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Alterations in mRNA and Protein Expression of Glutamate Receptor Subunits Following Pentylenetetrazole-induced Acute Seizures in Young Rats. Neuroscience 2021; 468:1-15. [PMID: 34102267 DOI: 10.1016/j.neuroscience.2021.05.035] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2021] [Revised: 05/27/2021] [Accepted: 05/28/2021] [Indexed: 12/28/2022]
Abstract
Acute seizures can severely affect brain function and development. However, the underlying pathophysiological mechanisms are still poorly understood. Disturbances of the glutamatergic system are considered one of the critical mechanisms of neurological abnormalities. In the present study, we analyzed changes in the expression of NMDA and AMPA receptor subunits in the different brain regions (dorsal hippocampus, amygdala, and the medial prefrontal, temporal, and entorhinal cortex) using a pentylenetetrazole (PTZ) model of seizures in 3-week-old rats. A distinctive feature of this model is that the administration of PTZ causes severe acute seizures, which are not followed by the development of spontaneous recurrent seizures later on. Subunit expression was analyzed using qRT-PCR and Western blotting during the first week after seizures. The most pronounced alterations of mRNA and protein levels were observed in the dorsal hippocampus. We found decreased expression of the GluA2 mRNA 7 days after seizures (PSE7), as well as reduced GluN2a protein levels on PSE7. Significant alterations in the expression of different receptor subunits in the mRNA but not protein levels were observed in the entorhinal cortex and amygdala. In contrast, in the medial prefrontal and temporal cortex, we found almost no changes in the expression of the studied genes. The identified changes deepen our understanding of post-seizure disturbances in the developing brain and confirm that although various brain structures are involved in seizures, the hippocampus is the most vulnerable.
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Yang J, Jiang Q, Yu X, Xu T, Wang Y, Deng J, Liu Y, Chen Y. STK24 modulates excitatory synaptic transmission in epileptic hippocampal neurons. CNS Neurosci Ther 2020; 26:851-861. [PMID: 32436359 PMCID: PMC7366740 DOI: 10.1111/cns.13391] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2020] [Revised: 04/14/2020] [Accepted: 04/20/2020] [Indexed: 01/03/2023] Open
Abstract
Introduction A large amount of literature has indicated that excitatory synaptic transmission plays a crucial role in epilepsy, but the detailed pathogenesis still needs to be clarified. Methods In the present study, we used samples from patients with temporal lobe epilepsy, pentylenetetrazole‐kindled mice, and Mg2+‐free‐induced epileptic cultured hippocampal neurons to detect the expression pattern of STK24. Then, the whole‐cell recording was carried out after STK24 overexpression in the Mg2+‐free‐induced epileptic cultured hippocampal neurons. In addition, coimmunoprecipitation was performed to detect the association between endogenous STK24 and main subunits of NMDARs and AMPARs in the hippocampus of PTZ‐kindled mice. Results Here, we reported that STK24 was specifically located in epileptic neurons of human and pentylenetetrazole‐kindled mice. Meanwhile, the expression of STK24 was significantly down‐regulated in these samples which are mentioned above. Besides, we found that the amplitude of miniature excitatory postsynaptic currents was increased in STK24 overexpressed epileptic hippocampal cultured neurons, which means the excitatory synaptic transmission was changed. Moreover, the coimmunoprecipitation, which further supported the previous experiment, indicated an association between STK24 and the subunits of the NMDA receptor. Conclusion These findings expand our understanding of how STK24 involved in the excitatory synaptic transmission in epilepsy and lay a foundation for exploring the possibility of STK24 as a drug target.
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Affiliation(s)
- Juan Yang
- Department of Neurology, the Second Affiliated Hospital of Chongqing Medical University, Chongqing, China
| | - Qian Jiang
- Department of Neurology, the Second Affiliated Hospital of Chongqing Medical University, Chongqing, China
| | - Xinyuan Yu
- Department of Neurology, the Second Affiliated Hospital of Chongqing Medical University, Chongqing, China
| | - Tao Xu
- Department of Neurology, the Second Affiliated Hospital of Chongqing Medical University, Chongqing, China
| | - You Wang
- Department of Neurology, the Second Affiliated Hospital of Chongqing Medical University, Chongqing, China
| | - Jing Deng
- Department of Neurology, the Second Affiliated Hospital of Chongqing Medical University, Chongqing, China
| | - Yong Liu
- Department of Neurology, the Second Affiliated Hospital of Chongqing Medical University, Chongqing, China
| | - Yangmei Chen
- Department of Neurology, the Second Affiliated Hospital of Chongqing Medical University, Chongqing, China
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Tezer FI, Firat A, Tuzun E, Unal I, Soylemezoglu F, Bilginer B, Kaymaz F, Oguz KK, Saygi S. Immunopathology in drug resistant mesial temporal lobe epilepsy with different types of hippocampal sclerosis. Int J Neurosci 2017; 128:421-428. [DOI: 10.1080/00207454.2017.1389928] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- F. Irsel Tezer
- Department of Neurology, Faculty of Medicine, Hacettepe University, Ankara, Turkey
| | - Aysegul Firat
- Department of Anatomy, Faculty of Medicine, Hacettepe University, Ankara, Turkey
| | - Erdem Tuzun
- Department of Neuroscience, Institute of Experimental Medical Research, Istanbul University, Istanbul, Turkey
| | - Isik Unal
- Department of Histology, Faculty of Medicine, Hacettepe University, Ankara, Turkey
| | - Figen Soylemezoglu
- Department of Pathology, Faculty of Medicine, Hacettepe University, Ankara, Turkey
| | - Burcak Bilginer
- Department of Neurosurgery, Faculty of Medicine, Hacettepe University, Ankara, Turkey
| | - Figen Kaymaz
- Department of Histology, Faculty of Medicine, Hacettepe University, Ankara, Turkey
| | - Kader K. Oguz
- Department of Radiology, Faculty of Medicine, Hacettepe University, Ankara, Turkey
| | - Serap Saygi
- Department of Neurology, Faculty of Medicine, Hacettepe University, Ankara, Turkey
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Activation of GABA A receptors controls mesiotemporal lobe epilepsy despite changes in chloride transporters expression: In vivo and in silico approach. Exp Neurol 2016; 284:11-28. [DOI: 10.1016/j.expneurol.2016.07.009] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2016] [Revised: 07/12/2016] [Accepted: 07/16/2016] [Indexed: 12/16/2022]
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Kandratavicius L, Hallak JE, Leite JP. What are the similarities and differences between schizophrenia and schizophrenia-like psychosis of epilepsy? A neuropathological approach to the understanding of schizophrenia spectrum and epilepsy. Epilepsy Behav 2014; 38:143-7. [PMID: 24508393 DOI: 10.1016/j.yebeh.2014.01.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/27/2013] [Revised: 01/10/2014] [Accepted: 01/12/2014] [Indexed: 10/25/2022]
Abstract
Temporal lobe epilepsy (TLE) and psychosis coexist more frequently than chance would predict. In this short review, clinical and neuropathological findings of schizophrenia, TLE, and psychosis of epilepsy are described to enhance our understanding of the noncoincidental association between these conditions. In addition, psychosis of epilepsy was included for the first time in the Diagnostic and Statistical Manual of Mental Disorders (DSM), in the recently launched 5th edition, and improvement in diagnostic criteria was highlighted. Since the hippocampus has long been considered an anatomical area involved in the pathophysiology of TLE and schizophrenia, neuropathological studies of psychoses of epilepsy may contribute to our understanding of the pathophysiology of psychosis in general. The discovery of shared mechanisms and/or affected neurochemicals in TLE and schizophrenia might disclose important clues on the vulnerability of patients with TLE to psychotic symptoms and be an opportunity for new treatment development.
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Affiliation(s)
- Ludmyla Kandratavicius
- Ribeirao Preto School of Medicine, Department of Neurosciences and Behavior, University of Sao Paulo (USP), Brazil; Center for Interdisciplinary Research on Applied Neurosciences (NAPNA), USP, Brazil
| | - Jaime Eduardo Hallak
- Ribeirao Preto School of Medicine, Department of Neurosciences and Behavior, University of Sao Paulo (USP), Brazil; Center for Interdisciplinary Research on Applied Neurosciences (NAPNA), USP, Brazil; National Institute of Science and Technology in Translational Medicine (INCT-TM-CNPq), Brazil
| | - Joao Pereira Leite
- Ribeirao Preto School of Medicine, Department of Neurosciences and Behavior, University of Sao Paulo (USP), Brazil; Center for Interdisciplinary Research on Applied Neurosciences (NAPNA), USP, Brazil.
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Soman S, Anju TR, Jayanarayanan S, Antony S, Paulose CS. Impaired motor learning attributed to altered AMPA receptor function in the cerebellum of rats with temporal lobe epilepsy: ameliorating effects of Withania somnifera and withanolide A. Epilepsy Behav 2013; 27:484-91. [PMID: 23602240 DOI: 10.1016/j.yebeh.2013.01.007] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/09/2012] [Revised: 01/09/2013] [Accepted: 01/10/2013] [Indexed: 12/01/2022]
Abstract
The aim of this study was to investigate the effect of Withania somnifera (WS) extract, withanolide A (WA), and carbamazepine (CBZ) on cerebellar AMPA receptor function in pilocarpine-induced temporal lobe epilepsy (TLE). In the present study, motor learning deficit was studied by rotarod test, grid walk test, and narrow beam test. Motor learning was significantly impaired in rats with epilepsy. The treatment with WS and WA significantly reversed the motor learning deficit in rats with epilepsy when compared with control rats. There was an increase in glutamate content and IP3 content observed in rats with epilepsy which was reversed in WS- and WA-treated rats with epilepsy. alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptor dysfunction was analyzed using radiolabeled AMPA receptor binding assay, AMPA receptor mRNA expression, and immunohistochemistry using anti-AMPA receptor antibody. Our results suggest that there was a decrease in Bmax, mRNA expression, and AMPA receptor expression indicating AMPA receptor dysfunction, which is suggested to have contributed to the motor learning deficit observed in rats with epilepsy. Moreover, treatment with WS and WA resulted in physiological expression of AMPA receptors. There was also alteration in GAD and GLAST expression which supplemented the increase in extracellular glutamate. The treatment with WS and WA reversed the GAD and GLAST expression. These findings suggest that WS and WA regulate AMPA receptor function in the cerebellum of rats with TLE, which has therapeutic application in epilepsy.
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Affiliation(s)
- Smijin Soman
- Molecular Neurobiology and Cell Biology Unit, Centre for Neuroscience, Department of Biotechnology, Cochin University of Science and Technology, Cochin 682 022, Kerala, India
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Ghasemi M, Schachter SC. The NMDA receptor complex as a therapeutic target in epilepsy: a review. Epilepsy Behav 2011; 22:617-40. [PMID: 22056342 DOI: 10.1016/j.yebeh.2011.07.024] [Citation(s) in RCA: 141] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/13/2011] [Revised: 07/01/2011] [Accepted: 07/18/2011] [Indexed: 01/02/2023]
Abstract
A substantial amount of research has shown that N-methyl-D-aspartate receptors (NMDARs) may play a key role in the pathophysiology of several neurological diseases, including epilepsy. Animal models of epilepsy and clinical studies demonstrate that NMDAR activity and expression can be altered in association with epilepsy and particularly in some specific seizure types. NMDAR antagonists have been shown to have antiepileptic effects in both clinical and preclinical studies. There is some evidence that conventional antiepileptic drugs may also affect NMDAR function. In this review, we describe the evidence for the involvement of NMDARs in the pathophysiology of epilepsy and provide an overview of NMDAR antagonists that have been investigated in clinical trials and animal models of epilepsy.
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Affiliation(s)
- Mehdi Ghasemi
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
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Monnerie H, Hsu FC, Coulter DA, Le Roux PD. Role of the NR2A/2B subunits of the N-methyl-D-aspartate receptor in glutamate-induced glutamic acid decarboxylase alteration in cortical GABAergic neurons in vitro. Neuroscience 2010; 171:1075-90. [PMID: 20923697 DOI: 10.1016/j.neuroscience.2010.09.050] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2010] [Revised: 09/22/2010] [Accepted: 09/23/2010] [Indexed: 12/21/2022]
Abstract
The vulnerability of brain neuronal cell subpopulations to neurologic insults varies greatly. Among cells that survive a pathological insult, for example ischemia or brain trauma, some may undergo morphological and/or biochemical changes that may compromise brain function. The present study is a follow-up of our previous studies that investigated the effect of glutamate-induced excitotoxicity on the GABA synthesizing enzyme glutamic acid decarboxylase (GAD65/67)'s expression in surviving DIV 11 cortical GABAergic neurons in vitro [Monnerie and Le Roux, (2007) Exp Neurol 205:367-382, (2008) Exp Neurol 213:145-153]. An N-methyl-D-aspartate receptor (NMDAR)-mediated decrease in GAD expression was found following glutamate exposure. Here we examined which NMDAR subtype(s) mediated the glutamate-induced change in GAD protein levels. Western blotting techniques on cortical neuron cultures showed that glutamate's effect on GAD proteins was not altered by NR2B-containing diheteromeric (NR1/NR2B) receptor blockade. By contrast, blockade of triheteromeric (NR1/NR2A/NR2B) receptors fully protected against a decrease in GAD protein levels following glutamate exposure. When receptor location on the postsynaptic membrane was examined, extrasynaptic NMDAR stimulation was observed to be sufficient to decrease GAD protein levels similar to that observed after glutamate bath application. Blocking diheteromeric receptors prevented glutamate's effect on GAD proteins after extrasynaptic NMDAR stimulation. Finally, NR2B subunit examination with site-specific antibodies demonstrated a glutamate-induced, calpain-mediated alteration in NR2B expression. These results suggest that glutamate-induced excitotoxic NMDAR stimulation in cultured GABAergic cortical neurons depends upon subunit composition and receptor location (synaptic vs. extrasynaptic) on the neuronal membrane. Biochemical alterations in surviving cortical GABAergic neurons in various disease states may contribute to the altered balance between excitation and inhibition that is often observed after injury.
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Affiliation(s)
- H Monnerie
- Department of Neurosurgery, University of Pennsylvania, Philadelphia, PA 19104, USA
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Amygdala gene expression of NMDA and GABAA receptors in patients with mesial temporal lobe epilepsy. Hippocampus 2010; 22:92-7. [DOI: 10.1002/hipo.20863] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/25/2010] [Indexed: 01/05/2023]
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10
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Glutamate alteration of glutamic acid decarboxylase (GAD) in GABAergic neurons: The role of cysteine proteases. Exp Neurol 2008; 213:145-53. [DOI: 10.1016/j.expneurol.2008.05.013] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2007] [Revised: 05/02/2008] [Accepted: 05/17/2008] [Indexed: 11/19/2022]
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Knopp A, Frahm C, Fidzinski P, Witte OW, Behr J. Loss of GABAergic neurons in the subiculum and its functional implications in temporal lobe epilepsy. Brain 2008; 131:1516-27. [PMID: 18504292 DOI: 10.1093/brain/awn095] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Clinical and experimental evidence suggest that the subiculum plays an important role in the maintenance of temporal lobe seizures. Using the pilocarpine-model of temporal lobe epilepsy (TLE), the present study examines the vulnerability of GABAergic subicular interneurons to recurrent seizures and determines its functional implications. In the subiculum of pilocarpine-treated animals, the density of glutamic acid decarboxylase (GAD) mRNA-positive cells was reduced in all layers. Our data indicate a substantial loss of parvalbumin-immunoreactive neurons in the pyramidal cell and molecular layer whereas calretinin-immunoreactive cells were predominantly reduced in the molecular layer. Though the subiculum of pilocarpine-treated rats showed an increased intensity of GAD65 immunoreactivity, the density of GAD65 containing synaptic terminals in the pyramidal cell layer was decreased indicating an increase in the GAD65 intensity of surviving synaptic terminals. We observed a decrease in evoked inhibitory post-synaptic currents that mediate dendritic inhibition as well as a decline in the frequency of miniature inhibitory post-synaptic currents (mIPSCs) that are restricted to the perisomatic region. The decrease in mIPSC frequency (-30%) matched with the reduced number of perisomatic GAD-positive terminals (-28%) suggesting a decrease of pre-synaptic GABAergic input onto pyramidal cells in epileptic animals. Though cell loss in the subiculum has not been considered as a pathogenic factor in human and experimental TLE, our data suggest that the vulnerability of subicular GABAergic interneurons causes an input-specific disturbance of the subicular inhibitory system.
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Affiliation(s)
- Andreas Knopp
- Dept. of Psychiatry and Psychotherapy, Charité-Universitätsmedizin Berlin, Charitéplatz 1, 10117 Berlin, Germany
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Kondziella D, Alvestad S, Vaaler A, Sonnewald U. Which clinical and experimental data link temporal lobe epilepsy with depression? J Neurochem 2007; 103:2136-52. [PMID: 17887964 DOI: 10.1111/j.1471-4159.2007.04926.x] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The association of temporal lobe epilepsy with depression and other neuropsychiatric disorders has been known since the early beginnings of neurology and psychiatry. However, only recently have in vivo and ex vivo techniques such as Positron Emission Tomography, Magnetic Resonance Imaging and Magnetic Resonance Spectroscopy in combination with refined animal models and behavioral tests made it possible to identify an emerging pattern of common pathophysiological mechanisms. We now have growing evidence that in both disorders altered interaction of serotonergic and noradrenergic neurons with glutamatergic systems is associated with abnormal neuronal circuits and hyperexcitability. Neuronal hyperexcitability can possibly evoke seizure activity as well as disturbed emotions. Moreover, decreased synaptic levels of neurotransmitters and high glucocorticoid levels influence intracellular signaling pathways such as cAMP, causing disturbances of brain-derived and other neurotrophic factors. These may be associated with hippocampal atrophy seen on Magnetic Resonance Imaging and memory impairment as well as altered fear processing and transient hypertrophy of the amygdala. Positron Emission Tomography studies additionally suggest hypometabolism of glucose in temporal and frontal lobes. Last, but not least, in temporal lobe epilepsy and depression astrocytes play a role that reaches far beyond their involvement in hippocampal sclerosis and ultimately, therapeutic regulation of glial-neuronal interactions may be a target for future research. All these mechanisms are strongly intertwined and probably bidirectional such that the structural and functional alterations from one disease increase the risk for developing the other. This review provides an integrative update of the most relevant experimental and clinical data on temporal lobe epilepsy and its association with depression.
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Affiliation(s)
- Daniel Kondziella
- Department of Neuroscience, Norwegian University of Science and Technology, Trondheim, Norway.
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Monnerie H, Le Roux PD. Reduced dendrite growth and altered glutamic acid decarboxylase (GAD) 65- and 67-kDa isoform protein expression from mouse cortical GABAergic neurons following excitotoxic injury in vitro. Exp Neurol 2007; 205:367-82. [PMID: 17433299 DOI: 10.1016/j.expneurol.2007.02.007] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2006] [Revised: 01/25/2007] [Accepted: 02/15/2007] [Indexed: 02/02/2023]
Abstract
The vulnerability of brain cells to neurologic insults varies greatly, depending on their neuronal subpopulation. However, cells surviving pathological insults such as ischemia or brain trauma may undergo structural changes, e.g., altered process growth, that could compromise brain function. In this study, we examined the effect of glutamate excitotoxicity on dendrite growth from surviving cortical GABAergic neurons in vitro. Glutamate exposure did not affect GABAergic neuron viability, however, it significantly reduced dendrite growth from GABAergic neurons. This effect was blocked by the AMPA receptor antagonists NBQX and CFM-2, and mimicked by AMPA, but not NMDA. Glutamate excitotoxicity also caused an NMDA receptor-mediated decrease in the GABA synthesizing enzyme glutamic acid decarboxylase (GAD65/67) immunoreactivity from GABAergic neurons, measured using immunocytochemical and Western blot techniques. GAD is necessary for GABA synthesis; however, reduction of GABA by 3-mercaptopropionic acid (3-MPA), which inhibits GABA synthesis, did not alter dendrite growth. These results suggest that GABAergic cortical neurons are relatively resistant to excitotoxic-induced cell death, but they can display morphological and biochemical alterations which may impair their function.
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Affiliation(s)
- Hubert Monnerie
- Department of Neurosurgery, University of Pennsylvania, 330 S 9th Street, 4th Floor, Philadelphia, PA 19107, USA
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Vorobyov V, Schibaev N, Kovalev G, Alzheimer C. Effects of neurotransmitter agonists on electrocortical activity in the rat kainate model of temporal lobe epilepsy and the modulatory action of basic fibroblast growth factor. Brain Res 2005; 1051:123-36. [PMID: 15996643 DOI: 10.1016/j.brainres.2005.06.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2004] [Revised: 06/02/2005] [Accepted: 06/02/2005] [Indexed: 11/28/2022]
Abstract
We used systemic kainic acid (KA) injection to investigate how the development of temporal lobe epilepsy and the associated network reorganization affect the electrocorticogram (ECoG) responses to various neurotransmitter agonists. Unrestrained rats chronically implanted with electrodes over somatosensory cortex and dorsal hippocampus and a cannula into the right lateral ventricle were used to investigate the ECoG frequency responses of intracerebroventricularly applied agonists (NMDA, clonidine, muscimol, and baclofen) at several types of receptors [NMDA, alpha2-adrenergic (NE), GABAA, and GABAB, respectively] in KA-treated versus naïve animals. The ECoG was analyzed 2, 5, and 9 weeks after intraperitoneal injection of KA alone or in combination with basic fibroblast growth factor (bFGF, intracerebroventricularly). Within the first 5 weeks of KA injection, the ECoG power shifted towards the lower-frequency range. Concurrently, the electrographic responses to NMDA and clonidine were potentiated, whereas the ECoG effects mediated by GABAA and GABAB receptors remained largely unaffected. In control rats, bFGF strongly enhanced the electrographic NMDA responses. In sharp contrast, bFGF potently mitigated the abnormally increased NMDA sensitivity of epileptic rats, if applied 4 weeks post KA injection. These data suggest that upregulation and downregulation of the NMDA receptor-mediated effects on cortical activity might be a prominent feature of bFGF signaling in the intact and the damaged brain, respectively.
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Affiliation(s)
- Vasily Vorobyov
- Institute of Cell Biophysics, Russian Academy of Sciences, 142290 Pushchino, Moscow Region, Russia.
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Abstract
Focal cerebral lesions in rat brain induced by photothrombosis lead to an impaired inhibitory neurotransmission. A reduced gamma-aminobutyric acid (GABA)-mediated inhibition has been revealed by electrophysiological recordings associated with a diminished immunostaining of GABA handling proteins. Changes were found in ipsi- as well as in contralateral brain areas. Inhibition is mediated by interneurons using GABA as neurotransmitter. These cells use GAD (glutamate decarboxylase) to synthesize GABA. To analyze the vulnerability of GABAergic neurons in rats with a lesioned hindlimb area, cells expressing GAD65/67 mRNA were labeled using in situ hybridization. Positive somata were counted 7 and 30 days after focal ischemia in different cortical (hindlimb cortex, frontal cortex, primary and secondary somatosensory cortex) and hippocampal subsectors (pyramidal cell layer, stratum oriens and stratum radiatum/lacunosum-moleculare). The lesioned hemispheres were compared with the intact brain sides and with control brains. GABAergic interneurons survived the injury for up to 30 days in all investigated brain regions. Therefore it is unlikely that a loss of GABAergic neurons contributes to the reduced inhibition.
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Affiliation(s)
- C Frahm
- Department of Neurology, Friedrich-Schiller-University, Erlanger Allee 101, 07745 Jena, Germany.
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