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Petralia RS, Wang YX, Mattson MP, Yao PJ. The Diversity of Spine Synapses in Animals. Neuromolecular Med 2016; 18:497-539. [PMID: 27230661 PMCID: PMC5158183 DOI: 10.1007/s12017-016-8405-y] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2016] [Accepted: 05/11/2016] [Indexed: 12/23/2022]
Abstract
Here we examine the structure of the various types of spine synapses throughout the animal kingdom. Based on available evidence, we suggest that there are two major categories of spine synapses: invaginating and non-invaginating, with distributions that vary among different groups of animals. In the simplest living animals with definitive nerve cells and synapses, the cnidarians and ctenophores, most chemical synapses do not form spine synapses. But some cnidarians have invaginating spine synapses, especially in photoreceptor terminals of motile cnidarians with highly complex visual organs, and also in some mainly sessile cnidarians with rapid prey capture reflexes. This association of invaginating spine synapses with complex sensory inputs is retained in the evolution of higher animals in photoreceptor terminals and some mechanoreceptor synapses. In contrast to invaginating spine synapse, non-invaginating spine synapses have been described only in animals with bilateral symmetry, heads and brains, associated with greater complexity in neural connections. This is apparent already in the simplest bilaterians, the flatworms, which can have well-developed non-invaginating spine synapses in some cases. Non-invaginating spine synapses diversify in higher animal groups. We also discuss the functional advantages of having synapses on spines and more specifically, on invaginating spines. And finally we discuss pathologies associated with spine synapses, concentrating on those systems and diseases where invaginating spine synapses are involved.
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Affiliation(s)
- Ronald S Petralia
- Advanced Imaging Core, NIDCD/NIH, 35A Center Drive, Room 1E614, Bethesda, MD, 20892-3729, USA.
| | - Ya-Xian Wang
- Advanced Imaging Core, NIDCD/NIH, 35A Center Drive, Room 1E614, Bethesda, MD, 20892-3729, USA
| | - Mark P Mattson
- Laboratory of Neurosciences, National Institute on Aging Intramural Research Program, Baltimore, MD, 21224, USA
| | - Pamela J Yao
- Laboratory of Neurosciences, National Institute on Aging Intramural Research Program, Baltimore, MD, 21224, USA
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2
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Orain D, Tasdelen E, Haessig S, Koller M, Picard A, Dubois C, Lingenhoehl K, Desrayaud S, Floersheim P, Carcache D, Urwyler S, Kallen J, Mattes H. Design and Synthesis of Selurampanel, a Novel Orally Active and Competitive AMPA Receptor Antagonist. ChemMedChem 2016; 12:197-201. [DOI: 10.1002/cmdc.201600467] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2016] [Revised: 10/24/2016] [Indexed: 11/11/2022]
Affiliation(s)
- David Orain
- Global Discovery Chemistry; Novartis Institute for Biomedical Research; 4002 Basel Switzerland
| | - Engin Tasdelen
- Global Discovery Chemistry; Novartis Institute for Biomedical Research; 4002 Basel Switzerland
| | - Samuel Haessig
- Global Discovery Chemistry; Novartis Institute for Biomedical Research; 4002 Basel Switzerland
| | - Manuel Koller
- Global Discovery Chemistry; Novartis Institute for Biomedical Research; 4002 Basel Switzerland
| | - Anne Picard
- Global Discovery Chemistry; Novartis Institute for Biomedical Research; 4002 Basel Switzerland
| | - Celine Dubois
- Global Discovery Chemistry; Novartis Institute for Biomedical Research; 4002 Basel Switzerland
| | - Kurt Lingenhoehl
- Previously: Neuroscience Disease Area; Novartis Institute for Biomedical Research; 4002 Basel Switzerland
| | - Sandrine Desrayaud
- Metabolism and Pharmacokinetics; Novartis Institute for Biomedical Research; 4002 Basel Switzerland
| | - Phillip Floersheim
- Global Discovery Chemistry; Novartis Institute for Biomedical Research; 4002 Basel Switzerland
| | - David Carcache
- Global Discovery Chemistry; Novartis Institute for Biomedical Research; 4002 Basel Switzerland
| | - Stephan Urwyler
- Previously: Neuroscience Disease Area; Novartis Institute for Biomedical Research; 4002 Basel Switzerland
| | - Joerg Kallen
- Center for Proteomic Chemistry; Novartis Institute for Biomedical Research; 4002 Basel Switzerland
| | - Henri Mattes
- Global Discovery Chemistry; Novartis Institute for Biomedical Research; 4002 Basel Switzerland
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3
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Rogawski MA, Löscher W, Rho JM. Mechanisms of Action of Antiseizure Drugs and the Ketogenic Diet. Cold Spring Harb Perspect Med 2016; 6:a022780. [PMID: 26801895 PMCID: PMC4852797 DOI: 10.1101/cshperspect.a022780] [Citation(s) in RCA: 175] [Impact Index Per Article: 21.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Antiseizure drugs (ASDs), also termed antiepileptic drugs, are the main form of symptomatic treatment for people with epilepsy, but not all patients become free of seizures. The ketogenic diet is one treatment option for drug-resistant patients. Both types of therapy exert their clinical effects through interactions with one or more of a diverse set of molecular targets in the brain. ASDs act by modulation of voltage-gated ion channels, including sodium, calcium, and potassium channels; by enhancement of γ-aminobutyric acid (GABA)-mediated inhibition through effects on GABAA receptors, the GABA transporter 1 (GAT1) GABA uptake transporter, or GABA transaminase; through interactions with elements of the synaptic release machinery, including synaptic vesicle 2A (SV2A) and α2δ; or by blockade of ionotropic glutamate receptors, including α-amino-3-hydroxy-5-methyl-4-isoxazole-propionate (AMPA) receptors. The ketogenic diet leads to increases in circulating ketones, which may contribute to the efficacy in treating pharmacoresistant seizures. Production in the brain of inhibitory mediators, such as adenosine, or ion channel modulators, such as polyunsaturated fatty acids, may also play a role. Metabolic effects, including diversion from glycolysis, are a further postulated mechanism. For some ASDs and the ketogenic diet, effects on multiple targets may contribute to activity. Better understanding of the ketogenic diet will inform the development of improved drug therapies to treat refractory seizures.
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Affiliation(s)
- Michael A Rogawski
- Department of Neurology, University of California, Davis, Sacramento, California 95817
| | - Wolfgang Löscher
- Department of Pharmacology, Toxicology, and Pharmacy, University of Veterinary Medicine, Hannover, Germany
| | - Jong M Rho
- Department of Pediatrics, University of Calgary, Calgary, Alberta, Canada Department of Clinical Neurosciences, University of Calgary, Calgary, Alberta, Canada Department of Physiology and Pharmacology, University of Calgary, Alberta, Canada
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4
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Mano Y, Takenaka O, Kusano K. HPLC with fluorescence detection assay of perampanel, a novel AMPA receptor antagonist, in human plasma for clinical pharmacokinetic studies. Biomed Chromatogr 2015; 29:1589-93. [DOI: 10.1002/bmc.3463] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2014] [Revised: 01/27/2015] [Accepted: 02/23/2015] [Indexed: 11/06/2022]
Affiliation(s)
- Yuji Mano
- Drug Metabolism and Pharmacokinetics; Biopharmaceutical Assessment Core Function Unit, Eisai Co. Ltd; Ibaraki Japan
| | - Osamu Takenaka
- Drug Metabolism and Pharmacokinetics; Biopharmaceutical Assessment Core Function Unit, Eisai Co. Ltd; Ibaraki Japan
| | - Kazutomi Kusano
- Drug Metabolism and Pharmacokinetics; Biopharmaceutical Assessment Core Function Unit, Eisai Co. Ltd; Ibaraki Japan
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5
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Mano Y, Takenaka O, Kusano K. High-performance liquid chromatography-tandem mass spectrometry method for the determination of perampanel, a novel α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor antagonist in human plasma. J Pharm Biomed Anal 2014; 107:56-62. [PMID: 25569285 DOI: 10.1016/j.jpba.2014.12.018] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2014] [Revised: 12/11/2014] [Accepted: 12/12/2014] [Indexed: 11/19/2022]
Abstract
Perampanel (Fycompa(®)) is a novel α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor antagonist registered for the adjunctive treatment of patients (≥12 years) with refractory partial onset seizures. In order to support clinical trials, as well as therapeutic drug monitoring, a sensitive bioanalytical method for the determination of perampanel concentrations in human plasma was established and validated using liquid chromatography with tandem mass spectrometry. Perampanel and an internal standard were extracted from human plasma (100 μL) by liquid extraction using methyl t-butyl ether, then evaporated and reconstituted. The chromatographic separation was conducted on a C8 column with isocratic elution at a flow rate of 0.2 mL/min. The established method showed linearity in the range 0.25-200 ng/mL with correlation coefficients of >0.99 that could be extended 10-fold as validated by dilution integrity analyses. No significant endogenous peaks were detected in the elution of analytes in blank human plasma and no significant matrix effect was observed. The intra- and inter-batch reproducibility analyses demonstrated accuracy and precision within the acceptance criteria. To check the impact of anti-epileptic drugs on the perampanel assay, accuracy, precision, and specificity were assessed in the presence of 14 anti-epileptic drugs. No anti-epileptic drugs at clinically relevant levels showed a significant impact on the perampanel assay.
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Affiliation(s)
- Yuji Mano
- Drug Metabolism and Pharmacokinetics, Biopharmaceutical Assessment Core Function Unit, Eisai Co., Ltd., 1-3, 5-chome, Tokodai, Tsukuba-shi, Ibaraki 300-2635, Japan.
| | - Osamu Takenaka
- Drug Metabolism and Pharmacokinetics, Biopharmaceutical Assessment Core Function Unit, Eisai Co., Ltd., 1-3, 5-chome, Tokodai, Tsukuba-shi, Ibaraki 300-2635, Japan
| | - Kazutomi Kusano
- Drug Metabolism and Pharmacokinetics, Biopharmaceutical Assessment Core Function Unit, Eisai Co., Ltd., 1-3, 5-chome, Tokodai, Tsukuba-shi, Ibaraki 300-2635, Japan
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6
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Hanada T. The discovery and development of perampanel for the treatment of epilepsy. Expert Opin Drug Discov 2014; 9:449-58. [DOI: 10.1517/17460441.2014.891580] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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Are alterations in transmitter receptor and ion channel expression responsible for epilepsies? ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2014; 813:211-29. [PMID: 25012379 DOI: 10.1007/978-94-017-8914-1_17] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Neuronal voltage-gated ion channels and ligand-gated synaptic receptors play a critical role in maintaining the delicate balance between neuronal excitation and inhibition within neuronal networks in the brain. Changes in expression of voltage-gated ion channels, in particular sodium, hyperpolarization-activated cyclic nucleotide-gated (HCN) and calcium channels, and ligand-gated synaptic receptors, in particular GABA and glutamate receptors, have been reported in many types of both genetic and acquired epilepsies, in animal models and in humans. In this chapter we review these and discuss the potential pathogenic role they may play in the epilepsies.
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Hubbard JA, Hsu MS, Fiacco TA, Binder DK. Glial cell changes in epilepsy: Overview of the clinical problem and therapeutic opportunities. Neurochem Int 2013; 63:638-51. [DOI: 10.1016/j.neuint.2013.01.017] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2012] [Revised: 01/14/2013] [Accepted: 01/18/2013] [Indexed: 12/20/2022]
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9
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Eid T, Tu N, Lee TSW, Lai JCK. Regulation of astrocyte glutamine synthetase in epilepsy. Neurochem Int 2013; 63:670-81. [PMID: 23791709 DOI: 10.1016/j.neuint.2013.06.008] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2012] [Revised: 05/28/2013] [Accepted: 06/08/2013] [Indexed: 11/20/2022]
Abstract
Astrocytes play a crucial role in regulating and maintaining the extracellular chemical milieu of the central nervous system under physiological conditions. Moreover, proliferation of phenotypically altered astrocytes (a.k.a. reactive astrogliosis) has been associated with many neurologic and psychiatric disorders, including mesial temporal lobe epilepsy (MTLE). Glutamine synthetase (GS), which is found in astrocytes, is the only enzyme known to date that is capable of converting glutamate and ammonia to glutamine in the mammalian brain. This reaction is important, because a continuous supply of glutamine is necessary for the synthesis of glutamate and GABA in neurons. The known stoichiometry of glutamate transport across the astrocyte plasma membrane also suggests that rapid metabolism of intracellular glutamate via GS is a prerequisite for efficient glutamate clearance from the extracellular space. Several studies have indicated that the activity of GS in astrocytes is diminished in several brain disorders, including MTLE. It has been hypothesized that the loss of GS activity in MTLE leads to increased extracellular glutamate concentrations and epileptic seizures. Understanding the mechanisms by which GS is regulated may lead to novel therapeutic approaches to MTLE, which is frequently refractory to antiepileptic drugs. This review discusses several known mechanisms by which GS expression and function are influenced, from transcriptional control to enzyme modification.
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Affiliation(s)
- Tore Eid
- Department of Laboratory Medicine, Yale University School of Medicine, New Haven, CT 06520, United States.
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10
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Seress L, Abrahám H, Horváth Z, Dóczi T, Janszky J, Klemm J, Byrne R, Bakay RAE. Survival of mossy cells of the hippocampal dentate gyrus in humans with mesial temporal lobe epilepsy. J Neurosurg 2010; 111:1237-47. [PMID: 19392605 DOI: 10.3171/2008.11.jns08779] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
OBJECT Hippocampal sclerosis can be identified in most patients with mesial temporal lobe epilepsy (TLE). Surgical removal of the sclerotic hippocampus is widely performed to treat patients with drug-resistant mesial TLE. In general, both epilepsy-prone and epilepsy-resistant neurons are believed to be in the hippocampal formation. The hilar mossy cells of the hippocampal dentate gyrus are usually considered one of the most vulnerable types of neurons. The aim of this study was to clarify the fate of mossy cells in the hippocampus in epileptic humans. METHODS Of the 19 patients included in this study, 15 underwent temporal lobe resection because of drug-resistant TLE. Four patients were used as controls because they harbored tumors that had not invaded the hippocampus and they had experienced no seizures. Histological evaluation of resected hippocampal tissues was performed using immunohistochemistry. RESULTS Mossy cells were identified in the control as well as the epileptic hippocampi by using cocaine- and amphetamine-regulated transcript peptide immunohistochemistry. In most cases the number of mossy cells was reduced and thorny excrescences were smaller in the epileptic hippocampi than in controls; however, there was a significant loss of pyramidal cells and a partial loss of granule cells in the same epileptic hippocampi in which mossy cell loss was apparent. The loss of mossy cells could be correlated with the extent of hippocampal sclerosis, patient age at seizure onset, duration of epilepsy, and frequency of seizures. CONCLUSIONS In many cases large numbers of mossy cells were present in the hilus of the dentate gyrus when most pyramidal neurons of the CA1 and CA3 areas of the Ammon's horn were lost, suggesting that mossy cells may not be more vulnerable to epileptic seizures than the hippocampal pyramidal neurons.
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Affiliation(s)
- László Seress
- Central Electron Microscopic Laboratory University of Pécs, Hungary
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11
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Abraham WC. Metaplasticity: tuning synapses and networks for plasticity. Nat Rev Neurosci 2008; 9:387. [PMID: 18401345 DOI: 10.1038/nrn2356] [Citation(s) in RCA: 669] [Impact Index Per Article: 41.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Synaptic plasticity is a key component of the learning machinery in the brain. It is vital that such plasticity be tightly regulated so that it occurs to the proper extent at the proper time. Activity-dependent mechanisms that have been collectively termed metaplasticity have evolved to help implement these essential computational constraints. Various intercellular signalling molecules can trigger lasting changes in the ability of synapses to express plasticity; their mechanisms of action are reviewed here, along with a consideration of how metaplasticity might affect learning and clinical conditions.
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Affiliation(s)
- Wickliffe C Abraham
- Department of Psychology and the Brain Health and Repair Research Centre, University of Otago, BOX 56, Dunedin, 9054, New Zealand.
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12
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Eid T, Hammer J, Rundén-Pran E, Roberg B, Thomas MJ, Osen K, Davanger S, Laake P, Torgner IA, Lee TSW, Kim JH, Spencer DD, Ottersen OP, de Lanerolle NC. Increased expression of phosphate-activated glutaminase in hippocampal neurons in human mesial temporal lobe epilepsy. Acta Neuropathol 2007; 113:137-52. [PMID: 17115168 DOI: 10.1007/s00401-006-0158-5] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2006] [Revised: 10/06/2006] [Accepted: 10/07/2006] [Indexed: 11/25/2022]
Abstract
Patients with mesial temporal lobe epilepsy (MTLE) have increased basal concentrations of extracellular glutamate in the epileptogenic versus the non-epileptogenic hippocampus. Such elevated glutamate levels have been proposed to underlie the initiation and maintenance of recurrent seizures, and a key question is what causes the elevation of glutamate in MTLE. Here, we explore the possibility that neurons in the hippocampal formation contain higher levels of the glutamate synthesizing enzyme phosphate-activated glutaminase (PAG) in patients with MTLE versus patients with other forms of temporal lobe epilepsy (non-MTLE). Increased PAG immunoreactivity was recorded in subpopulations of surviving neurons in the MTLE hippocampal formation, particularly in CA1 and CA3 and in the polymorphic layer of the dentate gyrus. Immunogold analysis revealed that PAG was concentrated in mitochondria. Double-labeling experiments indicated a positive correlation between the mitochondrial contents of PAG protein and glutamate, as well as between PAG enzyme activity and PAG protein as determined by Western blots. These data suggest that the antibodies recognize an enzymatically active pool of PAG. Western blots and enzyme activity assays of hippocampal homogenates revealed no change in PAG between MTLE and non-MTLE, despite a greatly (>50%) reduced number of neurons in the MTLE hippocampal formation compared to non-MTLE. Thus, the MTLE hippocampal formation contains an increased concentration and activity of PAG per neuron compared to non-MTLE. This increase suggests an enhanced capacity for glutamate synthesis-a finding that might contribute to the disrupted glutamate homeostasis in MTLE.
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Affiliation(s)
- Tore Eid
- Department of Neurosurgery, Yale University School of Medicine, 333 Cedar Street, P.O. Box 208082, New Haven, CT 06520-8082, USA.
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13
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Gylterud Owe S, Bogen IL, Walaas SI, Storm-Mathisen J, Bergersen LH. Ultrastructural quantification of glutamate receptors at excitatory synapses in hippocampus of synapsin I+II double knock-out mice. Neuroscience 2006; 136:769-77. [PMID: 16344150 DOI: 10.1016/j.neuroscience.2005.08.056] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2005] [Revised: 08/19/2005] [Accepted: 08/27/2005] [Indexed: 10/25/2022]
Abstract
Previous findings, mainly in in vitro systems, have shown that the density of vesicles and the synaptic efficacy at excitatory synapses are reduced in the absence of synapsins, despite the fact that transgenic mice lacking synapsins develop an epileptic phenotype. Here we study glutamate receptors by quantitative immunoblotting and by quantitative electron microscopic postembedding immunocytochemistry in hippocampus of perfusion fixed control wild type and double knock-out mice lacking synapsins I and II. In wild type hippocampus the densities of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor subunits were higher (indicated for glutamate receptor subunit 1, highly significant for glutamate receptor subunits 2/3) in mossy fiber-to-cornu ammonis 3 pyramidal cell synapses than in the Schaffer collateral/commissural-to-cornu ammonis 1 pyramidal cell synapses, the two synapse categories that carry the main excitatory throughput of the hippocampus. The opposite was true for N-methyl-D-aspartate receptors. The difference in localization of glutamate receptor subunit 1 receptor subunits was increased in the double knock-out mice while there was no change in the overall expression of the glutamate receptors in hippocampus as shown by quantitative Western blotting. The increased level of glutamate receptor subunit 1 at the mossy fiber-to-cornu ammonis 3 pyramidal cell synapse may result in alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors with reduced proportions of glutamate receptor subunit 2, and hence increased Ca2+ influx, which could cause increased excitability despite of impaired synaptic function (cf. [Krestel HE, Shimshek DR, Jensen V, Nevian T, Kim J, Geng Y, Bast T, Depaulis A, Schonig K, Schwenk F, Bujard H, Hvalby O, Sprengel R, Seeburg PH (2004) A genetic switch for epilepsy in adult mice. J Neurosci 24:10568-10578]), possibly underlying the seizure proneness in the synapsin double knock-out mice. In addition, the tendency to increased predominance of N-methyl-d-aspartate receptors at the main type of excitatory synapse onto cornu ammonis 1 pyramidal cells might contribute to the seizure susceptibility of the synapsin deficient mice. The results showed no significant changes in the proportion of 'silent' Schaffer collateral/commissural synapses lacking alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors or in the synaptic membrane size, indicating that plasticity involving these parameters is not preferentially triggered due to lack of synapsins.
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Affiliation(s)
- S Gylterud Owe
- Department of Anatomy and Centre for Molecular Biology and Neuroscience CMBN, University of Oslo, P.O. Box 1105 Blindern, N0317 Oslo, Norway
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14
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Gorji A, Straub H, Speckmann EJ. Epilepsy surgery: perioperative investigations of intractable epilepsy. ACTA ACUST UNITED AC 2006; 210:525-37. [PMID: 16180018 DOI: 10.1007/s00429-005-0043-3] [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] [Indexed: 10/25/2022]
Abstract
Recent advances in our understanding of the basic mechanisms of epilepsy have derived, to a large extent, from increasing ability to carry out detailed studies on patients surgically treated for intractable epilepsy. Clinical and experimental perioperative studies divide into three different phases: before the surgical intervention (preoperative studies), on the intervention itself (intraoperative studies), and on the period when the part of the brain that has to be removed is available for further investigations (postoperative studies). Before surgery, both structural and functional neuroimaging techniques, in addition to their diagnostic roles, could be used to investigate the pathophysiological mechanisms of seizure attacks in epileptic patients. During epilepsy surgery, it is possible to insert microdialysis catheters and electroencephalogram electrodes into the brain tissues in order to measure constituents of extracellular fluid and record the bioelectrical activity. Subsequent surgical resection provides tissue that can be used for electrophysiological, morphological, and molecular biological investigations. To take full advantage of these opportunities, carefully designed experimental protocols are necessary to compare the data from different phases and characterize abnormalities in the human epileptic brain.
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Affiliation(s)
- A Gorji
- Institut für Physiologie I, Universität Münster, Robert-Koch-Strasse 27a, 48149 Münster, Germany.
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15
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Thiagarajan TC, Lindskog M, Tsien RW. Adaptation to synaptic inactivity in hippocampal neurons. Neuron 2005; 47:725-37. [PMID: 16129401 DOI: 10.1016/j.neuron.2005.06.037] [Citation(s) in RCA: 386] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2005] [Revised: 06/17/2005] [Accepted: 06/28/2005] [Indexed: 11/16/2022]
Abstract
In response to activity deprivation, CNS neurons undergo slow adaptive modification of unitary synaptic transmission. The changes are comparable in degree to those induced by brief intense stimulation, but their molecular basis is largely unknown. Our data indicate that prolonged AMPAR blockade acts through loss of Ca2+ entry through L-type Ca2+ channels to bring about an increase in both vesicle pool size and turnover rate, as well as a postsynaptic enhancement of the contribution of GluR1 homomers, concentrated at the largest synapses. The changes were consistent with a morphological scaling of overall synapse size, but also featured a dramatic shift toward synaptic drive contributed by the Ca2+-permeable homomeric GluR1 receptors. These results extend beyond "synaptic homeostasis" to involve more profound changes that can be better described as "metaplasticity".
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MESH Headings
- Adaptation, Physiological/drug effects
- Adaptation, Physiological/physiology
- Animals
- Blotting, Western
- Calcium Channel Blockers/pharmacology
- Calcium Channels, L-Type/drug effects
- Calcium Channels, L-Type/metabolism
- Calcium Signaling/drug effects
- Calcium Signaling/physiology
- Cells, Cultured
- Electrophysiology
- Excitatory Postsynaptic Potentials/physiology
- Hippocampus/cytology
- Hippocampus/drug effects
- Hippocampus/physiology
- Homeostasis/drug effects
- Homeostasis/physiology
- Immunohistochemistry
- Neuronal Plasticity/physiology
- Neurons/drug effects
- Neurons/physiology
- Patch-Clamp Techniques
- Polyamines/pharmacology
- Pyramidal Cells/drug effects
- Pyramidal Cells/physiology
- Rats
- Receptors, AMPA/antagonists & inhibitors
- Receptors, AMPA/metabolism
- Receptors, Presynaptic/drug effects
- Receptors, Presynaptic/physiology
- Synapses/drug effects
- Synapses/physiology
- Transfection
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Affiliation(s)
- Tara C Thiagarajan
- Department of Molecular and Cellular Physiology, Beckman Center, Stanford University School of Medicine, Stanford, California 94305, USA
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16
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de Lanerolle NC, Lee TS. New facets of the neuropathology and molecular profile of human temporal lobe epilepsy. Epilepsy Behav 2005; 7:190-203. [PMID: 16098816 DOI: 10.1016/j.yebeh.2005.06.003] [Citation(s) in RCA: 110] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/27/2005] [Accepted: 06/01/2005] [Indexed: 11/27/2022]
Abstract
This review summarizes the salient features of the anatomical and molecular neuropathology of the hippocampus from patients with intractable temporal lobe epilepsy (TLE). It argues that sclerotic hippocampus is essential for seizure expression and that sclerosis is not a consequence of seizures, but is related to the epileptogenicity of the seizure focus. While neurons in sclerotic hippocampus may contribute to hippocampal hyperexcitability, this role is perhaps less important than that of the astrocytes. The astrocytes in sclerotic hippocampus may directly influence excitability through altered water homeostasis and K+ buffering by redistribution of AQP4 transporters on their plasma membrane. It is proposed that they contribute to a high extracellular glutamate level through reduced glutamine synthetase, and activation through pro-inflammatory factors that release chemokines and cytokines, which enhance calcium-dependent glutamate release. Such a focal pool of glutamate may diffuse to surrounding neuron-rich areas to generate seizure activity in TLE.
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Affiliation(s)
- Nihal C de Lanerolle
- Department of Neurosurgery, Yale University School of Medicine, New Haven, CT 06520, USA.
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17
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Tang FR, Chia SC, Zhang S, Chen PM, Gao H, Liu CP, Khanna S, Lee WL. Glutamate receptor 1-immunopositive neurons in the gliotic CA1 area of the mouse hippocampus after pilocarpine-induced status epilepticus. Eur J Neurosci 2005; 21:2361-74. [PMID: 15932595 DOI: 10.1111/j.1460-9568.2005.04071.x] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Significant reduction in glutamate receptor 1 (GluR1)- and GluR2/3-immunopositive neurons was demonstrated in the hilus of the dentate gyrus in mice killed on days 1, 7 and 60 after pilocarpine-induced status epilepticus (PISE). In addition, GluR1 and GluR2/3 immunostaining in the strata oriens, radiatum and lacunosum moleculare of areas CA1-3 decreased drastically on days 7 and 60 after PISE. Neuronal loss observed in the above regions may account, at least in part, for a decrease in GluR immunoreactivity. By contrast, many GluR1-immunopositive neurons were observed in the gliotic area of CA1. Of these, about 42.8% were immunopositive for markers for hippocampal interneurons, namely calretinin (7.6%), calbindin (12.8%) and parvalbumin (22.4%). GluR1 or GluR2/3 and BrdU double-labelling showed that the GluR1- and GluR2/3-immunopositive neurons at 60 days after PISE were neurons that had survived rather than newly generated neurons. Furthermore, anterograde tracer and double-labelling studies performed on animals at 60 days after PISE indicated a projection from the hilus of the dentate gyrus to gliotic areas in both CA3 and CA1, where the projecting fibres apparently established connections with GluR1-immunopositive neurons. The projection to CA1 was unexpected. These novel findings suggest that the intrinsic hippocampal neuronal network is altered after PISE. We speculate that GluR1-immunopositive neurons in gliotic CA1 act as a bridge between dentate gyrus and subiculum contributing towards epileptogenesis.
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Affiliation(s)
- Feng Ru Tang
- Epilepsy Research Laboratory, National Neuroscience Institute, 11 Jalan Tan Tock Seng, Singapore 308433.
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Fornai F, Busceti CL, Kondratyev A, Gale K. AMPA receptor desensitization as a determinant of vulnerability to focally evoked status epilepticus. Eur J Neurosci 2005; 21:455-63. [PMID: 15673444 DOI: 10.1111/j.1460-9568.2005.03873.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Within the area tempestas (AT) in the anterior piriform cortex, unilateral microinfusions of GABA receptor antagonists and glutamate receptor agonists trigger brief episodic limbic seizures. In the present study, we document a synergistic effect of coinfusing bicuculline (GABAA receptor antagonist) with either carbachol (muscarinic receptor agonist) or cyclothiazide (inhibitor of AMPA receptor desensitization) but not with glutamate receptor agonists (AMPA, NMDA or kainate) in the rat AT. In particular, coadministration of bicuculline (118 pmol) with either carbachol (328 pmol) or cyclothiazide (1.2 nmol) triggered continuous self-sustaining seizures (status epilepticus; SE). Cyclothiazide alone did not evoke seizures. Although blockade of NMDA receptors with AP-7 (100 or 500 pmol) prevented episodic seizures evoked by carbachol or bicuculline alone, it was without effect on the continuous seizures evoked by combined treatments. NMDA-insensitive self-sustaining seizures were also evoked by the combination of AMPA and cyclothiazide. Regardless of the mechanism by which SE was evoked, it was prevented only by an AMPA receptor antagonist, NBQX, thus reinforcing the crucial role of AMPA receptors in the transition to SE. Further evidence for AMPA receptor regulation of seizure severity came from the overexpression of the GluR1 AMPA receptor subunit in AT. This resulted in substantially increased severity of bicuculline-evoked seizures that was reversed by focal application of NBQX. Thus, desensitization of AMPA receptors appears to limit the duration and severity of seizure activity, and a failure of this mechanism, or an overabundance of slowly desensitizing AMPA receptors, predisposes to severe and prolonged seizures.
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Affiliation(s)
- Francesco Fornai
- Department of Pharmacology, W215 Research Bldg, 3970 Reservoir Road NW, Georgetown University, Washington, DC 20057, USA
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Bausch SB, McNamara JO. Contributions of Mossy Fiber and CA1 Pyramidal Cell Sprouting to Dentate Granule Cell Hyperexcitability in Kainic Acid–Treated Hippocampal Slice Cultures. J Neurophysiol 2004; 92:3582-95. [PMID: 15269228 DOI: 10.1152/jn.01028.2003] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Axonal sprouting like that of the mossy fibers is commonly associated with temporal lobe epilepsy, but its significance remains uncertain. To investigate the functional consequences of sprouting of mossy fibers and alternative pathways, kainic acid (KA) was used to induce robust mossy fiber sprouting in hippocampal slice cultures. Physiological comparisons documented many similarities in granule cell responses between KA- and vehicle-treated cultures, including: seizures, epileptiform bursts, and spontaneous excitatoty postsynaptic currents (sEPSCs) >600pA. GABAergic control and contribution of glutamatergic synaptic transmission were similar. Analyses of neurobiotin-filled CA1 pyramidal cells revealed robust axonal sprouting in both vehicle- and KA-treated cultures, which was significantly greater in KA-treated cultures. Hilar stimulation evoked an antidromic population spike followed by variable numbers of postsynaptic potentials (PSPs) and population spikes in both vehicle- and KA-treated cultures. Despite robust mossy fiber sprouting, knife cuts separating CA1 from dentate gyrus virtually abolished EPSPs evoked by hilar stimulation in KA-treated but not vehicle-treated cultures, suggesting a pivotal role of functional afferents from CA1 to dentate gyrus in KA-treated cultures. Together, these findings demonstrate striking hyperexcitability of dentate granule cells in long-term hippocampal slice cultures after treatment with either vehicle or KA. The contribution to hilar-evoked hyperexcitability of granule cells by the unexpected axonal projection from CA1 to dentate in KA-treated cultures reinforces the idea that axonal sprouting may contribute to pathologic hyperexcitability of granule cells.
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Affiliation(s)
- Suzanne B Bausch
- Department of Medicine, Duke University Medical Center, Durham, North Carolina 27710, USA
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Seress L, Abrahám H, Dóczi T, Lázár G, Kozicz T. Cocaine- and amphetamine-regulated transcript peptide (CART) is a selective marker of rat granule cells and of human mossy cells in the hippocampal dentate gyrus. Neuroscience 2004; 125:13-24. [PMID: 15051141 DOI: 10.1016/j.neuroscience.2003.12.035] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/11/2003] [Indexed: 11/16/2022]
Abstract
Cocaine- and amphetamine-regulated transcript (CART) peptide immunocytochemistry was used to reveal cellular localization in the dentate gyrus and in Ammon's horn of the rat and human hippocampal formations. In the rat dentate gyrus, only granule cells were labeled, whereas in humans, only mossy cells of the hilar region expressed CART peptide immunoreactivity. In the rat, CART-positive granule cells were located at the molecular layer border of the granule cell layer and had no features that would distinguish them from other granule cells. The mossy fiber bundle was labeled in the hilus as well as along the entire CA3 area of Ammon's horn. In the human, CART-immunoreactive mossy cells displayed the characteristic thorny excrescences both on their somata and their main dendrites. Axon collaterals of mossy cells could be seen in the hilus and the main axons formed a dense band in the inner molecular layer of the dentate gyrus, suggesting that mossy cells are the principal source of the associational pathway. Granule cells of the dentate gyrus and pyramidal neurons of the human hippocampal formation were devoid of CART peptide immunoreactivity. A few labeled non-pyramidal cells and a large group of strongly immunostained axons of unknown origin were present in all layers of CA1-3. Granule cells are the main excitatory cell population of the dentate gyrus while mossy cells are in a key position in controlling activity of granule cells. The specific location of CART peptide in the dentate granule cells of rodents and in the mossy cells of the human hippocampus may indicate involvement of neuronal circuitry of the dentate gyrus in the memory-related effects of cocaine and amphetamine. Independently of its functional role, CART peptide can be used as a specific marker of human mossy cells and of the dentate associational pathway. The sensitivity of CART peptide to postmortem autolysis may restrict the use of this marker in surgically removed hippocampi or in human brains removed and fixed shortly after death.
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Affiliation(s)
- L Seress
- Central Electron Microscopic Laboratory, Faculty of Medicine, University of Pécs, 7643 Pécs, Szigeti u. 12, Hungary.
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Seifert G, Hüttmann K, Schramm J, Steinhäuser C. Enhanced relative expression of glutamate receptor 1 flip AMPA receptor subunits in hippocampal astrocytes of epilepsy patients with Ammon's horn sclerosis. J Neurosci 2004; 24:1996-2003. [PMID: 14985442 PMCID: PMC6730392 DOI: 10.1523/jneurosci.3904-03.2004] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Astrocytes express ionotropic glutamate receptors (GluRs), and recent evidence suggests that these receptors contribute to direct signaling between neurons and glial cells in vivo. Here, we have used functional and molecular analyses to investigate receptor properties in astrocytes of human hippocampus resected from patients with pharmacoresistant temporal lobe epilepsy (TLE). Histopathological analysis allowed us to distinguish two forms of epilepsy: Ammon's horn sclerosis (AHS) and lesion-associated TLE. Human hippocampal astrocytes selectively expressed the AMPA subtype of ionotropic glutamate receptors. Single-cell RT-PCR found preferential expression of the subunits GluR1 and GluR2 in human astrocytes, and the expression patterns were similar in patients with AHS and lesion-associated epilepsy. The AMPA receptor-specific modulators, cyclothiazide (CTZ) and 4-[2-(phenylsulfonylamino)ethylthio]-2,6-difluoro-phenoxyacetamide (PEPA), were used to investigate splice variant expression. Astrocytes of sclerotic specimens displayed a slower dissociation of CTZ from the receptor and a lower ratio of current potentiation by PEPA to potentiation by CTZ, suggesting enhanced expression of flip receptor variants in AHS versus lesion-associated epilepsy. Real-time PCR and restriction analysis substantiated this presumption by identifying elevated flip-to-flop mRNA ratios of GluR1 in single astrocytes of AHS specimens. These findings imply that in AHS, glutamate may lead to prolonged depolarization of astrocytes, thereby facilitating the generation or spread of seizure activity.
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Affiliation(s)
- Gerald Seifert
- Experimental Neurobiology, Department of Neurosurgery, University of Bonn, 53105 Bonn, Germany.
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Eid T, Brines ML, Cerami A, Spencer DD, Kim JH, Schweitzer JS, Ottersen OP, de Lanerolle NC. Increased expression of erythropoietin receptor on blood vessels in the human epileptogenic hippocampus with sclerosis. J Neuropathol Exp Neurol 2004; 63:73-83. [PMID: 14748563 DOI: 10.1093/jnen/63.1.73] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Microvascular (capillary) proliferation is a readily observed, but largely ignored phenomenon of the mesial temporal lobe epilepsy (MTLE) hippocampus. Here, we report that the proliferated capillaries in surgically resected MTLE hippocampi were strongly immunoreactive for erythropoietin receptor (EPO-r). Further, we found that these capillaries were most prominent in areas of the MTLE hippocampus with extensive neuronal loss and gliosis, i.e. the CA3, CA1, and dentate hilus. High-resolution immunogold electron microscopy revealed that the capillary EPO-r was localized to the luminal and abluminal plasma membrane of endothelial cells, to endosome-like structures of these cells, and to pericapillary astrocytic end-feet. Previous studies have shown that systemically administered EPO appears in the cerebrospinal fluid in experimental animals, and the present results are consistent with the idea that EPO enters the brain via receptor-mediated endocytosis. The enrichment of EPO-r shown here suggests a highly efficient uptake of plasma EPO into the MTLE hippocampus and a possible role for this cytokine in epileptogenesis. Moreover, the presence of EPO-r in the MTLE hippocampus may provide a new vehicle for highly efficient delivery of hitherto impermeable drugs into the epileptic brain.
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Affiliation(s)
- Tore Eid
- Department of Neurosurgery, Yale University School of Medicine, New Haven, Connecticut 06520-8082, USA.
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Straessle A, Loup F, Arabadzisz D, Ohning GV, Fritschy JM. Rapid and long-term alterations of hippocampal GABAB receptors in a mouse model of temporal lobe epilepsy. Eur J Neurosci 2003; 18:2213-26. [PMID: 14622182 DOI: 10.1046/j.1460-9568.2003.02964.x] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Alterations of gamma-aminobutyric acid (GABA)B receptor expression have been reported in human temporal lobe epilepsy (TLE). Here, changes in regional and cellular expression of the GABAB receptor subunits R1 (GBR1) and R2 (GBR2) were investigated in a mouse model that replicates major functional and histopathological features of TLE. Adult mice received a single, unilateral injection of kainic acid (KA) into the dorsal hippocampus, and GABAB receptor immunoreactivity was analysed between 1 day and 3 months thereafter. In control mice, GBR1 and GBR2 were distributed uniformly across the dendritic layers of CA1-CA3 and dentate gyrus. In addition, some interneurons were labelled selectively for GBR1. At 1 day post-KA, staining for both GBR1 and GBR2 was profoundly reduced in CA1, CA3c and the hilus, and no interneurons were visible anymore. At later stages, the loss of GABAB receptors persisted in CA1 and CA3, whereas staining increased gradually in dentate gyrus granule cells, which become dispersed in this model. Most strikingly, a subpopulation of strongly labelled interneurons reappeared, mainly in the hilus and CA3 starting at 1 week post-KA. In double-staining experiments, these cells were selectively labelled for neuropeptide Y. The number of GBR1-positive interneurons also increased contralaterally in the hilus. The rapid KA-induced loss of GABAB receptors might contribute to epileptogenesis because of a reduction in both presynaptic control of transmitter release and postsynaptic inhibition. In turn, the long-term increase in GABAB receptors in granule cells and specific subtypes of interneurons may represent a compensatory response to recurrent seizures.
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Affiliation(s)
- Andrea Straessle
- Institute of Pharmacology and Toxicology, University of Zurich, Switzerland
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