] [Indexed: 11/19/2022]
Abstract
Dopamine depletion in Parkinson's disease results in a series of pathophysiological changes in the basal ganglia circuitry. Increased release of glutamate plays an important role in this motor disorder, therefore, agents interacting with glutamatergic transmission may have therapeutic potential. In this study we investigated changes in both mRNA expression and the number of binding sites of the mGlu5 receptor in a reserpinised rat model of Parkinson's disease. The in situ hybridisation demonstrated that acute reserpine treatment caused a significant decrease in the expression of mGlu5 receptor mRNA in the rostral and caudal parts of the rat striatum. At the same time, tritium-labelled 2-ethyl-6-(phenylethynyl)-pyridine ([(3)H]MPEP) ligand binding experiments detected a significant increase in the total number of mGlu5 receptors in the same region of the motor loop. These apparently contradictory data can be explained by mGlu5 receptor turnover being down-regulated in reserpinised rats, due possibly to an imbalance in the rates of synthesis/insertion and internalisation/degradation of the receptor. These findings suggest that changes such as these affecting mGlu5 receptors may be involved in the pathophysiological consequences of dopamine depletion in the brain.
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Affiliation(s)
- Naila Ismayilova
- The University of Manchester, Faculty of Life Sciences, 1.124 Stopford Building, Oxford Road, Manchester M13 9PT, UK
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21
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Leonetti M, Desvignes C, Bougault I, Souilhac J, Oury-Donat F, Steinberg R. 2-Chloro-N-[(S)-phenyl [(2S)-piperidin-2-yl] methyl]-3-trifluoromethyl benzamide, monohydrochloride, an inhibitor of the glycine transporter type 1, increases evoked-dopamine release in the rat nucleus accumbens in vivo via an enhanced glutamatergic neurotransmission. Neuroscience 2006; 137:555-64. [PMID: 16289893 DOI: 10.1016/j.neuroscience.2005.09.003] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2005] [Revised: 09/02/2005] [Accepted: 09/07/2005] [Indexed: 01/02/2023]
Abstract
2-Chloro-N-S-phenyl 2S-piperidin-2-yl methyl]-3-trifluoromethyl benzamide, monohydrochloride (SSR504734) is a potent and selective inhibitor of the glycine transporter type 1, which increases central N-methyl-D aspartate glutamatergic tone. Since glutamate has been shown to play a role in the regulation of the dopaminergic system in dopamine-related disorders, such as schizophrenia, we investigated the possibility that SSR504734 may modify the basolateral amygdala-elicited stimulation of dopamine release in the nucleus accumbens via an augmentation of glutamate receptor-mediated neurotransmission. First, our data confirmed that SSR504734 is an inhibitor of GlytT1. In the nucleus accumbens of anesthetized rat, SSR504734 (10 mg/kg, i.p.) induced an increase of extracellular levels of glycine as measured by microdialysis coupled with capillary electrophoresis with laser-induced fluorescence detection. Second, the data demonstrated that SSR504734 (10 mg/kg, i.p.) enhanced the facilitatory influence of glutamatergic afferents on dopamine neurotransmission in the nucleus accumbens. Using an electrochemical technique, we measured dopamine release in the nucleus accumbens evoked by an electrical stimulation of the basolateral amygdala. SSR504734 facilitated dopamine release evoked by a 20 or a 40 Hz frequency basolateral amygdala stimulation. This facilitatory effect was dependent on glutamatergic tone, as intra-nucleus accumbens application of 6-7-dinitroquinoxaline-2,3-dione (10(-3) M) or DL-2-amino-5-phosphonopentanoic acid (10(-3) M), alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid and N-methyl-D aspartate receptors antagonists, respectively, inhibited dopamine release evoked by basolateral amygdala stimulation. Furthermore DL-2-amino-5-phosphonopentanoic acid co-administrated with SSR504734 hampered the dopamine-evoked release facilitation. These data underline the in vivo implication of the glycine uptake mechanism in the control of subcortical glutamate/dopamine interactions.
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Affiliation(s)
- M Leonetti
- Sanofi-Aventis, 371 rue du Professeur Joseph Blayac, 34184 Montpellier Cedex 4, France.
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22
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Cauli O, Llansola M, Rodrigo R, El Mlili N, Errami M, Felipo V. Altered modulation of motor activity by group I metabotropic glutamate receptors in the nucleus accumbens in hyperammonemic rats. Metab Brain Dis 2005; 20:347-58. [PMID: 16382345 DOI: 10.1007/s11011-005-7918-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
One of the neurological complications in hepatic encephalopathy is the impairment of motor coordination and function. Clinical signs of basal ganglia, cortico-spinal and cerebellar dysfunction have been commonly detected in these patients. We are studying the molecular bases of the alterations in motor coordination and function in hepatic encephalopathy. Hyperammonemia is considered the main factor responsible for the neurological alterations in patients with hepatic encephalopathy. Activation of metabotropic glutamate receptors (mGluRs) in the nucleus accumbens (NAcc) induces locomotion in rats. Asa first step in our studies on the alterations in motor co-ordination and function in hyperammonemia and hepatic encephalopathy we studied whether the control of motor function by mGluRs in the NAcc is altered in hyperammonemic rats. The locomotor activity induced by injection into the nucleus accumbens (NAcc) of DHPG, an agonist of group I mGluRs was significantly increased in hyperammonemic rats. Injection of DHPG increased extracellular dopamine but not glutamate in the NAcc of control rats. In hyperammonemic rats DHPG-induced increase in dopamine was significantly reduced, and extracellular glutamate increased 6-fold. The content of mGluR 1 but not mGluR 5, is increased in the NAcc of hyperammonemic rats. Blockade of mGluR 1 completely prevented motor and neurochemical effects induced by DHPG. These results show that modulation of both motor function and extracellular concentration of neurotransmitters by mGluRs in the NAcc is altered in hyperammonemia. This may contribute to the alterations in motor function in hepatic encephalopathy.
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Affiliation(s)
- Omar Cauli
- Laboratory of Neurobiology, Fundación Valenciana de Investigaciones Biomédicas, Valencia, Spain.
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23
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Hong JT, Kim HC, Kim HS, Lee YM, Oh KW. The role of nitric oxide on glutaminergic modulation of dopaminergic activation. Pharmacol Res 2005; 52:298-301. [PMID: 15939623 DOI: 10.1016/j.phrs.2005.05.002] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/17/2003] [Revised: 04/29/2005] [Accepted: 05/04/2005] [Indexed: 11/18/2022]
Abstract
Biochemical studies have been demonstrated that N-methyl-D-aspartate (NMDA)-evoked dopaminergic (DAergic) activation can be modulated by nitric oxide (NO) systems. Therefore, behavioral study was performed to characterize the role of NO on NMDA modulation of DAergic activation. It is well known that apomorphine induces climbing behaviors in mice by the activation of DAergic receptors. Our previous studies showed that NMDA receptor antagonists reduced apomorphine-induced climbing behaviors. It was reported that nitric oxide synthase (NOS) inhibitors reduced the apomorphine-induced climbing behaviors. In this experiment, NO donor restored the apomorphine-induced climbing behavior, which was inhibited by NMDA receptor antagonist. NOS inhibitor inhibited the apomorphine-induced climbing behavior, which was enhanced by NMDA receptor agonist. These results suggest that DAergic activation is regulated by both NMDA receptors and NO systems, and NO in the down-stream of NMDA receptors play an important role on the glutaminergic NMDA modulation of DAergic function.
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Affiliation(s)
- Jin-Tae Hong
- Department of Pharmacy, College of Pharmacy, Chungbuk National University, Cheongju 371-763, South Korea
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24
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Yu MF, Chien CL, Lee WT, Yin HS. Effects of acute amphetamine administration on AMPA-mediated synaptic activity and expression of AMPA receptor subunit 2 of brain neurons. J Mol Neurosci 2005; 25:171-81. [PMID: 15784965 DOI: 10.1385/jmn:25:2:171] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2004] [Accepted: 05/12/2004] [Indexed: 11/11/2022]
Abstract
We investigated the role of alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate receptor (AMPAR) in mechanisms underlying the action of amphetamine (Amph) on brain neurons, for AMPAR has been proposed to participate in psychotic and neurodegenerative disorders. In the cultured rat brain cortical neurons pretreated with 1 microM Amph for 1 h, the accumulation of 45Ca2+ driven by 10 min incubation with 100 microM AMPA was reduced by about 36%. This Amph-induced decrease seems to involve L-type voltage-gated Ca2+ channels, because the AMPA-induced 45Ca2+ uptake was blocked by 70% and 80%, respectively, for untreated and Amph-treated neurons in the presence of nifedipine (1 microM), an antagonist to L-type calcium channels. Whole-cell, patch-clamp recording revealed that AMPA-elicited current amplitude became 26% lower than the control in Amph-treated cultured neurons. Moreover, Amph treatment down-regulated the level of flip-form glutamate receptor 2 (GluR2) mRNA by 27% in cultured neurons but did not change the expression of GluR2 proteins and flop-form mRNA, as detected by quantitative immunocytochemistry and in situ hybridization. In contrast, in postnatal day 4 rats at 1 h after receiving one intraperitoneal injection of 5 mg/kg of Amph, levels of flip GluR2 mRNA were up-regulated by 13% and 18% in neurons of motor cortex layer 5 and pyramidal neurons of hippocampal CA3, respectively. The data suggest that acute action of Amph on brain neurons is possibly associated with decreased AMPA-mediated Ca2+ influx and current amplitude, as well as modified expression of the GluR2 mRNA.
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Affiliation(s)
- Meng-Fen Yu
- Chang Gang Institute of Technology, School of Nursing, Tao-Yuan, Taiwan, ROC
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25
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Abstract
Fear conditioning, during which emotional significance is attached to an initially biologically insignificant conditioned stimulus, when such neutral stimulus is paired with an aversive unconditioned stimulus, provides an experimental paradigm that is most commonly used to study fear learning. The amygdala, a sub-cortical nuclear group, is a brain structure critically important for fear conditioning. Recent studies indicate that both fear conditioning-induced neuronal plasticity and LTP at the amygdala synapses share common mechanisms of induction and expression. These findings provide the most direct evidence yet available that the mechanisms of LTP are recruited in the experimental animals during behavioral training and that such mechanisms might be utilized for memory storage.
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Affiliation(s)
- Alexander E Dityatev
- Institute of Neurophysiology and Pathophysiology, University of Hamburg, Hamburg, Germany
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26
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Szumlinski KK, Frys KA, Kalivas PW. Dissociable roles for the dorsal and median raphé in the facilitatory effect of 5-HT1A receptor stimulation upon cocaine-induced locomotion and sensitization. Neuropsychopharmacology 2004; 29:1675-87. [PMID: 15127081 DOI: 10.1038/sj.npp.1300473] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
A distinct role for serotonin transmission from the dorsal and median raphé nuclei (DRN and MRN, respectively) was identified in regulating the behavioral and neurochemical effects of acute and repeated cocaine administration. Serotonin 1A (5-hydroxytryptophan (5-HT)1A) receptors were stimulated by intraraphé microinjection of 8-hydroxy-2-(di-n-propylamino)tetralin (DPAT; 5 or 10 microg) and behavior, as well as extracellular neurotransmitter content in the nucleus accumbens was measured. Pretreatment of the DRN with DPAT caused a sensitization-like potentiation of acute cocaine-induced motor activity and an elevation in extracellular dopamine and glutamate. In contrast, DPAT microinjection into the MRN did not alter acute cocaine-induced motor activity or extracellular levels of dopamine or glutamate. Acutely, DPAT microinjection into either raphé nucleus reduced the basal and acute cocaine-stimulated levels of extracellular serotonin. Pretreatment with DPAT before systemic cocaine administration was continued for 5 days, and 3 weeks after the last injection, all rats were administered a cocaine challenge injection. The sensitized behavioral and neurochemical response produced by repeated cocaine in control subjects was unaffected by the intra-DRN administration of DPAT. However, in animals administered DPAT into the MRN, both the sensitized motor response and the increase in glutamate were augmented, while the sensitized serotonin response was blocked, without altering dopamine sensitization. These data show a differential role for 5-HT1A receptors in the DRN and MRN in the acute and sensitized effects of cocaine. While the DRN is involved in the acute effects of cocaine, neuroadaptations in the MRN may regulate the long-term consequences of repeated cocaine exposure.
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Affiliation(s)
- Karen K Szumlinski
- Department of Physiology and Neuroscience, Medical University of South Carolina, Charleston, SC 29425, USA.
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27
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Delis F, Mitsacos A, Giompres P. Dopamine receptor and transporter levels are altered in the brain of Purkinje Cell Degeneration mutant mice. Neuroscience 2004; 125:255-68. [PMID: 15051164 DOI: 10.1016/j.neuroscience.2004.01.020] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/22/2004] [Indexed: 11/16/2022]
Abstract
The Purkinje Cell Degeneration (Nna1pcd, pcd) mutant mouse is mainly characterized by the complete, primary loss of the Purkinje cells and the secondary, partial, retrograde loss of the granule and inferior olive neurons and is considered a model of human degenerative ataxia. We determined, by in vitro quantitative autoradiography and in situ hybridization, the effects of the Purkinje cell deprivation on the dopaminergic system of the Nna1pcd mutant mouse. The dopamine transporters, as determined by [3H]WIN35428 binding, were increased compared with wild-type mice in the ventral mesencephalic dopaminergic nuclei and in the lateral striatum, motor cortex and septum. In the cerebellum of Nna1pcd mice, the dopamine transporters showed a significant increase in the deep cerebellar nuclei, but were significantly decreased in the molecular layer. The D1-like receptors, as determined by [3H]SCH23390 binding, increased significantly in the Nna1pcd substantia nigra. The D2/D3 receptors, as determined by [3H]raclopride binding, exhibited a significant decrease in lateral divisions of the striatum. Significant increases in D2-like receptors, as determined by [3H]nemonapride binding, were observed in most divisions of the striatum as well as in septum, hippocampus, and piriform cortex. This D2-like fraction most probably corresponds to the D4 receptor subtype. In the cerebellum of Nna1pcd mice, D2-like receptors were significantly decreased in the molecular layer. The results suggest an increased excitatory input on the dopaminergic mesencephalic neurons and an alteration of the dopaminergic neurotransmission in basal ganglia, cortical and limbic regions of the Nna1pcd mutant mouse. In the cerebellum, the significant downregulation of the dopamine transporters and D2-like receptors in the mutant cerebellar molecular layer is possibly due to the absence of the Purkinje cells.
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Affiliation(s)
- F Delis
- Laboratory of Human and Animal Physiology, Department of Biology, University of Patras, 26500 Rion, Greece
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28
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Canales JJ, Elayadi A, Errami M, Llansola M, Cauli O, Felipo V. Chronic hyperammonemia alters motor and neurochemical responses to activation of group I metabotropic glutamate receptors in the nucleus accumbens in rats in vivo. Neurobiol Dis 2004; 14:380-90. [PMID: 14678755 DOI: 10.1016/j.nbd.2003.08.023] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022] Open
Abstract
Hyperammonemia leads to altered cerebral function and neurological alterations in patients with hepatic encephalopathy. We studied the effects of hyperammonemia in rats on the modulation by group I metabotropic glutamate receptors (mGluR) of motor and neurochemical functions in vivo. Locomotion induced by injection of the mGluR agonist DHPG into nucleus accumbens was increased in hyperammonemic rats. In control rats DHPG increased extracellular dopamine (ca. 400%) but not glutamate. In contrast, in hyperammonemic rats DHPG increased extracellular glutamate (ca. 600%), while DHPG-induced dopamine increase was reduced. Blocking mGluR1 receptor with CPCCOEt prevented all DHPG effects, indicating that this receptor mediates its locomotor and neurochemical effects. Hyperammonemic rats showed increased (32%) mGluR1alpha, but not mGluR5 content in nucleus accumbens. These results show that modulation of locomotor and neurochemical functions by mGluRs in nucleus accumbens is strongly altered in hyperammonemia. These alterations may contribute to the neurological alterations in hyperammonemia and liver failure.
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Affiliation(s)
- Juan-José Canales
- Laboratory of Neurobiology, Instituto de Investigaciones Citológicas, Fundación Valenciana de Investigaciones Biomédicas, Valencia, Spain
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29
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Rieck RW, Ansari MS, Whetsell WO, Deutch AY, Kessler RM. Distribution of dopamine D2-like receptors in the human thalamus: autoradiographic and PET studies. Neuropsychopharmacology 2004; 29:362-72. [PMID: 14627996 DOI: 10.1038/sj.npp.1300336] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The distribution of dopamine (DA) D(2)-like receptors in the human thalamus was studied using in vitro autoradiographic techniques and in vivo positron emission tomography in normal control subjects. [(125)I]Epidepride, which binds with high affinity to DA D(2) and D(3) receptors, was used in autoradiographic studies to determine the distribution and density of D(2)-like receptors, and the epidepride analogue [(18)F]fallypride positron was used for positron emission tomography studies to delineate D(2)-like receptors in vivo. Both approaches revealed a heterogeneous distribution of thalamic D(2/3) receptors, with relatively high densities in the intralaminar and midline thalamic nuclei, including the paraventricular, parataenial, paracentral, centrolateral, and centromedian/parafascicular nuclei. Moderate densities of D(2/3) sites were seen in the mediodorsal and anterior nuclei, while other thalamic nuclei expressed lower levels of D(2)-like receptors. Most thalamic nuclei that express high densities of D(2)-like receptors project to forebrain DA terminal fields, suggesting that both the thalamic neurons expressing D(2)-like receptors and the projection targets of these neurons are regulated by DA. Because the midline/intralaminar nuclei receive prominent projections from both the ascending reticular activating core and the hypothalamus, these thalamic nuclei may integrate activity conveying both interoceptive and exteroceptive information to telencephalic DA systems involved in reward and cognition.
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Affiliation(s)
- Richard W Rieck
- Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, TN, USA
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30
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Dominguez JM, Muschamp JW, Schmich JM, Hull EM. Nitric oxide mediates glutamate-evoked dopamine release in the medial preoptic area. Neuroscience 2004; 125:203-10. [PMID: 15051159 DOI: 10.1016/j.neuroscience.2004.01.022] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/22/2004] [Indexed: 11/22/2022]
Abstract
Dopamine (DA) release in the medial preoptic area (MPOA) of the hypothalamus is an important facilitator of male sexual behavior. The presence of a receptive female increases extracellular DA in the MPOA, which increases further during copulation. However, the neurochemical events that mediate the increase of DA in the MPOA are not fully understood. Here we report that glutamate, reverse-dialyzed into the MPOA, increased extracellular DA, which returned to baseline after the glutamate was removed. This increase was prevented by co-administration of the nitric oxide synthase inhibitor NG-nitro-l-arginine methyl ester (L-NAME), but not by the inactive isomer, Nw-nitro-d-arginine methyl ester (D-NAME). In contrast, extracellular concentrations of the major metabolites of DA were decreased by glutamate, suggesting that the DA transporter was inhibited. These decreases were also inhibited by L-NAME, but not D-NAME. These results indicate that glutamate enhances extracellular DA in the MPOA, at least in part, via nitric oxide activity. Therefore, glutamatergic stimulation of nitric oxide synthase may generate the female-induced increase in extracellular DA in the MPOA, which is important for the expression of male sexual behavior.
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Affiliation(s)
- J M Dominguez
- Department of Psychology, University at Buffalo, The State University of New York, B71 Park Hall, Buffalo, NY 14260-4110, USA
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31
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Bauter MR, Brockel BJ, Pankevich DE, Virgolini MB, Cory-Slechta DA. Glutamate and dopamine in nucleus accumbens core and shell: sequence learning versus performance. Neurotoxicology 2003; 24:227-43. [PMID: 12606295 DOI: 10.1016/s0161-813x(02)00167-5] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
This study sought to determine whether neurochemical changes associated with chronic postweaning lead (Pb) exposure, namely, enhanced dopamine (DA) activity and/or blockade of NMDA function in nucleus accumbens (NAC), underlie the learning impairments also associated with this Pb regimen, and whether core or shell subregions of nucleus accumbens would be more important to such effects. If so, then mimicking these neurochemical changes in normal (control) rats should reproduce these Pb-induced learning impairments. For this purpose, the effects of DA (20-80 microg), the non-competitive NMDA antagonist MK-801 (1.0-2.5 microg) or DA+MK-801 (40+1.0, 80+2.5 microg) were infused in core or shell of nucleus accumbens in normal rats and effects on a multiple schedule of repeated learning (RL) and performance (P) evaluated. In core, MK-801 mimicked the effects of Pb exposure, selectively reducing RL accuracy with no corresponding changes in P accuracy, an effect derived from an increased frequency of perseverative errors. DA produced non-specific changes, reducing accuracy levels in RL and P components. Accuracy and rate effects of DA could be reversed by concurrent administration of the higher MK-801 dose. In shell, MK-801, primarily the lower dose, reduced accuracy in both the RL and P components, while DA did not produce any systematic effects. Collectively, these results point to a greater importance of core as compared to shell in the mediation of learning of spatial sequences, and suggest that inhibition of glutamatergic NMDA function may play a critical role in the selective learning impairments associated with chronic low level Pb exposure.
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Affiliation(s)
- M R Bauter
- Department of Environmental Medicine, University of Rochester School of Medicine, PO Box 706, Rochester, NY 14642, USA
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32
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Forster GL, Blaha CD. Pedunculopontine tegmental stimulation evokes striatal dopamine efflux by activation of acetylcholine and glutamate receptors in the midbrain and pons of the rat. Eur J Neurosci 2003; 17:751-62. [PMID: 12603265 DOI: 10.1046/j.1460-9568.2003.02511.x] [Citation(s) in RCA: 137] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The pedunculopontine tegmental nucleus appears to influence striatal dopamine activity via cholinergic and glutamatergic afferents to dopaminergic cells of the substantia nigra pars compacta. We measured changes in striatal dopamine oxidation current (dopamine efflux) in response to electrical stimulation of the pedunculopontine tegmental nucleus using in vivo electrochemistry in urethane-anaesthetized rats. Pedunculopontine tegmental nucleus stimulation evoked a three-component change in striatal dopamine efflux, consisting of: (i) an initial rapid increase of 2 min duration; followed by (ii) a decrease below prestimulation levels of 9 min duration; then by (iii) a prolonged increase lasting 35 min. Intra-nigral infusions of the ionotropic glutamate receptor antagonist kynurenate (10 microg/ microL) or the nicotinic cholinergic receptor antagonist mecamylamine (5 microg/0.5 microL) selectively attenuated the rapid first component, while systemic injections of the muscarinic cholinergic antagonist scopolamine (5 mg/kg, i.p.) diminished the second and third components. In addition, intra-pedunculopontine tegmental nucleus infusions of the M2 muscarinic antagonist methoctramine (50 microg/ microL) selectively abolished the inhibitory second component, while intranigral infusions of scopolamine (200 microg/ microL) selectively abolished the prolonged third component. Intra-nigral infusions of the metabotropic glutamate receptor antagonist (+)-alpha-methyl-4-carboxyphenylglycine (2 microg/ microL) had no effect on pedunculopontine tegmental nucleus-elicited striatal dopamine efflux. These results suggest that the pedunculopontine tegmental nucleus utilizes nicotinic and ionotropic glutamate receptors in the substantia nigra to mediate rapid activation, M2-like muscarinic autoreceptors in the pedunculopontine tegmental nucleus to mediate decreased activation, and muscarinic receptors in the substantia nigra (probably of the M5 subtype) to mediate prolonged activation, of the nigrostriatal dopaminergic system.
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Affiliation(s)
- Gina L Forster
- Department of Psychology, Macquarie University, Sydney, NSW 2109, Australia
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33
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De La Garza R, Jentsch JD, Verrico CD, Roth RH. Adaptation of monoaminergic responses to phencyclidine in nucleus accumbens and prefrontal cortex following repeated treatment with fluoxetine or imipramine. Brain Res 2002; 958:20-7. [PMID: 12468026 DOI: 10.1016/s0006-8993(02)03772-1] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The adaptive neuronal changes that follow chronic administration of antidepressant drugs are thought to underlie clinical improvement in patient populations. Recent evidence suggests that alterations specific to N-methyl-D-aspartate (NMDA) receptors may be a final common pathway to antidepressant action. To investigate this possibility, we sought to establish the effects of chronic fluoxetine or imipramine treatment on the monoamine stimulating effect of the non-competitive NMDA antagonist phencyclidine. Male, Sprague-Dawley rats (n=9/group) were treated with saline (1 ml/kg, i.p.), imipramine (10 mg/kg, i.p.) or fluoxetine (10 mg/kg, i.p.) once daily for 14 consecutive days. After a 7-day drug-free period, animals given an acute challenge of either saline or phencyclidine (5 mg/kg, i.p.). One hour later, animals were killed, brains were removed, and the prefrontal cortex, striatum, and nucleus accumbens were dissected. Samples were assayed for the monoamines and their primary metabolites by HPLC. Repeated treatment with fluoxetine or imipramine did not alter baseline dopamine or serotonin turnover. Acute phencyclidine treatment increased prefrontal cortex and nucleus accumbens dopamine turnover in saline-treated animals (P<0.01); however, the effect in the nucleus accumbens was prevented in animals pretreated with imipramine or fluoxetine. Acute phencyclidine challenge also increased serotonin turnover in prefrontal cortex of saline- or imipramine-pretreated rats (P<0.01), though this effect was attenuated in animals pretreated with fluoxetine. Overall, the data suggest that repeated antidepressant treatment alters monoamine turnover in specific brain regions in response to blockade of NMDA receptors. The data highlight the importance of adaptive responses to NMDA receptors resulting from chronic antidepressant treatment.
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Affiliation(s)
- Richard De La Garza
- Neuropsychopharmacology Laboratory, Department of Psychiatry, Yale University School of Medicine, 333 Cedar Street, Sterling Hall of Medicine, B-256, New Haven, CT 06510, USA.
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34
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Smith JC, Whitton PS. The regulation of NMDA-evoked dopamine release by nitric oxide in the frontal cortex and raphe nuclei of the freely moving rat. Brain Res 2001; 889:57-62. [PMID: 11166686 DOI: 10.1016/s0006-8993(00)03109-7] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The role of nitric oxide (NO) in the N-methyl-D-aspartate (NMDA)-regulated release of dopamine (DA) in the frontal cortex and raphe nuclei of the freely moving rat was measured using in vivo microdialysis. The effects of infusing the NMDA antagonist 2-amino-5-phosphonopentanoic acid (AP5; 100 microM), neuronal nitric oxide synthase (nNOS) inhibitor 7-nitroindazole (7NI; 1 mM) or the nitric oxide donor S-nitroso-N-acetylpenicillamine (SNAP; 500 microM-5 mM) were studied. The infusion of NMDA caused a significant decrease in DA levels in both regions and these effects were reversed by AP5. AP5 alone was seen to increase DA, indicating that NMDA receptors tonically regulate DA release in these brain regions. 7NI also increased extracellular DA levels when administered alone and reversed the effects of NMDA in both regions. The NO donor SNAP (500 microM(-1) mM) caused a dose-dependent decrease in extracellular DA in the RN. However in the frontal cortex the highest concentration of SNAP caused extracellular dopamine to increase. These results suggest that the regulation of NMDA-evoked DA release by NO occurs in both of the brain regions studied, although the manner in which the regulation occurs seems to differ between the two.
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Affiliation(s)
- J C Smith
- Department of Pharmacology, The School of Pharmacy, 29-39 Brunswick Square, WC1N 1AX, London, UK.
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35
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Bailey CH, Giustetto M, Huang YY, Hawkins RD, Kandel ER. Is heterosynaptic modulation essential for stabilizing Hebbian plasticity and memory? Nat Rev Neurosci 2000; 1:11-20. [PMID: 11252764 DOI: 10.1038/35036191] [Citation(s) in RCA: 231] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
In 1894, Ramón y Cajal first proposed that memory is stored as an anatomical change in the strength of neuronal connections. For the following 60 years, little evidence was recruited in support of this idea. This situation changed in the middle of the twentieth century with the development of cellular techniques for the study of synaptic connections and the emergence of new formulations of synaptic plasticity that redefined Ramón y Cajal's idea, making it more suitable for testing. These formulations defined two categories of plasticity, referred to as homosynaptic or Hebbian activity-dependent, and heterosynaptic or modulatory input-dependent. Here we suggest that Hebbian mechanisms are used primarily for learning and for short-term memory but often cannot, by themselves, recruit the events required to maintain a long-term memory. In contrast, heterosynaptic plasticity commonly recruits long-term memory mechanisms that lead to transcription and to synpatic growth. When jointly recruited, homosynaptic mechanisms assure that learning is effectively established and heterosynaptic mechanisms ensure that memory is maintained.
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Affiliation(s)
- C H Bailey
- Howard Hughes Medical Institute, Center for Neurobiology and Behavior, College of Physicians and Surgeons of Columbia University, New York State Psychiatric Institute, New York, New York 10032, USA
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36
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Both protein kinase A and mitogen-activated protein kinase are required in the amygdala for the macromolecular synthesis-dependent late phase of long-term potentiation. J Neurosci 2000. [PMID: 10964936 DOI: 10.1523/jneurosci.20-17-06317.2000] [Citation(s) in RCA: 192] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The lateral amygdala (LA) is thought to be critical for the specific acquisition of conditioned fear, and the emotionally charged memories related to fear are thought to require a form of synaptic plasticity related to long-term potentiation (LTP). Is LTP in the lateral amygdala enduring, and, if so, does it require gene expression and the synthesis of new protein? Using brain slices, we have examined the molecular-signaling pathway of LTP in the cortico-amygdala and the thalamo-amygdala pathways. We find that a single high-frequency train of stimuli induces a transient LTP (E-LTP); by contrast, five repeated high-frequency trains induce an enduring late phase of LTP (L-LTP), which is dependent on gene expression and on new protein synthesis. In both pathways the late phase of LTP is mediated by protein kinase A (PKA) and mitogen-activated protein kinase (MAPK). Application of the adenylyl cyclase activator forskolin induced L-LTP in both pathways, and this potentiation is blocked by inhibitors of protein synthesis. The late phase of LTP also is modulated importantly by beta-adrenergic agonists. An inhibitor of beta-adrenergic receptors blocks L-LTP; conversely, application of a beta-adrenergic agonist induces the L-LTP. Immunocytochemical studies show that both repeated tetanization and application of forskolin stimulate the phosphorylation of cAMP response element-binding proteins (CREB) in cells of the lateral nucleus of the amygdala. These results suggest that PKA and MAPK are critical for the expression of a persistent phase of LTP in the lateral amygdala and that this late component requires the synthesis of new protein and mRNA.
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37
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Javitt DC, Sershen H, Hashim A, Lajtha A. Inhibition of striatal dopamine release by glycine and glycyldodecylamide. Brain Res Bull 2000; 52:213-6. [PMID: 10822163 DOI: 10.1016/s0361-9230(00)00258-6] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Phencyclidine (PCP) and other N-methyl-D-aspartate (NMDA) antagonists induce schizophrenia-like symptoms in humans. In rodents, PCP induces a syndrome of stereotypies and hyperactivity that is accompanied by stimulation of striatal dopamine release. Glycine and other NMDA agonists reverse PCP-induced behaviors in rodents and ameliorate PCP psychosis-like symptoms of schizophrenia in clinical trials. Glycine levels in vivo are regulated by the actions of glycine (GLYT1) transporters. The present study investigates effects of glycine and the prototypic glycine transport inhibitor glycyldodecylamide (GDA) on striatal dopamine release in vitro using a mouse striatal assay. Glycine and GDA significantly inhibit NMDA-induced striatal dopamine release, consistent with their ability to enhance local striatal inhibitory neurotransmission in vitro and to reverse PCP-induced hyperactivity in vivo.
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Affiliation(s)
- D C Javitt
- Nathan S. Kline Institute for Psychiatric Research, Orangeburg, NY 10962, USA.
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38
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Louilot A, Besson C. Specificity of amygdalostriatal interactions in the involvement of mesencephalic dopaminergic neurons in affective perception. Neuroscience 2000; 96:73-82. [PMID: 10683412 DOI: 10.1016/s0306-4522(99)00530-8] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
We have recently shown that dopaminergic responses to an attractive or an aversive stimulus were respectively increased and decreased in the core part of the nucleus accumbens and the ventromedial dorsal striatum. By contrast, increases in dopaminergic responses were obtained in the shell part of the nucleus accumbens with stimuli of both affective values. In addition, the involvement of the basolateral amygdala in affective processes has been reported by several authors. Anatomo-functional relationships between the basolateral amygdala and striatal structures have also been described. Thus, in the present work we studied the regulation by the basolateral amygdala of affective dopaminergic responses in the two parts of the nucleus accumbens (core and shell) and the ventromedial dorsal striatum. More precisely, variations in extracellular levels of dopamine induced by an attractive or an aversive olfactory stimulus were studied using in vivo voltammetry in freely moving rats. Changes in dopamine levels in the three left striatal regions were measured after functional blockade of the ipsilateral basolateral amygdala with tetrodotoxin. Changes in place attraction or aversion toward the stimulus were studied in parallel to dopamine variations. The results obtained suggest a specific regulation of affective dopaminergic responses in the two parts of the nucleus accumbens by the basolateral amygdala and a lack of influence of the basolateral amygdala on the ventromedial dorsal striatum. The results suggest that attraction or aversion toward a stimulus are correlated with dopamine variations in the core of the nucleus accumbens and that the basolateral amygdala controls affective behavioural responses. These data may provide new insights into the pathophysiology of schizophrenic psychoses.
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Affiliation(s)
- A Louilot
- CNRS UMR 5541, Laboratoire de Neuropsychobiologie des Désadaptations, Université de Bordeaux II, 146 rue Léo Saignat, 33076, Bordeaux, France.
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39
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Segieth J, Fowler L, Whitton P, Pearce B. Nitric oxide-mediated regulation of dopamine release in the hippocampus in vivo. Neuropharmacology 2000; 39:571-7. [PMID: 10728878 DOI: 10.1016/s0028-3908(99)00178-1] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Infusion of N-methyl-D-aspartate (NMDA) into the hippocampus of freely moving rats produced a concentration-dependent decrease in the extracellular levels of dopamine, an effect which was reversed by D-2-amino-5-phosphonovaleric acid (D-AP5). To determine the involvement of nitric oxide (NO) in this response, two nitric oxide synthase (NOS) inhibitors, N-nitro-L-arginine methyl ester (L-NAME) and 7-nitroindazole (7-NI), were examined for their ability to modify both basal and NMDA-inhibited dopamine release. When infused alone both NOS inhibitors elicited an increase in extracellular dopamine concentration, moreover, when administered prior to the application of NMDA, the agonist failed to elicit a decrease in dopamine levels. Infusion of the NO donor S-nitroso-N-acetylpenicillamine (SNAP) over a 30 min period caused either an increase or a decrease in dopamine release depending upon the concentration used. At the lower concentration (0.5 mM) SNAP promoted dopamine release whilst at the higher concentration (5 mM), the donor elicited a long lasting reduction in basal dopamine levels. The effect of the lower concentration of SNAP was reversed by the prior application of D-AP5, but that of the higher concentration was unaffected by the antagonist.
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Affiliation(s)
- J Segieth
- Pharmacology Department, The School of Pharmacy, London, UK
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40
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Kuo MF, Wu RM, Wang HS, Lin SM. CPP antagonizes hypoxia-induced changes in dopamine metabolism in the striatum of newborn rat. Neurosci Res 1999; 35:347-50. [PMID: 10617326 DOI: 10.1016/s0168-0102(99)00084-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Treatment with 3-(2-carboxypiperazin-4-yl)-propyl-1-phosphonic acid (CPP), a potent and competitive N-methyl-D-aspartate antagonist, is able to reduce the hypoxia-induced increase in striatal dopamine level by 26% even after the hypoxic insult has occurred. The hypoxia-induced decrease of the striatal 3,4-dihydroxyphenylacetic acid level can also be reversed by CPP. This study demonstrates that CPP can antagonize the hypoxia-induced changes in the dopamine metabolism in the striatum of the newborn rat.
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Affiliation(s)
- M F Kuo
- Department of Neurosurgery, National Taiwan University Hospital, Taipei
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41
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Eradiri OL, Starr MS. Striatal dopamine depletion and behavioural sensitization induced by methamphetamine and 3-nitropropionic acid. Eur J Pharmacol 1999; 386:217-26. [PMID: 10618473 DOI: 10.1016/s0014-2999(99)00776-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The neurotoxic effects of methamphetamine (4 x 5 mg/kg i.p. at 2-h intervals) and 3-nitropropionic acid (20 mg/kg i.p. on days 1-4 and 6-9, saline on day 5), administered alone or in combination (3-nitropropionic acid as above and methamphetamine on day 5), were investigated in rats 1 week after the last injection. Neither methamphetamine nor 3-nitropropionic acid on their own altered brain dopamine levels, but in combination, they selectively lowered dopamine in the terminal regions of the corpus striatum and nucleus accumbens. Methamphetamine depleted 5-hydroxytryptamine (5-HT) in the striatum, while 3-nitropropionic acid depleted 5-HT in the accumbens and substantia nigra, but a combination of the two toxins failed to lower 5-HT in any of these brain regions. Measurements of aromatic L-amino acid decarboxylase activity disclosed no change in the capacity to decarboxylate L-3,4-dihydroxyphenylalanine in any region with any of the treatments, but a lowered capacity to decarboxylate 5-hydroxytryptophan in the nigra after all three treatments. Methamphetamine evoked characteristic hyperactivity and stereotypy in the animals, whereas 3-nitropropionic gave rise to early hypermotility followed by hypoactivity. At 1 week after treatment with 3-nitropropionic/methamphetamine, rats exhibited normal spontaneous motor behaviour, a poor response to dopamine D(1) receptor stimulation and an exaggerated response to dopamine D(2) receptor agonists. These results show that combined systemic treatment with methamphetamine and 3-nitropropionic acid partially depletes dopamine in the basal ganglia, rendering the animals supersensitive to dopamine D(2) receptor activation without altering their spontaneous locomotion.
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Affiliation(s)
- O L Eradiri
- Department of Pharmacology, The School of Pharmacy, 29-39 Brunswick Square, London, UK
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42
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Abstract
In recent years, several pathophysiological models of schizophrenia, i.e. the early and late brain neurodevelopmental and post-illness onset neurodegenerative models, have been proposed and theorists have often argued as if these explanations are mutually exclusive. We propose that all these mechanisms may interact cumulatively during successive critical 'windows of vulnerability' during brain development and during the early course of the illness to lead to the clinical manifestations of the illness. Early brain insults may lead to dysplasia of selective neural networks that account for the premorbid cognitive and psychosocial dysfunction seen in many patients. The onset of psychosis in adolescence may be related to an excessive elimination of synapses and secondarily, phasic dopaminergic overactivity. Following illness onset, these neurochemical alterations in relation to continuing untreated psychosis may lead to further neurodegenerative processes. A reduction in tonic glutamatergic neurotransmission and a phasic glutamatergic excess can potentially predispose to these processes and may have considerable explanatory power. This hypothesis is consistent with central characteristics of schizophrenia such as premorbid manifestations, adolescent onset, functional decline early in this illness, cognitive impairments, the role of dopamine and the role of genes and environment in pathophysiology. This 'three hit' model extends similar integrative conceptualization by other investigators and generates testable predictions of relevance to future pathophysiology and treatment research in schizophrenia.
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Affiliation(s)
- M S Keshavan
- University of Pittsburgh Medical Center, PA 15213, USA.
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43
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Swanson-Park JL, Coussens CM, Mason-Parker SE, Raymond CR, Hargreaves EL, Dragunow M, Cohen AS, Abraham WC. A double dissociation within the hippocampus of dopamine D1/D5 receptor and beta-adrenergic receptor contributions to the persistence of long-term potentiation. Neuroscience 1999; 92:485-97. [PMID: 10408599 DOI: 10.1016/s0306-4522(99)00010-x] [Citation(s) in RCA: 138] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
We compared the effects of the D1/D5 receptor antagonist SCH-23390 with the beta-adrenergic receptor antagonist propranolol on the persistence of long-term potentiation in the CA1 and dentate gyrus subregions of the hippocampus. In slices, SCH-23390 but not propranolol reduced the persistence of long-term potentiation in area CA1 without affecting its induction. The drugs exerted reverse effects in the dentate gyrus, although in this case the induction of long-term potentiation was also affected by propranolol. The lack of effect of SCH-23390 on the induction and maintenance of long-term potentiation in the dentate gyrus was confirmed in awake animals. The drug also had little or no effect on the expression of inducible transcription factors. In area CA1 of awake animals, SCH-23390 blocked persistence of long-term potentiation beyond 3 h, confirming the results in slices. To rule out a differential release of catecholamines induced by our stimulation protocols between brain areas, we compared the effects of the D1/D5 agonist SKF-38393 with the beta-adrenergic agonist isoproterenol on the persistence of a weakly induced, decremental long-term potentiation in CA1 slices. SKF-38393 but not isoproterenol promoted greater persistence of long-term potentiation over a 2-h period. In contrast, isoproterenol but not SKF-38392 facilitated the induction of long-term potentiation. These data demonstrate that there is a double dissociation of the catecholamine modulation of long-term potentiation between CA1 and the dentate gyrus, suggesting that long-term potentiation in these brain areas may be differentially consolidated according to the animal's behavioural state.
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Affiliation(s)
- J L Swanson-Park
- Department of Psychology and the Neuroscience Research Centre, University of Otago, Dunedin, New Zealand
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44
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Galarraga E, Hernández-López S, Tapia D, Reyes A, Bargas J. Action of substance P (neurokinin-1) receptor activation on rat neostriatal projection neurons. Synapse 1999; 33:26-35. [PMID: 10380848 DOI: 10.1002/(sici)1098-2396(199907)33:1<26::aid-syn3>3.0.co;2-4] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Substance P (SP) acts as a neurotransmitter in the neostriatum through the axon collaterals of spiny projection neurons. However, possible direct or indirect actions of SP on the neostriatal output neurons have not been described. Targets of SP terminals within the neostriatum include interneurons, spiny neurons, afferent fibers and boutons. SP induces the release of both dopamine (DA) and acetylcholine (ACh). Since some postsynaptic actions of both DA and ACh on spiny neurons are known, we asked if activation of neostriatal NK1-class receptors is able to reproduce them. The SP NK1-receptor agonist, GR73632 (1 microM), had both excitatory and inhibitory actions on virtually all spiny neurons tested at resting potential. The excitatory action was blocked by atropine and coursed with an increase in firing rate and input resistance (R(N)). The inhibitory action was blocked by haloperidol and coursed with a reduction in firing rate and R(N). Therefore, the release of both DA and ACh induced by NK1-receptor activation modulates indirectly the excitability of the projection neurons. SP facilitates the actions of these transmitters on the spiny neuron. A residual excitatory response to the NK1-receptor agonist was observed in 30% of a sample of neurons tested in the presence of both haloperidol and atropine. The increase in R(N) that accompanied this response could be observed in the presence of 1 microM TTX or 100 microM Cd2+, suggesting a direct effect. Double labeling showed that only SP-immunoreactive neurons were facilitated by NK1-receptor activation in these conditions.
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Affiliation(s)
- E Galarraga
- Departamento de Biofísica, Instituto de Fisiología Celular, UNAM, México City DF, México.
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Pallotta M, Segieth J, Whitton PS. Chronic clomipramine administration reverses NMDA-evoked decreases in dopamine release in the raphe nuclei. Brain Res 1999; 823:217-20. [PMID: 10095031 DOI: 10.1016/s0006-8993(99)01174-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The effect of acute or chronic treatment with the antidepressant clomipramine (CIM) on basal and N-methyl-d-aspartate (NMDA) evoked release of dopamine (DA) in rat raphe has been studied using microdialysis. Acute injection of CIM (10 or 20 mg/kg) caused a decrease in raphe DA release, as did infusion of NMDA (25-100 microM) into this region. When NMDA infusion was preceded by a single acute injection of CIM no differences between NMDA and NMDA plus CIM treated groups was observed. Chronic (15 day) treatment with CIM caused a dose-dependent increase in basal extracellular DA. In addition the effect of infusing NMDA into the raphe on DA release was markedly reduced or abolished. This suggests that adaptive changes occur in NMDA receptor function during treatment with CIM.
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Affiliation(s)
- M Pallotta
- Istituti Di Farmacologia i Tossicologia, Facolta Di Medicina E Chirugia, Universita Degli Studi Di Napoli 'Frederico II', Via Constantinaopli 16, 80138, Naples, Italy
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Pallotta M, Segieth J, Whitton PS. Chronic but not acute clomipramine alters the effect of NMDA receptor regulation of dopamine release in rat frontal cortex. Neurosci Lett 1999; 262:187-90. [PMID: 10218887 DOI: 10.1016/s0304-3940(99)00058-0] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The effect of acute or chronic treatment with the antidepressant clomipramine (CIM) on N-methyl-D-aspartate (NMDA) evoked release of dopamine (DA) in the frontal cortex of the rat has been studied using microdialysis. Acute injection of CIM (10 or 20 mg/kg) caused a decrease in dialysate DA in the frontal cortex. Infusion of 25-100 microM NMDA into the frontal cortex decreased DA release in this region. When NMDA infusion was preceded by a single injection of CIM no marked differences between NMDA and NMDA + CIM treated groups were observed. Chronic (15 day) treatment with CIM (10 or 20 mg/kg) caused a dose-dependent increase in basal extracellular DA. In these animals, however, the effects of infusion of NMDA on DA release in the cortex were greatly attenuated or abolished. This suggests that adaptive changes occur in NMDA receptor function during treatment with an antidepressant. The possible significance of this in the aetiology and treatment of depression is discussed.
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Affiliation(s)
- M Pallotta
- Istituti Di Farmacologia i Tossicologia, Facolta Di Medicina E Chirugia, Universita Degli Studi Di Napoli, Frederico II, Italy
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Cacabelos R, Takeda M, Winblad B. The glutamatergic system and neurodegeneration in dementia: preventive strategies in Alzheimer's disease. Int J Geriatr Psychiatry 1999; 14:3-47. [PMID: 10029935 DOI: 10.1002/(sici)1099-1166(199901)14:1<3::aid-gps897>3.0.co;2-7] [Citation(s) in RCA: 106] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- R Cacabelos
- Institute for CNS Disorders, EuroEspes Biomedical Research Center, La Coruña, Spain.
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Fisher A, Biggs CS, Starr MS. Differential effects of NMDA and non-NMDA antagonists on the activity of aromatic L-amino acid decarboxylase activity in the nigrostriatal dopamine pathway of the rat. Brain Res 1998; 792:126-32. [PMID: 9593857 DOI: 10.1016/s0006-8993(98)00129-2] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
This study examined the acute effects of a variety of NMDA and non-NMDA antagonists on the activity of aromatic l-amino acid decarboxylase (AADC) in the corpus striatum (CS) and substantia nigra (SN) of the rat. Sixty min pretreatment with the high affinity NMDA receptor-channel blockers MK 801 (0.01, 0.1 and 1 mg/kg) and phencyclidine (4 mg/kg) elevated AADC activity in both the CS and SN (2- to 3-fold). Even more striking increases in AADC were noted with 40 mg/kg amantadine (3.8-fold for CS, 9.0-fold for SN), 40 mg/kg memantine (3.4-fold for CS, 3.1-fold for SN; 20 mg/kg no effect) and 40 mg/kg dextromethorphan (3.4-fold for CS, 6.2-fold for SN, in 6/10 'responders'). Similarly pronounced increases in AADC activity in CS (1.9-fold) and SN (2.8-fold) were detected after administering clonidine (2 mg/kg). R-HA 966 (5 mg/kg, not 1 mg/kg) modestly raised AADC activity in CS (0.45-fold) and not SN. Other drugs had no effect on the activity of the decarboxylase enzyme, including CGP 40116 (1 and 5 mg/g), eliprodil (10 mg/kg), NBQX (10 mg/kg, 30 min pretreatment) and atropine (1 mg/kg). These experiments indicate that blocking the NMDA receptor-channel (and to a lesser extent the glycine site) or stimulating alpha2-adrenoceptors, profoundly increases AADC activity, more especially in the SN than CS. By contrast, inhibiting the NMDA glutamate recognition or polyamine sites, AMPA or muscarinic receptors is without effect on AADC in either brain region. The ability of amantadine and memantine to potentiate the antiparkinsonian actions of l-DOPA in the clinic, may be due to facilitated decarboxylation of l-DOPA by the brain.
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Affiliation(s)
- A Fisher
- Department of Pharmacology, The School of Pharmacy, 29-39 Brunswick Square, London WC1N 1AX, UK
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