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Zheng B, Abdulrazeq H, Shao B, Liu DD, Leary O, Lauro PM, Bartolini L, Blum AS, Asaad WF. Seizure and anatomical outcomes of repeat laser amygdalohippocampotomy for temporal lobe epilepsy: A single-institution case series. Epilepsy Behav 2023; 146:109365. [PMID: 37523797 DOI: 10.1016/j.yebeh.2023.109365] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/15/2023] [Revised: 07/12/2023] [Accepted: 07/20/2023] [Indexed: 08/02/2023]
Abstract
OBJECTIVE In patients with treatment-refractory temporal lobe epilepsy (TLE), a single stereotactic laser interstitial thermotherapy (LITT) procedure is sometimes insufficient to ablate epileptogenic tissue, particularly the medial structures often implicated in TLE. In patients with seizure recurrence after initial ablation, the extent to which a second ablation may achieve improved seizure outcomes is uncertain. The objective of this study was to investigate the feasibility and potential efficacy of repeat LITT amygdalohippocampotomy as a worthwhile strategy for intractable temporal lobe epilepsy by quantifying changes to targeted mesial temporal lobe structures and seizure outcomes. METHODS Patients who underwent two LITT procedures for drug-resistant mesial TLE at our institution were included in the study. Lesion volumes for both procedures were calculated by comparing post-ablation intraoperative sequences to preoperative anatomy. Clinical outcomes after the initial procedure and repeat procedure were classified according to Engel scores. RESULTS Five consecutive patients were included in this retrospective case series: 3 with right- and 2 with left-sided TLE. The median interval between LITT procedures was 294 days (range: 227-1918). After the first LITT, 3 patients experienced class III outcomes, 1 experienced a class IV, and 1 experienced a class IB outcome. All patients achieved increased seizure freedom after a second procedure, with class I outcomes (3 IA, 2 IB). CONCLUSIONS Repeat LITT may be sufficient to achieve satisfactory seizure outcomes in some individuals who might otherwise be considered for more aggressive resection or palliative neuromodulation. A larger study to establish the potential value of repeat LITT amygdalohippocampotomy vs. other re-operation strategies for persistent, intractable temporal lobe epilepsy is worth pursuing.
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Affiliation(s)
- Bryan Zheng
- The Warren Alpert Medical School of Brown University, Providence, RI, USA; Department of Neurosurgery, Rhode Island Hospital, Providence, RI, USA
| | - Hael Abdulrazeq
- Department of Neurosurgery, Rhode Island Hospital, Providence, RI, USA.
| | - Belinda Shao
- Department of Neurosurgery, Rhode Island Hospital, Providence, RI, USA
| | - David D Liu
- Department of Neurosurgery, Brigham and Womens Hospital, Boston, MA, USA
| | - Owen Leary
- The Warren Alpert Medical School of Brown University, Providence, RI, USA
| | - Peter M Lauro
- The Warren Alpert Medical School of Brown University, Providence, RI, USA; Department of Neuroscience, Brown University, Providence, RI, USA
| | - Luca Bartolini
- Department of Neurosurgery, Rhode Island Hospital, Providence, RI, USA; Deparment of Neurology, Rhode Island Hospital, Providence, RI, USA; Deparment of Pediatrics, Hasbro Children's Hospital, Providence, RI, USA
| | - Andrew S Blum
- Deparment of Neurology, Rhode Island Hospital, Providence, RI, USA
| | - Wael F Asaad
- Department of Neurosurgery, Rhode Island Hospital, Providence, RI, USA; Department of Neuroscience, Brown University, Providence, RI, USA; The Carney Institute for Brain Science, Brown University, Providence, RI, USA; The Norman Prince Neurosciences Institute, Rhode Island Hospital, Providence, RI, USA
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Liu J, Tang F, Hu D, Zhang Z, Yan Y, Ma Y. TMT-based proteomics profile reveals changes of the entorhinal cortex in a kainic acid model of epilepsy in mice. Neurosci Lett 2023; 800:137127. [PMID: 36792025 DOI: 10.1016/j.neulet.2023.137127] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2022] [Revised: 01/29/2023] [Accepted: 02/10/2023] [Indexed: 02/16/2023]
Abstract
Experimental modeling and clinical neuroimaging of patients has shown that certain seizures are capable of causing neuronal death. Research into cell death after seizures has identified the induction of the molecular machinery of apoptosis. Temporal lobe epilepsy (TLE) is the most common type of epilepsy in adults, which is characterized by substantial pathological abnormalities in the temporal lobe, including the hippocampus and entorhinal cortex (EC). Although decades of studies have revealed numerous molecular abnormalities in the hippocampus that are linked to TLE, the biochemical mechanisms associated with TLE in EC remain unclear. In this study, we explored these early phenotypical alterations in the EC 5 days after mice were given a systemic injection of kainic acid (KA) to induce status epilepticus (KA-SE). we used the Tandem Mass Tag (TMT) combined with LC-MS/MS approach to identify distinct proteins in the EC in a mouse model of KA-SE model. According to the findings, 355 differentially abundant proteins including 199 upregulated and 156 downregulated differentially abundant proteins were discovered. The first-ranked biological process according to Gene Ontology (GO) analysis was "negative control of extrinsic apoptotic signaling". "Apoptosis" was the most significantly enriched Kyoto Encyclopaedia of Genes and Genomes (KEGG) pathway. Compared with those in control mice, BCL2L1, NTRK2 and MAPK10 abundance levels were reduced in KA mice. MAPK10 and NTRK2 act as upstream regulators to regulate BCL2L1, and BCL2L1 Inhibits cell death by blocking the voltage- dependent anion channel (VDAC) and preventing the release of the caspase activator, CYC1, from the mitochondrial membrane. However, ITPR1 was increased at the mRNA and protein levels in KA mice. Furthermore, there was no significant difference in ACTB, TUBA1A and TUBA4A levels between the two groups. Our results offer clues to help identify biomarkers for the development of pharmacological therapies targeted at epilepsy.
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Affiliation(s)
- Jie Liu
- Department of Neurology, The First Affiliated Hospital of Chongqing Medical University, Chongqing Key Laboratory of Neurology, Chongqing 400016, China
| | - Fenglin Tang
- Department of Neurology, The First Affiliated Hospital of Chongqing Medical University, Chongqing Key Laboratory of Neurology, Chongqing 400016, China
| | - Danmei Hu
- Department of Neurology, Third Hospital of Shanxi Medical University, Shanxi Bethune Hospital, Shanxi Academy of Medical Sciences, Tongji Shanxi Hospital, Taiyuan 030032, China
| | - Zhijuan Zhang
- Department of Neurology, The First Affiliated Hospital of Chongqing Medical University, Chongqing Key Laboratory of Neurology, Chongqing 400016, China
| | - Yin Yan
- Department of Neurology, The First Affiliated Hospital of Chongqing Medical University, Chongqing Key Laboratory of Neurology, Chongqing 400016, China
| | - Yuanlin Ma
- Department of Neurology, The First Affiliated Hospital of Chongqing Medical University, Chongqing Key Laboratory of Neurology, Chongqing 400016, China.
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Petanjek Z, Sedmak D, Džaja D, Hladnik A, Rašin MR, Jovanov-Milosevic N. The Protracted Maturation of Associative Layer IIIC Pyramidal Neurons in the Human Prefrontal Cortex During Childhood: A Major Role in Cognitive Development and Selective Alteration in Autism. Front Psychiatry 2019; 10:122. [PMID: 30923504 PMCID: PMC6426783 DOI: 10.3389/fpsyt.2019.00122] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/30/2018] [Accepted: 02/18/2019] [Indexed: 12/12/2022] Open
Abstract
The human specific cognitive shift starts around the age of 2 years with the onset of self-awareness, and continues with extraordinary increase in cognitive capacities during early childhood. Diffuse changes in functional connectivity in children aged 2-6 years indicate an increase in the capacity of cortical network. Interestingly, structural network complexity does not increase during this time and, thus, it is likely to be induced by selective maturation of a specific neuronal subclass. Here, we provide an overview of a subclass of cortico-cortical neurons, the associative layer IIIC pyramids of the human prefrontal cortex. Their local axonal collaterals are in control of the prefrontal cortico-cortical output, while their long projections modulate inter-areal processing. In this way, layer IIIC pyramids are the major integrative element of cortical processing, and changes in their connectivity patterns will affect global cortical functioning. Layer IIIC neurons have a unique pattern of dendritic maturation. In contrast to other classes of principal neurons, they undergo an additional phase of extensive dendritic growth during early childhood, and show characteristic molecular changes. Taken together, circuits associated with layer IIIC neurons have the most protracted period of developmental plasticity. This unique feature is advanced but also provides a window of opportunity for pathological events to disrupt normal formation of cognitive circuits involving layer IIIC neurons. In this manuscript, we discuss how disrupted dendritic and axonal maturation of layer IIIC neurons may lead into global cortical disconnectivity, affecting development of complex communication and social abilities. We also propose a model that developmentally dictated incorporation of layer IIIC neurons into maturing cortico-cortical circuits between 2 to 6 years will reveal a previous (perinatal) lesion affecting other classes of principal neurons. This "disclosure" of pre-existing functionally silent lesions of other neuronal classes induced by development of layer IIIC associative neurons, or their direct alteration, could be found in different forms of autism spectrum disorders. Understanding the gene-environment interaction in shaping cognitive microcircuitries may be fundamental for developing rehabilitation and prevention strategies in autism spectrum and other cognitive disorders.
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Affiliation(s)
- Zdravko Petanjek
- Department of Anatomy and Clinical Anatomy, School of Medicine, University of Zagreb, Zagreb, Croatia
- Department of Neuroscience, Croatian Institute for Brain Research, School of Medicine, University of Zagreb, Zagreb, Croatia
- Center of Excellence for Basic, Clinical and Translational Neuroscience, School of Medicine, University of Zagreb, Zagreb, Croatia
| | - Dora Sedmak
- Department of Anatomy and Clinical Anatomy, School of Medicine, University of Zagreb, Zagreb, Croatia
- Department of Neuroscience, Croatian Institute for Brain Research, School of Medicine, University of Zagreb, Zagreb, Croatia
- Center of Excellence for Basic, Clinical and Translational Neuroscience, School of Medicine, University of Zagreb, Zagreb, Croatia
| | - Domagoj Džaja
- Department of Anatomy and Clinical Anatomy, School of Medicine, University of Zagreb, Zagreb, Croatia
- Department of Neuroscience, Croatian Institute for Brain Research, School of Medicine, University of Zagreb, Zagreb, Croatia
- Center of Excellence for Basic, Clinical and Translational Neuroscience, School of Medicine, University of Zagreb, Zagreb, Croatia
| | - Ana Hladnik
- Department of Anatomy and Clinical Anatomy, School of Medicine, University of Zagreb, Zagreb, Croatia
- Department of Neuroscience, Croatian Institute for Brain Research, School of Medicine, University of Zagreb, Zagreb, Croatia
- Center of Excellence for Basic, Clinical and Translational Neuroscience, School of Medicine, University of Zagreb, Zagreb, Croatia
| | - Mladen Roko Rašin
- Department of Neuroscience and Cell Biology, Rutgers University, Robert Wood Johnson Medical School, Piscataway, NJ, United States
| | - Nataša Jovanov-Milosevic
- Department of Neuroscience, Croatian Institute for Brain Research, School of Medicine, University of Zagreb, Zagreb, Croatia
- Center of Excellence for Basic, Clinical and Translational Neuroscience, School of Medicine, University of Zagreb, Zagreb, Croatia
- Department of Medical Biology, School of Medicine, University of Zagreb, Zagreb, Croatia
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Sedmak D, Hrvoj-Mihić B, Džaja D, Habek N, Uylings HB, Petanjek Z. Biphasic dendritic growth of dorsolateral prefrontal cortex associative neurons and early cognitive development. Croat Med J 2018. [PMID: 30394011 PMCID: PMC6240825 DOI: 10.3325/cmj.2018.59.189] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Aim To analyze postnatal development and life-span changes of apical dendrite side branches (oblique dendrites) from associative layer IIIC magnopyramidal neurons in the human dorsolateral prefrontal cortex and to compare the findings with the previously established pattern of basal dendrite development. Methods We analyzed dendritic morphology from 352 rapid-Golgi impregnated neurons (10-18 neurons per subject) in Brodmann area 9 from the post-mortem tissue of 25 subjects ranging in age from 1 week to 91 years. Data were collected in the period between 1994 and 1996, and the analysis was performed between September 2017 and February 2018. Quantitative dendritic parameters were statistically analyzed using one-way analysis of variance and two-tailed t tests. Results Oblique dendrites grew rapidly during the first postnatal months, and the increase in the dendrite length was accompanied by the outgrowth of new dendritic segments. After a more than one-year-long “dormant” period of only fine dendritic rearrangements (2.5-16 months), oblique dendrites displayed a second period of marked growth, continuing through the third postnatal year. Basal and oblique dendrites displayed roughly the same growth pattern, but had considerably different topological organization in adulthood. Conclusion Our analysis confirmed that a biphasic pattern of postnatal dendritic development, together with a second growth spurt at the age of 2-3 years, represents a unique feature of the associative layer IIIC magnopyramidal neurons in the human dorsolateral prefrontal cortex. We propose that these structural changes relate to rapid cognitive development during early childhood.
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Affiliation(s)
| | | | | | | | | | - Zdravko Petanjek
- Zdravko Petanjek, Department of Anatomy and Clinical Anatomy, University of Zagreb School of Medicine, Šalata 11, Zagreb, Croatia,
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5
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Sedmak D, Hrvoj-Mihić B, Džaja D, Habek N, Uylings HB, Petanjek Z. Biphasic dendritic growth of dorsolateral prefrontal cortex associative neurons and early cognitive development. Croat Med J 2018; 59:189-202. [PMID: 30394011 PMCID: PMC6240825] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2018] [Accepted: 10/31/2018] [Indexed: 10/05/2023] Open
Abstract
AIM To analyze postnatal development and life-span changes of apical dendrite side branches (oblique dendrites) from associative layer IIIC magnopyramidal neurons in the human dorsolateral prefrontal cortex and to compare the findings with the previously established pattern of basal dendrite development. METHODS We analyzed dendritic morphology from 352 rapid-Golgi impregnated neurons (10-18 neurons per subject) in Brodmann area 9 from the post-mortem tissue of 25 subjects ranging in age from 1 week to 91 years. Data were collected in the period between 1994 and 1996, and the analysis was performed between September 2017 and February 2018. Quantitative dendritic parameters were statistically analyzed using one-way analysis of variance and two-tailed t tests. RESULTS Oblique dendrites grew rapidly during the first postnatal months, and the increase in the dendrite length was accompanied by the outgrowth of new dendritic segments. After a more than one-year-long "dormant" period of only fine dendritic rearrangements (2.5-16 months), oblique dendrites displayed a second period of marked growth, continuing through the third postnatal year. Basal and oblique dendrites displayed roughly the same growth pattern, but had considerably different topological organization in adulthood. CONCLUSION Our analysis confirmed that a biphasic pattern of postnatal dendritic development, together with a second growth spurt at the age of 2-3 years, represents a unique feature of the associative layer IIIC magnopyramidal neurons in the human dorsolateral prefrontal cortex. We propose that these structural changes relate to rapid cognitive development during early childhood.
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Affiliation(s)
| | | | | | | | | | - Zdravko Petanjek
- Zdravko Petanjek, Department of Anatomy and Clinical Anatomy, University of Zagreb School of Medicine, Šalata 11, Zagreb, Croatia,
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Janz P, Savanthrapadian S, Häussler U, Kilias A, Nestel S, Kretz O, Kirsch M, Bartos M, Egert U, Haas CA. Synaptic Remodeling of Entorhinal Input Contributes to an Aberrant Hippocampal Network in Temporal Lobe Epilepsy. Cereb Cortex 2017; 27:2348-2364. [PMID: 27073230 DOI: 10.1093/cercor/bhw093] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The hippocampus is reciprocally connected with the entorhinal cortex. Although several studies emphasized a role for the entorhinal cortex in mesial temporal lobe epilepsy (MTLE), it remains uncertain whether its synaptic connections with the hippocampus are altered. To address this question, we traced hippocampo-entorhinal and entorhino-hippocampal projections, assessed their connectivity with the respective target cells and examined functional alterations in a mouse model for MTLE. We show that hippocampal afferents to the dorsal entorhinal cortex are lost in the epileptic hippocampus. Conversely, entorhino-dentate projections via the medial perforant path (MPP) are preserved, but appear substantially altered on the synaptic level. Confocal imaging and 3D-reconstruction revealed that new putative contacts are established between MPP fibers and dentate granule cells (DGCs). Immunohistochemical identification of pre- and postsynaptic elements indicated that these contacts are functionally mature synapses. On the ultrastructural level, pre- and postsynaptic compartments of MPP synapses were strongly enlarged. The length and complexity of postsynaptic densities were also increased pointing to long-term potentiation-related morphogenesis. Finally, whole-cell recordings of DGCs revealed an enhancement of evoked excitatory postsynaptic currents. In conclusion, the synaptic rearrangement of excitatory inputs to DGCs from the medial entorhinal cortex may contribute to the epileptogenic circuitry in MTLE.
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Affiliation(s)
- Philipp Janz
- Experimental Epilepsy Research, Department of Neurosurgery.,Faculty of Biology
| | | | - Ute Häussler
- Experimental Epilepsy Research, Department of Neurosurgery
| | - Antje Kilias
- Faculty of Biology.,Laboratory for Biomicrotechnology, Department of Microsystems Engineering, Freiburg im Breisgau 79110, Germany.,Bernstein Center Freiburg, Freiburg im Breisgau 79104, Germany
| | - Sigrun Nestel
- Neuroanatomy, Department of Anatomy and Cell Biology
| | - Oliver Kretz
- Renal Division, Department of Medicine, University Medical Center Freiburg, Freiburg im Breisgau 79106, Germany
| | | | - Marlene Bartos
- Institute for Physiology I, Systemic and Cellular Neurophysiology.,Bernstein Center Freiburg, Freiburg im Breisgau 79104, Germany.,BrainLinks-BrainTools Cluster of Excellence, University of Freiburg, Freiburg im Breisgau 79110, Germany
| | - Ulrich Egert
- Laboratory for Biomicrotechnology, Department of Microsystems Engineering, Freiburg im Breisgau 79110, Germany.,Bernstein Center Freiburg, Freiburg im Breisgau 79104, Germany.,BrainLinks-BrainTools Cluster of Excellence, University of Freiburg, Freiburg im Breisgau 79110, Germany
| | - Carola A Haas
- Experimental Epilepsy Research, Department of Neurosurgery.,Bernstein Center Freiburg, Freiburg im Breisgau 79104, Germany.,BrainLinks-BrainTools Cluster of Excellence, University of Freiburg, Freiburg im Breisgau 79110, Germany
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Olsen LC, O'Reilly KC, Liabakk NB, Witter MP, Sætrom P. MicroRNAs contribute to postnatal development of laminar differences and neuronal subtypes in the rat medial entorhinal cortex. Brain Struct Funct 2017; 222:3107-3126. [PMID: 28260163 PMCID: PMC5585308 DOI: 10.1007/s00429-017-1389-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2016] [Accepted: 02/13/2017] [Indexed: 01/23/2023]
Abstract
The medial entorhinal cortex (MEC) is important in spatial navigation and memory formation and its layers have distinct neuronal subtypes, connectivity, spatial properties, and disease susceptibility. As little is known about the molecular basis for the development of these laminar differences, we analyzed microRNA (miRNA) and messenger RNA (mRNA) expression differences between rat MEC layer II and layers III–VI during postnatal development. We identified layer and age-specific regulation of gene expression by miRNAs, which included processes related to neuron specialization and locomotor behavior. Further analyses by retrograde labeling and expression profiling of layer II stellate neurons and in situ hybridization revealed that the miRNA most up-regulated in layer II, miR-143, was enriched in stellate neurons, whereas the miRNA most up-regulated in deep layers, miR-219-5p, was expressed in ependymal cells, oligodendrocytes and glia. Bioinformatics analyses of predicted mRNA targets with negatively correlated expression patterns to miR-143 found that miR-143 likely regulates the Lmo4 gene, which is known to influence hippocampal-based spatial learning.
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Affiliation(s)
- Lene C Olsen
- Department of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology, Trondheim, Norway
| | - Kally C O'Reilly
- Kavli Institute for Systems Neuroscience and Centre for Neural Computation, Norwegian University for Science and Technology, Trondheim, Norway
| | - Nina B Liabakk
- Department of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology, Trondheim, Norway
| | - Menno P Witter
- Kavli Institute for Systems Neuroscience and Centre for Neural Computation, Norwegian University for Science and Technology, Trondheim, Norway
| | - Pål Sætrom
- Department of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology, Trondheim, Norway. .,Department of Computer and Information Science, Norwegian University for Science and Technology, Trondheim, Norway. .,Bioinformatics core facility-BioCore, Norwegian University of Science and Technology, Trondheim, Norway.
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D'Amour J, Magagna-Poveda A, Moretto J, Friedman D, LaFrancois JJ, Pearce P, Fenton AA, MacLusky NJ, Scharfman HE. Interictal spike frequency varies with ovarian cycle stage in a rat model of epilepsy. Exp Neurol 2015; 269:102-19. [PMID: 25864929 PMCID: PMC4446145 DOI: 10.1016/j.expneurol.2015.04.003] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2014] [Revised: 12/27/2014] [Accepted: 04/02/2015] [Indexed: 01/31/2023]
Abstract
In catamenial epilepsy, seizures exhibit a cyclic pattern that parallels the menstrual cycle. Many studies suggest that catamenial seizures are caused by fluctuations in gonadal hormones during the menstrual cycle, but this has been difficult to study in rodent models of epilepsy because the ovarian cycle in rodents, called the estrous cycle, is disrupted by severe seizures. Thus, when epilepsy is severe, estrous cycles become irregular or stop. Therefore, we modified kainic acid (KA)- and pilocarpine-induced status epilepticus (SE) models of epilepsy so that seizures were rare for the first months after SE, and conducted video-EEG during this time. The results showed that interictal spikes (IIS) occurred intermittently. All rats with regular 4-day estrous cycles had IIS that waxed and waned with the estrous cycle. The association between the estrous cycle and IIS was strong: if the estrous cycles became irregular transiently, IIS frequency also became irregular, and when the estrous cycle resumed its 4-day pattern, IIS frequency did also. Furthermore, when rats were ovariectomized, or males were recorded, IIS frequency did not show a 4-day pattern. Systemic administration of an estrogen receptor antagonist stopped the estrous cycle transiently, accompanied by transient irregularity of the IIS pattern. Eventually all animals developed severe, frequent seizures and at that time both the estrous cycle and the IIS became irregular. We conclude that the estrous cycle entrains IIS in the modified KA and pilocarpine SE models of epilepsy. The data suggest that the ovarian cycle influences more aspects of epilepsy than seizure susceptibility.
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Affiliation(s)
- James D'Amour
- The Nathan Kline Institute for Psychiatric Research, 140 Old Orangeburg Rd., Bldg. 35, Orangeburg, NY 10962, USA; Cantonal Hospital of Basel, Land Institute of Pathology, Mühlemattstrasse 11, CH-4410 Liestal, Switzerland; Sackler Program in Biomedical Sciences, New York University Langone Medical Center, 550 First Ave., New York, NY 10016, USA
| | - Alejandra Magagna-Poveda
- Cantonal Hospital of Basel, Land Institute of Pathology, Mühlemattstrasse 11, CH-4410 Liestal, Switzerland
| | - Jillian Moretto
- The Nathan Kline Institute for Psychiatric Research, 140 Old Orangeburg Rd., Bldg. 35, Orangeburg, NY 10962, USA
| | - Daniel Friedman
- The Nathan Kline Institute for Psychiatric Research, 140 Old Orangeburg Rd., Bldg. 35, Orangeburg, NY 10962, USA; Comprehensive Epilepsy Center, New York University Langone Medical Center, 334 34th St., New York, NY 10016, USA
| | - John J LaFrancois
- The Nathan Kline Institute for Psychiatric Research, 140 Old Orangeburg Rd., Bldg. 35, Orangeburg, NY 10962, USA
| | - Patrice Pearce
- Department of Neurology, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Andre A Fenton
- Center for Neural Science, New York University, 4 Washington Place, New York, NY 10003, USA
| | - Neil J MacLusky
- Department of Biomedical Sciences, Ontario Veterinary College, University of Guelph, 50 Stone Rd, Guelph, ON N1G 2W1, Canada
| | - Helen E Scharfman
- The Nathan Kline Institute for Psychiatric Research, 140 Old Orangeburg Rd., Bldg. 35, Orangeburg, NY 10962, USA; Department of Child & Adolescent Psychiatry, Physiology & Neuroscience, and Psychiatry, New York University Langone Medical Center, One Park Ave, New York, NY 10016, USA.
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Interaction of Hydrogen Sulfide with Oxygen Sensing under Hypoxia. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2015; 2015:758678. [PMID: 26078818 PMCID: PMC4442289 DOI: 10.1155/2015/758678] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/30/2014] [Accepted: 01/22/2015] [Indexed: 01/18/2023]
Abstract
Based on the discovery of endogenous H2S production, many in depth studies show this gasotransmitter with a variety of physiological and pathological functions. Three enzymes, cystathionine β-synthase (CBS), cystathionine γ-lyase (CSE), and 3-mercaptopyruvate sulfurtransferase (MST), are involved in enzymatic production of H2S. Emerging evidence has elucidated an important protective role of H2S in hypoxic conditions in many mammalian systems. However, the mechanisms by which H2S senses and responses to hypoxia are largely elusive. Hypoxia-inducible factors (HIFs) function as key regulators of oxygen sensing, activating target genes expression under hypoxia. Recent studies have shown that exogenous H2S regulates HIF action in different patterns. The activation of carotid bodies is a sensitive and prompt response to hypoxia, rapidly enhancing general O2 supply. H2S has been identified as an excitatory mediator of hypoxic sensing in the carotid bodies. This paper presents a brief review of the roles of these two pathways which contribute to hypoxic sensing of H2S.
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Chung S, Spruston N, Koh S. Age-dependent changes in intrinsic neuronal excitability in subiculum after status epilepticus. PLoS One 2015; 10:e0119411. [PMID: 25775210 PMCID: PMC4361192 DOI: 10.1371/journal.pone.0119411] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2012] [Accepted: 01/30/2015] [Indexed: 12/03/2022] Open
Abstract
Kainic acid-induced status epilepticus (KA-SE) in mature rats results in the development of spontaneous recurrent seizures and a pattern of cell death resembling hippocampal sclerosis in patients with temporal lobe epilepsy. In contrast, KA-SE in young animals before postnatal day (P) 18 is less likely to cause cell death or epilepsy. To investigate whether changes in neuronal excitability occur in the subiculum after KA-SE, we examined the age-dependent effects of SE on the bursting neurons of subiculum, the major output region of the hippocampus. Patch-clamp recordings were used to monitor bursting in pyramidal neurons in the subiculum of rat hippocampal slices. Neurons were studied either one or 2-3 weeks following injection of KA or saline (control) in immature (P15) or more mature (P30) rats, which differ in their sensitivity to KA as well as the long-term sequelae of the KA-SE. A significantly greater proportion of subicular pyramidal neurons from P15 rats were strong-bursting neurons and showed increased frequency-dependent bursting compared to P30 animals. Frequency-dependent burst firing was enhanced in P30, but not in P15 rats following KA-SE. The enhancement of bursting induced by KA-SE in more mature rats suggests that the frequency-dependent limitation of repetitive burst firing, which normally occurs in the subiculum, is compromised following SE. These changes could facilitate the initiation of spontaneous recurrent seizures or their spread from the hippocampus to other parts of the brain.
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Affiliation(s)
- Sungkwon Chung
- Department of Physiology, Samsung Biomedical Research Institute, Sungkyunkwan University School of Medicine, Suwon, South Korea
| | - Nelson Spruston
- Scientific Program, Janelia Research Campus, Ashburn, Virginia, United States of America
| | - Sookyong Koh
- Neurobiology Program, Stanley Manne Children’s Research Institute, Northwestern University Feinberg School of Medicine, Chicago, Illinois, United States of America
- * E-mail:
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Rotstein HG. Abrupt and gradual transitions between low and hyperexcited firing frequencies in neuronal models with fast synaptic excitation: a comparative study. CHAOS (WOODBURY, N.Y.) 2013; 23:046104. [PMID: 24387583 DOI: 10.1063/1.4824320] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Hyperexcitability of neuronal networks is one of the hallmarks of epileptic brain seizure generation, and results from a net imbalance between excitation and inhibition that promotes excessive abnormal firing frequencies. The transition between low and high firing frequencies as the levels of recurrent AMPA excitation change can occur either gradually or abruptly. We used modeling, numerical simulations, and dynamical systems tools to investigate the biophysical and dynamic mechanisms that underlie these two identified modes of transition in recurrently connected neurons via AMPA excitation. We compare our results and demonstrate that these two modes of transition are qualitatively different and can be linked to different intrinsic properties of the participating neurons.
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Affiliation(s)
- Horacio G Rotstein
- Department of Mathematical Sciences, New Jersey Institute of Technology, Newark, New Jersey 07102, USA
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12
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Kandratavicius L, Rosa-Neto P, Monteiro MR, Guiot MC, Assirati JA, Carlotti CG, Kobayashi E, Leite JP. Distinct increased metabotropic glutamate receptor type 5 (mGluR5) in temporal lobe epilepsy with and without hippocampal sclerosis. Hippocampus 2013; 23:1212-30. [PMID: 23804486 PMCID: PMC4165311 DOI: 10.1002/hipo.22160] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/31/2013] [Indexed: 12/04/2022]
Abstract
Metabotropic glutamate receptor type 5 (mGluR5) upregulation in temporal lobe epilepsy (TLE) and the correlation of its expression with features of hippocampal sclerosis (HS) remains unclear. Here we characterized mGluR5 immunoreactivity in hippocampus, entorhinal cortex (EC), and subiculum of TLE specimens with confirmed HS, with neocortical TLE (non-HS) and necropsy controls. We correlated mGluR5 immunoreactivity with neuronal density, mossy fiber sprouting, astrogliosis (GFAP), and dendritic alterations (MAP2). TLE specimens showed increased mGluR5 expression, which was most pronounced in the EC, subiculum, CA2, and dentate gyrus outer molecular layer. Increased mGluR5 expression was seen in hippocampal head and body segments and was independent of neuronal density, astrogliosis, or dendritic alterations. Positive correlation between mGluR5 expression with mossy fiber sprouting and with MAP2 in CA3 and CA1 was found only in HS specimens. Negative correlation between mGluR5 expression with seizure frequency and epilepsy duration was found only in non-HS cases. Specimens from HS patients without previous history of febrile seizure (FS) showed higher mGluR5 and MAP2 expression in CA2. Our study suggests that mGluR5 upregulation is part of a repertoire of post-synaptic adaptations that might control overexcitation and excessive glutamate release rather than a dysfunction that leads to seizure facilitation. That would explain why non-HS cases, on which seizures are likely to originate outside the hippocampal formation, also exhibit upregulated mGluR5. On the other hand, lower mGluR5 expression was related to increased seizure frequency. In addition to its role in hyperexcitability, mGluR5 upregulation could play a role in counterbalance mechanisms along the hyperexcitable circuitry uniquely altered in sclerotic hippocampal formation. Inefficient post-synaptic compensatory morphological (dendritic branching) and glutamatergic (mGluR5 expression) mechanisms in CA2 subfield could potentially underlie the association of FS with HS and TLE. © 2013 Wiley Periodicals, Inc.
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Affiliation(s)
- Ludmyla Kandratavicius
- Department of Neurosciences and Behavior, Ribeirao Preto Medical School, University of Sao PauloBrazil
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill UniversityMontreal, Canada
| | - Pedro Rosa-Neto
- Translational Neuroimaging Laboratory, Department of Neurology and Neurosurgery, Douglas Research Institute, McGill UniversityMontreal, Canada
| | - Mariana Raquel Monteiro
- Department of Neurosciences and Behavior, Ribeirao Preto Medical School, University of Sao PauloBrazil
| | - Marie-Christine Guiot
- Department of Pathology, Montreal Neurological Institute, McGill UniversityMontreal, Canada
| | | | | | - Eliane Kobayashi
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill UniversityMontreal, Canada
| | - Joao Pereira Leite
- Department of Neurosciences and Behavior, Ribeirao Preto Medical School, University of Sao PauloBrazil
- *Correspondence to: Joao Pereira Leite, Ribeirao Preto Medical School, Department of Neurosciences and Behavior, University of Sao Paulo, Av Bandeirantes 3900, 14049-900, Ribeirao Preto, SP, Brazil. E-mail:
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13
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Kispersky T, White JA, Rotstein HG. The mechanism of abrupt transition between theta and hyper-excitable spiking activity in medial entorhinal cortex layer II stellate cells. PLoS One 2010; 5:e13697. [PMID: 21079802 PMCID: PMC2973955 DOI: 10.1371/journal.pone.0013697] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2010] [Accepted: 09/04/2010] [Indexed: 11/18/2022] Open
Abstract
Recent studies have shown that stellate cells (SCs) of the medial entorhinal cortex become hyper-excitable in animal models of temporal lobe epilepsy. These studies have also demonstrated the existence of recurrent connections among SCs, reduced levels of recurrent inhibition in epileptic networks as compared to control ones, and comparable levels of recurrent excitation among SCs in both network types. In this work, we investigate the biophysical and dynamic mechanism of generation of the fast time scale corresponding to hyper-excitable firing and the transition between theta and fast firing frequency activity in SCs. We show that recurrently connected minimal networks of SCs exhibit abrupt, threshold-like transition between theta and hyper-excitable firing frequencies as the result of small changes in the maximal synaptic (AMPAergic) conductance. The threshold required for this transition is modulated by synaptic inhibition. Similar abrupt transition between firing frequency regimes can be observed in single, self-coupled SCs, which represent a network of recurrently coupled neurons synchronized in phase, but not in synaptically isolated SCs as the result of changes in the levels of the tonic drive. Using dynamical systems tools (phase-space analysis), we explain the dynamic mechanism underlying the genesis of the fast time scale and the abrupt transition between firing frequency regimes, their dependence on the intrinsic SC's currents and synaptic excitation. This abrupt transition is mechanistically different from others observed in similar networks with different cell types. Most notably, there is no bistability involved. 'In vitro' experiments using single SCs self-coupled with dynamic clamp show the abrupt transition between firing frequency regimes, and demonstrate that our theoretical predictions are not an artifact of the model. In addition, these experiments show that high-frequency firing is burst-like with a duration modulated by an M-current.
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Affiliation(s)
- Tilman Kispersky
- Program in Neuroscience and Center for BioDynamics, Boston University, Boston, Massachusetts, United States of America
| | - John A. White
- Department of Bioengineering, University of Utah, Salt Lake City, Utah, United States of America
| | - Horacio G. Rotstein
- Department of Mathematical Sciences and Center for Applied Mathematics and Statistics, New Jersey Institute of Technology, Newark, New Jersey, United States of America
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14
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Norwood BA, Bumanglag AV, Osculati F, Sbarbati A, Marzola P, Nicolato E, Fabene PF, Sloviter RS. Classic hippocampal sclerosis and hippocampal-onset epilepsy produced by a single "cryptic" episode of focal hippocampal excitation in awake rats. J Comp Neurol 2010; 518:3381-407. [PMID: 20575073 DOI: 10.1002/cne.22406] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
In refractory temporal lobe epilepsy, seizures often arise from a shrunken hippocampus exhibiting a pattern of selective neuron loss called "classic hippocampal sclerosis." No single experimental injury has reproduced this specific pathology, suggesting that hippocampal atrophy might be a progressive "endstage" pathology resulting from years of spontaneous seizures. We posed the alternative hypothesis that classic hippocampal sclerosis results from a single excitatory event that has never been successfully modeled experimentally because convulsive status epilepticus, the insult most commonly used to produce epileptogenic brain injury, is too severe and necessarily terminated before the hippocampus receives the needed duration of excitation. We tested this hypothesis by producing prolonged hippocampal excitation in awake rats without causing convulsive status epilepticus. Two daily 30-minute episodes of perforant pathway stimulation in Sprague-Dawley rats increased granule cell paired-pulse inhibition, decreased epileptiform afterdischarge durations during 8 hours of subsequent stimulation, and prevented convulsive status epilepticus. Similarly, one 8-hour episode of reduced-intensity stimulation in Long-Evans rats, which are relatively resistant to developing status epilepticus, produced hippocampal discharges without causing status epilepticus. Both paradigms immediately produced the extensive neuronal injury that defines classic hippocampal sclerosis, without giving any clinical indication during the insult that an injury was being inflicted. Spontaneous hippocampal-onset seizures began 16-25 days postinjury, before hippocampal atrophy developed, as demonstrated by sequential magnetic resonance imaging. These results indicate that classic hippocampal sclerosis is uniquely produced by a single episode of clinically "cryptic" excitation. Epileptogenic insults may often involve prolonged excitation that goes undetected at the time of injury.
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Affiliation(s)
- Braxton A Norwood
- Department of Pharmacology, University of Arizona College of Medicine, Tucson, Arizona 85724, USA
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15
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Bragin DE, Sanderson JL, Peterson S, Connor JA, Müller WS. Development of epileptiform excitability in the deep entorhinal cortex after status epilepticus. Eur J Neurosci 2009; 30:611-24. [PMID: 19674083 PMCID: PMC2776653 DOI: 10.1111/j.1460-9568.2009.06863.x] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Epileptiform neuronal activity during seizures is observed in many brain areas, but its origins following status epilepticus (SE) are unclear. We have used the Li low-dose pilocarpine rat model of temporal lobe epilepsy to examine early development of epileptiform activity in the deep entorhinal cortex (EC). We show that during the 3-week latent period that follows SE, an increasing percentage of neurons in EC layer 5 respond to a single synaptic stimulus with polysynaptic burst depolarizations. This change is paralleled by a progressive depolarizing shift of the inhibitory postsynaptic potential reversal potential in layer 5 neurons, apparently caused by upregulation of the Cl(-) inward transporter NKCC1 and concurrent downregulation of the Cl(-) outward transporter KCC2, both changes favoring intracellular Cl(-) accumulation. Inhibiting Cl(-) uptake in the latent period restored more negative GABAergic reversal potentials and eliminated polysynaptic bursts. The changes in the Cl(-) transporters were highly specific to the deep EC. They did not occur in layers 1-3, perirhinal cortex, subiculum or dentate gyrus during this period. We propose that the changes in Cl(-) homeostasis facilitate hyperexcitability in the deep entorhinal cortex leading to epileptiform discharge there, which subsequently affects downstream cortical regions.
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Affiliation(s)
- Denis E Bragin
- Department of Neurosurgery, University of New Mexico School of Medicine, University of New Mexico, Albuquerque, NM, USA
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16
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Effects of repeated electroconvulsive shock seizures and pilocarpine-induced status epilepticus on emotional behavior in the rat. Epilepsy Behav 2009; 14:293-9. [PMID: 19068237 DOI: 10.1016/j.yebeh.2008.11.004] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/20/2008] [Revised: 11/16/2008] [Accepted: 11/18/2008] [Indexed: 10/21/2022]
Abstract
Affective symptoms are frequently observed in patients with epilepsy. Although the etiology of these behavioral complications remains unknown, it is possible that brain damage associated with frequent or prolonged seizures may contribute to their development. To address this issue, we examined the behavioral sequelae of repeated brief seizures evoked by electroconvulsive shock (ECS) and compared them with those resulting from prolonged status epilepticus (SE) induced with pilocarpine. Using the open-field and elevated plus-maze tests, we detected the presence of behavioral alterations indicative of elevated levels of anxiety in rats that were administered a course of ECS seizures. Fear conditioning was also enhanced in these animals. However, the rats that had experienced SE exhibited less anxiety-like behavior than controls and were severely impaired in fear conditioning. These results support the notion that brain lesions caused by either brief repeated seizures or SE is sufficient to induce some affective disturbances.
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Cardoso A, Madeira MD, Paula-Barbosa MM, Lukoyanov NV. Retrosplenial granular b cortex in normal and epileptic rats: A stereological study. Brain Res 2008; 1218:206-14. [DOI: 10.1016/j.brainres.2008.04.074] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2008] [Revised: 04/29/2008] [Accepted: 04/29/2008] [Indexed: 11/29/2022]
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18
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Metabolic changes in temporal lobe structures measured by HR-MAS NMR at early stage of electrogenic rat epilepsy. Exp Neurol 2008; 212:377-85. [PMID: 18538323 DOI: 10.1016/j.expneurol.2008.04.013] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2007] [Revised: 04/04/2008] [Accepted: 04/10/2008] [Indexed: 02/04/2023]
Abstract
The purpose of this study was to determine cerebral metabolic profile changes in response to electric stimulation to the right dorsal hippocampus (HPC) for the establishment of an epileptic rat model. Electroencephalogram measurements and behavioral results indicated that the experimental rats were in an early stage of epilepsy. Metabolites were determined by high-resolution magic-angle-spinning nuclear magnetic resonance (HR-MAS NMR) spectroscopy of the following intact brain tissue: bilateral hippocampi, entorhinal cortices (ECs), and temporal lobes (TLs). The NMR data was statistically analyzed using principal component analysis (PCA). Results demonstrated that metabolic profiles were significantly different between the experimental and sham rats in the bilateral hippocampi and the ipsilateral EC. Significant increases in total creatine in the ipsilateral HPC and alanine in the ipsilateral TL were measured (p<0.05). Some metabolite levels were disturbed in the bilateral HPC-EC loops. In the sham group, glutamate and choline concentrations were significantly higher or lower in the ipsilateral EC than bilateral hippocampi, respectively (p<0.01). However, such differences were not observed in the experimental group. In addition, N-acetylaspartate levels in the experimental group were significantly less in the ipsilateral HPC than in bilateral ECs (p<0.05). The level of myo-inositol in the ipsilateral EC significantly increased in the experimental group, compared to the contralateral EC (p<0.05). These results may provide metabolic information about temporal lobe structures to provide more knowledge about epileptic abnormalities at the early stage.
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Keller SS, Roberts N. Voxel-based morphometry of temporal lobe epilepsy: an introduction and review of the literature. Epilepsia 2007; 49:741-57. [PMID: 18177358 DOI: 10.1111/j.1528-1167.2007.01485.x] [Citation(s) in RCA: 322] [Impact Index Per Article: 18.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
We review the applications and results of voxel-based morphometry (VBM) studies that have reported brain changes associated with temporal lobe epilepsy (TLE). A PubMed search yielded 18 applications of VBM to study brain abnormalities in patients with TLE up to May 2007. Across studies, 26 brain regions were found to be significantly reduced in volume relative to healthy controls. There was a strong asymmetrical distribution of temporal lobe abnormalities preferentially observed ipsilateral to the seizure focus, particularly of the hippocampus (82.35% of all studies), parahippocampal gyrus (47.06%), and entorhinal (23.52%) cortex. The contralateral hippocampus was reported as abnormal in 17.65% of studies. There was a much more bilateral distribution of extratemporal lobe atrophy, preferentially affecting the thalamus (ipsilateral = 61.11%, contralateral = 50%) and parietal lobe (ipsilateral = 47.06%, contralateral = 52.94%). VBM generally reveals a distribution of brain abnormalities in patients with TLE consistent with the region-of-interest neuroimaging and postmortem literature. It is unlikely that VBM has any clinical utility given the lack of robustness for individual comparisons. However, VBM may help elucidate some unresolved important research questions such as how recurrent temporal lobe seizures affect hippocampal and extrahippocampal morphology using serial imaging acquisitions.
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Affiliation(s)
- Simon Sean Keller
- The Magnetic Resonance and Image Analysis Research Centre, University of Liverpool, Liverpool, United Kingdom.
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20
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Wolansky T, Pagliardini S, Greer JJ, Dickson CT. Immunohistochemical characterization of substance P receptor (NK(1)R)-expressing interneurons in the entorhinal cortex. J Comp Neurol 2007; 502:427-41. [PMID: 17366610 DOI: 10.1002/cne.21338] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
It has been reported that application of substance P (SP) to the medial portion of the entorhinal cortex (EC) induces a powerful antiepileptic effect (Maubach et al. [1998] Neuroscience 83:1047-1062). This effect is presumably mediated via inhibitory interneurons expressing the neurokinin-1 receptor (NK(1)R), but the existence of NK(1)R-expressing inhibitory interneurons in the EC has not yet been reported. The present immunohistochemical study was performed in the rat to examine the existence and distribution of NK(1)R-expressing neurons in the EC as well as any co-expression of other neurotransmitters/neuromodulators known to be associated with inhibitory interneurons: gamma-aminobutyric acid (GABA), parvalbumin (PARV), calretinin (CT), calbindin (CB), somatostatin (SST), and neuropeptide Y (NPY). Our results indicated that NK(1)R-positive neurons were distributed rather sparsely (especially in the medial EC), primarily in layers II, V, and VI. The results of our double-immunohistochemical staining indicated that the vast majority of NK(1)R-expressing neurons also expressed GABA, SST, and NPY. In addition, CT was co-expressed in a weakly stained subgroup of NK(1)R-expressing neurons, and CB was co-expressed very rarely in the lateral EC, but not in the medial EC. In contrast, SP-immunopositive axons with fine varicosities were distributed diffusely throughout all layers of the EC, appearing to radiate from the angular bundle. SP may be released in a paracrine manner to activate a group of NK(1)R-expressing entorhinal neurons that co-express GABA, SST, and NPY, exerting a profound inhibitory influence on synchronized network activity in the EC.
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Affiliation(s)
- Trish Wolansky
- Centre for Neuroscience, University of Alberta, Edmonton, Alberta, Canada T6G 2R3
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21
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West PJ, Dalpé-Charron A, Wilcox KS. Differential contribution of kainate receptors to excitatory postsynaptic currents in superficial layer neurons of the rat medial entorhinal cortex. Neuroscience 2007; 146:1000-12. [PMID: 17395391 PMCID: PMC2921318 DOI: 10.1016/j.neuroscience.2007.02.035] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2006] [Revised: 02/02/2007] [Accepted: 02/19/2007] [Indexed: 02/02/2023]
Abstract
Although in situ hybridization studies have revealed the presence of kainate receptor (KAR) mRNA in neurons of the rat medial entorhinal cortex (mEC), the functional presence and roles of these receptors are only beginning to be examined. To address this deficiency, whole cell voltage clamp recordings of locally evoked excitatory postsynaptic currents (EPSCs) were made from mEC layer II and III neurons in combined entorhinal cortex-hippocampal brain slices. Three types of neurons were identified by their electroresponsive membrane properties, locations, and morphologies: stellate-like "Sag" neurons in layer II (S), pyramidal-like "No Sag" neurons in layer III (NS), and "Intermediate Sag" neurons with varied morphologies and locations (IS). Non-NMDA EPSCs in these neurons were composed of two components, and the slow decay component in NS neurons had larger amplitudes and contributed more to the combined EPSC than did those observed in S and IS neurons. This slow component was mediated by KARs and was characterized by its resistance to either 1-(4-aminophenyl)-4-methyl-7,8-methylenedioxy-5H-2,3-benzodiazepine hydrochloride (GYKI 52466, 100 microM) or 1,2,3,4-tetrahydro-6-nitro-2,3-dioxo-benzo[lsqb]f[rsqb]quinoxaline-7-sulfonamide (NBQX, 1 microM), relatively slow decay kinetics, and sensitivity to 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX, 10-50 microM). KAR-mediated EPSCs in pyramidal-like NS neurons contributed significantly more to the combined non-NMDA EPSC than did those from S and IS neurons. Layer III neurons of the mEC are selectively susceptible to degeneration in human temporal lobe epilepsy (TLE) and animal models of TLE such as kainate-induced status epilepticus. Characterizing differences in the complement of postsynaptic receptors expressed in injury prone versus injury resistant mEC neurons represents an important step toward understanding the vulnerability of layer III neurons seen in TLE.
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Affiliation(s)
- P J West
- Department of Pharmacology and Toxicology, University of Utah, Salt Lake City, UT 84112, USA
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22
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Kumar SS, Jin X, Buckmaster PS, Huguenard JR. Recurrent circuits in layer II of medial entorhinal cortex in a model of temporal lobe epilepsy. J Neurosci 2007; 27:1239-46. [PMID: 17287497 PMCID: PMC6673582 DOI: 10.1523/jneurosci.3182-06.2007] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Patients and laboratory animal models of temporal lobe epilepsy display loss of layer III pyramidal neurons in medial entorhinal cortex and hyperexcitability and hypersynchrony of less vulnerable layer II stellate cells. We sought to test the hypothesis that loss of layer III pyramidal neurons triggers synaptic reorganization and formation of recurrent, excitatory synapses among layer II stellate cells in epileptic pilocarpine-treated rats. Laser-scanning photo-uncaging of glutamate focally activated neurons in layer II while excitatory synaptic responses were recorded in stellate cells. Photostimulation revealed previously unidentified, functional, recurrent, excitatory synapses between layer II stellate cells in control animals. Contrary to the hypothesis, however, control and epileptic rats displayed similar levels of recurrent excitation. Recently, hyperexcitability of layer II stellate cells has been attributed, at least in part, to loss of GABAergic interneurons and inhibitory synaptic input. To evaluate recurrent inhibitory circuits in layer II, we focally photostimulated interneurons while recording inhibitory synaptic responses in stellate cells. IPSCs were evoked more than five times more frequently in slices from control versus epileptic animals. These findings suggest that in this model of temporal lobe epilepsy, reduced recurrent inhibition contributes to layer II stellate cell hyperexcitability and hypersynchrony, but increased recurrent excitation does not.
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Affiliation(s)
- Sanjay S Kumar
- Department of Comparative Medicine, Stanford University, Stanford, California 94305, USA
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23
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Abstract
The organization of intrinsic connections within the entorhinal cortex was investigated in Macaca fascicularis monkeys. Anterograde tracers ((3)H-amino acids, Phaseolus vulgaris-leucoagglutinin, biotinylated dextran amine, or Fluoro-Ruby) were injected into the deep or superficial layers of the entorhinal cortex in 24 animals. These injections labeled extensive intrinsic projections that terminated throughout all layers of the entorhinal cortex. Labeling was typically continuous i.e., there was no evidence of a patchy or columnar organization. Each injection produced a rostrocaudally oriented band of labeled fibers and terminals that extended for one-third to one-half of the length of the entorhinal cortex. The more extensive distributions of labeled fibers were more typical of caudally placed injection sites. Taken together, the projections identified at least two mediolaterally differentiated bands: a lateral band that encompasses fields Elr, Elc, and the most lateral aspect of fields Ec and Ecl and a wider, medially situated band that encompasses much of fields Er, Ei, Ec, and Ecl. We obtained some evidence that field Eo constitutes a third, very medially placed band. The rostrocaudal organization of labeled fibers and the extent of labeling within the deep and superficial layers were unrelated to the laminar position of the injection. These data suggest that intrinsic associatonal connections in the monkey entorhinal cortex are organized into separate associational networks. Our findings are discussed with reference to the role of interlaminar connections in mediating physiological interactions between the neocortex and the hippocampus.
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Affiliation(s)
- James J Chrobak
- Department of Psychology, University of Connecticut, Storrs, Connecticut 06269, USA
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24
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Cardoso A, Assunção M, Andrade JP, Pereira PA, Madeira MD, Paula-Barbosa MM, Lukoyanov NV. Loss of synapses in the entorhinal-dentate gyrus pathway following repeated induction of electroshock seizures in the rat. J Neurosci Res 2007; 86:71-83. [PMID: 17705293 DOI: 10.1002/jnr.21474] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The goal of this study was to answer the question of whether repeated administration of electroconvulsive shock (ECS) seizures causes structural changes in the entorhinal-dentate projection system, whose neurons are known to be particularly vulnerable to seizure activity. Adult rats were administered six ECS seizures, the first five of which were spaced by 24-hr intervals, whereas the last two were only 2 hr apart. Stereological approaches were employed to compare the total neuronal and synaptic numbers in sham- and ECS-treated rats. Golgi-stained material was used to analyze dendritic arborizations of the dentate gyrus granule cells. Treatment with ECS produced loss of neurons in the entorhinal layer III and in the hilus of the dentate gyrus. The number of neurons in the entorhinal layer II, which provides the major source of dentate afferents, and in the granular layer of the dentate gyrus, known to receive entorhinal projections, remained unchanged. Despite this, the number of synapses established between the entorhinal layer II neurons and their targets, dentate granule cells, was reduced in ECS-treated rats. In addition, administration of ECS seizures produced atrophic changes in the dendritic arbors of dentate granule cells. The total volumes of entorhinal layers II, III, and V-VI were also found to be reduced in ECS-treated rats. By showing that treatment with ECS leads to partial disconnection of the entorhinal cortex and dentate gyrus, these findings shed new light on cellular processes that may underlie structural and functional brain changes induced by brief, generalized seizures.
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Affiliation(s)
- Armando Cardoso
- Department of Anatomy, Porto Medical School, Porto, Portugal
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25
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Abstract
The most useful information about the anatomy of human memory comes from cases where there has been extensive neuropsychological testing followed by detailed post-mortem neurohistological analysis. To our knowledge, only eight such cases have been reported (four with medial temporal lobe damage and four with diencephalic damage). Here we present neuropsychological and post-mortem neurohistological findings for one patient (NC) with bilateral damage to the medial temporal lobe and two patients (MG, PN) with diencephalic damage due to bilateral thalamic infarction and Korsakoff's syndrome, respectively. All three patients exhibited a similar phenotype of amnesia with markedly impaired declarative memory (anterograde and retrograde) but normal performance on tests of nondeclarative memory (e.g., priming and adaptation-level effects) as well as on tests of other cognitive functions. Patient NC had damage to the hippocampus (dentate gyrus and the CA1 and CA3 fields) and layer III of the entorhinal cortex, but with relative sparing of the CA2 field and the subiculum. Patient MG had damage to the internal medullary lamina and mediodorsal thalamic nuclei. Patient PN had damage to the mammillary nuclei, mammillothalamic tracts, and the anterior thalamic nuclei. These findings illuminate several issues regarding the relation between diencephalic and medial temporal lobe amnesia, the status of recognition memory in amnesia, and the neuroanatomy of memory.
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Affiliation(s)
- Jeffrey J. Gold
- Department of Neurosciences, University of California–San Diego, La Jolla, California 92093, USA
| | - Larry R. Squire
- Veterans Affairs Medical Center, San Diego, California 92161, USA
- Department of Psychiatry, University of California–San Diego, La Jolla, California 92093, USA
- Department of Neurosciences, University of California–San Diego, La Jolla, California 92093, USA
- Department of Psychology, University of California–San Diego, La Jolla, California 92093, USA
- Corresponding author.E-mail ; fax (858) 552-7457
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Hughlings Jackson and the role of the entorhinal cortex in temporal lobe epilepsy: from patient A to Doctor Z. Epilepsy Behav 2006; 9:524-31. [PMID: 16942917 DOI: 10.1016/j.yebeh.2006.07.017] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/15/2006] [Revised: 07/14/2006] [Accepted: 07/19/2006] [Indexed: 10/24/2022]
Abstract
Hughlings Jackson's insightful bedside observations of patients with epilepsy paved the way for the first effective surgical epilepsy treatments. Jackson's most famous case, that of Doctor Z, concerned a medical doctor with partial complex seizures who was reported to have a discrete and circumscribed medial temporal lobe (mTL) lesion on autopsy. Although integral to Jackson's argument for mTL resection, the case remains controversial due to inadequate pathological descriptions of Doctor Z's lesion. This motivated us to describe the case of a patient, whom we call Patient A, who suffered from a form of epilepsy similar to that of Doctor Z, accompanied by a discrete and circumscribed mTL lesion in the exact same location. The lesion, a cavernous hemangioma, spared the hippocampus and was restricted to the lateral aspect of the entorhinal cortex. This finding validates Jackson's original description and suggests that the entorhinal cortex can play a role in seizure genesis.
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27
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Kumar SS, Buckmaster PS. Hyperexcitability, interneurons, and loss of GABAergic synapses in entorhinal cortex in a model of temporal lobe epilepsy. J Neurosci 2006; 26:4613-23. [PMID: 16641241 PMCID: PMC6674073 DOI: 10.1523/jneurosci.0064-06.2006] [Citation(s) in RCA: 137] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Temporal lobe epilepsy is the most common type of epilepsy in adults, and its pathophysiology remains unclear. Layer II stellate cells of the entorhinal cortex, which are hyperexcitable in animal models of temporal lobe epilepsy, provide the predominant synaptic input to the hippocampal dentate gyrus. Previous studies have ascribed the hyperexcitability of layer II stellate cells to GABAergic interneurons becoming "dormant" after disconnection from their excitatory synaptic inputs, which has been reported to occur during preferential loss of layer III pyramidal cells. We used whole-cell recording from slices of entorhinal cortex in pilocarpine-treated epileptic rats to test the dormant interneuron hypothesis. Hyperexcitability appeared as multiple action potentials and prolonged depolarizations evoked in layer II stellate cells of epileptic rats but not controls. However, blockade of glutamatergic synaptic transmission caused similar percentage reductions in the frequency of spontaneous IPSCs in layer II stellate cells of control and epileptic rats, suggesting similar levels of excitatory synaptic input to GABAergic interneurons. Direct recordings and biocytin labeling revealed two major types of interneurons in layer III whose excitatory synaptic drive in epileptic animals was undiminished. Interneurons in layer III did not appear to be dormant; therefore, we tested whether loss of GABAergic synapses might underlie hyperexcitability of layer II stellate cells. Stereological evidence of fewer GABAergic interneurons, fewer gephyrin-immunoreactive punctae, and reduced frequency of spontaneous IPSCs and miniature IPSCs (recorded in tetrodotoxin) confirmed that layer II stellate cell hyperexcitability is attributable, at least in part, to reduced inhibitory synaptic input.
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Affiliation(s)
- Sanjay S Kumar
- Department of Comparative Medicine, Stanford University, Stanford, California 94305, USA
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Bernabeu R, Thiriet N, Zwiller J, Di Scala G. Lesion of the lateral entorhinal cortex amplifies odor-induced expression of c-fos, junB, and zif 268 mRNA in rat brain. Synapse 2006; 59:135-43. [PMID: 16342059 DOI: 10.1002/syn.20224] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Paradoxical facilitation of olfactory learning following entorhinal cortex (EC) lesion has been described, which may result from widespread functional alterations taking place within the olfactory system. To test this hypothesis, expression of the immediate early genes c-fos, junB, and zif 268 was studied in response to an olfactory stimulation in several brain areas in control and in EC-lesioned rats. Olfactory stimulation in control rats induced the expression of the three genes in the granular/mitral and glomerular layers of the olfactory bulb, as well as c-fos and junB expression in the piriform cortex. However EC lesion was devoid of effects in nonstimulated animals; it significantly amplified the odor-induced expression of the three genes in these areas, as well as in the amygdala, hippocampus, and parietal-temporal cortices. The data suggest that EC lesion modifies the neural processing of odor by suppressing an inhibitory influence on brain areas connected to this cortex.
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Affiliation(s)
- Ramón Bernabeu
- Laboratoire de Neurosciences Comportementales et Cognitives, UMR 7521, Université Louis Pasteur/CNRS, Strasbourg 67000, France
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Rocha L, Arida RM, Carvalho RDA, Scorza FA, Neri-Bazan L, Cavalheiro EA. GABA and opioid binding distribution in the brain of the seizure-resistantProechimys guyannensis: An autoradiography study. Synapse 2006; 60:392-8. [PMID: 16847947 DOI: 10.1002/syn.20312] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Proechimys guyannensis rodents present resistance to epilepsy. Autoradiography was used to map GABA(A) ((3)H-Muscimol), benzodiazepine ((3)H-Flunitrazepam), mu ((3)H-DAMGO), and delta ((3)H-DPDPE) opioid receptor binding in adult Proechimys guyannensis brain under normal conditions. Results were compared with values obtained from adult Wistar rats. Proechimys presented reduced (3)H-Muscimol binding in several cortices, thalamus, medial amygdala nucleus, and dorsal dentate gyrus. (3)H-Flunitrazepam binding was reduced in periaqueductal gray, frontal and entorhinal cortices, and enhanced in piriform cortex and ventral CA2 field of Ammons horn. Concerning (3)H-DAMGO binding, high values were found in several cortices, medial amygdala nucleus, dorsal dentate gyrus, and periaqueductal gray, whereas reduced binding was detected in anterior olfactory tubercle, cingulated cortex, thalamus, basolateral amygdala, substantia nigra, and dorsal and ventral CA fields. High (3)H-DPDPE binding was noticed in CA1 field from dorsal hippocampus, while reduced values were found in cingulate cortex, olfactory tubercle, thalamus, and substantia nigra. These findings provide the first description of receptor binding distribution of the Proechimys brain and suggest natural endogenous anticonvulsant mechanisms of theses rodents under normal conditions.
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MESH Headings
- Animals
- Autoradiography/methods
- Benzodiazepines/metabolism
- Binding, Competitive/physiology
- Brain/anatomy & histology
- Brain/metabolism
- Brain/physiopathology
- Epilepsy/metabolism
- Epilepsy/physiopathology
- GABA Agonists/metabolism
- Genetic Predisposition to Disease/genetics
- Male
- Narcotics/metabolism
- Neural Inhibition/genetics
- Radioligand Assay
- Rats
- Rats, Wistar/metabolism
- Receptors, GABA-A/drug effects
- Receptors, GABA-A/metabolism
- Receptors, Opioid, delta/drug effects
- Receptors, Opioid, delta/metabolism
- Receptors, Opioid, mu/drug effects
- Receptors, Opioid, mu/metabolism
- Rodentia/metabolism
- gamma-Aminobutyric Acid/metabolism
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Affiliation(s)
- Luisa Rocha
- Department of Pharmacobiology, Center of Research and Advanced Studies, México City, México.
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Wu HQ, Rassoulpour A, Goodman JH, Scharfman HE, Bertram EH, Schwarcz R. Kynurenate and 7-chlorokynurenate formation in chronically epileptic rats. Epilepsia 2005; 46:1010-6. [PMID: 16026552 DOI: 10.1111/j.1528-1167.2005.67404.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
PURPOSE The tryptophan metabolite kynurenic acid (KYNA) and its synthetic derivative, 7-chlorokynurenic acid (7-Cl-KYNA), are antagonists of the glycine co-agonist ("glycine(B)") site of the N-methyl-D-aspartate (NMDA)-receptor. Both compounds have neuroprotective and anticonvulsive properties but do not readily penetrate the blood-brain barrier. However, KYNA and 7-Cl-KYNA can be formed in, and released from, astrocytes after the peripheral administration of their transportable precursors kynurenine and 4-chlorokynurenine, respectively. The present study was designed to examine these biosynthetic processes, as well as astrogliosis, in animals with spontaneously recurring seizures. METHODS The fate and formation of KYNA and 7-Cl-KYNA was studied in vivo (microdialysis) and in vitro (tissue slices) in rats exhibiting chronic seizure activity (pilocarpine model) and in appropriate controls. Neuronal loss and gliosis in these animals were examined immunohistochemically. RESULTS In vivo microdialysis revealed higher ambient extracellular KYNA levels and enhanced de novo formation of 7-Cl-KYNA in the entorhinal cortex and hippocampus in epileptic rats. Complementary studies in tissue slices showed increased neosynthesis of KYNA and 7-Cl-KYNA in the same two brain areas. Microscopic analysis revealed pronounced astrocytic reactions in entorhinal cortex and hippocampus in epileptic animals. CONCLUSIONS These results demonstrate that the epileptic brain can synthesize glycine(B) receptor antagonists in situ. Astrogliosis probably accounts for their enhanced production in chronically epileptic rats. These results bode well for the use of 4-chlorokynurenine in the treatment of chronic seizure disorders.
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Affiliation(s)
- Hui-Qiu Wu
- Maryland Psychiatric Research Center, University of Maryland School of Medicine, Baltimore, MD 21228, U.S.A
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Arida RM, Scorza FA, Carvalho RDA, Cavalheiro EA. Long-term cosequences of intrahippocampal kainate injection in the Proechimys guyannensis rodent. Epilepsy Res 2005; 65:201-10. [PMID: 16084693 DOI: 10.1016/j.eplepsyres.2005.07.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2005] [Accepted: 07/03/2005] [Indexed: 10/25/2022]
Abstract
The Proechimys guyannensis (PG), a spiny rodent specie living in the Amazonian region has been recently studied as an animal model of anti-convulsant mechanisms. The PG was found to be resistant to the administration of the muscarinic cholinergic agonist pilocarpine or the amygdala kindling development. This study examined the susceptibility of this animal species to the intrahippocampal kainic acid (KA) injection. Electrographic, behavioral and neuropathological changes induced by intrahippocampal KA injections were analyzed. PG showed to be extremely sensitive to the acute effects of the KA injection. Although the EEG findings in PG rodents were similar to those typically obtained in Wistar rats the pattern of electrographic activity in PG animals was longer than in Wistar rats. Neuropathological examinations of PG brains that survived KA-induced SE revealed severe cell loss in CA1/CA3 areas of the hippocampus, an extensive cell dispersion in the hilus of DG at the injected site with mossy fiber sprouting in the dentate gyrus supragranular layer. None of PG animals presented spontaneous seizures during the 120 days of observation. These findings confirm our previous observation on the resistance of this animal specie to experimental models of limbic epilepsy.
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Affiliation(s)
- Ricardo Mario Arida
- Disciplina de Neurologia Experimental, Universidade Federal de São Paulo (UNIFESP), Rua Botucatú 862, Vila Clementino, CEP 04023-9000, São Paulo, SP, Brazil.
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Abstract
Although there are many types of epilepsy of both genetic and acquired forms, temporal lobe epilepsy (TLE) with hippocampal sclerosis is probably the single most common human epilepsy, and the one most intensely studied. Despite a wealth of descriptive data obtained from patient histories, imaging techniques, electroencephalographic recording, and histological studies, the epileptogenic process remains poorly understood. Progress toward understanding the etiology of an acquired neurological disorder is largely dependent on the degree to which experimental animal models reflect the human condition. Recent observations suggest that significant disparities exist between the features of human TLE with hippocampal sclerosis and those of animal models that involve prolonged status epilepticus to initiate the epileptogenic process. TLE most commonly involves patients with focal seizures who exhibit limited and often asymmetrical brain damage, did not experience status epilepticus prior to the onset of epilepsy, and who appear relatively normal on neurological examination. Conversely, animals subjected to prolonged status epilepticus exhibit severe brain damage, behavioral abnormalities, and frequent generalized seizures. In addition, although many TLE patients exhibit an atrophic hippocampus that may, or may not, be a source of spontaneous seizures, hippocampal damage in animals subjected to status epilepticus is an inconsistent and often minor part of a much greater constellation of damage to other brain structures. Furthermore, many patients exhibit developmental structural abnormalities that presumably play a role in the clinical etiology, whereas most animal models involve severe insults in initially normal laboratory rats. Although much has been learned using the current animal models, the available data suggest the need for a critical reappraisal of the assumptions underlying their use, and the need to develop experimental preparations that may more closely model the human epileptic state.
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Affiliation(s)
- Robert S Sloviter
- Departments of Pharmacology and Neurology, University of Arizona College of Medicine, 1501 N. Campbell Avenue, Tucson, AZ 85724, USA.
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Harvey BD, Sloviter RS. Hippocampal granule cell activity and c-Fos expression during spontaneous seizures in awake, chronically epileptic, pilocarpine-treated rats: Implications for hippocampal epileptogenesis. J Comp Neurol 2005; 488:442-63. [PMID: 15973680 DOI: 10.1002/cne.20594] [Citation(s) in RCA: 90] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The process of postinjury hippocampal epileptogenesis may involve gradually developing dentate granule cell hyperexcitability caused by neuron loss and synaptic reorganization. We tested this hypothesis by repeatedly assessing granule cell excitability after pilocarpine-induced status epilepticus (SE) and monitoring granule cell behavior during 235 spontaneous seizures in awake, chronically implanted rats. During the first week post-SE, granule cells exhibited diminished paired-pulse suppression and decreased seizure discharge thresholds in response to afferent stimulation. Spontaneous seizures often began during the first week after SE, recruited granule cell discharges that followed behavioral seizure onsets, and evoked c-Fos expression in all hippocampal neurons. Paired-pulse suppression and epileptiform discharge thresholds increased gradually after SE, eventually becoming abnormally elevated. In the chronic epileptic state, interictal granule cell hyperinhibition extended to the ictal state; granule cells did not discharge synchronously before any of 191 chronic seizures. Instead, granule cells generated only low-frequency voltage fluctuations (presumed "field excitatory postsynaptic potentials") during 89% of chronic seizures. Granule cell epileptiform discharges were recruited during 11% of spontaneous seizures, but these occurred only at the end of each behavioral seizure. Hippocampal c-Fos after chronic seizures was expressed primarily by inhibitory interneurons. Thus, granule cells became progressively less excitable, rather than hyperexcitable, as mossy fiber sprouting progressed and did not initiate the spontaneous behavioral seizures. These findings raise doubts about dentate granule cells as a source of spontaneous seizures in rats subjected to prolonged SE and suggest that dentate gyrus neuron loss and mossy fiber sprouting are not primary epileptogenic mechanisms in this animal model.
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Affiliation(s)
- Brian D Harvey
- Department of Pharmacology, University of Arizona College of Medicine, Tucson, Arizona 85724, USA
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Tolner EA, van Vliet EA, Holtmaat AJGD, Aronica E, Witter MP, da Silva FHL, Gorter JA. GAP-43 mRNA and protein expression in the hippocampal and parahippocampal region during the course of epileptogenesis in rats. Eur J Neurosci 2003; 17:2369-80. [PMID: 12814368 DOI: 10.1046/j.1460-9568.2003.02687.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In order to reveal axonal rewiring in the hippocampal and parahippocampal regions after status epilepticus, we investigated the temporal evolution of growth-associated protein-43 (GAP-43) mRNA and protein expression in two rat models of mesial temporal lobe epilepsy (MTLE). Status epilepticus (SE) was induced by electrical stimulation of the angular bundle or by intraperitoneal kainic acid (KA) injections. Despite increased GAP-43 mRNA expression in dentate granule cells at 24 h after SE, GAP-43 protein expression in the inner molecular layer (IML) of the dentate gyrus decreased progressively after 24 h after SE in both models. Nevertheless robust mossy fiber sprouting (MFS) was evident in the IML of chronic epileptic rats. Remaining GAP-43 protein expression in the IML in chronic epileptic rats did not correlate with the extent of MFS, but with the number of surviving hilar neurons. In the parahippocampal region, GAP-43 mRNA expression was decreased in layer III of the medial entorhinal area (MEAIII) in parallel with extensive neuronal loss in this layer. There was a tendency of GAP-43 mRNA up-regulation in the presubiculum, a region that projects to MEAIII. With regard to this parahippocampal region, however, changes in GAP-43 mRNA expression were not followed by protein changes. The presence of the presynaptic protein GAP-43 in a neurodegenerated MEAIII indicates that fibers still project to this layer. Whether reorganization of fibers has occurred in this region after SE needs to be investigated with tools other than GAP-43.
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Affiliation(s)
- Else A Tolner
- Swammerdam Institute of Life Sciences, Section of Neurobiology, University of Amsterdam, Graduate School of Neurosciences Amsterdam, 1098 SM, Amsterdam, The Netherlands
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