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Shao Z, Venton BJ. Different Electrochemical Behavior of Cationic Dopamine from Anionic Ascorbic Acid and DOPAC at CNT Yarn Microelectrodes. JOURNAL OF THE ELECTROCHEMICAL SOCIETY 2022; 169:026506. [PMID: 35221350 PMCID: PMC8871592 DOI: 10.1149/1945-7111/ac4d67] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Carbon nanotube yarn microelectrodes (CNTYMEs) have micron-scale surface crevices that momentarily trap molecules. CNTYMEs improve selectivity among cationic catecholamines because secondary reactions are enhanced, but no anions have been studied. Here, we compared fast-scan cyclic voltammetry (FSCV) of dopamine and anionic interferents 3,4 dihydroxyphenylacetic acid (DOPAC) and L-ascorbic acid (AA) at CNTYMEs and carbon fiber microelectrodes (CFMEs). At CFMEs, dopamine current decreases with increasing FSCV repetition frequency at pH 7.4, whereas DOPAC and AA have increasing currents with increasing frequency, because of less repulsion at the negative holding potential. Both DOPAC and AA have side reactions after being oxidized, which are enhanced by trapping. At pH 4, the current increases for DOPAC and AA because they are not repelled. In addition, AA has a different oxidation pathway at pH 4, and an extra peak in the CV is enhanced by trapping effects at CNTYMEs. At pH 8.5, co-detection of dopamine in the presence of DOPAC and AA is enhanced at 100 Hz frequency because of differences in secondary peaks. Thus, the trapping effects at CNTYMEs affects anions differently than cations and secondary peaks can be used to identify dopamine in mixture of AA and DOPAC with FSCV.
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Affiliation(s)
- Zijun Shao
- Department of Chemistry, University of Virginia, Charlottesville, Virginia 22904-4319, USA
| | - B. Jill Venton
- Department of Chemistry, University of Virginia, Charlottesville, Virginia 22904-4319, USA
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2
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Covarrubias-Pinto A, Parra AV, Mayorga-Weber G, Papic E, Vicencio I, Ehrenfeld P, Rivera FJ, Castro MA. Impaired intracellular trafficking of sodium-dependent vitamin C transporter 2 contributes to the redox imbalance in Huntington's disease. J Neurosci Res 2020; 99:223-235. [PMID: 32754987 DOI: 10.1002/jnr.24693] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2020] [Revised: 06/10/2020] [Accepted: 06/27/2020] [Indexed: 12/18/2022]
Abstract
Huntington's disease (HD) is a neurodegenerative disorder caused by a glutamine expansion at the first exon of the huntingtin gene. Huntingtin protein (Htt) is ubiquitously expressed and it is localized in several organelles, including endosomes. HD is associated with a failure in energy metabolism and oxidative damage. Ascorbic acid is a powerful antioxidant highly concentrated in the brain where it acts as a messenger, modulating neuronal metabolism. It is transported into neurons via the sodium-dependent vitamin C transporter 2 (SVCT2). During synaptic activity, ascorbic acid is released from glial reservoirs to the extracellular space, inducing an increase in SVCT2 localization at the plasma membrane. Here, we studied SVCT2 trafficking and localization in HD. SVCT2 is decreased at synaptic terminals in YAC128 male mice. Using cellular models for HD (STHdhQ7 and STHdhQ111 cells), we determined that SVCT2 trafficking through secretory and endosomal pathways is altered in resting conditions. We observed Golgi fragmentation and SVCT2/Htt-associated protein-1 mis-colocalization. Additionally, we observed altered ascorbic acid-induced calcium signaling that explains the reduced SVCT2 translocation to the plasma membrane in the presence of extracellular ascorbic acid (active conditions) described in our previous results. Therefore, SVCT2 trafficking to the plasma membrane is altered in resting and active conditions in HD, explaining the redox imbalance observed during early stages of the disease.
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Affiliation(s)
- Adriana Covarrubias-Pinto
- Instituto de Bioquímica y Microbiología, Facultad de Ciencias, Universidad Austral de Chile, Valdivia, Chile
| | - Alejandra V Parra
- Instituto de Bioquímica y Microbiología, Facultad de Ciencias, Universidad Austral de Chile, Valdivia, Chile
| | - Gonzalo Mayorga-Weber
- Instituto de Bioquímica y Microbiología, Facultad de Ciencias, Universidad Austral de Chile, Valdivia, Chile
| | - Eduardo Papic
- Instituto de Bioquímica y Microbiología, Facultad de Ciencias, Universidad Austral de Chile, Valdivia, Chile
| | - Isidora Vicencio
- Instituto de Bioquímica y Microbiología, Facultad de Ciencias, Universidad Austral de Chile, Valdivia, Chile
| | - Pamela Ehrenfeld
- Center for Interdisciplinary Studies on the Nervous System (CISNe), Universidad Austral de Chile, Valdivia, Chile.,Instituto de Anatomía, Histología y Patología, Facultad de Medicina, Universidad Austral de Chile, Valdivia, Chile
| | - Francisco J Rivera
- Center for Interdisciplinary Studies on the Nervous System (CISNe), Universidad Austral de Chile, Valdivia, Chile.,Instituto de Anatomía, Histología y Patología, Facultad de Medicina, Universidad Austral de Chile, Valdivia, Chile.,Institute of Molecular Regenerative Medicine, Paracelsus Medical University, Salzburg, Austria.,Spinal Cord Injury and Tissue Regeneration Center Salzburg (SCI-TReCS), Salzburg, Austria
| | - Maite A Castro
- Instituto de Bioquímica y Microbiología, Facultad de Ciencias, Universidad Austral de Chile, Valdivia, Chile.,Center for Interdisciplinary Studies on the Nervous System (CISNe), Universidad Austral de Chile, Valdivia, Chile.,Janelia Research Campus, HHMI, Ashburn, VA, USA
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3
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Ballaz SJ, Rebec GV. Neurobiology of vitamin C: Expanding the focus from antioxidant to endogenous neuromodulator. Pharmacol Res 2019; 146:104321. [PMID: 31229562 DOI: 10.1016/j.phrs.2019.104321] [Citation(s) in RCA: 48] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/26/2019] [Revised: 06/16/2019] [Accepted: 06/18/2019] [Indexed: 01/06/2023]
Abstract
Ascorbic acid (AA) is a water-soluble vitamin (C) found in all bodily organs. Most mammals synthesize it, humans are required to eat it, but all mammals need it for healthy functioning. AA reaches its highest concentration in the brain where both neurons and glia rely on tightly regulated uptake from blood via the glucose transport system and sodium-coupled active transport to accumulate and maintain AA at millimolar levels. As a prototype antioxidant, AA is not only neuroprotective, but also functions as a cofactor in redox-coupled reactions essential for the synthesis of neurotransmitters (e.g., dopamine and norepinephrine) and paracrine lipid mediators (e.g., epoxiecoisatrienoic acids) as well as the epigenetic regulation of DNA. Although redox capacity led to the promotion of AA in high doses as potential treatment for various neuropathological and psychiatric conditions, ample evidence has not supported this therapeutic strategy. Here, we focus on some long-neglected aspects of AA neurobiology, including its modulatory role in synaptic transmission as demonstrated by the long-established link between release of endogenous AA in brain extracellular fluid and the clearance of glutamate, an excitatory amino acid. Evidence that this link can be disrupted in animal models of Huntington´s disease is revealing opportunities for new research pathways and therapeutic applications (e.g., epilepsy and pain management). In fact, we suggest that improved understanding of the regulation of endogenous AA and its interaction with key brain neurotransmitter systems, rather than administration of AA in excess, should be the target of future brain-based therapies.
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Affiliation(s)
- Santiago J Ballaz
- School of Biological Sciences and Engineering, Yachay Tech University, Urcuqui, Ecuador.
| | - George V Rebec
- Program in Neuroscience, Department Psychological & Brain Sciences, Indiana University, Bloomington, USA.
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4
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Rebec GV. Corticostriatal network dysfunction in Huntington's disease: Deficits in neural processing, glutamate transport, and ascorbate release. CNS Neurosci Ther 2018; 24:281-291. [PMID: 29464896 PMCID: PMC6489880 DOI: 10.1111/cns.12828] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2017] [Revised: 01/10/2018] [Accepted: 01/27/2018] [Indexed: 12/25/2022] Open
Abstract
AIMS This review summarizes evidence for dysfunctional connectivity between cortical and striatal neurons in Huntington's disease (HD), a fatal neurodegenerative condition caused by a single gene mutation. The focus is on data derived from recording of electrophysiological signals in behaving transgenic mouse models. DISCUSSIONS Firing patterns of individual neurons and the frequency oscillations of local field potentials indicate a disruption in corticostriatal processing driven, in large part, by interactions between cells that contain the mutant gene rather than the mutant gene alone. Dysregulation of glutamate, an excitatory amino acid released by cortical afferents, plays a key role in the breakdown of corticostriatal communication, a process modulated by ascorbate, an antioxidant vitamin found in high concentration in striatum. Up-regulation of glutamate transport by drug administration or viral-vector delivery improves ascorbate homeostasis and neurobehavioral processing in HD mice. Further analysis of electrophysiological data, including the use of sophisticated computational strategies, is required to discern how behavioral demands modulate the flow of corticostriatal information and its disruption by HD. CONCLUSIONS Long before massive cell loss occurs, HD impairs the mechanisms by which cortical and striatal neurons communicate. A key problem identified in transgenic animal models is dysregulation of the dynamic changes in extracellular glutamate and ascorbate. Improved understanding of how these neurochemical systems impact corticostriatal communication is necessary before an effective therapeutic strategy can emerge.
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Affiliation(s)
- George V. Rebec
- Program in NeuroscienceDepartment of Psychological and Brain SciencesIndiana UniversityBloomingtonINUSA
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5
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Xiao T, Wu F, Hao J, Zhang M, Yu P, Mao L. In Vivo Analysis with Electrochemical Sensors and Biosensors. Anal Chem 2016; 89:300-313. [DOI: 10.1021/acs.analchem.6b04308] [Citation(s) in RCA: 138] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Tongfang Xiao
- Beijing
National Laboratory for Molecular Sciences, CAS Key Laboratory of
Analytical Chemistry for Living Biosystems and Photochemistry, Institute
of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Fei Wu
- Beijing
National Laboratory for Molecular Sciences, CAS Key Laboratory of
Analytical Chemistry for Living Biosystems and Photochemistry, Institute
of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Jie Hao
- Beijing
National Laboratory for Molecular Sciences, CAS Key Laboratory of
Analytical Chemistry for Living Biosystems and Photochemistry, Institute
of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Meining Zhang
- Beijing
National Laboratory for Molecular Sciences, CAS Key Laboratory of
Analytical Chemistry for Living Biosystems and Photochemistry, Institute
of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Ping Yu
- Beijing
National Laboratory for Molecular Sciences, CAS Key Laboratory of
Analytical Chemistry for Living Biosystems and Photochemistry, Institute
of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Lanqun Mao
- Beijing
National Laboratory for Molecular Sciences, CAS Key Laboratory of
Analytical Chemistry for Living Biosystems and Photochemistry, Institute
of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
- University of Chinese Academy of Sciences, Beijing 100049, China
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6
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Old Things New View: Ascorbic Acid Protects the Brain in Neurodegenerative Disorders. Int J Mol Sci 2015; 16:28194-217. [PMID: 26633354 PMCID: PMC4691042 DOI: 10.3390/ijms161226095] [Citation(s) in RCA: 87] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2015] [Revised: 09/23/2015] [Accepted: 10/14/2015] [Indexed: 12/13/2022] Open
Abstract
Ascorbic acid is a key antioxidant of the Central Nervous System (CNS). Under brain activity, ascorbic acid is released from glial reservoirs to the synaptic cleft, where it is taken up by neurons. In neurons, ascorbic acid scavenges reactive oxygen species (ROS) generated during synaptic activity and neuronal metabolism where it is then oxidized to dehydroascorbic acid and released into the extracellular space, where it can be recycled by astrocytes. Other intrinsic properties of ascorbic acid, beyond acting as an antioxidant, are important in its role as a key molecule of the CNS. Ascorbic acid can switch neuronal metabolism from glucose consumption to uptake and use of lactate as a metabolic substrate to sustain synaptic activity. Multiple evidence links oxidative stress with neurodegeneration, positioning redox imbalance and ROS as a cause of neurodegeneration. In this review, we focus on ascorbic acid homeostasis, its functions, how it is used by neurons and recycled to ensure antioxidant supply during synaptic activity and how this antioxidant is dysregulated in neurodegenerative disorders.
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Acuña AI, Esparza M, Kramm C, Beltrán FA, Parra AV, Cepeda C, Toro CA, Vidal RL, Hetz C, Concha II, Brauchi S, Levine MS, Castro MA. A failure in energy metabolism and antioxidant uptake precede symptoms of Huntington's disease in mice. Nat Commun 2014; 4:2917. [PMID: 24336051 PMCID: PMC3905737 DOI: 10.1038/ncomms3917] [Citation(s) in RCA: 74] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2013] [Accepted: 11/12/2013] [Indexed: 01/22/2023] Open
Abstract
Huntington's disease has been associated with a failure in energy metabolism and oxidative damage. Ascorbic acid is a powerful antioxidant highly concentrated in the brain where it acts as a messenger, modulating neuronal metabolism. Using an electrophysiological approach in R6/2 HD slices, we observe an abnormal ascorbic acid flux from astrocytes to neurons, which is responsible for alterations in neuronal metabolic substrate preferences. Here using striatal neurons derived from knock-in mice expressing mutant huntingtin (STHdhQ cells), we study ascorbic acid transport. When extracellular ascorbic acid concentration increases, as occurs during synaptic activity, ascorbic acid transporter 2 (SVCT2) translocates to the plasma membrane, ensuring optimal ascorbic acid uptake for neurons. In contrast, SVCT2 from cells that mimic HD symptoms (dubbed HD cells) fails to reach the plasma membrane under the same conditions. We reason that an early impairment of ascorbic acid uptake in HD neurons could lead to early metabolic failure promoting neuronal death.
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Affiliation(s)
- Aníbal I Acuña
- 1] Instituto de Bioquímica y Microbiología, Facultad de Ciencias, Universidad Austral de Chile, Campus Isla Teja s/n, Valdivia, 5090000 Chile [2] Centro de Investigación Sur-Austral en Enfermedades del Sistema Nervioso (CISNe), Universidad Austral de Chile, Campus Isla Teja s/n, Valdivia, 5090000 Chile [3] Escuela de Graduados, Facultad de Ciencias, Universidad Austral de Chile, Campus Isla Teja s/n, Valdivia, 5090000 Chile [4]
| | - Magdalena Esparza
- 1] Instituto de Bioquímica y Microbiología, Facultad de Ciencias, Universidad Austral de Chile, Campus Isla Teja s/n, Valdivia, 5090000 Chile [2] Centro de Investigación Sur-Austral en Enfermedades del Sistema Nervioso (CISNe), Universidad Austral de Chile, Campus Isla Teja s/n, Valdivia, 5090000 Chile [3]
| | - Carlos Kramm
- 1] Instituto de Bioquímica y Microbiología, Facultad de Ciencias, Universidad Austral de Chile, Campus Isla Teja s/n, Valdivia, 5090000 Chile [2] Centro de Investigación Sur-Austral en Enfermedades del Sistema Nervioso (CISNe), Universidad Austral de Chile, Campus Isla Teja s/n, Valdivia, 5090000 Chile [3]
| | - Felipe A Beltrán
- 1] Instituto de Bioquímica y Microbiología, Facultad de Ciencias, Universidad Austral de Chile, Campus Isla Teja s/n, Valdivia, 5090000 Chile [2] Centro de Investigación Sur-Austral en Enfermedades del Sistema Nervioso (CISNe), Universidad Austral de Chile, Campus Isla Teja s/n, Valdivia, 5090000 Chile [3] Escuela de Graduados, Facultad de Ciencias, Universidad Austral de Chile, Campus Isla Teja s/n, Valdivia, 5090000 Chile
| | - Alejandra V Parra
- 1] Instituto de Bioquímica y Microbiología, Facultad de Ciencias, Universidad Austral de Chile, Campus Isla Teja s/n, Valdivia, 5090000 Chile [2] Centro de Investigación Sur-Austral en Enfermedades del Sistema Nervioso (CISNe), Universidad Austral de Chile, Campus Isla Teja s/n, Valdivia, 5090000 Chile
| | - Carlos Cepeda
- Intellectual and Developmental Disabilities Research Center, Semel Institute for Neuroscience and Human Behavior, Brain Research Institute, The David Geffen School of Medicine, 760 Westwood Plaza, University of California Los Angeles, Los Angeles, California 90095-1759, USA
| | - Carlos A Toro
- 1] Escuela de Graduados, Facultad de Ciencias, Universidad Austral de Chile, Campus Isla Teja s/n, Valdivia, 5090000 Chile [2] Instituto de Fisiología, Facultad de Medicina, Universidad Austral de Chile, Campus Isla Teja s/n, Valdivia, 5090000 Chile
| | - René L Vidal
- Instituto de Ciencias Biomédicas, Universidad de Chile, Avda, Independencia 1027, Santiago, Chile
| | - Claudio Hetz
- Neurounion Biomedical Foundation, Independencia 1027, Santiago, Chile
| | - Ilona I Concha
- Instituto de Bioquímica y Microbiología, Facultad de Ciencias, Universidad Austral de Chile, Campus Isla Teja s/n, Valdivia, 5090000 Chile
| | - Sebastián Brauchi
- 1] Centro de Investigación Sur-Austral en Enfermedades del Sistema Nervioso (CISNe), Universidad Austral de Chile, Campus Isla Teja s/n, Valdivia, 5090000 Chile [2] Instituto de Fisiología, Facultad de Medicina, Universidad Austral de Chile, Campus Isla Teja s/n, Valdivia, 5090000 Chile
| | - Michael S Levine
- Intellectual and Developmental Disabilities Research Center, Semel Institute for Neuroscience and Human Behavior, Brain Research Institute, The David Geffen School of Medicine, 760 Westwood Plaza, University of California Los Angeles, Los Angeles, California 90095-1759, USA
| | - Maite A Castro
- 1] Instituto de Bioquímica y Microbiología, Facultad de Ciencias, Universidad Austral de Chile, Campus Isla Teja s/n, Valdivia, 5090000 Chile [2] Centro de Investigación Sur-Austral en Enfermedades del Sistema Nervioso (CISNe), Universidad Austral de Chile, Campus Isla Teja s/n, Valdivia, 5090000 Chile
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8
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Rebec GV. Dysregulation of corticostriatal ascorbate release and glutamate uptake in transgenic models of Huntington's disease. Antioxid Redox Signal 2013; 19:2115-28. [PMID: 23642110 PMCID: PMC3869431 DOI: 10.1089/ars.2013.5387] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/19/2013] [Accepted: 05/05/2013] [Indexed: 11/13/2022]
Abstract
SIGNIFICANCE Dysregulation of cortical and striatal neuronal processing plays a critical role in Huntington's disease (HD), a dominantly inherited condition that includes a progressive deterioration of cognitive and motor control. Growing evidence indicates that ascorbate (AA), an antioxidant vitamin, is released into striatal extracellular fluid when glutamate is cleared after its release from cortical afferents. Both AA release and glutamate uptake are impaired in the striatum of transgenic mouse models of HD owing to a downregulation of glutamate transporter 1 (GLT1), the protein primarily found on astrocytes and responsible for removing most extracellular glutamate. Improved understanding of an AA-glutamate interaction could lead to new therapeutic strategies for HD. RECENT ADVANCES Increased expression of GLT1 following treatment with ceftriaxone, a beta-lactam antibiotic, increases striatal glutamate uptake and AA release and also improves the HD behavioral phenotype. In fact, treatment with AA alone restores striatal extracellular AA to wild-type levels in HD mice and not only improves behavior but also improves the firing pattern of neurons in HD striatum. CRITICAL ISSUES Although evidence is growing for an AA-glutamate interaction, several key issues require clarification: the site of action of AA on striatal neurons; the precise role of GLT1 in striatal AA release; and the mechanism by which HD interferes with this role. FUTURE DIRECTIONS Further assessment of how the HD mutation alters corticostriatal signaling is an important next step. A critical focus is the role of astrocytes, which express GLT1 and may be the primary source of extracellular AA.
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Affiliation(s)
- George V Rebec
- Program in Neuroscience, Department of Psychological and Brain Sciences, Indiana University , Bloomington, Indiana
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9
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Striatal interaction among dopamine, glutamate and ascorbate. Neuropharmacology 2012; 63:1308-14. [DOI: 10.1016/j.neuropharm.2012.08.007] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2012] [Revised: 07/24/2012] [Accepted: 08/13/2012] [Indexed: 11/23/2022]
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10
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Beltrán FA, Acuña AI, Miró MP, Angulo C, Concha II, Castro MA. Ascorbic acid-dependent GLUT3 inhibition is a critical step for switching neuronal metabolism. J Cell Physiol 2011; 226:3286-94. [PMID: 21321936 DOI: 10.1002/jcp.22674] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Intracellular ascorbic acid is able to modulate neuronal glucose utilization between resting and activity periods. We have previously demonstrated that intracellular ascorbic acid inhibits deoxyglucose transport in primary cultures of cortical and hippocampal neurons and in HEK293 cells. The same effect was not seen in astrocytes. Since this observation was valid only for cells expressing glucose transporter 3 (GLUT3), we evaluated the importance of this transporter on the inhibitory effect of ascorbic acid on glucose transport. Intracellular ascorbic acid was able to inhibit (3)H-deoxyglucose transport only in astrocytes expressing GLUT3-EGFP. In C6 glioma cells and primary cultures of cortical neurons, which natively express GLUT3, the same inhibitory effect on (3)H-deoxyglucose transport and fluorescent hexose 2-[N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino]-2-deoxyglucose (2-NBDG) was observed. Finally, knocking down the native expression of GLUT3 in primary cultured neurons and C6 cells using shRNA was sufficient to abolish the ascorbic acid-dependent inhibitory effect on uptake of glucose analogs. Uptake assays using real-time confocal microscopy demonstrated that ascorbic acid effect abrogation on 2-NBDG uptake in cultured neurons. Therefore, ascorbic acid would seem to function as a metabolic switch inhibiting glucose transport in neurons under glutamatergic synaptic activity through direct or indirect inhibition of GLUT3.
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Affiliation(s)
- Felipe A Beltrán
- Facultad de Ciencias, Instituto de Bioquímica, Universidad Austral de Chile, Valdivia, Chile
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11
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Takmakov P, Zachek MK, Keithley RB, Bucher ES, McCarty GS, Wightman RM. Characterization of local pH changes in brain using fast-scan cyclic voltammetry with carbon microelectrodes. Anal Chem 2010; 82:9892-900. [PMID: 21047096 DOI: 10.1021/ac102399n] [Citation(s) in RCA: 94] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Transient local pH changes in the brain are important markers of neural activity that can be used to follow metabolic processes that underlie the biological basis of behavior, learning and memory. There are few methods that can measure pH fluctuations with sufficient time resolution in freely moving animals. Previously, fast-scan cyclic voltammetry at carbon-fiber microelectrodes was used for the measurement of such pH transients. However, the origin of the potential dependent current in the cyclic voltammograms for pH changes recorded in vivo was unclear. The current work explored the nature of these peaks and established the origin for some of them. A peak relating to the capacitive nature of the pH CV was identified. Adsorption of electrochemically inert species, such as aromatic amines and calcium could suppress this peak, and is the origin for inconsistencies regarding in vivo and in vitro data. Also, we identified an extra peak in the in vivo pH CV relating to the presence of 3,4-dihydroxyacetic acid (DOPAC) in the brain extracellular fluid. To evaluate the in vivo performance of the carbon-fiber sensor, carbon dioxide inhalation by an anesthetized rat was used to induce brain acidosis induced by hypercapnia. Hypercapnia is demonstrated to be a useful tool to induce robust in vivo pH changes, allowing confirmation of the pH signal observed with FSCV.
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Affiliation(s)
- Pavel Takmakov
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
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12
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Harrison FE, Green RJ, Dawes SM, May JM. Vitamin C distribution and retention in the mouse brain. Brain Res 2010; 1348:181-6. [PMID: 20570663 DOI: 10.1016/j.brainres.2010.05.090] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2010] [Revised: 05/26/2010] [Accepted: 05/27/2010] [Indexed: 12/12/2022]
Abstract
Vitamin C (VC) is a crucial antioxidant in the brain. To assess whether different brain regions vary in their sensitivity to oxidative stress induced by VC depletion, we used the gulonolactone oxidase (gulo) knockout mouse. This mouse, like humans, cannot synthesize VC and thus its tissue VC levels can be varied by dietary VC intake. Gulo knockout mice were fed drinking water containing standard (0.33g/L), low (0.033g/L) or zero (0g/L) VC supplementation levels. After 4weeks, mice were sacrificed and different brain regions removed for assay of VC and malondialdehyde, a marker of lipid peroxidation. Compared to age-matched wild-type controls, the cerebellum, olfactory bulbs and frontal cortex had the highest VC content, whereas the pons and spinal chord had the lowest. However, in mice that did not receive VC, area differences were no longer significant as all values trended towards zero. Malondialdehyde increased in the cortex as VC supplementation was decreased. The same changes were not observed in the cerebellum or pons, suggesting that cortex is more susceptible to oxidative damage from low VC. These results suggest enhanced susceptibility of the cortex to oxidative stress induced by low VC compared to other brain regions.
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Affiliation(s)
- Fiona E Harrison
- Department of Medicine, Vanderbilt University, Nashville, TN, 37232, USA
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13
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Pelkonen A, Hiltunen M, Kiianmaa K, Yavich L. Stimulated dopamine overflow and alpha-synuclein expression in the nucleus accumbens core distinguish rats bred for differential ethanol preference. J Neurochem 2010; 114:1168-76. [PMID: 20533994 DOI: 10.1111/j.1471-4159.2010.06844.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The key neurochemical systems and structures involved in the predisposition to substance abuse and preference to ethanol (EtOH) are not known in detail but clearly dopamine (DA) is an important modulator of addiction. Recent data indicate that alpha-synuclein (alpha-syn), a pre-synaptic protein, plays a role in regulation of DA release from the pre-synaptic terminals in striatum and the expression of this protein is different after drug abuse or following abstinence. In the present work, we analysed stimulated DA overflow in the dorsal and ventral striatum in EtOH naïve alko alchohol (AA) and alko non-alchohol (ANA) rats selected for more than 100 generations for their differential EtOH preference. In the same structures, we studied the expression of alpha-syn using western blotting. AA rats, in comparison with ANA rats, showed a marked reduction of stimulated peak DA overflow and higher levels of alpha-syn in the nucleus accumbens core. In the same structure, DA re-uptake was increased in AA rats in comparison with ANA rats. The effects of EtOH at low (0.1 g/kg) and higher (3 mg/kg) doses on DA overflow measured in the nucleus accumbens shell were similar in both lines. These results indicate that high expression of alpha-syn may contribute to the reduced DA overflow and the possible activation of re-uptake in the nucleus accumbens core of AA rats in comparison with ANA rats.
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Affiliation(s)
- Anssi Pelkonen
- School of Pharmacy, University of Eastern Finland, Kuopio, Finland.
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14
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Castro MA, Beltrán FA, Brauchi S, Concha II. A metabolic switch in brain: glucose and lactate metabolism modulation by ascorbic acid. J Neurochem 2009; 110:423-40. [PMID: 19457103 DOI: 10.1111/j.1471-4159.2009.06151.x] [Citation(s) in RCA: 95] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
In this review, we discuss a novel function of ascorbic acid in brain energetics. It has been proposed that during glutamatergic synaptic activity neurons preferably consume lactate released from glia. The key to this energetic coupling is the metabolic activation that occurs in astrocytes by glutamate and an increase in extracellular [K(+)]. Neurons are cells well equipped to consume glucose because they express glucose transporters and glycolytic and tricarboxylic acid cycle enzymes. Moreover, neuronal cells express monocarboxylate transporters and lactate dehydrogenase isoenzyme 1, which is inhibited by pyruvate. As glycolysis produces an increase in pyruvate concentration and a decrease in NAD(+)/NADH, lactate and glucose consumption are not viable at the same time. In this context, we discuss ascorbic acid participation as a metabolic switch modulating neuronal metabolism between rest and activation periods. Ascorbic acid is highly concentrated in CNS. Glutamate stimulates ascorbic acid release from astrocytes. Ascorbic acid entry into neurons and within the cell can inhibit glucose consumption and stimulate lactate transport. For this switch to occur, an ascorbic acid flow is necessary between astrocytes and neurons, which is driven by neural activity and is part of vitamin C recycling. Here, we review the role of glucose and lactate as metabolic substrates and the modulation of neuronal metabolism by ascorbic acid.
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Affiliation(s)
- Maite A Castro
- Instituto de Bioquímica, Universidad Austral de Chile, Valdivia, Chile.
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15
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Dynamic regional changes of extracellular ascorbic acid during global cerebral ischemia: Studied with in vivo microdialysis coupled with on-line electrochemical detection. Brain Res 2009; 1253:161-8. [DOI: 10.1016/j.brainres.2008.11.096] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2008] [Revised: 11/22/2008] [Accepted: 11/26/2008] [Indexed: 01/19/2023]
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Castro MA, Pozo M, Cortés C, García MDLA, Concha II, Nualart F. Intracellular ascorbic acid inhibits transport of glucose by neurons, but not by astrocytes. J Neurochem 2007; 102:773-82. [PMID: 17630983 DOI: 10.1111/j.1471-4159.2007.04631.x] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
It has been demonstrated that glutamatergic activity induces ascorbic acid (AA) depletion in astrocytes. Additionally, different data indicate that AA may inhibit glucose accumulation in primary cultures of rat hippocampal neurons. Thus, our hypothesis postulates that AA released from the astrocytes during glutamatergic synaptic activity may inhibit glucose uptake by neurons. We observed that cultured neurons express the sodium-vitamin C cotransporter 2 and the facilitative glucose transporters (GLUT) 1 and 3, however, in hippocampal brain slices GLUT3 was the main transporter detected. Functional activity of GLUTs was confirmed by means of kinetic analysis using 2-deoxy-d-glucose. Therefore, we showed that AA, once accumulated inside the cell, inhibits glucose transport in both cortical and hippocampal neurons in culture. Additionally, we showed that astrocytes are not affected by AA. Using hippocampal slices, we observed that upon blockade of monocarboxylate utilization by alpha-cyano-4-hydroxycinnamate and after glucose deprivation, glucose could rescue neuronal response to electrical stimulation only if AA uptake is prevented. Finally, using a transwell system of separated neuronal and astrocytic cultures, we observed that glutamate can reduce glucose transport in neurons only in presence of AA-loaded astrocytes, suggesting the essential role of astrocyte-released AA in this effect.
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Affiliation(s)
- Maite A Castro
- Instituto de Bioquímica, Facultad de Ciencias Biológicas, Universidad Austral de Chile, Valdivia, Chile
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17
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Extracellular ascorbate modulates glutamate dynamics: role of behavioral activation. BMC Neurosci 2007; 8:32. [PMID: 17506898 PMCID: PMC1884166 DOI: 10.1186/1471-2202-8-32] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2006] [Accepted: 05/16/2007] [Indexed: 11/10/2022] Open
Abstract
Background A physiological increase in extracellular ascorbate (AA), an antioxidant vitamin found throughout the striatum, elevates extracellular glutamate (GLU). To determine the role of behavioral arousal in this interaction, microdialysis was used to measure striatal GLU efflux in rats tested in either a lights-off or lights-on condition while reverse dialysis either maintained the concentration of AA at 250 μM or increased it to 1000 μM to approximate endogenous changes. Results When lights were off, both locomotion and GLU increased regardless of AA dose. In contrast, animals in the lights-on condition were behaviorally inactive, and infusion of 1000, but not 250, μM AA significantly increased extracellular GLU. Interestingly, when ambient light returned to the lights-off group, 1000 μM prolonged the GLU increase relative to the 250 μM group. Conclusion Our results not only support evidence that elevated striatal AA increases extracellular GLU but also indicate that this effect depends on behavioral state and the corresponding level of endogenous GLU release.
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Xiang L, Lin Y, Yu P, Su L, Mao L. Laccase-catalyzed oxidation and intramolecular cyclization of dopamine: A new method for selective determination of dopamine with laccase/carbon nanotube-based electrochemical biosensors. Electrochim Acta 2007. [DOI: 10.1016/j.electacta.2006.11.040] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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19
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Dorner JL, Miller BR, Barton SJ, Brock TJ, Rebec GV. Sex differences in behavior and striatal ascorbate release in the 140 CAG knock-in mouse model of Huntington's disease. Behav Brain Res 2007; 178:90-7. [PMID: 17239451 PMCID: PMC1868463 DOI: 10.1016/j.bbr.2006.12.004] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2006] [Revised: 12/01/2006] [Accepted: 12/02/2006] [Indexed: 12/11/2022]
Abstract
Ethological assessment of murine models of Huntington's disease (HD), an inherited neurodegenerative disorder, enables correlation between phenotype and pathophysiology. Currently, the most characterized model is the R6/2 line that develops a progressive behavioral and neurological phenotype by 6 weeks of age. A recently developed knock-in model with 140 CAG repeats (KI) exhibits a subtle phenotype with a longer progressive course, more typical of adult-onset HD in humans. We evaluated rotarod performance, open-field behavior, and motor activity across the diurnal cycle in KI mice during early to mid-adulthood. Although we did not observe any effects of age, relative to wild-type (WT) mice, KI mice showed significant deficits in both open-field climbing behavior and home-cage running wheel activity during the light phase of the diurnal cycle. An interesting sex difference also emerged. KI females spent more time in the open-field grooming and more time running during the diurnal dark phase than KI males and WT mice of both sexes. In striatum, the primary site of HD pathology, we measured behavior-related changes in extracellular ascorbate (AA), which is abnormally low in the R6/2 line, consistent with a loss of antioxidant protection in HD. KI males exhibited a 20-40% decrease in striatal AA from anesthesia baseline to behavioral activation that was not observed in other groups. Collectively, our results indicate behavioral deficits in KI mice that may be specific to the diurnal cycle. Furthermore, sex differences observed in behavior and striatal AA release suggest sex-dependent variation in the phenotype and neuropathology of HD.
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Affiliation(s)
- Jenelle L Dorner
- Program in Neuroscience and Department of Psychological and Brain Sciences, Indiana University, 1101 E. 10th Street, Bloomington, IN 47405, USA.
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20
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Cortright JJ, Rebec GV. Ascorbate modulation of sensorimotor processing in striatum of freely moving rats. Brain Res 2006; 1092:108-16. [PMID: 16753136 DOI: 10.1016/j.brainres.2006.03.079] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2005] [Revised: 03/22/2006] [Accepted: 03/23/2006] [Indexed: 10/24/2022]
Abstract
The striatum, which receives projections from the entire cortical mantle, is highly responsive to sensorimotor activity. Because either systemic or intra-striatal injections of ascorbate (AA) influence behavior known to involve striatal circuits, it is possible that the level of striatal AA, which is known to fluctuate with behavioral activation, directly alters striatal neuronal processing. To test this hypothesis, we recorded the activity of 94 presumed medium spiny striatal neurons in behaving rats treated with AA or vehicle and examined firing rate during periods of quiescence and sensorimotor stimulation (e.g., stroking of the whiskers, mid-back, and rump). Slow-scan voltammetry was used in separate rats to determine the extent to which AA treatment elevated striatal AA. Vehicle-treated rats had relatively slow basal firing rates at rest that routinely increased during sensorimotor stimulation. Comparable results were obtained in rats treated with 100 mg/kg AA, which failed to alter AA levels in striatum. Dose-dependent increases in striatal AA, however, occurred after injection of 500 and 1000 mg/kg AA, and at these doses, there was a significant decrease in the number of sensorimotor-related excitations. In fact, treatment with 1000 mg/kg AA reversed a significant proportion of excitations to inhibitions. Our results substantiate the role of the striatum in sensorimotor processing and emphasize extracellular AA as a modulator of striatal neuronal function.
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Affiliation(s)
- James J Cortright
- Program in Neuroscience, Department of Psychological and Brain Sciences, Psychology Building, 1101 E. Tenth Street, Indiana University, Bloomington, IN 47405-7007, USA
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21
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Extracellular ascorbate modulates cortically evoked glutamate dynamics in rat striatum. Neurosci Lett 2005; 378:166-70. [PMID: 15781152 DOI: 10.1016/j.neulet.2004.12.027] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2004] [Revised: 12/09/2004] [Accepted: 12/13/2004] [Indexed: 11/21/2022]
Abstract
To determine if extracellular ascorbate, which may increase by several hundred micromolar in striatum during behavioral activation, directly alters glutamate transmission, we monitored striatal glutamate transients evoked by electrical stimulation of cerebral cortex in anesthetized rats tested with varying concentrations of ascorbate (0, 50, 200, and 500 microM) by reverse dialysis. Capillary electrophoresis coupled with laser-induced fluorescence detection was used to analyze dialysates collected at 3-s intervals. Ascorbate elevated striatal glutamate in a concentration-dependent fashion. Addition of 500 microM ascorbate not only more than doubled basal glutamate levels relative to the ascorbate-free condition, but significantly increased both the magnitude of the electrically evoked glutamate response as well as its subsequent return to baseline. In fact, the time required to return to within 10% of the pre-stimulation baseline increased by >100s. Reverse dialysis of iso-ascorbate, in contrast, had no effect on stimulation-evoked glutamate release arguing against an antioxidant effect. It appears, therefore, that the level of extracellular ascorbate plays a critical role in regulating corticostriatal glutamate transmission.
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Teagarden MA, Rebec GV. Effects of long-term haloperidol treatment on glutamate-evoked ascorbate release in rat striatum. Eur J Pharmacol 2001; 418:213-6. [PMID: 11343692 DOI: 10.1016/s0014-2999(01)00942-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Repeated haloperidol injections increase extracellular striatal ascorbate. Because ascorbate release depends on glutamate uptake, we assessed this mechanism in the haloperidol effect. Linear staircase voltammetry was combined with intrastriatal infusions of L- or D-glutamate or saline in behaving rats after 7 or 21 days of haloperidol (0.5 mg/kg, s.c.). Control animals, receiving either vehicle or no treatment, responded to L-, but not D-glutamate or saline infusion with a 50% increase in ascorbate. In contrast, glutamate-evoked ascorbate release disappeared after 7 but reappeared after 21 days of haloperidol. Thus, increased striatal ascorbate release following chronic haloperidol cannot be explained by an enhanced response to glutamate.
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Affiliation(s)
- M A Teagarden
- Program in Neural Science, Department of Psychology, Indiana University, Psychology Building, Bloomington, IN 47405-7007, USA
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23
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Abstract
Ascorbate (vitamin C) is found in high concentrations in the striatum in which it may play a role in behavioral activation. To test this hypothesis, freely behaving rats received bilateral intrastriatal infusions of ascorbate oxidase (AAO) to inactivate extracellular ascorbate. Slow-scan voltammetry was used simultaneously to assess changes in ascorbate and 3,4-dihydroxyphenylacetic acid (DOPAC), a major dopamine metabolite, near the infusion site. Intrastriatal AAO, but not saline vehicle, caused a rapid decline in both ascorbate and behavioral activation. Within 20 min, an ascorbate loss of 50-70% led to a near-total inhibition of all recorded behavior, including open-field locomotion, approach of novel objects, and social interactions with other rats. DOPAC levels remained stable, arguing against an AAO-induced disruption of dopamine transmission. Consistent with this interpretation, subsequent injection of 1.0 mg/kg d-amphetamine, an indirect dopamine agonist, quickly restored behavioral activation, which also was accompanied by a marked rise in extracellular ascorbate. Bilateral AAO infusions into dorsal hippocampus, which also has a high level of extracellular ascorbate, failed to alter behavioral activation, indicating that a loss of brain ascorbate per se does not suppress behavior. Collectively, these results implicate ascorbate in the behavioral operations of the striatum and suggest that the extracellular level of this vitamin plays a critical role in behavioral activation.
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Yamamoto F, Shibata S, Watanabe S, Masuda K, Maeda M. Positron-labeled antioxidant 6-deoxy-6-[18F]fluoro-L-ascorbic acid: increased uptake in transient global ischemic rat brain. Nucl Med Biol 1996; 23:479-86. [PMID: 8832703 DOI: 10.1016/0969-8051(96)00025-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The in vivo uptake and distribution of 6-deoxy-6-[18F]fluoro-L-ascorbic acid (18F-DFA) were investigated in rat brains following postischemic reperfusion. Global cerebral ischemia was induced in male Wistar rats for 20 min by occlusion of four major arteries. Two time points were chosen for 18F-DFA injection to rats subjected to cerebral ischemia, at the start of recirculation and 5 days following recirculation. The rats were then killed at 2 h after tail-vein administration of 18F-DFA and tissue radioactivity concentration was determined. Increased uptake of radioactivity in particular brain regions, including the cerebral cortex, hypothalamus, and amygdala following injection of 18F-DFA, compared to the sham-operated control, was observed 5 days after reperfusion. Similar results were also obtained in in vitro experiments using brain slices. Abnormal in vivo accumulation of 45Ca, a marker of regional postischemic injury, was observed in these brain regions in tissue dissection experiments. Furthermore, metabolite analysis of nonradioactive DFA using 19F-NMR showed that DFA remained intact in the postischemic reperfusion brain. The present results indicate that 18F-DFA increasingly accumulates in damaged regions of postischemic reperfusion brain.
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Affiliation(s)
- F Yamamoto
- Faculty of Pharmaceutical Sciences, Kyushu University, Fukuoka, Japan
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25
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Affiliation(s)
- H Katsuki
- Department of Chemical Pharmacology, University of Tokyo, Japan
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26
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Lada MW, Kennedy RT. Quantitative in vivo measurements using microdialysis on-line with capillary zone electrophoresis. J Neurosci Methods 1995; 63:147-52. [PMID: 8788059 DOI: 10.1016/0165-0270(95)00104-2] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
A system which couples microdialysis with capillary zone electrophoresis (CZE) on-line is used to monitor ascorbate and lactate in the caudate nucleus of rat brain. On-line interface of microdialysis probe and electrophoresis capillary, along with the high mass sensitivity of CZE, allows the probe to be operated at flow rates as low as 40 nl/min. Under these conditions, the relative recovery is nearly 100% and quantitative monitoring is possible. The microscale system also facilitates calibration by the low flow rate method. In spite of the low flow rate, temporal resolution in the 45-125 s range is possible for these compounds. The system is demonstrated by observing changes in ascorbate due to infusions of elevated K+ through the dialysis probe and systemic injections of amphetamine and an anesthetic (ketamine/xylazine/acepromazine mixture). Lactate is monitored in response to elevated K+ infusions.
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Affiliation(s)
- M W Lada
- Department of Chemistry, University of Florida, Gainesville 32611, USA
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27
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O'Neill RD, Lowry JP. On the significance of brain extracellular uric acid detected with in-vivo monitoring techniques: a review. Behav Brain Res 1995; 71:33-49. [PMID: 8747173 DOI: 10.1016/0166-4328(95)00035-6] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The concentration of uric acid [UA] in the extracellular fluid (ECF) estimated with in-vivo voltammetry and microdialysis data is compared for probes of different diameters from the day of implantation (acute) to several days (chronic) or even months after surgery. For small probes (diameter < 160 microns) the acute [UA] of ca. 5 microM decreased significantly to ca. 1 microM under chronic conditions. For larger probes (e.g., 320-microns diameter) the acute [UA] was also ca. 5 microM, but this value significantly increased to ca. 50 microM under chronic conditions. Associated with this difference in [UA], there were parallel differences in the extent of gliosis around the probes. These findings are discussed in terms of possible sources of extracellular UA and their implications for in-vivo monitoring techniques in behaving animals.
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Affiliation(s)
- R D O'Neill
- Department of Chemistry, University College Dublin, Belfield, Ireland.
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28
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Lada MW, Schaller G, Carriger MH, Vickroy TW, Kennedy RT. On-line interface between microdialysis and capillary zone electrophoresis. Anal Chim Acta 1995. [DOI: 10.1016/0003-2670(94)00505-g] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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29
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Pierce RC, Clemens AJ, Shapiro LA, Rebec GV. Repeated treatment with ascorbate or haloperidol, but not clozapine, elevates extracellular ascorbate in the neostriatum of freely moving rats. Psychopharmacology (Berl) 1994; 116:103-9. [PMID: 7862921 DOI: 10.1007/bf02244879] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Acute administration of neuroleptic drugs alters the extracellular level of ascorbate in the neostriatum, and increasing evidence suggests a role for this vitamin in the behavioral, and possibly therapeutic, effects of these drugs. To shed further light on this issue, extracellular ascorbate was recorded in the neostriatum and nucleus accumbens of awake, behaving rats following chronic treatment with either classical (haloperidol) or atypical (clozapine) neuroleptics or ascorbate itself. Electrochemically modified, carbon-fiber microelectrodes were lowered in place the day after the last of 21 daily injections of either haloperidol (0.5 mg/kg, SC), clozapine (20 mg/kg, IP), sodium ascorbate (500 mg/kg, IP) or vehicle. Voltammetric measurements were obtained during quiet rest and following administration of d-amphetamine (2.5 mg/kg). Repeated treatment with either haloperidol or ascorbate elevated basal extracellular ascorbate and potentiated the amphetamine-induced increase in ascorbate release in neostriatum but not nucleus accumbens. Both treatment groups also showed a significant increase in amphetamine-induced sniffing and repetitive head movements compared to vehicle-treated animals. In contrast, repeated clozapine had no effect on extracellular ascorbate in either neostriatum or nucleus accumbens, but increased the locomotor response to an amphetamine challenge. Thus, to the extent that increases in neostriatal ascorbate exert neuroleptic-like effects, such effects are likely to parallel haloperidol rather than clozapine.
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Affiliation(s)
- R C Pierce
- Department of Psychology, Indiana University, Bloomington 47405
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30
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Rebec GV, Pierce RC. A vitamin as neuromodulator: ascorbate release into the extracellular fluid of the brain regulates dopaminergic and glutamatergic transmission. Prog Neurobiol 1994; 43:537-65. [PMID: 7816935 DOI: 10.1016/0301-0082(94)90052-3] [Citation(s) in RCA: 263] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Ascorbate is an antioxidant vitamin that the brain accumulates from the blood supply and maintains at a relatively high concentration under widely varying conditions. Although neurons are known to use this vitamin in many different chemical and enzymatic reactions, only recently has sufficient evidence emerged to suggest a role for ascorbate in interneuronal communication. Ascorbate is released from glutamatergic neurons as part of the glutamate reuptake process, in which the high-affinity glutamate transporter exchanges ascorbate for glutamate. This heteroexchange process, which also may occur in glial cells, ensures a relatively high level of extracellular ascorbate in many forebrain regions. Ascorbate release is regulated, at least in part, by dopaminergic mechanisms, which appear to involve both the D1 and D2 family of dopamine receptors. Thus, amphetamine, GBR-12909, apomorphine, and the combined administration of D1 and D2 agonists all facilitate ascorbate release from glutamatergic terminals in the neostriatum, and this effect is blocked by dopamine receptor antagonists. Even though the neostriatum itself contains a high concentration of dopamine receptors, the critical site for dopamine-mediated ascorbate release in the neostriatum is the substantia nigra. Intranigral dopamine regulates the activity of nigrothalamic efferents, which in turn regulate thalamocortical fibers and eventually the glutamatergic corticoneostriatal pathway. In addition, neostriatonigral fibers project to nigrothalamic efferents, completing a complex multisynaptic loop that plays a major role in neostriatal ascorbate release. Although extracellular ascorbate appears to modulate the synaptic action of dopamine, the mechanisms underlying this effect are unclear. Evidence from receptor binding studies suggests that ascorbate alters dopamine receptors either as an allosteric inhibitor or as an inducer of iron-dependent lipid peroxidation. The applicability of these studies to dopamine receptor function, however, remains to be established in view of reports that ascorbate can protect against lipid peroxidation in vivo. Nevertheless, ample behavioral evidence supports an antidopaminergic action of ascorbate. Systemic, intraventricular, or intraneostriatal ascorbate administration, for example, attenuates the behavioral effects of amphetamine and potentiates the behavioral response to haloperidol. Some of these behavioral effects, however, may be dose-dependent in that treatment with relatively low doses of ascorbate has been reported to enhance dopamine-mediated behaviors. Ascorbate also appears to modulate glutamatergic transmission in the neostriatum. In fact, by facilitating glutamate release, ascorbate may indirectly oppose the action of dopamine, though the nature of the neostriatal dopaminergic-glutamatergic interaction is far from settled. Ascorbate also may alter the redox state of the NMDA glutamate receptor thus block NMDA-gated channel function.(ABSTRACT TRUNCATED AT 400 WORDS)
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Affiliation(s)
- G V Rebec
- Department of Psychology, Indiana University, Bloomington 47405
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31
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O'Neill RD. Sensor-tissue interactions in neurochemical analysis with carbon paste electrodes in vivo. Analyst 1993; 118:433-8. [PMID: 7684207 DOI: 10.1039/an9931800433] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Characterization of voltammetric signals recorded with microelectrodes in the living brain is fraught with difficulties. In addition to being anatomically complicated, brain tissue presents the analytical electrochemist with a complex chemical environment that includes surfactants (lipids), electrode poisons (proteins), electrocatalysts such as glutathione and ascorbic acid, and a tissue matrix that both restricts mass transport to the electrode surface and reacts physiologically to the presence of the probe. Identification of electrochemical signals recorded in vivo with carbon paste electrodes is discussed in the context of these problems. This examination shows that modification of both the electrode surface by tissue, and of the tissue environment by the electrode have important implications for voltammetric signal analysis in vivo. Despite these problems, valuable data on the relationship between behaviour and chemical changes in the brain can be obtained using in vivo electrochemical techniques.
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Affiliation(s)
- R D O'Neill
- Chemistry Department, University College Dublin, Belfield, Ireland
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32
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Abstract
Ascorbic acid is highly concentrated in the central nervous system. Measurement of the extracellular concentration of ascorbate in animals, mainly by the technique of voltammetry in vivo, has demonstrated fluctuation in release from neuropil, both spontaneously and in response to physical stimulation of the animal and to certain drugs. Although in the adrenal medulla ascorbate is co-released with catecholamines, release of ascorbate from brain cells is associated principally with the activity of glutamatergic neurones, mainly by glutamate-ascorbate heteroexchange across cell membranes of neurones or glia. This phenomenon is discussed in relation to a possible role of ascorbate as a neuromodulator or neuroprotective agent in the brain.
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Affiliation(s)
- R A Grünewald
- Institute of Neurology, National Hospital for Neurology, London, UK
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33
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Pierce RC, Miller DW, Reising DB, Rebec GV. Unilateral neostriatal kainate, but not 6-OHDA, lesions block dopamine agonist-induced ascorbate release in the neostriatum of freely moving rats. Brain Res 1992; 597:138-43. [PMID: 1477726 DOI: 10.1016/0006-8993(92)91515-g] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Unilateral kainate lesions of the neostriatum and 6-hydroxydopamine (6-OHDA) lesions of the medial forebrain bundle were used to assess the role of neostriatal and ascending dopaminergic neurons, respectively, on dopamine-agonist induced release of neostriatal ascorbate as measured voltammetrically in freely moving rats. Electrochemically modified, carbon-fiber electrodes recorded the effects of direct (a combination of 10 mg/kg SKF-38393 and 1.0 mg/kg quinpirole) as well as indirect (2.5 mg/kg D-amphetamine or 20.0 mg/kg GBR-12909) dopamine agonists. Relative to controls, kainate, but not 6-OHDA, lesions abolished the ability of both direct and indirect dopamine agonists to induce neostriatal ascorbate release. These results suggest that unlike dopaminergic afferents, neostriatal output pathways play a critical role in the modulation of neostriatal ascorbate levels.
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Affiliation(s)
- R C Pierce
- Department of Psychology, Indiana University, Bloomington 47405
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34
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Smith AD, Olson RJ, Justice JB. Quantitative microdialysis of dopamine in the striatum: effect of circadian variation. J Neurosci Methods 1992; 44:33-41. [PMID: 1279321 DOI: 10.1016/0165-0270(92)90111-p] [Citation(s) in RCA: 108] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Two quantitative microdialysis methods were used to determine the concentration of extracellular dopamine in the anterior striatum of the rat. In the first method, the slow perfusion flow rate method, perfusion was at 57 nl/min and dialysate samples were collected every 90 min for 18 h and assayed for dopamine (DA), DOPAC (3,4-dihydroxy-phenylacetic acid), homovanillic acid (HVA) and 5-hydroxy-indoleacetic acid (5-HIAA). There was a significant increase in the concentration of dopamine during the dark cycle compared with the light cycle (14.7 +/- 1 nM vs. 9.3 +/- 0.7 nM; mean +/- SEM; P less than 0.0001), indicating possible circadian variations in the extracellular concentration of DA. There was a steady decrease in the level of DOPAC and HVA, and no change in the level of 5-HIAA. For the point of no-net-flux method, animals were perfused with 4 concentrations of DA or DOPAC, bracketing the extracellular concentrations. The extracellular concentrations of DA and DOPAC using this method were 10.2 +/- 1.7 nM and 17.4 +/- 2.6 microM, respectively. The in vivo recoveries for DA and DOPAC as derived from the slope of the linear regression curves were 72 +/- 3% and 43 +/- 5%. These values were shown to be significantly different (P less than 0.001). Both methods gave similar results for the level of DA in the striatum.
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Affiliation(s)
- A D Smith
- Department of Chemistry, Emory University, Atlanta, GA 30322
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35
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Yamamoto F, Sasaki S, Maeda M. Positron labeled antioxidants: synthesis and tissue biodistribution of 6-deoxy-6-[18F]fluoro-L-ascorbic acid. INTERNATIONAL JOURNAL OF RADIATION APPLICATIONS AND INSTRUMENTATION. PART A, APPLIED RADIATION AND ISOTOPES 1992; 43:633-9. [PMID: 1325422 DOI: 10.1016/0883-2889(92)90032-a] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
A one-pot synthesis of 6-deoxy-6-[18F]fluoro-L-ascorbic acid (18F-DFA) has been developed via nucleophilic displacement of a cyclic sulfate with no-carrier-added [18F]fluoride ion. Isolated radiochemical yields of around 15% were obtained with radiochemical purity of over 99% after overall synthesis time of 90 min. Tissue distribution studies with 18F-DFA in rats showed high uptake of radioactivity in the adrenals, kidneys, liver and small intestine--organs known to have high concentrations of L-ascorbic acid. The slow and low uptake of radioactivity in the brain was observed between 10 and 120 min after i.v. injection. In vivo behavior of 18F-DFA in mice bearing 3-methylcholanthrene-induced fibrosarcoma demonstrated its ability to accumulate in the tumor.
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Affiliation(s)
- F Yamamoto
- Faculty of Pharmaceutical Sciences, Kyushu University, Fukuoka, Japan
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36
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Pierce RC, Rebec GV. Dopamine-, NMDA- and sigma-receptor antagonists exert differential effects on basal and amphetamine-induced changes in neostriatal ascorbate and DOPAC in awake, behaving rats. Brain Res 1992; 579:59-66. [PMID: 1352478 DOI: 10.1016/0006-8993(92)90741-q] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Amphetamine and other dopamine agonists elevate the extracellular level of neostriatal ascorbate, which has been shown to modulate neuronal function. To assess the receptor mechanisms underlying neostriatal ascorbate release, drug-induced changes in both basal and amphetamine-induced ascorbate release were monitored voltammetrically in the neostriatum of freely moving rats. A variety of dopamine receptor antagonists decreased basal ascorbate and reversed the increase induced by 2.5 mg/kg D-amphetamine. Thus, compared to vehicle treatment, administration of classical (haloperidol) and atypical (clozapine) neuroleptics or selective D1 (SCH-23390) and D2 (sulpiride) antagonists completely reversed the amphetamine-induced rise in ascorbate and also lowered basal levels by 20-40%. These same effects occurred following injection of dizocilpine (MK-801), a non-competitive NMDA antagonist, whereas BMY-14802, a sigma ligand, reversed the amphetamine-induced rise without altering basal levels. Simultaneous measurements of extracellular DOPAC, a major dopamine metabolite, revealed that haloperidol, clozapine, sulpiride and BMY-14802 elevated basal levels and reversed the amphetamine-induced decline. Dizocilpine also increased basal DOPAC but failed to alter the DOPAC response to amphetamine, whereas both basal and amphetamine-induced changes in DOPAC were unaffected by SCH-23390. A combination of subthreshold doses of SCH-23390 and sulpiride, however, reversed both the amphetamine-induced release of ascorbate and the corresponding decline in DOPAC. Collectively, these results suggest that whereas dopamine, sigma, and NMDA receptors modulate neostriatal ascorbate release, they exert an opposing influence on extracellular DOPAC. All drugs attenuated at least some components of the amphetamine behavioral response, suggesting a role for multiple mechanisms in the behavioral effects of this drug.
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Affiliation(s)
- R C Pierce
- Department of Psychology, Indiana University, Bloomington 47405
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37
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Yount SE, Kraft ME, Pierce RC, Langley PE, Rebec GV. Acute and long-term amphetamine treatments alter extracellular ascorbate in neostriatum but not nucleus accumbens of freely moving rats. Life Sci 1991; 49:1237-44. [PMID: 1943438 DOI: 10.1016/0024-3205(91)90136-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The ability of amphetamine to alter the extracellular level of ascorbate, an apparent modulator of neostriatal function, was assessed voltammetrically in the neostriatum and nucleus accumbens of awake, behaving rats. Whereas acute administration (1.0 and 5.0 mg/kg d-amphetamine) produced a dose-dependent rise in neostriatal ascorbate, there was no change in the nucleus accumbens. Vehicle injections had no significant effect on ascorbate levels in either location. Administration of 5.0 mg/kg d-amphetamine for one week enhanced neostriatal ascorbate release even further, but this effect returned to acute levels when treatment continued for a second week. Multiple amphetamine injections for up to two weeks failed to alter extracellular ascorbate in the nucleus accumbens. The results of these experiments confirm a site-specific action of amphetamine on ascorbate release and suggest complex changes in the extracellular level of this substance in the neostriatum with long-term treatment.
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Affiliation(s)
- S E Yount
- Department of Psychology, Indiana University, Bloomington 47405
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