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Pajarillo E, Digman A, Nyarko-Danquah I, Son DS, Soliman KFA, Aschner M, Lee E. Astrocytic transcription factor REST upregulates glutamate transporter EAAT2, protecting dopaminergic neurons from manganese-induced excitotoxicity. J Biol Chem 2021; 297:101372. [PMID: 34756885 PMCID: PMC8626589 DOI: 10.1016/j.jbc.2021.101372] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2021] [Revised: 10/18/2021] [Accepted: 10/27/2021] [Indexed: 11/25/2022] Open
Abstract
Chronic exposure to high levels of manganese (Mn) leads to manganism, a neurological disorder with similar symptoms to those inherent to Parkinson's disease. However, the underlying mechanisms of this pathological condition have yet to be established. Since the human excitatory amino acid transporter 2 (EAAT2) (glutamate transporter 1 in rodents) is predominantly expressed in astrocytes and its dysregulation is involved in Mn-induced excitotoxic neuronal injury, characterization of the mechanisms that mediate the Mn-induced impairment in EAAT2 function is crucial for the development of novel therapeutics against Mn neurotoxicity. Repressor element 1-silencing transcription factor (REST) exerts protective effects in many neurodegenerative diseases. But the effects of REST on EAAT2 expression and ensuing neuroprotection are unknown. Given that the EAAT2 promoter contains REST binding sites, the present study investigated the role of REST in EAAT2 expression at the transcriptional level in astrocytes and Mn-induced neurotoxicity in an astrocyte–neuron coculture system. The results reveal that astrocytic REST positively regulates EAAT2 expression with the recruitment of an epigenetic modifier, cAMP response element-binding protein–binding protein/p300, to its consensus binding sites in the EAAT2 promoter. Moreover, astrocytic overexpression of REST attenuates Mn-induced reduction in EAAT2 expression, leading to attenuation of glutamate-induced neurotoxicity in the astrocyte–neuron coculture system. Our findings demonstrate that astrocytic REST plays a critical role in protection against Mn-induced neurotoxicity by attenuating Mn-induced EAAT2 repression and the ensuing excitotoxic dopaminergic neuronal injury. This indicates that astrocytic REST could be a potential molecular target for the treatment of Mn toxicity and other neurological disorders associated with EAAT2 dysregulation.
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Affiliation(s)
- Edward Pajarillo
- Department of Pharmaceutical Sciences, Florida A&M University, Tallahassee, Florida, USA
| | - Alexis Digman
- Department of Pharmaceutical Sciences, Florida A&M University, Tallahassee, Florida, USA
| | - Ivan Nyarko-Danquah
- Department of Pharmaceutical Sciences, Florida A&M University, Tallahassee, Florida, USA
| | - Deok-Soo Son
- Department of Biochemistry and Cancer Biology, Meharry Medical College, Nashville, Tennessee, USA
| | - Karam F A Soliman
- Department of Pharmaceutical Sciences, Florida A&M University, Tallahassee, Florida, USA
| | - Michael Aschner
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, New York, USA; Laboratory of Molecular Nutrition of the Institute for Personalized Medicine, Sechenov First Moscow State Medical University, Moscow, Russia
| | - Eunsook Lee
- Department of Pharmaceutical Sciences, Florida A&M University, Tallahassee, Florida, USA.
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Oldenziel WH, Dijkstra G, Cremers TIFH, Westerink BHC. In vivo monitoring of extracellular glutamate in the brain with a microsensor. Brain Res 2006; 1118:34-42. [PMID: 16956598 DOI: 10.1016/j.brainres.2006.08.015] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2006] [Revised: 07/26/2006] [Accepted: 08/04/2006] [Indexed: 11/22/2022]
Abstract
Recent discoveries have revealed that glutamatergic neurotransmission in the central nervous system is mediated by a dynamic interplay between neurons and astrocytes. To enhance our understanding of this process, the study of extracellular glutamate is crucial. At present, microdialysis is the most frequently used analytical technique to monitor extracellular glutamate levels directly in the brain. However, the neuronal and physiological origin of the detected glutamate levels is questioned as they do not fulfil the classical release criteria for exocytotic release, such as calcium dependency or response to the sodium channel blocker tetrodotoxine (TTX). It is hypothesized that an analytical technique with a higher spatial and temporal resolution is required. Glutamate microsensors provide a promising analytical solution to meet this requirement. In the present study, we applied a 10 micro m diameter hydrogel-coated glutamate microsensor to monitor extracellular glutamate levels in the striatum of anesthetized rats. To explore the potential of the microsensor, different pharmacological agents were injected in the vicinity of the sensor at an approximate distance of 100 micro m. It was observed that KCl, exogenous glutamate, kainate and the reuptake inhibitor DL-threo-beta-benzyloxyaspartate (DL-TBOA) increased the extracellular glutamate levels significantly. TTX decreased the basal extracellular glutamate levels approximately 90%, which indicates that the microsensor is capable of detecting neuronally derived glutamate. This is one of the first studies in which a microsensor is applied in vivo on a routine base, and it is concluded that microsensor research can contribute significantly to improve our understanding of the physiology of glutamatergic neurotransmission in the brain.
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Affiliation(s)
- W H Oldenziel
- Department of Biomonitoring and Sensoring, University Center for Pharmacy, Antonius Deusinglaan 1, 9713 AV, Groningen, The Netherlands.
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Hillered L, Vespa PM, Hovda DA. Translational neurochemical research in acute human brain injury: the current status and potential future for cerebral microdialysis. J Neurotrauma 2005; 22:3-41. [PMID: 15665601 DOI: 10.1089/neu.2005.22.3] [Citation(s) in RCA: 223] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Microdialysis (MD) was introduced as an intracerebral sampling method for clinical neurosurgery by Hillered et al. and Meyerson et al. in 1990. Since then MD has been embraced as a research tool to measure the neurochemistry of acute human brain injury and epilepsy. In general investigators have focused their attention to relative chemical changes during neurointensive care, operative procedures, and epileptic seizure activity. This initial excitement surrounding this technology has subsided over the years due to concerns about the amount of tissue sampled and the complicated issues related to quantification. The interpretation of mild to moderate MD fluctuations in general remains an issue relating to dynamic changes of the architecture and size of the interstitial space, blood-brain barrier (BBB) function, and analytical imprecision, calling for additional validation studies and new methods to control for in vivo recovery variations. Consequently, the use of this methodology to influence clinical decisions regarding the care of patients has been restricted to a few institutions. Clinical studies have provided ample evidence that intracerebral MD monitoring is useful for the detection of overt adverse neurochemical conditions involving hypoxia/ischemia and seizure activity in subarachnoid hemorrhage (SAH), traumatic brain injury (TBI), thromboembolic stroke, and epilepsy. There is some data strongly suggesting that MD changes precede the onset of secondary neurological deterioration following SAH, hemispheric stroke, and surges of increased ICP in fulminant hepatic failure. These promising investigations have relied on MD-markers for disturbed glucose metabolism (glucose, lactate, and pyruvate) and amino acids. Others have focused on trying to capture other important neurochemical events, such as excitotoxicity, cell membrane degradation, reactive oxygen species (ROS) and nitric oxide (NO) formation, cellular edema, and BBB dysfunction. However, these other applications need additional validation. Although these cerebral events and their corresponding changes in neurochemistry are important, other promising MD applications, as yet less explored, comprise local neurochemical provocations, drug penetration to the human brain, MD as a tool in clinical drug trials, and for studying the proteomics of acute human brain injury. Nevertheless, MD has provided new important insights into the neurochemistry of acute human brain injury. It remains one of very few methods for neurochemical measurements in the interstitial compartment of the human brain and will continue to be a valuable translational research tool for the future. Therefore, this technology has the potential of becoming an established part of multimodality neuro-ICU monitoring, contributing unique information about the acute brain injury process. However, in order to reach this stage, several issues related to quantification and bedside presentation of MD data, implantation strategies, and quality assurance need to be resolved. The future success of MD as a diagnostic tool in clinical neurosurgery depends heavily on the choice of biomarkers, their sensitivity, specificity, and predictive value for secondary neurochemical events, and the availability of practical bedside methods for chemical analysis of the individual markers. The purpose of this review was to summarize the results of clinical studies using cerebral MD in neurosurgical patients and to discuss the current status of MD as a potential method for use in clinical decision-making. The approach was to focus on adverse neurochemical conditions in the injured human brain and the MD biomarkers used to study those events. Methodological issues that appeared critical for the future success of MD as a routine intracerebral sampling method were addressed.
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Affiliation(s)
- Lars Hillered
- Division of Neurosurgery, Department of Surgery, The David Geffen UCLA School of Medicine, Los Angeles, California, USA.
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García Dopico J, Perdomo Díaz J, Alonso TJ, González Hernández T, Castro Fuentes R, Rodríguez Díaz M. Extracellular taurine in the substantia nigra: Taurine-glutamate interaction. J Neurosci Res 2004; 76:528-38. [PMID: 15114625 DOI: 10.1002/jnr.20108] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Taurine has been proposed as an inhibitory transmitter in the substantia nigra (SN), but the mechanisms involved in its release and uptake remain practically unexplored. We studied the extracellular pool of taurine in the rat's SN by using microdialysis methods, paying particular attention to the taurine-glutamate (GLU) interaction. Extracellular taurine increased after cell depolarization with high-K(+) in a Ca(2+)-dependent manner, being modified by the local perfusion of GLU, GLU receptor agonists, and zinc. Nigral administration of taurine increased the extracellular concentration of gamma-aminobutyric acid (GABA) and GLU, the transmitters of the two main inputs of the SN. The modification of the glial metabolism with fluocitrate and L-methionine sulfoximine also changed the extracellular concentration of taurine. The complex regulation of the extracellular pool of taurine, its interaction with GABA and GLU, and the involvement of glial cells in its regulation suggest a volume transmission role for taurine in the SN.
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Affiliation(s)
- José García Dopico
- Unidad de Investigación del Hospital Universitario de Canarias, La Laguna, Tenerife, Canary Islands, Spain
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Andrade da Costa BL, de Mello FG, Hokoç JN. Transporter-mediated GABA release induced by excitatory amino acid agonist is associated with GAD-67 but not GAD-65 immunoreactive cells of the primate retina. Brain Res 2000; 863:132-42. [PMID: 10773201 DOI: 10.1016/s0006-8993(00)02111-9] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The release of GABA from amacrine and interplexiform cells after exposure to excitatory amino acids (EAAs) agonists was investigated by immunohistochemistry. Cebus monkey retinas were treated in vitro with 50 microM kainate (KA) or 5 mM L-Glutamate (L-Glu), for 30 min at 37 degrees C. The effects of the EAAs were measured by detecting immunocytochemically the GABA remaining in the tissue after stimulation. L-Glu and KA reduced the number of GABA-immunoreactive perikarya in the innermost part of the inner nuclear layer by approximately 60% and 80%, respectively, as compared to controls. The cell processes in the inner plexiform layer (IPL) were restricted to only three defined bands in the strata 1, 3 and 5, as compared to an intense and homogeneous labeling in the IPL of the untreated retinas. The effect of KA was inhibited by 100 microM CNQX, 100 microM NNC-711, or when Na(+) was replaced by choline. The release of GABA was Ca(2+)-independent, suggesting the mobilization of GABA from the cytoplasmic pool of this neurotransmitter. At least two subsets of retinal neurons including amacrine and interplexiform cells retained GABA-immunoreactivity after stimulation with EAAs, as revealed by glutamic acid decarboxylase (GAD) immunocytochemistry. Our results suggest that non-NMDA receptor activation by KA and glutamate are associated with the efflux of GABA from cells of the inner retina (amacrine and interplexiform cells). The data also show that cells containing GAD-67 released GABA via its transporter, while cells containing exclusively GAD-65 apparently did not release the neurotransmitter by the reversal of the transporter.
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Geddes JW, Chang NG, Ackley DC, Soultanian NS, McGillis JP, Yokel RA. Postmortem elevation in extracellular glutamate in the rat hippocampus when brain temperature is maintained at physiological levels: implications for the use of human brain autopsy tissues. Brain Res 1999; 831:104-12. [PMID: 10411988 DOI: 10.1016/s0006-8993(99)01403-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Postmortem alterations in the neuronal cytoskeleton resemble some aspects of the cytoskeletal disruption associated with neurodegenerative disorders, and are also similar to those observed following ischemia and produced by excitotoxins in vivo and in vitro. This suggests the involvement of excitotoxic mechanisms during the postmortem interval. The purpose of this study was to determine if extracellular levels of glutamate are elevated postmortem. Extracellular levels of GABA and taurine were also monitored using in vivo microdialysis. These three amino acids were analyzed using high-performance liquid chromatography. When postmortem rat brain temperature cooled rapidly to near room temperature, dialysate concentrations of glutamate were not increased in the hippocampal CA1 region during a 2-h postmortem interval, although increased extracellular levels of GABA and taurine were observed. In contrast, maintenance of brain temperature at 37 degrees C resulted in a 12-to-40 fold elevation in extracellular glutamate levels 20-120 min postmortem. In addition, the elevation in dialysate taurine concentration was greater than that observed in rats in which postmortem brain temperature was not maintained. Excitatory amino acid antagonists, NBQX (2, 3-dihydroxy-6-nitro-7-sulfamoyl-benzo(F)quinoxaline) and MK-801 (dizocilpine, (+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cylohepten-5, 10-imine hydrogen maleate blocked the additional elevation in taurine associated with maintaining brain at 37 degrees C, but had less robust effects against glutamate and GABA release. The results indicate that extracellular concentrations of glutamate, taurine and GABA increase in postmortem rat brain when physiologic temperatures are maintained, but that these increases are blunted when brain temperature decreases. After death, the human brain cools much more slowly than does the rat brain. Therefore, extracellular glutamate levels are likely to increase in the postmortem human brain and may contribute to excitotoxic neuronal damage occurring in the interval between death and autopsy.
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Affiliation(s)
- J W Geddes
- Sanders-Brown Center on Aging, University of Kentucky, Lexington, KY 40536-0230, USA.
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Ruotsalainen M, Majasaari M, Salimäki J, Ahtee L. Locally infused taurine, GABA and homotaurine alter differently the striatal extracellular concentrations of dopamine and its metabolites in rats. Amino Acids 1999; 15:117-34. [PMID: 9871492 DOI: 10.1007/bf01345285] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
We studied in vivo the effects of locally infused taurine (50, 150, and 450 mM) on the striatal dopamine and its metabolites in comparison with those of GABA and homotaurine, a GABAA receptor agonist, in freely moving rats. The extracellular dopamine concentration was elevated maximally 2.5-, 2- and 4-fold by taurine, GABA and homotaurine, respectively. At 150 mM concentration, at which the maximum effects occurred, homotaurine increased the extracellular dopamine more than taurine or GABA. When taurine and GABA were infused simultaneously with tetrodotoxin the output of dopamine did not differ from that in the presence of tetrodotoxin alone. In comparison, tetrodotoxin did not inhibit the increase in extracellular dopamine caused by homotaurine. Furthermore, omission of calcium from the perfusion fluid inhibited the increase of extracellular dopamine caused by GABA. However, it did not block the increase of dopamine caused by taurine or homotaurine. The present study suggests that the effects of intrastriatal taurine, GABA and homotaurine on the striatal extracellular dopamine differ. Thus, these amino acids seem to affect the striatal dopaminergic neurons via more than one mechanism.
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8
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Bianchi L, Colivicchi MA, Bolam JP, Della Corte L. The release of amino acids from rat neostriatum and substantia nigra in vivo: a dual microdialysis probe analysis. Neuroscience 1998; 87:171-80. [PMID: 9722150 DOI: 10.1016/s0306-4522(98)00090-6] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
It has previously been demonstrated, in dual probe microdialysis studies, that stimulation of the neostriatum with kainic acid causes the release of GABA both locally within the neostriatum and distally in the substantia nigra, observations that are consistent with the known anatomy of the basal ganglia. The object of the present study was to further examine the characteristics of GABA release and to determine whether taurine, which has been proposed to be present in striatonigral neurons, has similar characteristics of release, and to examine the release of excitatory amino acids under the same conditions. To this end, dual probe microdialysis studies were carried out on freely-moving rats. The application of kainic acid to neostriatum enhanced the release of GABA, taurine, aspartate and glutamate locally in the neostriatum and distally in the substantia nigra. The distal release of each amino acid in the substantia nigra was sensitive to the administration of 6,7-dinitroquinoxaline-2,3-dione and tetrodotoxin to the neostriatum. Similarly the local release of GABA, aspartate and glutamate but not taurine was sensitive to the intrastriatal application of 6,7-dinitroquinoxaline-2,3-dione or tetrodotoxin. It is concluded that the release of taurine from the substantia nigra has similar characteristics to that of GABA and may be released from the terminals of striatonigral neurons following the stimulation of their cell bodies in the neostriatum. The release of taurine in the neostriatum however, is likely to be mediated mainly by different mechanisms and not related to neuronal activity. The release of excitatory amino acids is likely to involve indirect effects in the neostriatum and polysynaptic pathways in the substantia nigra.
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Affiliation(s)
- L Bianchi
- Dipartimento di Farmacologia Preclinica e Clinica M. Aiazzi Mancini, Università degli Studi di Firenze, Italy
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Ding R, Asada H, Obata K. Changes in extracellular glutamate and GABA levels in the hippocampal CA3 and CA1 areas and the induction of glutamic acid decarboxylase-67 in dentate granule cells of rats treated with kainic acid. Brain Res 1998; 800:105-13. [PMID: 9685600 DOI: 10.1016/s0006-8993(98)00507-1] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
For the evaluation of glutamatergic and GABAergic transmission during seizures, rat hippocampal CA1 and CA3 areas were separately assessed by brain microdialysis, and extracelluar glutamate and GABA were measured through the course of the seizures after a systemic administration of kainic acid (KA). The generalized convulsion started at about 1.5 h and was suppressed by diazepam at 2 h after the KA treatment. In the CA3 area, extracellular glutamate started to increase soon after the KA injection and returned to the control level at about 1.5 h. A decrease and then slight increase of the extracellular glutamate level in CA3 followed the diazepam injection. In the CA1 area, in contrast, a long-lasting decrease of extracellular glutamate was observed. The extracellular GABA concentration in the CA3 area increased immediately after the systemic administration of KA and returned to the normal level at about 3.5 h. A second increase in the extracellular GABA in this area began at about 4.5 h after the KA treatment. In the CA1 area, an increase of extracellular GABA began at about 3.5 h after KA administration (much later than that observed in the CA3 area) and was maintained throughout the observation. In situ hybridization showed a transient expression of glutamic acid decarboxylase (GAD)-67 mRNA in the granule cell layer of the dentate gyrus at 4 and 6 h, whereas GAD65 mRNA was unaffected. GABA immunoreactivity in the same area and mossy fibers in the CA3 were increased most significantly at 8 h after administration of KA. The possible relation of GABA induction in mossy fibers with the delayed increase in extracellular GABA in CA3 was discussed.
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Affiliation(s)
- R Ding
- Laboratory of Neurochemistry, National Institute for Physiological Sciences, Myodaiji, Okazaki, Aichi 444-8585, Japan
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10
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Abstract
Microdialysis has become a frequently used method to study extracellular levels of GABA and glutamate in the central nervous system. However, the fact that the major part of GABA and glutamate as measured by microdialysis does not fulfill the classical criteria for exocytotic release questions the vesicular origin of the amino acids in dialysates. Glial metabolism or reversal of the (re)uptake sites has been suggested to be responsible for the pool of nonexocytotically released amino-acid transmitters that seem to predominate over the neuronal exocytotic pool. The origin of extracellular GABA and glutamate levels and, as a consequence, the implications of changes in these levels upon manipulations are therefore obscure. This review critically analyzes what microdialysis data signify, i.e., whether amino-acid neurotransmitters sampled by microdialysis represent synaptic release, carrier-mediated release, or glial metabolism. The basal levels of GABA and glutamate are virtually tetrodotoxin- and calcium-independent. Given the fact that evidence for nonexocytotic release mediated by reversal of the uptake sites as a release mechanism relevant for normal neurotransmission is so far limited to conditions of "excessive stimulation," basal levels most likely reflect a nonneuronal pool of amino acids. Extracellular GABA and glutamate concentrations can be enhanced by a wide variety of pharmacological and physiological manipulations. However, it is presently impossible to ascertain that the stimulated GABA and glutamate in dialysates are of neuronal origin. On the other hand, under certain stimulatory conditions, increases in amino-acid transmitters can be obtained in the presence of tetrodotoxin, again suggesting that aspecific factors not directly related to neurotransmission underlie these changes in extracellular levels. It is concluded that synaptic transmission of GABA and glutamate is strictly compartmentalized and as a result, these amino acids can hardly leak out of the synaptic cleft and reach the extracellular space where the dialysis probe samples.
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Affiliation(s)
- W Timmerman
- University Center for Pharmacy, Department of Medicinal Chemistry, University of Groningen, The Netherlands
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MacGregor DG, Graham DI, Stone TW. The attenuation of kainate-induced neurotoxicity by chlormethiazole and its enhancement by dizocilpine, muscimol, and adenosine receptor agonists. Exp Neurol 1997; 148:110-23. [PMID: 9398454 DOI: 10.1006/exnr.1997.6625] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Systemically administered kainate (10 mg.kg-1) caused neuronal loss in both the hippocampus and the entorhinal regions of the rat brain. This resulted in a loss of 68.3 +/- 13.8 and 53.3 +/- 12.8% of pyramidal neurones in the hippocampal CA1 and CA3a regions, respectively. Chlormethiazole attenuated the loss of neurones in the hippocampal cell layers CA1 (cell loss 10 +/- 3.2%) and CA3a (cell loss 10 +/- 7.7%). The neuroprotective activity of chlormethiazole was apparent in the presence or absence of a low dose of clonazepam (200 micrograms.kg-1 i.p.). The kainate-induced damage could also be measured by the increase in binding of the peripheral benzodiazepine ligand ([3H]PK11195) in the hippocampus. In kainate-treated rats there was a 350-500% increase in binding indicative of reactive gliosis. Chlormethiazole prevented this elevation in a dose- and time-dependent manner, with an ED50 of 10.64 mg.kg-1 and an effective therapeutic window from 1 to 4 h posttreatment. Dizocilpine also attenuated damage significantly. The GABAA agonist muscimol was also able to attenuate the increase in [3H]PK11195 binding in a dose-dependent manner, with an ED50 of approximately 0.1 mg.kg-1. If muscimol, dizocilpine, or the adenosine A1 receptor agonist R-N6-phenylisopropyl-adenosine were administered together with chlormethiazole at their respective ED25 doses, a potentiation was apparent in the degree of neuroprotection. It is concluded that the combination of neuroprotective agents with different mechanisms of action can lead to a synergistic protection against excitotoxicity.
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Affiliation(s)
- D G MacGregor
- Division of Neuroscience and Biomedical Systems, University of Glasgow, Scotland, United Kingdom
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Shiraishi M, Kamiyama Y, Hüttemeier PC, Benveniste H. Extracellular glutamate and dopamine measured by microdialysis in the rat striatum during blockade of synaptic transmission in anesthetized and awake rats. Brain Res 1997; 759:221-7. [PMID: 9221940 DOI: 10.1016/s0006-8993(97)00258-8] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
We investigated the effect of high dose tetrodotoxin (TTX) on microdialysis measurements of extracellular striatal glutamate and dopamine in normal female rats. Both halothane-anesthetized rats with acutely implanted microdialysis probes and awake rats with microdialysis probes implanted for 24 h were tested. Glutamate levels in awake rats were 45% higher than those of anesthetized rats. Extracellular glutamate remained TTX-insensitive regardless of TTX concentration, anesthesia, or time lapsed after probe implantation. In contrast, TTX reduced dialysate dopamine in all TTX concentrations tested. We speculate that the lower glutamate levels in anesthetized rats reflect the effect of anesthesia. Because glutamate is involved, either as a reactant or a product in a variety of reactions critical to intermediary metabolism in the brain, basal dialysate glutamate levels might indirectly reflect brain metabolism. Further, we conclude that extracellular glutamate collected during non-stimulated conditions is TTX-insensitive. The fact that glutamate levels are TTX-independent does not rule out that glutamate is synaptic in origin but rather demonstrates that it is not nerve impulse-dependent. However, the brain interstitial glutamate pool accessible to the microdialysis probe during control conditions is most likely isolated from the synapse, and therefore does not impose a neurotoxic potential.
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Affiliation(s)
- M Shiraishi
- Department of Anesthesiology, Juntendo University Urayasu Hospital, Tokyo, Japan
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13
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Lazarewicz JW, Puka-Sundvall M, Gadamski R, Sandberg M, Hagberg H. Differential effects of N-methyl-D-aspartate on Ca2+ homeostasis in developing and adult rat striatum: in vivo microdialysis approach. Int J Dev Neurosci 1995; 13:685-704. [PMID: 8787860 DOI: 10.1016/0736-5748(95)00061-5] [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: 02/02/2023] Open
Abstract
This in vivo study concerns developmental differences in the sensitivity of striatal neurons to N-methyl-D-aspartate (NMDA). Changes in calcium homeostasis in adult vs immature rats at postnatal days 8-10, evoked by NMDA, were evaluated by measurements of 45Ca efflux and of Ca2+ taurine and phosphoethanolamine concentrations in striatal microdialysates. The efflux of [14C]sucrose was employed in order to measure changes in extracellular space volume. In adult rats the addition of 5 mM NMDA for 20 min to the perfusion medium resulted in a 30-40% increase in 45Ca efflux, and in a 15% increase in [14C]sucrose efflux. Ten minutes after NMDA perfusion, 45Ca and [14C] sucrose efflux returned to the baseline. No significant changes in Ca2+ or amino acid concentrations were observed in the dialysate of the adult rat striatum. NMDA perfusion in the striatum of immature rats initially induced a transient (5 min) increase in the efflux of 45Ca (by 13%) and [14C]sucrose (by 9%). This was followed by a prolonged (lasting 45-50 min) 45% decrease in 45Ca efflux, an 80% reduction of Ca2+ concentration, and increases in taurine and phosphoethanolamine concentrations in the dialysate, whereas [14C]sucrose efflux recovered within 10 min. These data illustrate differences in the NMDA response between developing and adult rat striatum. Only in developing rats did NMDA induce a large and prolonged influx of extracellular calcium to neurons that may explain the enhanced NMDA neurotoxicity in immature rats.
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Affiliation(s)
- J W Lazarewicz
- Medical Research Centre, Polish Academy of Sciences, Warsaw
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14
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Semba J, Kito S, Toru M. Characterisation of extracellular amino acids in striatum of freely moving rats by in vivo microdialysis. J Neural Transm (Vienna) 1995; 100:39-52. [PMID: 8748662 DOI: 10.1007/bf01276864] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
To investigate the characteristics of extracellular amino acids released from the striatum, we performed in vivo microdialysis in non-anaesthetised, freely moving rats. Amino acids were determined after precolumn derivatisation with o-phthalaldehyde by high-performance liquid chromatography and fluorescence detection. The omission of Ca2+ in the perfusion medium partially decreased the basal concentration of aspartate and glutamate. This shows that a small fraction of basal concentration of aspartate and glutamate is of neuronal origin. The effect of high K+ and veratrine stimulation was evaluated in the presence or absence of Ca2+ or tetrodotoxin (1 microM). High K+ and veratrine caused a remarkable increase in the aspartate and glutamate efflux. The omission of Ca2+ only partially decreased K(+)-stimulated aspartate and glutamate efflux. Tetrodotoxin completely antagonised veratrine-stimulated aspartate and glutamate efflux. Although glycine and taurine releases were stimulated by high K+ and veratrine, their release was not always antagonised with Ca2+ omission or tetrodotoxin inclusion. Thus, the neuronal origin of stimulated release of glycine and taurine is unclear. Although tetrodotoxin sensitivity and Ca2(+)-dependency are regarded as a basic criterion for classical neurotransmitters in microdialysis experiments, they should not be adapted to the physiological characteristics of the release of amino acids.
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Affiliation(s)
- J Semba
- Division of Health Sciences, University of the Air, Chiba, Japan
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15
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Interactions of Dopamine, Excitatory Amino Acids, and Inhibitory Amino Acids in the Basal Ganglia of the Conscious Rat. ACTA ACUST UNITED AC 1994. [DOI: 10.1007/978-1-4613-0485-2_46] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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16
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Shibanoki S, Kogure M, Sugahara M, Ishikawa K. Effect of systemic administration of N-methyl-D-aspartic acid on extracellular taurine level measured by microdialysis in the hippocampal CA1 field and striatum of rats. J Neurochem 1993; 61:1698-704. [PMID: 7901330 DOI: 10.1111/j.1471-4159.1993.tb09806.x] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The extracellular concentrations of amino acids in the hippocampal CA1 field and striatum of conscious freely moving rats were monitored simultaneously by in vivo brain microdialysis using HPLC with electrochemical detection. Under basal conditions, aspartate, glutamate, glutamine, glycine, taurine, and alanine were detected, but gamma-aminobutyric acid was undetectable in both regions. Intraperitoneal injection of N-methyl-D-aspartic acid (NMDA; 10 mg/kg) caused a significant increase (three- to fivefold) in the taurine concentration in the dialysate obtained from both the hippocampal CA1 and striatum, whereas other amino acids (aspartate, glutamate, and alanine) did not show significant changes. Local application of NMDA (300 microM) to both regions via the dialysis probes also caused a similar increase (three- to fivefold) in both regions. Under infusion of hypertonic Ringer's solution containing 150 mM sucrose, the effect of NMDA on the level of taurine in both the regional dialysates was not affected. The effect of NMDA was totally reduced by intraperitoneal administration of MK-801 (0.3-1.0 mg/kg), a noncompetitive antagonist of NMDA receptors. Continuous infusion of DL-2-amino-5-phosphonovaleric acid (1.0 mM), a competitive antagonist of NMDA receptors, via the dialysis probes completely inhibited the effect of NMDA. These findings suggest that systemic administration of NMDA is effective as well as local administration into the brain and that NMDA receptors might be involved in the regulation of the extracellular taurine level in the brain without dependence on cell swelling.
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Affiliation(s)
- S Shibanoki
- Department of Pharmacology, Nihon University School of Medicine, Tokyo, Japan
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17
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MacGregor DG, Stone TW. Inhibition by the adenosine analogue, (R-)-N6-phenylisopropyladenosine, of kainic acid neurotoxicity in rat hippocampus after systemic administration. Br J Pharmacol 1993; 109:316-21. [PMID: 8358536 PMCID: PMC2175678 DOI: 10.1111/j.1476-5381.1993.tb13572.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
1. Binding of the peripheral benzodiazepine receptor ligand, [3H]-PK 11195, to rat hippocampal membranes has been used to quantify the reactive gliosis resulting from neuronal death induced by intraperitoneally administered kainic acid. 2. Intraperitoneal administration of kainic acid (10 mg kg-1) caused a 350-500% increase in [3H]-PK 11195 binding measured in rat hippocampal P2 membranes 7 days later. Co-treatment with the adenosine derivative R-phenylisopropyladenosine (R-PIA) (100, 25 or 10 micrograms kg-1, i.p.) abolished this elevation. The protective action of R-PIA could itself be abolished by co-treatment with 8-phenyltheophylline (1 mg kg-1). 3. Body temperatures were recorded in the antagonist experiments and no significant changes were recorded, suggesting that the protective action of R-PIA was not mediated by hypothermia. 4. Since systemic kainic acid-induced neurotoxicity has been claimed as a good model of neuronal death in temporal lobe epilepsy, the results suggest that the systemic administration of purines in low doses may provide protection against certain neurodegenerative insults.
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18
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Campbell K, Kalén P, Wictorin K, Lundberg C, Mandel RJ, Björklund A. Characterization of GABA release from intrastriatal striatal transplants: dependence on host-derived afferents. Neuroscience 1993; 53:403-15. [PMID: 8098510 DOI: 10.1016/0306-4522(93)90204-s] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Extracellular levels of GABA, derived from cell suspension transplants of embryonic day 14-15 rat striatal primordia implanted into the previously excitotoxically lesioned striatum, were measured using intracerebral microdialysis in halothane-anaesthetized rats. GABA overflow was monitored using loop type dialysis probes implanted into grafted, age-matched ibotenic acid-lesioned and intact striata, under baseline conditions and after different pharmacological manipulations. Basal and evoked GABA release, which was reduced by 58 and 96%, respectively, in the excitotoxin-lesioned striatum, was restored by the striatal grafts to levels close to or above those observed in normal striata. The graft-derived release of GABA was most likely of neuronal origin, since the K(+)-evoked (100 mM) GABA overflow was reduced by almost 80% when Ca++ was replaced by 20 mM Mg++ in the perfusion medium, and blockade of GABA uptake by nipecotic acid (0.5 mM), induced a greater than six-fold increase in GABA overflow. However, perfusion of the graft with 1 microM tetrodotoxin in combination with K+ (100 mM) resulted in little if any reduction in the K(+)-evoked overflow. Histological analysis demonstrated a dense tyrosine hydroxylase-positive fibre network in the grafts, which was removed after a 6-hydroxydopamine lesion of the ipsilateral nigrostriatal pathway. The dopamine denervating lesion resulted in an increased K(+)-evoked GABA overflow both in the intact (+76%) and the grafted striata (+181%), suggesting that the tonic dopaminergic inhibitory control of GABA release, seen in the intact striatum, is also present in the grafted striata. The glutamate analogue, kainic acid (1 mM added to the perfusion fluid), evoked a 60-74% increase in GABA overflow both in intact striata (with or without dopaminergic denervation) and in the striatal grafts. This effect seemed to be dependent on an intact corticostriatal projection, since knife-cut transections of the frontal cortex at the level of the forceps minor, abolished the response in both the intact and grafted striata. These results demonstrate that grafts of fetal striatal tissue implanted into the excitotoxically lesioned striatum restore striatal GABA overflow in a neuron-dependent manner, close to or above that seen in the normal intact striatum. Furthermore, the graft-derived GABA release appears to be under normal regulatory control from the host dopaminergic and glutamatergic systems. Since the GABAergic striatal output system is critical for the expression of striatum-related behaviours, it is proposed that the graft-induced behavioural recovery in the striatal lesion model, at least in part, may depend on the restoration of striatal GABAergic neurotransmission.
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Affiliation(s)
- K Campbell
- Department of Medical Cell Research, University of Lund, Sweden
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19
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Young AM, Bradford HF. N-methyl-D-aspartate releases gamma-aminobutyric acid from rat striatum in vivo: a microdialysis study using a novel preloading method. J Neurochem 1993; 60:487-92. [PMID: 8093478 DOI: 10.1111/j.1471-4159.1993.tb03176.x] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
In vivo microdialysis was used in conjunction with a novel dual-label preloading method to monitor changes in extracellular levels of gamma-aminobutyric acid (GABA) and glutamate due to N-methyl-D-aspartate (NMDA) infusion in the striatum of conscious, unrestrained rats. [14C]GABA and [3H]glutamate were applied in the dialysis stream for a preloading period of 30 min, after which dialysis perfusion was continued for up to 6 h and dialysate samples were collected for analysis by liquid scintillation spectrometry. NMDA (300 microM in the dialysate) caused significant rises in both 14C and 3H content measured in the dialysates, the majority of which remained associated with the preloaded GABA and glutamate, respectively. The NMDA-evoked release of both GABA and glutamate was blocked by the specific NMDA receptor antagonist 3-[(+/-)-2-carboxypiperazin-4-yl]propyl-1-phosphonic acid (CPP), indicating that the response was receptor mediated. The NMDA-stimulated release of glutamate was also totally abolished by concomitant application of the adenosine agonist 2-chloroadenosine or by prior frontal decortication. However, these two treatments caused little change in NMDA-evoked GABA release. These results show that NMDA causes release of GABA from the striatum in vivo by an NMDA receptor-mediated mechanism and that the majority of this release is not secondary to glutamate release from terminals of the corticostriate pathway. In addition, they confirm the results of previous studies investigating the effect of NMDA on endogenous glutamate release.
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Affiliation(s)
- A M Young
- Department of Biochemistry, Imperial College of Science, Technology and Medicine, London, England
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20
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Nakamura F, Kuno M, Matsuura S. Glutamate-induced inhibition of paired pulse facilitation of monosynaptic excitatory post-synaptic potentials in frog spinal motoneurons. Brain Res 1992; 597:124-30. [PMID: 1362131 DOI: 10.1016/0006-8993(92)91513-e] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
To evaluate actions of glutamate on excitatory synaptic transmission in the central nervous system, we examined glutamate-induced changes in the paired pulse facilitation of monosynaptic excitatory post-synaptic potentials evoked by stimulation of the lateral column fibers (LC-EPSPs) on lumbar motoneurons in the frog spinal cord. Glutamate (1 mM) depolarized motoneurons both in the presence and absence of Mg2+. In most cells perfused with Mg(2+)-free or high Ca(2+)-Mg2+ solutions, the glutamate potential was accompanied by a reduction in peak amplitude of EPSPs, although the degree of change varied with the cells. Glutamate enhanced the EPSP amplitude in a few cells with Mg(2+)-free and high Ca(2+)-Mg2+ solutions, and in most cells with high Mg2+ medium. In 3/5 cells tested, the paired pulse facilitation of EPSPs was reduced by glutamate when the EPSP amplitude either increased or decreased. NMDA (50 microM), kainate (50-100 microM), quisqualate (5-50 microM) and L-2-amino-4-phosphonobutyrate (L-AP4, 1 mM) also decreased the facilitation in about half of the cells tested. The glutamate-induced decrease in the facilitation was observed in both the presence and absence of Mg2+ and was not affected by the concomitant application of glutamate and antagonists for non-NMDA or NMDA receptors, such as 6-cyano-7-nitro-quinoxalinediones (CNQX, 60 microM) or 2-amino-5-phosphonovalerate (APV, 250 microM). Glutamate reduced the facilitation of excitatory post-synaptic currents (EPSCs) recorded at a constant membrane potential under voltage clamp, when the EPSC amplitude either increased or decreased and when the input conductance either increased or decreased.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- F Nakamura
- Department of Physiology, Osaka City University Medical School, Japan
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21
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Abstract
This study was conducted to assess the functional integrity of the kainate receptor-mediated seizure response in aged rats. Kainic acid was administered systemically to aged female Long-Evans (LE) rats and aged male F344 rats and the proconvulsant actions of kainic acid was compared to adult controls. The effects of kainic acid on brain regional content of monoamines and amino acids was also determined in the aged female LE and adult control rats. The latency to full clonic-tonic seizures was significantly reduced in aged female LE rats, and the number of seizures was significantly increased above that of the controls. There was increased mortality and a reduction in the latency to exhibit wet dog shakes in the aged F344 rats. Studies were also conducted to evaluate the role of ovarian hormones, route of administration, and dose of kainic acid in mediating the enhanced proconvulsant actions of kainic acid in aged rats. The neurochemical studies suggested that kainic acid significantly enhanced the release of ASP, GLU, and norepinephrine (NE) in the aged rats exhibiting clonic-tonic seizures. The adult rats given the same dose of kainic acid (15 mg/kg, IP) did not exhibit any significant change in brain content of monoamines or amino acids except for a reduction in mediobasal hypothalamic NE. An in vitro study was also conducted using brain slices from adult and aged F344 and it was found that aged rats released significantly more ASP than adults in response to kainic acid. These neurochemical findings were discussed in relation to previous studies of age-related alterations in excitatory amino acids (EAAs) and the role of EAA and NE in modulating limbic seizures. This study has clearly demonstrated that aged rats may be more susceptible to the excitotoxic action of EEAs acting through kainetic receptors.
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Affiliation(s)
- R Dawson
- Department of Pharmacodynamics, University of Florida, College of Pharmacy, Gainesville 32610
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22
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Bourdelais AJ, Kalivas PW. Modulation of extracellular gamma-aminobutyric acid in the ventral pallidum using in vivo microdialysis. J Neurochem 1992; 58:2311-20. [PMID: 1315380 DOI: 10.1111/j.1471-4159.1992.tb10979.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Intracranial microdialysis was used to investigate the origin of extracellular gamma-aminobutyric acid (GABA) in the ventral pallidum. Changes in basal GABA levels in response to membrane depolarizers, ion-channel blockers, and receptor agonists were determined. Antagonism of Ca2+ fluxes with high Mg2+ in a Ca(2+)-free perfusion buffer decreased GABA levels by up to 30%. Inhibition of voltage-dependent Na+ channels by the addition of tetrodotoxin also significantly decreased basal extracellular GABA concentrations by up to 45%, and blockade of Ca2+ and Na+ channels with verapamil reduced extracellular GABA by as much as 30%. The addition of either the GABAA agonist, muscimol, or the GABAB agonist, baclofen, produced a 40% reduction in extracellular GABA. GABA release was stimulated by high K+ and the addition of veratridine to increase Na+ influx. High K(+)-induced release was predominantly Ca(2+)-dependent, whereas the effect of veratridine was potentiated in the absence of extracellular Ca2+. Both high K(+)- and veratridine-induced elevations in extracellular GABA were inhibited by baclofen, whereas only veratridine-induced release was antagonized by muscimol. These results demonstrate that at least 50% of basal extracellular GABA in the ventral pallidum is derived from Ca(2+)- or Na(+)-dependent mechanisms. They also suggest that Na(+)-dependent release of GABA via reversal of the uptake carrier can be shown in vivo.
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Affiliation(s)
- A J Bourdelais
- Department of VCAPP, Washington State University, Pullman 99164-6520
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23
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Affiliation(s)
- S Bernath
- University of Pittsburgh, Department of Behavioral Neuroscience, PA 15260
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24
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Abstract
The measurement of GABA in brain dialysis experiments involves precolumn derivatization of the amino acid with o-phthaldehyde (OPA) in the presence of a thiol and subsequent high-pressure liquid chromatography with electrochemical detection. A method is described which employs an internal standard and coulometric preoxidation (+ 0.2 V) to eliminate unconjugated OPA/thiol prior to final oxidation (+ 0.4 V) of the derivatized sample. This allows for more efficient separation, providing a retention time for GABA of 9-10 min, a detection sensitivity of 2 to 5 x 10(-14) mol/sample and chromatographic stability for at least 2 weeks of daily use.
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Affiliation(s)
- A Bourdelais
- Department of Veterinary Comparative Anatomy, Pharmacology and Physiology, Washington State University, Pullman 99164-6520
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25
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Récasens M, Guiramand J, Vignes M. The putative molecular mechanism(s) responsible for the enhanced inositol phosphate synthesis by excitatory amino acids: an overview. Neurochem Res 1991; 16:659-68. [PMID: 1686474 DOI: 10.1007/bf00965552] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- M Récasens
- Laboratoire de Neurobiologie de l'Audition, Université Montpellier II, Hôpital St Charles, France
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26
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Young AM, Bradford HF. N-methyl-D-aspartate releases excitatory amino acids in rat corpus striatum in vivo. J Neurochem 1991; 56:1677-83. [PMID: 1826519 DOI: 10.1111/j.1471-4159.1991.tb02067.x] [Citation(s) in RCA: 63] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
There is a considerable amount of conflicting evidence from several studies as to the action of applied N-methyl-D-aspartate (NMDA) on the release of glutamate and aspartate in the brain. In the present study the effect of NMDA on extracellular levels of endogenous amino acids was investigated in conscious, unrestrained rats using intracerebral microdialysis. NMDA caused dose-related increases in extracellular levels of glutamate and aspartate; threonine and glutamine were unaffected. The NMDA-evoked release of glutamate and aspartate was significantly decreased by the specific NMDA receptor antagonist 3-[(+-)-2-carboxypiperazin-4-yl]-propyl-l-phosphonic acid. In addition, increasing the perfusate concentration (and therefore the extracellular concentration) of Ca2+ significantly enhanced the NMDA-evoked release of glutamate and aspartate, whereas removal of Ca2+ and addition of a high Mg2+ concentration to the perfusate caused a significant reduction in their NMDA-evoked release. Moreover, the NMDA-evoked release of glutamate and aspartate was reduced in decorticate animals. These results demonstrate that, in the striatum in vivo, NMDA causes selective release of endogenous glutamate and aspartate from neurone terminals and that this action occurs through an NMDA receptor-mediated mechanism. The ability of NMDA receptor activation to induce release of glutamate and aspartate, perhaps by a positive feedback mechanism, may be relevant to the pathologies underlying epilepsy and ischaemic and hypoglycaemic brain damage.
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Affiliation(s)
- A M Young
- Department of Biochemistry, Imperial College of Science, Technology and Medicine, London, England
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27
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Carrozza DP, Ferraro TN, Golden GT, Reyes PF, Hare TA. Partial characterization of kainic acid-induced striatal dopamine release using in vivo microdialysis. Brain Res 1991; 543:69-76. [PMID: 2054676 DOI: 10.1016/0006-8993(91)91049-7] [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: 12/30/2022]
Abstract
The aim of this study was to characterize interactions between striatal kainate (KA) receptors and dopamine (DA) release using in vivo microdialysis. After insertion of a microdialysis probe and establishment of baseline DA release, each preparation was standardized with a pulse of an iso-osmotic solution of 100 mM KCl in Ringer's solution. DA release following pharmacological manipulation was compared to potassium-induced release and expressed as a percent value. In one group of animals, KA (12.5 mM in Ringer's solution) was administered via the microdialysis probe in 2, 3, 5 or 10 min pulses 30 min following standardization with potassium resulting in release of DA which was 15.7 +/- 3.9, 30.3 +/- 11.3, 67.5 +/- 15.0 and 92.9 +/- 19.8% of potassium-induced DA release, respectively. Perfusion of CdCl2 (0.6 mM in Ringer's solution) 30-45 min prior to a 10 min KA pulse significantly reduced KA-induced DA release compared to control values. Intrastriatal administration of kynurenate (Kyn) attenuated KA-induced DA release in a dose-dependent manner. Levels of DA metabolites in striatal perfusates were significantly reduced following KA administration. This effect was partially reversed by cadmium pretreatment but not affected by Kyn pretreatment. Findings of this study indicate that KA induces striatal DA release in a dose-dependent manner, and this effect is at least partially dependent upon activation of calcium channels. Results also indicate dose-dependent inhibition of KA-induced striatal DA release by the excitatory amino acid receptor antagonist, Kyn, suggesting that this compound interacts with striatal KA receptors and that these receptors are involved with modulating striatal DA release in vivo.
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Affiliation(s)
- D P Carrozza
- Department of Pharmacology, Thomas Jefferson University, Philadelphia, PA 19107
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28
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Berg M, Bruhn T, Johansen FF, Krogsgaard-Larsen P, Diemer NH. Kainic acid neurotoxicity: in vivo test of two new non-N-methyl-D-aspartate receptor antagonists. Acta Neuropathol 1991; 81:255-60. [PMID: 1829311 DOI: 10.1007/bf00305866] [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 possible neuroprotective effects of two new non-N-methyl-D-aspartate receptor antagonists were determined by quantitative light microscopy after intracerebral administration of kainic acid (KA) in two rat brain regions. KA alone or KA in combination with the antagonists alpha-amino-3-carboxy-methoxy-5-methyl-4-isoxazolepropionic acid (AMOA) and alpha-amino-2-(3-hydroxy-5-methyl-4-isoxazolyl)methyl-5-methyl-3 -oxo-4-isoxazoline-4-propionic acid (AMNH) were stereotaxically injected into the striatum or into the CA3 region of hippocampus. Seven days later neuropathological examination including cell counts was performed on paraffin sections from the two brain regions. In the striatum, AMOA almost completely attenuated KA-induced cell damage, whereas AMNH showed no protective effect. In the hippocampal CA3 region none of the test compounds possessed neuroprotective properties against KA. These results seem to be consistent with a difference in the mechanisms responsible for the neurotoxic action of KA in the hippocampus compared to the striatum.
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Affiliation(s)
- M Berg
- PharmaBiotec Research Center, University of Copenhagen, Denmark
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29
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Influence of neural grafting on rat brain with damaged temporal cortex. NEUROPHYSIOLOGY+ 1991. [DOI: 10.1007/bf01052511] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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30
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Herbison AE, Heavens RP, Dyer RG. Endogenous release of gamma-aminobutyric acid from the medial preoptic area measured by microdialysis in the anaesthetised rat. J Neurochem 1990; 55:1617-23. [PMID: 2213014 DOI: 10.1111/j.1471-4159.1990.tb04947.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The characteristics of gamma-aminobutyric acid (GABA) release as monitored by microdialysis have been investigated in the chloral hydrate anaesthetised rat. The high outflow of GABA following insertion of the microdialysis probe (membrane 2 mm in length, 0.5 mm in diameter) into the medial preoptic area was found to decline to a stable baseline level after 2 h. After this time, perfusion with a medium containing 100 mM potassium ions evoked a 56-fold increase in GABA outflow. The addition of the calcium channel blocker verapamil (100 microM) to the perfusion medium induced significant 25 and 50% reductions in basal and potassium-stimulated GABA outflow, respectively. In the same animals, verapamil caused an 80% decrease in potassium-stimulated noradrenaline outflow. The glutamic acid decarboxylase inhibitors 3-mercaptopropionic acid and L-allylglycine added to the perfusion medium at a concentration of 10 mM reduced basal GABA release by approximately 50% with different time-courses of action. Ethanolamine-O-sulfate, a GABA-transaminase inhibitor, induced significant increases in basal GABA outflow 90 min after inclusion in the perfusion medium. These results demonstrate that microdialysis is a suitable technique with which to monitor extracellular levels of GABA and provide in vivo data on GABA release and degradation mechanisms.
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Affiliation(s)
- A E Herbison
- Department of Neuroendocrinology, AFRC Institute of Animal Physiology and Genetics Research, Babraham, Cambridge, England
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31
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Menéndez N, Solís JM, Herreras O, Sánchez Herranz A, Martín del Río R. Role of endogenous taurine on the glutamate analogue-induced neurotoxicity in the rat hippocampus in vivo. J Neurochem 1990; 55:714-7. [PMID: 2196339 DOI: 10.1111/j.1471-4159.1990.tb04191.x] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The glutamate analogues N-methyl-D-aspartate (NMDA), kainic acid (KA), and quisqualic acid (QA), prepared in different hypertonic media, were perfused in vivo in the hippocampal CA1 field of rats using a microdialysis technique. Extracellular taurine levels, estimated after analysis of the taurine content of dialysates, increased during perfusion of all three agonists but varied according to the osmolarity of the medium. The NMDA-induced increase in extracellular taurine content was only slightly inhibited by perfusion of 150 and 300 mM sucrose. The KA-evoked increase was partially dependent on extracellular osmolarity, because addition of 50 and 150 mM sucrose caused a dose-dependent inhibition that was not augmented using higher sucrose concentrations. QA caused a taurine increase that was totally abolished by addition of 50 mM sucrose. These results indicate that the rise in extracellular taurine level elicited by QA and part of the increase elicited by KA are probably due to a release caused by the cellular swelling that these substances evoke, a finding substantiating the previously proposed osmoregulatory role of taurine. However, almost all the increase in extracellular taurine content caused by NMDA and all the osmotically insensitive part of the KA-evoked rise cannot be explained as release triggered by cell swelling and may reflect a function of taurine other than osmoregulation.
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Affiliation(s)
- N Menéndez
- Departamento de Investigación, Hospital Ramón y Cajal, Madrid, Spain
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32
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Kapoor V, Nakahara D, Blood RJ, Chalmers JP. Preferential release of neuroactive amino acids from the ventrolateral medulla of the rat in vivo as measured by microdialysis. Neuroscience 1990; 37:187-91. [PMID: 2173812 DOI: 10.1016/0306-4522(90)90203-g] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The basal overflow of extracellular endogenous amino acids was measured from the ventrolateral medulla of urethane anaesthetized rats in vivo by microdialysis. Inclusion of a mercury salt, p-chloromercuriphenylsulphonic acid, in the dialysate (Krebs' solution), results in a preferential increase in the overflow of aspartate, glutamate, glycine and GABA. A smaller increase in the overflow of the glutamate precursor and metabolite, glutamine, was also found. There was no significant change in the basal extracellular levels of taurine, asparagine, alanine, serine, ornithine or lysine. Inclusion of a specific GABA uptake inhibitor, nipecotic acid, in the dialysate results in an immediate, dose dependent increase in the overflow of GABA, and to a lesser extent, taurine. Since it is likely that mercury salts increase neurotransmitter release by increasing free intracellular calcium ion concentrations, it is suggested that these results provide further evidence for a physiologically relevant neurotransmitter role for aspartate, glutamate, glycine and GABA in the ventrolateral medulla.
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Affiliation(s)
- V Kapoor
- Department of Medicine, Flinders Medical Centre, Bedford Park, Australia
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33
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Frandsen A, Schousboe A. Development of excitatory amino acid induced cytotoxicity in cultured neurons. Int J Dev Neurosci 1990; 8:209-16. [PMID: 1970220 DOI: 10.1016/0736-5748(90)90013-r] [Citation(s) in RCA: 122] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
The neurotoxicity of the excitatory amino acids (EAAs) L-glutamate (L-glu), L-aspartate (L-asp), N-methyl-D-aspartate (NMDA), kainate (KA), quisqualate (QA) and RS-alpha-amino-3-hydroxy-5-methyl-4-isoxazolopropionate (AMPA) was followed as a function of development in primary cultures of cerebral cortex neurons and cerebellar granule cells. These two types of neurons express, respectively, glutamate receptor subtypes with sensitivity to all of these excitatory amino acids or only to glutamate and aspartate. None of the EAAs were toxic in cerebral cortex neurons at 2 days in culture, whereas at culture day 4 the neurons became sensitive to glutamate, at day 5 to KA followed by sensitivity to QA at day 6, and finally to NMDA, L-asp and AMPA at day 7. The rank order of potency of the EAAs was in cerebral cortex neurons cultured for 12 days: L-asp (ED50 = 0.5 microM) = L-glu (ED50 = 1 microM) greater than AMPA (ED50 = 10 microM) greater than NMDA (ED50 = 65 microM) greater than QA = KA (ED50 = 100 microM). Cerebellar granule cells were insensitive to all of the EAAs at 3 and 5 days in culture but at day 8 the cells became sensitive to toxicity induced by L-glu (ED50 = 70 microM) and L-asp (ED50 = 30 microM). In order to determine ED50 values for L-asp and L-glu accurately, media in these experiments also contained 500 microM of the glutamate uptake inhibitor L-aspartate-beta-hydroxamate.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- A Frandsen
- PharmaBiotec Research Center, Department of Biochemistry A, Panum Institute, University of Copenhagen, Denmark
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Affiliation(s)
- H Benveniste
- Department of Medicine, Duke University Medical Center, Durham, NC 27710
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Arvin B, Neville LF, Pan J, Roberts PJ. 2-chloroadenosine attenuates kainic acid-induced toxicity within the rat straitum: relationship to release of glutamate and Ca2+ influx. Br J Pharmacol 1989; 98:225-35. [PMID: 2804547 PMCID: PMC1854680 DOI: 10.1111/j.1476-5381.1989.tb16886.x] [Citation(s) in RCA: 54] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
1. The mechanism by which 2-chloroadenosine (2-chloroado) exerts a neuroprotective action against the excitotoxic effect of kainic acid (KA) when injected into the rat striatum was investigated. 2. Histological examination two weeks after a single injection of KA (2.2 nmol) into rat striatum revealed widespread neuronal damage. Co-injection of 2-chloroado (6-25 nmol) with the neurotoxin afforded dose-dependent neuroprotection. This effect was reversed by administration of an equimolar concentration of the adenosine receptor antagonist theophylline. 3. Both K+ (30 mM) and KA (1 mM) enhanced the release of endogenous glutamate from guinea-pig purified cerebrocortical synaptosomes in a predominantly (approximately 70%) Ca2+-dependent manner. 2-Chloroado (10 nM-1 microM) inhibited the release of glutamate evoked by both KA and K+. These effects were partially reversed by the selective A1-adenosine receptor antagonist 8-cyclopentyltheophylline (CPT) (1 microM). 4. Crude rat cortical synaptosomes were loaded with the fluorescent calcium indicator quin-2 and Ca2+ influx monitored following two successive depolarising stimuli (30 mM K+; 'S1' and 'S2'). 2-Chloroado (10 nM-1 microM) produced a dose-dependent reduction in the S2:S1 ratio when added before the S2 period of stimulation. This effect was reversed by 1 microM theophylline. However, KA (1 mM) failed to enhance Ca2+ influx in the same preparation. 5. These results suggest that the anti-excitotoxic action of 2-chloroado is mediated primarily through a specific presynaptic receptor mechanism involving reduction of transmitter glutamate release, possibly occurring through an inhibition of Ca2+ influx.
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Affiliation(s)
- B Arvin
- Department of Physiology & Pharmacology, University of Southampton
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Menéndez N, Herreras O, Solis JM, Herranz AS, Martín del Río R. Extracellular taurine increase in rat hippocampus evoked by specific glutamate receptor activation is related to the excitatory potency of glutamate agonists. Neurosci Lett 1989; 102:64-9. [PMID: 2571110 DOI: 10.1016/0304-3940(89)90308-x] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Taurine increases in brain extracellular space due to glutamate agonists were studied in vivo in the rat hippocampus using a dialysis technique, both in the absence and in the presence of glutamate receptor antagonists. Extracellular taurine levels increased during perfusions of agonists, listed in descending order of potency: kainate (KA), N-methyl-D-aspartate (NMDA), and quisqualate (QA). While taurine increases due to KA or QA perfusions were inhibited by 6,7-dinitro-quinoxaline-2,3-dione (DNQX), those induced by NMDA were abolished in the presence of 3-(carboxypiperazin-4-yl)-propyl-1-phosphonic acid (CPP). These results indicate that increases in extracellular taurine levels evoked by NMDA, KA or QA in the rat hippocampus are caused by activation of their specific receptors. Field potentials, concomitantly recorded, were quickly abolished during NMDA or KA perfusions (0.1 mM), while QA (0.25 mM) induced the appearance of bicuculline-like evoked responses. Since taurine has been proposed as an osmoregulatory substance in the rat brain, and cell swelling is known to be an early component of glutamate agonists neurotoxicity, the increases in extracellular taurine reported here could be due to taurine released through an osmoregulatory process, counteracting the neurotoxic cellular oedema induced by glutamate agonists.
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Affiliation(s)
- N Menéndez
- Departamento de Investigación, Hospital 'Ramón y Cajal', Madrid, Spain
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Barbeito L, Girault JA, Godeheu G, Pittaluga A, Glowinski J, Cheramy A. Activation of the bilateral corticostriatal glutamatergic projection by infusion of GABA into thalamic motor nuclei in the cat: an in vivo release study. Neuroscience 1989; 28:365-74. [PMID: 2564170 DOI: 10.1016/0306-4522(89)90183-8] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The unilateral application of GABA (10(-5) M; 30 min) into thalamic motor nuclei of the cat increases the release of dopamine in both caudate nuclei. This effect has been suggested to be related to an activation of the bilateral corticostriatal glutamatergic projection, glutamate exerting a presynaptic facilitatory influence on dopamine release. To explore this hypothesis further, halothane-anesthetized cats implanted with push-pull cannulae were used in order to examine the effects of such a GABA application on the release of glutamate in both caudate nuclei. Aspartate, alanine, glutamine, serine and tyrosine were also measured in the superfusates. The unilateral application of GABA (10(-5) M; 30 min) into thalamic motor nuclei increased the release of glutamate bilaterally. Although less pronounced, ipsi- or bilateral increases in the efflux of alanine, glutamine and tyrosine were also observed. Contralateral changes in the efflux of glutamate, alanine and tyrosine were prevented following acute section of the corpus callosum. In addition, when applied continuously into one caudate nucleus, 2-amino-5-phosphonovaleric acid, a blocker of N-methyl-D-aspartate receptors, prevented the GABA-induced increase in alanine or tyrosine efflux but did not affect the enhanced release of glutamate. These results confirm that the unilateral application of GABA in thalamic motor nuclei activates a thalamo-cortico-striatal neuronal loop leading to the stimulation of glutamate release in both caudate nuclei. Changes in the efflux of other amino acids could be linked to increased metabolic activity of striatal target cells resulting from the increased release of glutamate and from its effect on N-methyl-D-aspartate receptors.
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Affiliation(s)
- L Barbeito
- Chaire de Neuropharmacologie, Collège de France, INSERM U.114, Paris
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Lehmann A, Hanssoń E. Kainate-induced stimulation of amino acid release from primary astroglial cultures of the rat hippocampus. Neurochem Int 1988; 13:557-61. [DOI: 10.1016/0197-0186(88)90088-5] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/1988] [Accepted: 06/29/1988] [Indexed: 11/26/2022]
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Lehmann A. Alterations in hippocampal extracellular amino acids and purine catabolites during limbic seizures induced by folate injections into the rabbit amygdala. Neuroscience 1987; 22:573-8. [PMID: 3670597 DOI: 10.1016/0306-4522(87)90354-x] [Citation(s) in RCA: 58] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The effects on hippocampal extra- and intracellular amino acids of focal injection of folic acid into the amygdala in the rabbit were studied with brain dialysis. Folate seizures were accompanied by pronounced elevations of extracellular alanine and phosphoethanolamine. The increase of extracellular alanine was related to an enhanced level of this amino acid in total hippocampal tissue, whereas phosphoethanolamine was unaltered in tissue biopsies. Folate seizures did not significantly affect extracellular aspartate and extracellular glutamate was only slightly elevated (50-75% over baseline values). The tissue concentration of glutamate remained at control levels during the seizures and tissue aspartate was decreased by 28%. Extracellular glutamine decreased rapidly after folate injection with a concomitant increase of total hippocampal glutamine. Neither extra- nor intracellular taurine was affected by folate epilepsy. The experiments also encompassed measurements of the extracellular purine catabolites inosine, hypoxanthine and xanthine. Folic acid-induced epilepsy produced changes in these compounds indicative of moderately accelerated degradation of adenosine 5'-triphosphate. The findings support the view of glutamate as a mediator of epilepsy-related brain damage. It is, however, questionable if the small enhancement of extracellular glutamate is enough to provoke neuronal necrosis associated with folate epilepsy.
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Affiliation(s)
- A Lehmann
- Institute of Neurobiology, University of Göteborg, Sweden
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Abstract
The effects of N-methylaspartate (NMA) on extracellular amino acids and purine catabolites in the hippocampus were studied with brain dialysis in rats with unilateral hippocampal NMA lesions. In the lesioned side, an increased basal output of glutamine was observed while glutamate was significantly decreased. NMA evoked a drop in extracellular glutamine. The effect was not observed in the lesioned hippocampus. NMA markedly enhanced the release of taurine and phosphoethanolamine (PEA). This response was unchanged in NMA-lesioned hippocampus. Analysis of the tissue content of endogenous amino acids revealed decrements in glutamate and GABA whereas other amino acids were not significantly altered. The resting and NMA-stimulated efflux of inosine was higher in the intact hippocampus. However, the extracellular concentrations of the inosine break-down products hypoxanthine and xanthine were not influenced by a prior NMA lesion, neither before nor after NMA administration. The present findings indicate that NMA releases amino acids (mainly taurine and PEA) from non-neuronal cells. The depression of extracellular glutamine elicited by NMA is probably a neuronal event. A direct stimulation of the energy metabolism of non-neuronal cells by NMA appears to exist as measured by the efflux of purine catabolites. I propose that non-neuronal cells, possibly glia, possess NMA receptors which, upon stimulation, initiate biochemical changes. The physiological significance of these responses remains to be elucidated.
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