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Kitaura H, Shirozu H, Masuda H, Fukuda M, Fujii Y, Kakita A. Pathophysiological Characteristics Associated With Epileptogenesis in Human Hippocampal Sclerosis. EBioMedicine 2018; 29:38-46. [PMID: 29478873 PMCID: PMC5925580 DOI: 10.1016/j.ebiom.2018.02.013] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2017] [Revised: 02/07/2018] [Accepted: 02/15/2018] [Indexed: 12/29/2022] Open
Abstract
Mesial temporal lobe epilepsy (MTLE) is the most frequent focal epileptic syndrome in adults, and the majority of seizures originate primarily from the hippocampus. The resected hippocampal tissue often shows severe neuronal loss, a condition referred to as hippocampal sclerosis (HS). In order to understand hippocampal epileptogenesis in MTLE, it seems important to clarify any discrepancies between the clinical and pathological features of affected patients. Here we investigated epileptiform activities ex vivo using living hippocampal tissue taken from patients with MTLE. Flavoprotein fluorescence imaging and local field potential recordings revealed that epileptiform activities developed from the subiculum. Moreover, physiological and morphological experiments revealed possible impairment of K+ clearance in the subiculum affected by HS. Stimulation of mossy fibers induced recurrent trans-synaptic activity in the granule cell layer of the dentate gyrus, suggesting that mossy fiber sprouting in HS also contributes to the epileptogenic mechanism. These results indicate that pathophysiological alterations involving the subiculum and dentate gyrus could be responsible for epileptogenesis in patients with MTLE.
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Affiliation(s)
- Hiroki Kitaura
- Department of Pathology, Brain Research Institute, Niigata University, 1 Asahimachi, Chuo-ku, Niigata 951-8585, Japan.
| | - Hiroshi Shirozu
- Department of Neurosurgery, Nishi-Niigata Chuo National Hospital, 1 Masago, Nishi-ku, Niigata 950-2085, Japan
| | - Hiroshi Masuda
- Department of Neurosurgery, Nishi-Niigata Chuo National Hospital, 1 Masago, Nishi-ku, Niigata 950-2085, Japan
| | - Masafumi Fukuda
- Department of Neurosurgery, Nishi-Niigata Chuo National Hospital, 1 Masago, Nishi-ku, Niigata 950-2085, Japan
| | - Yukihiko Fujii
- Department of Neurosurgery, Brain Research Institute, Niigata University, 1 Asahimachi, Chuo-ku, Niigata 951-8585, Japan
| | - Akiyoshi Kakita
- Department of Pathology, Brain Research Institute, Niigata University, 1 Asahimachi, Chuo-ku, Niigata 951-8585, Japan
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Wang J, Bast T, Wang YC, Zhang WN. Hippocampus and two-way active avoidance conditioning: Contrasting effects of cytotoxic lesion and temporary inactivation. Hippocampus 2015; 25:1517-31. [PMID: 25926084 DOI: 10.1002/hipo.22471] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/23/2015] [Indexed: 11/11/2022]
Abstract
Hippocampal lesions tend to facilitate two-way active avoidance (2WAA) conditioning, where rats learn to cross to the opposite side of a conditioning chamber to avoid a tone-signaled footshock. This classical finding has been suggested to reflect that hippocampus-dependent place/context memory inhibits 2WAA (a crossing response to the opposite side is inhibited by the memory that this is the place where a shock was received on the previous trial). However, more recent research suggests other aspects of hippocampal function that may support 2WAA learning. More specifically, the ventral hippocampus has been shown to contribute to behavioral responses to aversive stimuli and to positively modulate the meso-accumbens dopamine system, whose activation has been implicated in 2WAA learning. Permanent hippocampal lesions may not reveal these contributions because, following complete and permanent loss of hippocampal output, other brain regions may mediate these processes or because deficits could be masked by lesion-induced extra-hippocampal changes, including an upregulation of accumbal dopamine transmission. Here, we re-examined the hippocampal role in 2WAA learning in Wistar rats, using permanent NMDA-induced neurotoxic lesions and temporary functional inhibition by muscimol or tetrodotoxin (TTX) infusion. Complete hippocampal lesions tended to facilitate 2WAA learning, whereas ventral (VH) or dorsal hippocampal (DH) lesions had no effect. In contrast, VH or DH muscimol or TTX infusions impaired 2WAA learning. Ventral infusions caused an immediate impairment, whereas after dorsal infusions rats showed intact 2WAA learning for 40-50 min, before a marked deficit emerged. These data show that functional inhibition of ventral hippocampus disrupts 2WAA learning, while the delayed impairment following dorsal infusions may reflect the time required for drug diffusion to ventral hippocampus. Overall, using temporary functional inhibition, our study shows that the ventral hippocampus contributes to 2WAA learning. Permanent lesions may not reveal these contributions due to functional compensation and extra-hippocampal lesion effects.
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Affiliation(s)
- Jia Wang
- School of Medicine, JiangSu University, Zhenjiang, Jiangsu Province, 212013, People's Republic of China
| | - Tobias Bast
- School of Psychology, Neuroscience@Nottingham and Brain & Body Centre, University of Nottingham, University Park, Nottingham, Ng7 2RD, United Kingdom
| | - Yu-Cong Wang
- School of Medicine, JiangSu University, Zhenjiang, Jiangsu Province, 212013, People's Republic of China
| | - Wei-Ning Zhang
- School of Medicine, JiangSu University, Zhenjiang, Jiangsu Province, 212013, People's Republic of China
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Hester MS, Danzer SC. Hippocampal granule cell pathology in epilepsy - a possible structural basis for comorbidities of epilepsy? Epilepsy Behav 2014; 38:105-16. [PMID: 24468242 PMCID: PMC4110172 DOI: 10.1016/j.yebeh.2013.12.022] [Citation(s) in RCA: 65] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/13/2013] [Revised: 12/17/2013] [Accepted: 12/21/2013] [Indexed: 01/31/2023]
Abstract
Temporal lobe epilepsy in both animals and humans is characterized by abnormally integrated hippocampal dentate granule cells. Among other abnormalities, these cells make axonal connections with inappropriate targets, grow dendrites in the wrong direction, and migrate to ectopic locations. These changes promote the formation of recurrent excitatory circuits, leading to the appealing hypothesis that these abnormal cells may by epileptogenic. While this hypothesis has been the subject of intense study, less attention has been paid to the possibility that abnormal granule cells in the epileptic brain may also contribute to comorbidities associated with the disease. Epilepsy is associated with a variety of general findings, such as memory disturbances and cognitive dysfunction, and is often comorbid with a number of other conditions, including schizophrenia and autism. Interestingly, recent studies implicate disruption of common genes and gene pathways in all three diseases. Moreover, while neuropsychiatric conditions are associated with changes in a variety of brain regions, granule cell abnormalities in temporal lobe epilepsy appear to be phenocopies of granule cell deficits produced by genetic mouse models of autism and schizophrenia, suggesting that granule cell dysmorphogenesis may be a common factor uniting these seemingly diverse diseases. Disruption of common signaling pathways regulating granule cell neurogenesis may begin to provide mechanistic insight into the cooccurrence of temporal lobe epilepsy and cognitive and behavioral disorders.
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Affiliation(s)
- Michael S Hester
- Department of Anesthesia, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, USA; Molecular and Developmental Biology Graduate Program, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, USA
| | - Steve C Danzer
- Department of Anesthesia, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, USA; Department of Anesthesia, University of Cincinnati, Cincinnati, OH 45267, USA; Department of Pediatrics, University of Cincinnati, Cincinnati, OH 45267, USA; Molecular and Developmental Biology Graduate Program, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, USA.
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Accumulation of abnormal adult-generated hippocampal granule cells predicts seizure frequency and severity. J Neurosci 2013; 33:8926-36. [PMID: 23699504 DOI: 10.1523/jneurosci.5161-12.2013] [Citation(s) in RCA: 103] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Accumulation of abnormally integrated, adult-born, hippocampal dentate granule cells (DGCs) is hypothesized to contribute to the development of temporal lobe epilepsy (TLE). DGCs have long been implicated in TLE, because they regulate excitatory signaling through the hippocampus and exhibit neuroplastic changes during epileptogenesis. Furthermore, DGCs are unusual in that they are continually generated throughout life, with aberrant integration of new cells underlying the majority of restructuring in the dentate during epileptogenesis. Although it is known that these abnormal networks promote abnormal neuronal firing and hyperexcitability, it has yet to be established whether they directly contribute to seizure generation. If abnormal DGCs do contribute, a reasonable prediction would be that the severity of epilepsy will be correlated with the number or load of abnormal DGCs. To test this prediction, we used a conditional, inducible transgenic mouse model to fate map adult-generated DGCs. Mossy cell loss, also implicated in epileptogenesis, was assessed as well. Transgenic mice rendered epileptic using the pilocarpine-status epilepticus model of epilepsy were monitored continuously by video/EEG for 4 weeks to determine seizure frequency and severity. Positive correlations were found between seizure frequency and (1) the percentage of hilar ectopic DGCs, (2) the amount of mossy fiber sprouting, and (3) the extent of mossy cell death. In addition, mossy fiber sprouting and mossy cell death were correlated with seizure severity. These studies provide correlative evidence in support of the hypothesis that abnormal DGCs contribute to the development of TLE and also support a role for mossy cell loss.
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Tejada J, Costa KM, Bertti P, Garcia-Cairasco N. The epilepsies: complex challenges needing complex solutions. Epilepsy Behav 2013; 26:212-28. [PMID: 23146364 DOI: 10.1016/j.yebeh.2012.09.029] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/13/2012] [Accepted: 09/16/2012] [Indexed: 12/19/2022]
Abstract
It is widely accepted that epilepsies are complex syndromes due to their multi-factorial origins and manifestations. Different mathematical and computational descriptions use appropriate methods to address nonlinear relationships, chaotic behaviors and emergent properties. These theoretical approaches can be divided into two major categories: descriptive, such as flowcharts, graphs and other statistical analyses, and explicative, which include both realistic and abstract models. Although these modeling tools have brought great advances, a common framework to guide their design, implementation and evaluation, with the goal of future integration, is still needed. In the current review, we discuss two examples of complexity analysis that can be performed with epilepsy data: behavioral sequences of temporal lobe seizures and alterations in an experimental cellular model. We also highlight the importance of the creation of model repositories for the epileptology field and encourage the development of mathematical descriptions of complex systems, together with more accurate simulation techniques.
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Affiliation(s)
- Julián Tejada
- Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, Brazil
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Kwon YS, Pineda E, Auvin S, Shin D, Mazarati A, Sankar R. Neuroprotective and antiepileptogenic effects of combination of anti-inflammatory drugs in the immature brain. J Neuroinflammation 2013; 10:30. [PMID: 23442201 PMCID: PMC3599749 DOI: 10.1186/1742-2094-10-30] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2012] [Accepted: 02/15/2013] [Indexed: 02/05/2023] Open
Abstract
BACKGROUND Inflammatory signaling elicited by prolonged seizures can be contributory to neuronal injury as well as adverse plasticity leading to the development of spontaneous recurrent seizures (epilepsy) and associated co-morbidities. In this study, developing rat pups were subjected to lithium-pilocarpine status epilepticus (SE) at 2 and 3 weeks of age to study the effect of anti-inflammatory drugs (AID) on SE-induced hippocampal injury and the development of spontaneous seizures. FINDINGS We selected AIDs directed against interleukin-1 receptors (IL-1ra), a cyclooxygenase-2 (COX-2) inhibitor (CAY 10404), and an antagonist of microglia activation of caspase-1 (minocycline). Acute injury after SE was studied in the 2-week-old rats 24 h after SE. Development of recurrent spontaneous seizures was studied in 3-week-old rats subjected to SE 4 months after the initial insult.None of those AIDs were effective in attenuating CA1 injury in the 2-week-old pups or in limiting the development of spontaneous seizures in 3-week-old pups when administered individually. When empiric binary combinations of these drugs were tried, the combined targeting of IL-1r and COX-2 resulted in attenuation of acute CA1 injury, as determined 24 h after SE, in those animals. The same combination administered for 10 days following SE in 3-week-old rats, reduced the development of spontaneous recurrent seizures and limited the extent of mossy fiber sprouting. CONCLUSIONS Deployment of an empirically designed 'drug cocktail' targeting multiple inflammatory signaling pathways for a limited duration after an initial insult like SE may provide a practical approach to neuroprotection and anti-epileptogenic therapy.
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Affiliation(s)
- Young Se Kwon
- Department of Pediatrics, Division of Neurology, David Geffen School of Medicine at UCLA, 22-474 MDCC in CHS, Los Angeles, CA 90095-1752, USA
- Department of Pediatrics, College of Medicine, Inha University, Incheon, Republic of Korea
| | - Eduardo Pineda
- Department of Pediatrics, Division of Neurology, David Geffen School of Medicine at UCLA, 22-474 MDCC in CHS, Los Angeles, CA 90095-1752, USA
| | - Stéphane Auvin
- Department of Pediatrics, Division of Neurology, David Geffen School of Medicine at UCLA, 22-474 MDCC in CHS, Los Angeles, CA 90095-1752, USA
- Department of Pediatric Neurology, Hôpital Robert Debré, INSERM U676, Paris, 75019, France
| | - Don Shin
- Department of Pediatrics, Division of Neurology, David Geffen School of Medicine at UCLA, 22-474 MDCC in CHS, Los Angeles, CA 90095-1752, USA
| | - Andrey Mazarati
- Department of Pediatrics, Division of Neurology, David Geffen School of Medicine at UCLA, 22-474 MDCC in CHS, Los Angeles, CA 90095-1752, USA
| | - Raman Sankar
- Department of Pediatrics, Division of Neurology, David Geffen School of Medicine at UCLA, 22-474 MDCC in CHS, Los Angeles, CA 90095-1752, USA
- Department of Neurology, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
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Remodeling of hippocampal network in pilocarpine-treated mice expressing synaptopHluorin in the mossy fiber terminals. Neurosci Res 2012; 74:25-31. [PMID: 22801461 DOI: 10.1016/j.neures.2012.07.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2011] [Revised: 07/03/2012] [Accepted: 07/04/2012] [Indexed: 11/20/2022]
Abstract
Pilocarpine-induced seizures induce an ectopic projection of hippocampal mossy fibers (MFs). Here, the sprouting was directly examined using TV-42 mice that express synaptopHluorin (SpH) selectively in the MF boutons. The SpH was ectopically expressed in the inner molecular layer (IML) of the dentate gyrus in typical mice after seizures, but were not always accompanied by the zinc fluorescence. The expression of SpH also has a tendency to be enhanced in layers of the CA3a region. It is suggested that the abnormal connection of neurons is more widespread than expected based on the previous zinc-detecting methods.
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Increased glial glutamate transporter EAAT2 expression reduces epileptogenic processes following pilocarpine-induced status epilepticus. Neurobiol Dis 2012; 47:145-54. [PMID: 22513140 DOI: 10.1016/j.nbd.2012.03.032] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2012] [Accepted: 03/24/2012] [Indexed: 11/21/2022] Open
Abstract
Several lines of evidence indicate that glutamate plays a crucial role in the initiation of seizures and their propagation; abnormal glutamate release causes synchronous firing of large populations of neurons, leading to seizures. In the present study, we investigated whether enhanced glutamate uptake by increased glial glutamate transporter EAAT2, the major glutamate transporter, could prevent seizure activity and reduce epileptogenic processes. EAAT2 transgenic mice, which have a 1.5-2 fold increase in EAAT2 protein levels as compared to their non-transgenic counterparts, were tested in a pilocarpine-induced status epilepticus (SE) model. Several striking phenomena were observed in EAAT2 transgenic mice compared with their non-transgenic littermates. First, the post-SE mortality rate and chronic seizure frequency were significantly decreased. Second, neuronal degeneration in hippocampal subfields after SE were significantly reduced. Third, the SE-induced neurogenesis and mossy fiber sprouting were significantly decreased. The severity of cell loss in epileptic mice was positively correlated with that of mossy fiber sprouting and chronic seizure frequency. Our results suggest that increased EAAT2 expression can protect mice against SE-induced death, neuropathological changes, and chronic seizure development. This study suggests that enhancing EAAT2 protein expression is a potential therapeutic approach.
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Increased excitatory synaptic input to granule cells from hilar and CA3 regions in a rat model of temporal lobe epilepsy. J Neurosci 2012; 32:1183-96. [PMID: 22279204 DOI: 10.1523/jneurosci.5342-11.2012] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
One potential mechanism of temporal lobe epilepsy is recurrent excitation of dentate granule cells through aberrant sprouting of their axons (mossy fibers), which is found in many patients and animal models. However, correlations between the extent of mossy fiber sprouting and seizure frequency are weak. Additional potential sources of granule cell recurrent excitation that would not have been detected by markers of mossy fiber sprouting in previous studies include surviving mossy cells and proximal CA3 pyramidal cells. To test those possibilities in hippocampal slices from epileptic pilocarpine-treated rats, laser-scanning glutamate uncaging was used to randomly and focally activate neurons in the granule cell layer, hilus, and proximal CA3 pyramidal cell layer while measuring evoked EPSCs in normotopic granule cells. Consistent with mossy fiber sprouting, a higher proportion of glutamate-uncaging spots in the granule cell layer evoked EPSCs in epileptic rats compared with controls. In addition, stimulation spots in the hilus and proximal CA3 pyramidal cell layer were more likely to evoke EPSCs in epileptic rats, despite significant neuron loss in those regions. Furthermore, synaptic strength of recurrent excitatory inputs to granule cells from CA3 pyramidal cells and other granule cells was increased in epileptic rats. These findings reveal substantial levels of excessive, recurrent, excitatory synaptic input to granule cells from neurons in the hilus and proximal CA3 field. The aberrant development of these additional positive-feedback circuits might contribute to epileptogenesis in temporal lobe epilepsy.
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Rapamycin suppresses mossy fiber sprouting but not seizure frequency in a mouse model of temporal lobe epilepsy. J Neurosci 2011; 31:2337-47. [PMID: 21307269 DOI: 10.1523/jneurosci.4852-10.2011] [Citation(s) in RCA: 182] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Temporal lobe epilepsy is prevalent and can be difficult to treat effectively. Granule cell axon (mossy fiber) sprouting is a common neuropathological finding in patients with mesial temporal lobe epilepsy, but its role in epileptogenesis is unclear and controversial. Focally infused or systemic rapamycin inhibits the mammalian target of rapamycin (mTOR) signaling pathway and suppresses mossy fiber sprouting in rats. We tested whether long-term systemic treatment with rapamycin, beginning 1 d after pilocarpine-induced status epilepticus in mice, would suppress mossy fiber sprouting and affect the development of spontaneous seizures. Mice that had experienced status epilepticus and were treated for 2 months with rapamycin displayed significantly less mossy fiber sprouting (42% of vehicle-treated animals), and the effect was dose dependent. However, behavioral and video/EEG monitoring revealed that rapamycin- and vehicle-treated mice displayed spontaneous seizures at similar frequencies. These findings suggest mossy fiber sprouting is neither pro- nor anti-convulsant; however, there are caveats. Rapamycin treatment also reduced epilepsy-related hypertrophy of the dentate gyrus but did not significantly affect granule cell proliferation, hilar neuron loss, or generation of ectopic granule cells. These findings are consistent with the hypotheses that hilar neuron loss and ectopic granule cells might contribute to temporal lobe epileptogenesis.
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Hippocampal dysfunction and cognitive impairments provoked by chronic early-life stress involve excessive activation of CRH receptors. J Neurosci 2010; 30:13005-15. [PMID: 20881118 DOI: 10.1523/jneurosci.1784-10.2010] [Citation(s) in RCA: 302] [Impact Index Per Article: 21.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Chronic stress impairs learning and memory in humans and rodents and disrupts long-term potentiation (LTP) in animal models. These effects are associated with structural changes in hippocampal neurons, including reduced dendritic arborization. Unlike the generally reversible effects of chronic stress on adult rat hippocampus, we have previously found that the effects of early-life stress endure and worsen during adulthood, yet the mechanisms for these clinically important sequelae are poorly understood. Stress promotes secretion of the neuropeptide corticotropin-releasing hormone (CRH) from hippocampal interneurons, activating receptors (CRF(1)) located on pyramidal cell dendrites. Additionally, chronic CRF(1) occupancy negatively affects dendritic arborization in mouse organotypic slice cultures, similar to the pattern observed in middle-aged, early-stressed (CES) rats. Here we found that CRH expression is augmented in hippocampus of middle-aged CES rats, and then tested whether the morphological defects and poor memory performance in these animals involve excessive activation of CRF(1) receptors. Central or peripheral administration of a CRF(1) blocker following the stress period improved memory performance of CES rats in novel-object recognition tests and in the Morris water maze. Consonant with these effects, the antagonist also prevented dendritic atrophy and LTP attenuation in CA1 Schaffer collateral synapses. Together, these data suggest that persistently elevated hippocampal CRH-CRF(1) interaction contributes importantly to the structural and cognitive impairments associated with early-life stress. Reducing CRF(1) occupancy post hoc normalized hippocampal function during middle age, thus offering potential mechanism-based therapeutic interventions for children affected by chronic stress.
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Laitinen T, Sierra A, Pitkänen A, Gröhn O. Diffusion tensor MRI of axonal plasticity in the rat hippocampus. Neuroimage 2010; 51:521-30. [DOI: 10.1016/j.neuroimage.2010.02.077] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2009] [Revised: 02/03/2010] [Accepted: 02/26/2010] [Indexed: 10/19/2022] Open
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Scorza FA, Arida RM, Naffah-Mazzacoratti MDG, Scerni DA, Calderazzo L, Cavalheiro EA. The pilocarpine model of epilepsy: what have we learned? AN ACAD BRAS CIENC 2010; 81:345-65. [PMID: 19722008 DOI: 10.1590/s0001-37652009000300003] [Citation(s) in RCA: 117] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2008] [Accepted: 08/25/2008] [Indexed: 12/24/2022] Open
Abstract
The systemic administration of a potent muscarinic agonist pilocarpine in rats promotes sequential behavioral and electrographic changes that can be divided into 3 distinct periods: (a) an acute period that built up progressively into a limbic status epilepticus and that lasts 24 h, (b) a silent period with a progressive normalization of EEG and behavior which varies from 4 to 44 days, and (c) a chronic period with spontaneous recurrent seizures (SRSs). The main features of the SRSs observed during the long-term period resemble those of human complex partial seizures and recurs 2-3 times per week per animal. Therefore, the pilocarpine model of epilepsy is a valuable tool not only to study the pathogenesis of temporal lobe epilepsy in human condition, but also to evaluate potential antiepileptogenic drugs. This review concentrates on data from pilocarpine model of epilepsy.
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Affiliation(s)
- Fulvio A Scorza
- Disciplina de Neurologia Experimental, Universidade Federal de São Paulo/Escola Paulista de Medicina, Rua Botucatu, 862, Edifício José Leal Prado, 04023-900 São Paulo, SP, Brasil
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Valente SG, Marques RH, Baracat EC, Cavalheiro EA, Naffah-Mazzacoratti MG, Amado D. Effect of hormonal replacement therapy in the hippocampus of ovariectomized epileptic female rats using the pilocarpine experimental model. Epilepsy Res 2008; 82:46-56. [PMID: 18760902 DOI: 10.1016/j.eplepsyres.2008.07.003] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2007] [Revised: 07/03/2008] [Accepted: 07/08/2008] [Indexed: 01/01/2023]
Abstract
Amado and Cavalheiro [Amado, D., Cavalheiro, E.A., 1998. Hormonal and gestational parameters in female rats submitted to the pilocarpine model of epilepsy. Epilepsy Res. 32, 266-274], studying the establishment of the pilocarpine epilepsy model in female rats observed that the estrous cycle was dramatically altered during the three periods of this experimental model. This work was delineated to study the function of sexual hormones in the development of the epilepsy model induced by pilocarpine in ovariectomized rats. Experimental groups were: (a) control animals during estrus phase of the estrous cycle (E) and ovariectomized female rats (OVX) treated with saline instead of pilocarpine in the same volume, (b) experimental animals, that developed status epilepticus (SE) and were studied during the chronic phase of this model: intact chronic rats (CHRON) and ovariectomized chronic rats (OVX+CHRON) and (c) ovariectomized chronic rats, that were submitted to hormonal replacement therapy treated with: medroxyprogesterone (OVX+CHRON+MPA); 17beta-estradiol (OVX+CHRON+E2), or both (OVX+CHRON+E2+MPA). All ovariectomized animals showed genital atrophy 4 days after the surgical procedure. Moreover, all animals that developed SE and survived showed spontaneous recurrent seizures during the chronic phase. Concerning to seizure frequency, animals receiving medroxyprogesterone associated with 17beta-estradiol showed decreased seizures' number. However, animals that received only medroxyprogesterone therapy also showed reduction in the number of seizures. In addition, hormonal treatment was also able to stabilize the mossy fibers sprouting process, showing the importance of these hormones in the development of the epilepsy in female rats.
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Affiliation(s)
- S G Valente
- Departamento de Neurologia e Neurocirurgia - Disciplina de Neurologia Experimental, Brazil; Departamento de Ortopedia e Traumatologia - Escola Paulista de Medicina/Universidade Federal de São Paulo, Brazil
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Andrade-Valença LPA, Valença MM, Velasco TR, Carlotti CG, Assirati JA, Galvis-Alonso OY, Neder L, Cendes F, Leite JP. Mesial temporal lobe epilepsy: clinical and neuropathologic findings of familial and sporadic forms. Epilepsia 2008; 49:1046-54. [PMID: 18294201 DOI: 10.1111/j.1528-1167.2008.01551.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
PURPOSE To evaluate the clinical and hippocampal histological features of patients with mesial temporal lobe epilepsy (MTLE) in both familial (FMTLE) and sporadic (SMTLE) forms. METHODS Patients with FMTLE (n = 20) and SMTLE (n = 39) who underwent surgical treatment for refractory seizures were studied at the University of São Paulo School of Medicine at Ribeirão Preto. FMTLE was defined when at least two individuals in a family had clinical diagnosis of MTLE. Hippocampi from all patients were processed for Nissl/HE and Timm's stainings. Both groups were compared for clinical variables, hippocampal cell densities, and intensity of supragranular mossy fiber staining. RESULTS There were no significant differences between FMTLE and SMTLE groups in the following: age at the surgery, age of first usual epileptic seizure, history of initial precipitating injury (IPI), age of IPI, latent period, ictal and interictal video-EEG patterns, presence of hippocampal atrophy and signal changes at MRI, and postoperative outcome. In addition, no differences were found in cell densities in hippocampal cornu ammonis subfields (CA1, CA2, CA3, CA4), fascia dentata, polymorphic region, subiculum, prosubiculum, and presubiculum. However, patients with SMTLE had greater intensity of mossy fiber Timm's staining in the fascia dentata-inner molecular layer (p< 0.05). DISCUSSION Patients with intractable FMTLE present a clinical profile and most histological findings comparable to patients with SMTLE. Interestingly, mossy fiber sprouting was less pronounced in patients with FMTLE, suggesting that, when compared to SMTLE, patients with FMTLE respond differently to plastic changes plausibly induced by cell loss, neuronal deafferentation, or epileptic seizures.
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Williams PA, Dudek FE. A chronic histopathological and electrophysiological analysis of a rodent hypoxic-ischemic brain injury model and its use as a model of epilepsy. Neuroscience 2007; 149:943-61. [PMID: 17935893 PMCID: PMC2897748 DOI: 10.1016/j.neuroscience.2007.07.067] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2007] [Revised: 07/24/2007] [Accepted: 08/15/2007] [Indexed: 11/24/2022]
Abstract
Ischemic brain injury is one of the leading causes of epilepsy in the elderly, and there are currently no adult rodent models of global ischemia, unilateral hemispheric ischemia, or focal ischemia that report the occurrence of spontaneous motor seizures following ischemic brain injury. The rodent hypoxic-ischemic (H-I) model of brain injury in adult rats is a model of unilateral hemispheric ischemic injury. Recent studies have shown that an H-I injury in perinatal rats causes hippocampal mossy fiber sprouting and epilepsy. These experiments aimed to test the hypothesis that a unilateral H-I injury leading to severe neuronal loss in young-adult rats also causes mossy fiber sprouting and spontaneous motor seizures many months after the injury, and that the mossy fiber sprouting induced by the H-I injury forms new functional recurrent excitatory synapses. The right common carotid artery of 30-day old rats was permanently ligated, and the rats were placed into a chamber with 8% oxygen for 30 min. A quantitative stereologic analysis revealed that the ipsilateral hippocampus had significant hilar and CA1 pyramidal neuronal loss compared with the contralateral and sham-control hippocampi. The septal region from the ipsilateral and contralateral hippocampus had small but significantly increased amounts of Timm staining in the inner molecular layer compared with the sham-control hippocampi. Three of 20 lesioned animals (15%) were observed to have at least one spontaneous motor seizure 6-12 months after treatment. Approximately 50% of the ipsilateral and contralateral hippocampal slices displayed abnormal electrophysiological responses in the dentate gyrus, manifest as all-or-none bursts to hilar stimulation. This study suggests that H-I injury is associated with synaptic reorganization in the lesioned region of the hippocampus, and that new recurrent excitatory circuits can predispose the hippocampus to abnormal electrophysiological activity and spontaneous motor seizures.
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Williams PA, Hellier JL, White AM, Staley KJ, Dudek FE. Development of spontaneous seizures after experimental status epilepticus: implications for understanding epileptogenesis. Epilepsia 2007; 48 Suppl 5:157-63. [PMID: 17910596 DOI: 10.1111/j.1528-1167.2007.01304.x] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
This report examines several concepts concerning the latent period to the first convulsive seizure, subsequent increases in seizure frequency, and possible mechanisms of epileptogenesis after kainate-induced status epilepticus. Previous data concerning the latent period and seizure progression from intermittent and continuous behavioral monitoring are compared, and hypothetical mechanisms of acquired epilepsy are discussed. Data involving electrographic recordings with tethered animals or with radiotelemetry are assessed in terms of their potential for addressing different hypotheses concerning the latent period and progressive changes in seizure frequency. Experimental analyses of the time course of occurrence of spontaneous seizures are interpreted in terms of possible cellular mechanisms underlying epileptogenesis.
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Affiliation(s)
- Philip A Williams
- Department of Biomedical Sciences, Colorado State University, Fort Collins, Colorado, USA
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Dietrich J, Kempermann G. Role of Endogenous Neural Stem Cells in Neurological Disease and Brain Repair. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2007; 557:191-220. [PMID: 16955712 DOI: 10.1007/0-387-30128-3_12] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
These examples show that stem-cell-based therapy of neuro-psychiatric disorders will not follow a single scheme, but rather include widely different approaches. This is in accordance with the notion that the impact of stem cell biology on neurology will be fundamental, providing a shift in perspective, rather than introducing just one novel therapeutic tool. Stem cell biology, much like genomics and proteomics, offers a "view from within" with an emphasis on a theoretical or real potential and thereby the inherent openness, which is central to the concept of stem cells. Thus, stem cell biology influences many other, more traditional therapeutic approaches, rather than introducing one distinct novel form of therapy. Substantial advances have been made i n neural stemcell research during the years. With the identification of stem and progenitor cells in the adult brain and the complex interaction of different stem cell compartments in the CNS--both, under physiological and pathological conditions--new questions arise: What is the lineage relationship between t he different progenitor cells in the CNS and how much lineage plasticity exists? What are the signals controlling proliferation and differentiation of neural stem cells and can these be utilized to allow repair of the CNS? Insights in these questions will help to better understand the role of stem cells during development and aging and the possible relation of impaired or disrupted stem cell function and their impact on both the development and treatment of neurological disease. A number o f studies have indicated a limited neuronal and glial regeneration certain pathological conditions. These fundamental observations have already changed our view on understanding neurological disease and the brain's capacity for endogenous repair. The following years will have to show how we can influence andmodulate endogenous repair nisms by increasing the cellular plasticity in the young and aged CNS.
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Affiliation(s)
- Jörg Dietrich
- Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, USA
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19
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Sutula TP, Dudek FE. Unmasking recurrent excitation generated by mossy fiber sprouting in the epileptic dentate gyrus: an emergent property of a complex system. PROGRESS IN BRAIN RESEARCH 2007; 163:541-63. [PMID: 17765737 DOI: 10.1016/s0079-6123(07)63029-5] [Citation(s) in RCA: 151] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Seizure-induced sprouting of the mossy fiber pathway in the dentate gyrus has been observed nearly universally in experimental models of limbic epilepsy and in the epileptic human hippocampus. The observation of progressive mossy fiber sprouting induced by kindling demonstrated that even a few repeated seizures are sufficient to alter synaptic connectivity and circuit organization. As it is now recognized that seizures induce synaptic reorganization in hippocampal and cortical pathways, the implications of seizure-induced synaptic reorganization for circuit properties and function have been subjects of intense interest. Detailed anatomical characterization of the sprouted mossy fiber pathway has revealed that the overwhelming majority of sprouted synapses in the inner molecular layer of the dentate gyrus form recurrent excitatory connections, and are thus likely to contribute to recurrent excitation and potentially to enhanced susceptibility to seizures. Nevertheless, difficulties in detecting functional abnormalities in circuits reorganized by mossy fiber sprouting and the fact that some sprouted axons appear to form synapses with inhibitory interneurons have been cited as evidence that sprouting may not contribute to seizure susceptibility, but could form recurrent inhibitory circuits and be a compensatory response to prevent seizures. Quantitative analysis of the synaptic connections of the sprouted mossy fiber pathway, assessment of the functional features of sprouted circuitry using reliable physiological measures, and the perspective of complex systems analysis of neural circuits strongly support the view that the functional effects of the recurrent excitatory circuits formed by mossy fiber sprouting after seizures or injury emerge only conditionally and intermittently, as observed with spontaneous seizures in human epilepsy. The recognition that mossy fiber sprouting is induced after hippocampal injury and seizures and contributes conditionally to emergence of recurrent excitation has provided a conceptual framework for understanding how injury and seizure-induced circuit reorganization may contribute to paroxysmal network synchronization, epileptogenesis, and the consequences of repeated seizures, and thus has had a major influence on understanding of fundamental aspects of the epilepsies.
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Affiliation(s)
- Thomas P Sutula
- Department of Neurology H6/570 CSC, University of Wisconsin, 600 Highland Avenue, Madison, WI 53792, USA.
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Rao MS, Hattiangady B, Reddy DS, Shetty AK. Hippocampal neurodegeneration, spontaneous seizures, and mossy fiber sprouting in the F344 rat model of temporal lobe epilepsy. J Neurosci Res 2006; 83:1088-105. [PMID: 16493685 DOI: 10.1002/jnr.20802] [Citation(s) in RCA: 114] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The links among the extent of hippocampal neurodegeneration, the frequency of spontaneous recurrent motor seizures (SRMS), and the degree of aberrant mossy fiber sprouting (MFS) in temporal lobe epilepsy (TLE) are a subject of contention because of variable findings in different animal models and human studies. To understand these issues further, we quantified these parameters at 3-5 months after graded injections of low doses of kainic acid (KA) in adult F344 rats. KA was administered every 1 hr for 4 hr, for a cumulative dose of 10.5 mg/kg bw, to induce continuous stages III-V motor seizures for >3 hr. At 4 days post-KA, the majority of rats (77%) exhibited moderate bilateral neurodegeneration in different regions of the hippocampus; however, 23% of rats exhibited massive neurodegeneration in all hippocampal regions. All KA-treated rats displayed robust SRMS at 3 months post-KA, and the severity of SRMS increased over time. Analyses of surviving neurons at 5 months post-KA revealed two subgroups of rats, one with moderate hippocampal injury (HI; 55% of rats) and another with widespread HI (45%). Rats with widespread HI exhibited greater loss of CA3 pyramidal neurons and robust aberrant MFS than rats with moderate HI. However, the frequency of SRMS (approximately 3/hr) was comparable between rats with moderate and widespread HI. Thus, in comparison with TLE model using Sprague-Dawley rats (Hellier et al. [1998] Epilepsy Res. 31:73-84), a much lower cumulative dose of KA leads to robust chronic epilepsy in F344 rats. Furthermore, the occurrence of SRMS in this model is always associated with considerable bilateral hippocampal neurodegeneration and aberrant MFS. However, more extensive hippocampal CA3 cell loss and aberrant MFS do not appear to increase the frequency of SRMS. Because most of the features are consistent with mesial TLE in humans, the F344 model appears ideal for testing the efficacy of potential treatment strategies for mesial TLE.
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Affiliation(s)
- Muddanna S Rao
- Department of Surgery (Neurosurgery), Duke University Medical Center, Durham, North Carolina 27710, USA
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21
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Ikegaya Y. [Potential roles for mossy fiber sprouting in temporal lobe epilepsy]. Nihon Yakurigaku Zasshi 2006; 127:355-61. [PMID: 16819240 DOI: 10.1254/fpj.127.355] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
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Hasegawa T, Kondziolka D, Choi SJ, Balzer J, Dixon EC, Fellows-Mayle W, Elder E. Hippocampal neurotransplantation evaluated in the rat kainic acid epilepsy model. Neurosurgery 2004; 55:191-8; discussion 198-200. [PMID: 15214989 DOI: 10.1227/01.neu.0000126881.40748.93] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2003] [Accepted: 03/03/2004] [Indexed: 11/19/2022] Open
Abstract
OBJECTIVE Neurotransplantation has focused on disorders that involve subcortical brain targets. We evaluated the concepts of epileptic focus repair and changes in animal behavior through replacement of lost hippocampal neurons. The safety of hippocampal neurotransplantation was assessed in the rat kainic acid (KA) epilepsy model. METHODS Sixty-three rats were studied and classified into six groups: KA plus 40,000 LBS-Neurons (Layton BioScience, Sunnyvale, CA; n = 13); KA plus 80,000 cells (n = 12); KA plus media (n = 9); no-KA plus 40,000 cells (n = 12); no-KA plus 80,000 cells (n = 12); and no-KA plus media (n = 5). Clinical observation (2 h daily) and electroencephalogram recording (3 h every other week) were performed to check for seizures until Week 11 after KA injection. On Week 12, the Morris water maze test was performed to assess spatial learning and memory. RESULTS Four rats were excluded because of intracranial hematoma or abscess. In the clinical observation of seizures, the no-KA plus media group had significantly fewer seizures than rats that received KA followed by injection of 40,000 cells, 80,000 cells, or media (P = 0.001, 0.0004, and 0.004, respectively). On electroencephalographic analysis, there was no significant difference between any of the groups. Transplanted rats with KA-induced epilepsy did not have an increased number of seizures. In the Morris water maze test, the hidden platform task showed that the KA plus 80,000 cell group had significantly longer swim latencies than groups with no-KA plus 40,000 cells (P = 0.035) or no-KA plus 80,000 cells (P = 0.015), demonstrating the behavioral deficits caused by KA injection. The probe trial showed no significant difference for the percentage of time in the target quadrant between any of the groups. Histological studies showed that 26 (59%) of 44 transplanted rats had evidence of graft survival. CONCLUSION The safety of cortical neurotransplantation was demonstrated, even in an animal model predisposed to epilepsy. We did not find evidence for cessation of seizures or improvement in behavior using this model.
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Affiliation(s)
- Toshinori Hasegawa
- Department of Neurological Surgery, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
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Robinson M, Lighthall G. Asystole during successive electroconvulsive therapy sessions: a report of two cases. J Clin Anesth 2004; 16:210-3. [PMID: 15217662 DOI: 10.1016/j.jclinane.2003.07.009] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2003] [Revised: 07/14/2003] [Accepted: 07/14/2003] [Indexed: 11/24/2022]
Abstract
Intense vagal discharge often follows stimulus application during electroconvulsive therapy (ECT). Related periods of asystole during ECT have been reported sporadically in psychiatric journals, but to date not in the anesthesia literature. We report here two cases of prolonged asystole that occurred in our facility in spite of the fact that published suggestions for its prevention were followed. With careful monitoring of these patients--including echocardiography for one patient--we document the onset of asystole at the exact time of ECT stimulus application. With these data, we discuss why asystole is likely to result from a direct central pathway rather than via a baroreceptor reflex, and discuss a neuroanatomic pathway potentially responsible for our findings. We also demonstrate that high-dose atropine (0.8 mg) can effectively prevent most cases of asystole in susceptible patients, and that administration of esmolol following cessation of seizures effectively reduces the elevated heart rate without causing asystole or bradycardia.
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Affiliation(s)
- Marnie Robinson
- Department of Anesthesia Stanford University Medical Center, Stanford, CA 94305, USA
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Velísek L, Moshé SL. Temporal Lobe Epileptogenesis and Epilepsy in the Developing Brain: Bridging the Gap Between the Laboratory and the Clinic. Progression, But in What Direction? Epilepsia 2003; 44 Suppl 12:51-9. [PMID: 14641561 DOI: 10.1111/j.0013-9580.2003.12008.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The origins of human mesial temporal lobe epilepsy and hippocampal sclerosis are still not well understood. Hippocampal sclerosis and temporal lobe epileptogenesis involve a series of pathologies including hippocampal neuronal loss and gliosis, axonal reorganization, and maybe hippocampal neoneurogenesis. However, the causality of these events is unclear as well as their relation to the factors that may precipitate epileptogenesis. Significant differences between temporal lobe epileptogenesis in the adult and immature brain may require differential approaches. Hereditary factors also may participate in some cases of hippocampal sclerosis. The key point is to identify the significance of these age-dependent changes and to design preventive treatments. Novel strategies for the prevention and treatment of mesial temporal lobe epilepsy and hippocampal sclerosis may include rational use of neuroprotective agents, hormonotherapy, immunizations, and immunotherapy.
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Affiliation(s)
- L Velísek
- Department of Neurology K314, and Montefiore/Einstein Epilepsy Management Center, Albert Einstein College of Medicine, 1410 Pelham Parkway South, Bronx, NY 10461, U.S.A.
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Longo BM, Sanabria ERG, Gabriel S, Mello LEAM. Electrophysiologic abnormalities of the hippocampus in the pilocarpine/cycloheximide model of chronic spontaneous seizures. Epilepsia 2002; 43 Suppl 5:203-8. [PMID: 12121322 DOI: 10.1046/j.1528-1157.43.s.5.4.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
PURPOSE Mossy fiber sprouting (MFS) and synaptic reorganization in the dentate gyrus (DG) is considered one of the physiopathologic mechanisms in temporal lobe epilepsy. Supragranular MFS can be blocked by cycloheximide (CHX) without interfering with the genesis of spontaneous recurrent seizures. The aim of this study was to investigate electrophysiologic properties of the hippocampus in the CHX/pilocarpine (CHX/PILO) model as compared with the conventional PILO model. METHODS In vitro electrophysiology was performed 2 months after status epilepticus (SE) induction using extracellular recordings in hippocampal slices from PILO (n = 8) and CHX/PILO animals (n = 10). Field potential responses were evoked in the CA1 and DG regions during perfusion with normal artificial cerebrospinal fluid (aCSF) and aCSF containing 3.5, 5, or 8 mM K+ without or with bicuculline added. Neo-Timm staining was used for the assessment of supragranular MFS. RESULTS Evoked potentials in PILO- and CHX/PILO-treated rats displayed small-amplitude polyspiking activity (epileptiform responses) in CA1 and an apparently normal isolated population spike in DG. More important, PILO and CHX/PILO animals did not differ regarding electrophysiologic abnormalities, even under high K+ or high K+/bicuculline. Analysis of the neo-Timm staining revealed strong supragranular MFS in PILO-injected rats and significantly less staining in CHX/PILO rats. Thus, occurrence of abnormal stimulus responses and high K+- or high K+/bicuculline-induced epileptiform activities did not depend on the degree of MFS. CONCLUSIONS We therefore suggest that other mechanisms such as anomalous intrinsic bursting and disinhibition rather than MFS might account for the increased hippocampal hyperexcitability in this model.
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Affiliation(s)
- Beatriz M Longo
- Department of Physiology, UNIFESP, Rua Botucatu 862, 04023-062 São Paulo, SP, Brazil
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Nissinen J, Lukasiuk K, Pitkänen A. Is mossy fiber sprouting present at the time of the first spontaneous seizures in rat experimental temporal lobe epilepsy? Hippocampus 2002; 11:299-310. [PMID: 11769311 DOI: 10.1002/hipo.1044] [Citation(s) in RCA: 95] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The contribution of mossy fiber sprouting to the generation of spontaneous seizures in the epileptic brain is under dispute. The present study addressed this question by examining whether sprouting of mossy fibers is present at the time of appearance of the first spontaneous seizures in rats, and whether all animals with increased sprouting have spontaneous seizures. Epileptogenesis was induced in 16 rats by electrically stimulating the lateral nucleus of the amygdala for 20-30 min until the rats developed self-sustained status epilepticus (SSSE). During and after SSSE, rats were monitored in long-term by continuous video-electroencephalography until they developed a second spontaneous seizure (8-54 days). Thereafter, monitoring was continued for 11 days to follow seizure frequency. The density of mossy fiber sprouting was analyzed from Timm-stained preparations. The density of hilar neurons was assessed from thionin-stained sections. Of 16 rats, 14 developed epilepsy. In epileptic rats, the density of mossy fiber sprouting did not correlate with the severity or duration (115-620 min) of SSSE, delay from SSSE to occurrence of first (8-51 days) or second (8-54 days) spontaneous seizure, or time from SSSE to perfusion (20-63 days). In the temporal end of the hippocampus, the sprouting correlated with the severity of neuronal damage (ipsilateral: r = -0.852, P < 0.01 contralateral: r = -0.748, P < 0.01). The two animals without spontaneous seizures also had sprouting. Increased density of sprouting in animals without seizures, and its association with the severity of neuronal loss was confirmed in another series of 30 stimulated rats that were followed-up with video-EEG monitoring for 60 d. Our data indicate that although mossy fiber sprouting is present in all animals with spontaneous seizures, its presence is not necessarily associated with the occurrence of spontaneous seizures.
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Affiliation(s)
- J Nissinen
- Epilepsy Research Laboratory, A.I. Virtanen Institute for Molecular Sciences, University of Kuopio, Finland
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Sutula T. Seizure-Induced Axonal Sprouting: Assessing Connections Between Injury, Local Circuits, and Epileptogenesis. Epilepsy Curr 2002. [PMID: 15309153 DOI: 10.1046/j.1535-7597.2002.00032.x] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Neurons and neural circuits undergo extensive structural and functional remodeling in response to seizures. Sprouting of axons in the mossy fiber pathway of the hippocampus is a prominent example of a seizure-induced structural alteration which has received particular attention because it is easily detected, is induced by intense or repeated brief seizures in focal chronic models of epilepsy, and is also observed in the human epileptic hippocampus. During the last decade the association of mossy fiber sprouting with seizures and epilepsy has been firmly established. Many anatomical features of mossy fiber sprouting have been described in considerable detail, and there is evidence that sprouting occurs in a variety of other pathways in association with seizures and injury. There is uncertainty, however, about how or when mossy fiber sprouting may contribute to hippocampal dysfunction and generation of seizures. Study of mossy fiber sprouting has provided a strong theoretical and conceptual framework for efforts to understand how seizures and injury may contribute to epileptogenesis and its consequences. It is likely that investigation of mossy fiber sprouting will continure to offer significant opportunities for insights into seizure-induced plasticity of neural circuits at molecular, cellular, and systems levels.
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Affiliation(s)
- Thomas Sutula
- Departments of Neurology and Anatomy, University of Wisconsin, Madison, Wisconsin
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Sutula T. Seizure-Induced Axonal Sprouting: Assessing Connections between Injury, Local Circuits, and Epileptogenesis. Epilepsy Curr 2002; 2:86-91. [PMID: 15309153 PMCID: PMC321023 DOI: 10.1111/j.1535-7597.2002.00032.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Neurons and neural circuits undergo extensive structural and functional remodeling in response to seizures. Sprouting of axons in the mossy fiber pathway of the hippocampus is a prominent example of a seizure-induced structural alteration which has received particular attention because it is easily detected, is induced by intense or repeated brief seizures in focal chronic models of epilepsy, and is also observed in the human epileptic hippocampus. During the last decade the association of mossy fiber sprouting with seizures and epilepsy has been firmly established. Many anatomical features of mossy fiber sprouting have been described in considerable detail, and there is evidence that sprouting occurs in a variety of other pathways in association with seizures and injury. There is uncertainty, however, about how or when mossy fiber sprouting may contribute to hippocampal dysfunction and generation of seizures. Study of mossy fiber sprouting has provided a strong theoretical and conceptual framework for efforts to understand how seizures and injury may contribute to epileptogenesis and its consequences. It is likely that investigation of mossy fiber sprouting will continure to offer significant opportunities for insights into seizure-induced plasticity of neural circuits at molecular, cellular, and systems levels.
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Affiliation(s)
- Thomas Sutula
- Departments of Neurology and Anatomy, University of Wisconsin, Madison, Wisconsin
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Lehmann TN, Gabriel S, Eilers A, Njunting M, Kovacs R, Schulze K, Lanksch WR, Heinemann U. Fluorescent tracer in pilocarpine-treated rats shows widespread aberrant hippocampal neuronal connectivity. Eur J Neurosci 2001; 14:83-95. [PMID: 11488952 DOI: 10.1046/j.0953-816x.2001.01632.x] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Neuronal fibres of the hippocampal formation of normal and chronic epileptic rats were investigated by fluorescent tracing methods using the pilocarpine model of limbic epilepsy. Two months after onset of spontaneous limbic seizures, hippocampal slices were prepared and maintained in vitro for 10 h. Small crystals of fluorescent dye [fluorescein (fluoro-emerald) and tetramethylrhodamine (fluoro-ruby)] were applied to different hippocampal regions. The main findings were: (i) in control rats there was no supragranular labelling when the mossy fibre tract was stained in stratum radiatum of area CA3. However, in epileptic rats a fibre network in the inner molecular layer of the dentate gyrus was retrogradely labelled; (ii) a retrograde innervation of area CA3 by CA1 pyramidal cells was disclosed by labelling remote CA1 neurons after dye injection into the stratum radiatum of area CA3 in chronic epileptic rats; (iii) labelling of CA1 neurons apart from the injection site within area CA1 was observed in epileptic rats but not in control animals; and (iv), a subicular-hippocampal projection was present in pilocarpine-treated rats when the tracer was injected just below the stratum pyramidale of area CA1. The findings show that fibre rearrangement in distinct regions of the epileptic hippocampal formation can occur as an aftermath of pilocarpine-induced status epilepticus.
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Affiliation(s)
- T N Lehmann
- Department of Neurosurgery, Charité Campus Virchow-Klinikum, Humboldt University of Berlin, Germany
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Gorter JA, van Vliet EA, Aronica E, Lopes da Silva FH. Progression of spontaneous seizures after status epilepticus is associated with mossy fibre sprouting and extensive bilateral loss of hilar parvalbumin and somatostatin-immunoreactive neurons. Eur J Neurosci 2001; 13:657-69. [PMID: 11207801 DOI: 10.1046/j.1460-9568.2001.01428.x] [Citation(s) in RCA: 240] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The development of spontaneous limbic seizures was investigated in a rat model in which electrical tetanic stimulation of the angular bundle was applied for up to 90 min. This stimulation produced behavioural and electrographic seizures that led to a status epilepticus (SE) in most rats (71%). Long-term EEG monitoring showed that the majority of the rats (67%) that underwent SE, displayed a progressive increase of seizure activity once the first seizure was recorded after a latent period of about 1 week. The other SE rats (33%) did not show this progression of seizure activity. We investigated whether these different patterns of evolution of spontaneous seizures could be related to differences in cellular or structural changes in the hippocampus. This was the case regarding the following changes. (i) Cell loss in the hilar region: in progressive SE rats this was extensive and bilateral whereas in nonprogressive SE rats it was mainly unilateral. (ii) Parvalbumin and somatostatin-immunoreactive neurons: in the hilar region these were almost completely eliminated in progressive SE rats but were still largely present unilaterally in nonprogressive SE rats. (iii) Mossy fibre sprouting: in progressive SE rats, extensive mossy fibre sprouting was prominent in the inner molecular layer. In nonprogressive SE rats, mossy fibre sprouting was also present but less prominent than in progressive SE rats. Although mossy fibre sprouting has been proposed to be a prerequisite for chronic seizure activity in experimental temporal lobe epilepsy, the extent of hilar cell death also appears to be an important factor that differentiates between whether or not seizure progression will occur.
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Affiliation(s)
- J A Gorter
- Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, The Netherlands.
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