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Myhrer T, Mariussen E, Aas P. Development of neuropathology following soman poisoning and medical countermeasures. Neurotoxicology 2018; 65:144-165. [DOI: 10.1016/j.neuro.2018.02.009] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2017] [Revised: 02/12/2018] [Accepted: 02/14/2018] [Indexed: 01/12/2023]
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Zhang Z, Liao W, Chen H, Mantini D, Ding JR, Xu Q, Wang Z, Yuan C, Chen G, Jiao Q, Lu G. Altered functional–structural coupling of large-scale brain networks in idiopathic generalized epilepsy. Brain 2011; 134:2912-28. [PMID: 21975588 DOI: 10.1093/brain/awr223] [Citation(s) in RCA: 417] [Impact Index Per Article: 32.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Affiliation(s)
- Zhiqiang Zhang
- Department of Medical Imaging, Jinling Hospital, Nanjing University School of Medicine, Nanjing 210002, PR China
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DeSalvo MN, Schridde U, Mishra AM, Motelow JE, Purcaro MJ, Danielson N, Bai X, Hyder F, Blumenfeld H. Focal BOLD fMRI changes in bicuculline-induced tonic-clonic seizures in the rat. Neuroimage 2010; 50:902-9. [PMID: 20079442 DOI: 10.1016/j.neuroimage.2010.01.006] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2009] [Revised: 11/15/2009] [Accepted: 01/05/2010] [Indexed: 10/20/2022] Open
Abstract
Generalized tonic-clonic seizures cause widespread physiological changes throughout the cerebral cortex and subcortical structures in the brain. Using combined blood oxygen level dependent (BOLD) functional magnetic resonance imaging (fMRI) at 9.4 T and electroencephalography (EEG), these changes can be characterized with high spatiotemporal resolution. We studied BOLD changes in anesthetized Wistar rats during bicuculline-induced tonic-clonic seizures. Bicuculline, a GABA(A) receptor antagonist, was injected systemically and seizure activity was observed on EEG as high-amplitude, high-frequency polyspike discharges followed by clonic paroxysmal activity of lower frequency, with mean electrographic seizure duration of 349 s. Our aim was to characterize the spatial localization, direction, and timing of BOLD signal changes during the pre-ictal, ictal and post-ictal periods. Group analysis was performed across seizures using paired t-maps of BOLD signal superimposed on high-resolution anatomical images. Regional analysis was then performed using volumes of interest to quantify BOLD timecourses. In the pre-ictal period we found focal BOLD increases in specific areas of somatosensory cortex (S1, S2) and thalamus several seconds before seizure onset. During seizures we observed BOLD increases in cortex, brainstem and thalamus and BOLD decreases in the hippocampus. The largest ictal BOLD increases remained in the focal regions of somatosensory cortex showing pre-ictal increases. During the post-ictal period we observed widespread BOLD decreases. These findings support a model in which "generalized" tonic-clonic seizures begin with focal changes before electrographic seizure onset, which progress to non-uniform changes during seizures, possibly shedding light on the etiology and pathophysiology of similar seizures in humans.
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Affiliation(s)
- Matthew N DeSalvo
- Department of Neurology, Yale University School of Medicine, New Haven, CT 06520, USA
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5
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Seizures and impairment of consciousness. HANDBOOK OF CLINICAL NEUROLOGY 2008. [PMID: 18631826 DOI: 10.1016/s0072-9752(07)01713-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register]
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Abstract
Interest in temporal lobe seizure pathways has a long history based initially on the human condition of temporal lobe epilepsy (TLE). This interest in TLE has extended more recently into explorations of experimental models. In this review, the network structures in the temporal lobe that are recruited in animal models during various forms of limbic seizures and status epilepticus are described. Common to all of the various models is recruitment of the parahippocampal cortices, including the piriform, perirhinal, and entorhinal areas. This cortical involvement is seen in in vitro and in vivo electrophysiological recordings throughout the network, in trans-synaptic neuroplastic changes in associated network structures manifest at the molecular level, in network energy utilization visualized by 14C2-deoxyglucose uptake, and finally, in the behavioral consequences of network lesions. The conclusions of the animal models reviewed here are very similar to those described for the human condition presented recently in the 2006 Lennox lecture by Warren Blume, and addressed 53 years ago in the quadrennial meeting of the ILAE in 1953 by Henri Gastaut.
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Affiliation(s)
- Dan C McIntyre
- Department of Psychology, Institute of Neuroscience, Carleton University, Ottawa, Ontario, Canada.
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Enev M, McNally KA, Varghese G, Zubal IG, Ostroff RB, Blumenfeld H. Imaging onset and propagation of ECT-induced seizures. Epilepsia 2007; 48:238-44. [PMID: 17295616 DOI: 10.1111/j.1528-1167.2007.00919.x] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
PURPOSE Regions of seizure onset and propagation in human generalized tonic-clonic seizures are not well understood. Cerebral blood flow (CBF) measurements with single photon emission computed tomography (SPECT) during electroconvulsive therapy (ECT)-induced seizures provide a unique opportunity to investigate seizure onset and propagation under controlled conditions. METHODS ECT stimulation induces a typical generalized tonic-clonic seizure, resembling spontaneous generalized seizures in both clinical and electroencephalogram (EEG) manifestations. Patients were divided into two groups based on timing of ictal (during seizure) SPECT tracer injections: 0 s after ECT stimulation (early group), and 30 s after ECT (late group). Statistical parametric mapping (SPM) was used to determine regions of significant CBF changes between ictal and interictal scans on a voxel-by-voxel basis. RESULTS In the early injection group, we saw increases near the regions of the bitemporal stimulating electrodes as well as some thalamic and basal ganglia activation. With late injections, we observed increases mainly in the parietal and occipital lobes, regions that were quiescent 30 s prior. Significant decreases occurred only at the later injection time, and these were localized to the bilateral cingulate gyrus and left dorsolateral frontal cortex. CONCLUSIONS Activations in distinct regions at the two time points, as well as sparing of intermediary brain structures, suggest that ECT-induced seizures propagate from the site of initiation to other specific brain regions. Further work will be needed to determine if this propagation occurs through cortical-cortical or cortico-thalamo-cortical networks. A better understanding of seizure propagation mechanisms may lead to improved treatments aimed at preventing seizure generalization.
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MESH Headings
- Brain Mapping
- Cerebral Cortex/diagnostic imaging
- Cerebral Cortex/pathology
- Cerebral Cortex/physiopathology
- Cerebrovascular Circulation/physiology
- Depressive Disorder/therapy
- Depressive Disorder, Major/therapy
- Electric Stimulation/methods
- Electroconvulsive Therapy/methods
- Electroencephalography/statistics & numerical data
- Epilepsy, Generalized/diagnostic imaging
- Epilepsy, Generalized/etiology
- Epilepsy, Generalized/physiopathology
- Epilepsy, Tonic-Clonic/diagnostic imaging
- Epilepsy, Tonic-Clonic/etiology
- Epilepsy, Tonic-Clonic/physiopathology
- Functional Laterality/physiology
- Humans
- Image Processing, Computer-Assisted
- Magnetic Resonance Imaging/statistics & numerical data
- Technetium Tc 99m Exametazime
- Thalamus/diagnostic imaging
- Thalamus/physiopathology
- Tomography, Emission-Computed, Single-Photon/statistics & numerical data
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Affiliation(s)
- Miro Enev
- Departments of Neurology, Yale University School of Medicine, New Haven, Connecticut 06520-8018, USA
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8
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Shi LH, Luo F, Woodward DJ, McIntyre DC, Chang JY. Temporal sequence of ictal discharges propagation in the corticolimbic basal ganglia system during amygdala kindled seizures in freely moving rats. Epilepsy Res 2006; 73:85-97. [PMID: 17049434 PMCID: PMC1941664 DOI: 10.1016/j.eplepsyres.2006.08.008] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2006] [Revised: 08/16/2006] [Accepted: 08/29/2006] [Indexed: 10/24/2022]
Abstract
We used a multiple channel, single unit recording technique to investigate the neural activity in different corticolimbic and basal ganglia regions in freely moving rats before and during generalized amygdala kindled seizures. Neural activity was recorded simultaneously in the sensorimotor cortex (Ctx), hippocampus, amygdala, substantia nigra pars reticulata (SNr) and the subthalamic nucleus (STN). We observed massive synchronized activity among neurons of different brain regions during seizure episodes. Neurons in the kindled amygdala led other regions in synchronized firing, revealed by time lags of neurons in other regions in crosscorrelogram analysis. While there was no obvious time lag between Ctx and SNr, the STN and hippocampus did lag behind the Ctx and SNr in correlated firing. Activity in the amygdala and SNr contralateral to the kindling stimulation site lagged behind their ipsilateral counterparts. However, no time lag was found between the kindling and contralateral sides of Ctx, hippocampus and STN. Our data confirm that the amygdala is an epileptic focus that emits ictal discharges to other brain regions. The observed temporal pattern indicates that ictal discharges from the amygdala arrive first at Ctx and SNr, and then spread to the hippocampus and STN. The simultaneous activation of both sides of the Ctx suggests that the neocortex participates in kindled seizures as a unisonant entity to provoke the clonic motor seizures. Early activation of the SNr (before the STN and hippocampus) points to an important role of the SNr in amygdala kindled seizures and supports the view that different SNr manipulations may be effective ways to control seizures.
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Affiliation(s)
- Li-Hong Shi
- Department of Physiology and Pharmacology, Wake Forest University School of Medicine, Winston-Salem, NC 27157, USA
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Tilelli CQ, Del Vecchio F, Fernandes A, Garcia-Cairasco N. Different types of status epilepticus lead to different levels of brain damage in rats. Epilepsy Behav 2005; 7:401-10. [PMID: 16140590 DOI: 10.1016/j.yebeh.2005.06.013] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/16/2004] [Revised: 06/08/2005] [Accepted: 06/10/2005] [Indexed: 10/25/2022]
Abstract
We investigated a possible correlation between behavior during status epilepticus (SE) and underlying brain damage. Adult rats were electrically stimulated in the left amygdala to induce SE, which was stopped 2 hours later. We observed two different types of SE: (1) typical SE (TSE), with facial automatisms, neck and forelimb myoclonus, rearing and falling, and tonic-clonic seizures; (2) ambulatory SE (ASE), with facial automatisms, neck myoclonus, and concomitant ambulatory behavior. TSE was behaviorally more severe than ASE (P<0.05). Histology revealed neuronal loss in several brain areas. There was a positive correlation between SE type and amount of injured areas 24 hours and 14 days after SE (P<0.01). The areas more affected were piriform cortex and hippocampal formation. We suggest quality of seizures during SE may be considered in further SE studies, as our results indicate its influence on the severity of brain damage following this paradigm.
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Affiliation(s)
- Cristiane Queixa Tilelli
- Departamento de Fisiologia, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brazil
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Chassagnon S, de Vasconcelos AP, Ferrandon A, Koning E, Marescaux C, Nehlig A. Time course and mapping of cerebral perfusion during amygdala secondarily generalized seizures. Epilepsia 2005; 46:1178-87. [PMID: 16060926 DOI: 10.1111/j.1528-1167.2005.07505.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
PURPOSE Measurement of local cerebral blood flow (LCBF) is routinely used to locate the areas involved in generation and spread of seizures in epilepsy patients. Because the spatial distribution and extent of ictal CBF depends on the epileptogenic network, but also on the timing of injection of tracer, we used a rat model of amygdala-kindled seizures to follow the time-dependent changes in the distribution of LCBF changes. METHODS Rats were implanted in the left amygdala and were fully kindled. LCBF was measured by the quantitative [(14)C]iodoantipyrine autoradiographic technique bilaterally in 35 regions. The tracer was injected at 30 s before seizure induction (early ictal), simultaneous with the application of stimulation (ictal), at 60 s after stimulation (late ictal), at the end of the electrical afterdischarge (early postictal), and at 6 min after the stimulation (late postictal). RESULTS Rates of LCBF increased over control levels during the early ictal phase ipsilaterally in medial amygdala, frontal cortex, and ventromedian thalamus and bilaterally in the whole hippocampus, thalamic nuclei, and basal ganglia. During the ictal phase, all regions underwent hyperperfusion (81-416% increases). By 60 s after stimulation, rates of LCBF returned to control levels in most brain areas, despite ongoing seizure activity. At later times, localized foci of hypoperfusion were observed in hippocampus bilaterally, with a slight predominance in CA1 on the side of origin of the seizures. CONCLUSION This study shows a rapid spread of activation from the stimulated amygdala bilaterally to numerous limbic, cortical, and subcortical structures. The largest hyperperfusion was recorded during the ictal period with tracer injections simultaneous with the stimulation. The unilateral site of origin of seizures led to minor asymmetrical and lateralized findings, merely at early ictal and late postictal times, whereas intermediate tracer injections induced bilateral changes. Only late postictal measurements allowed the identification of significant changes in focal structures: the hippocampus is known to play a critical role in the spread of limbic seizures.
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Mohapel P, Ekdahl CT, Lindvall O. Status epilepticus severity influences the long-term outcome of neurogenesis in the adult dentate gyrus. Neurobiol Dis 2004; 15:196-205. [PMID: 15006689 DOI: 10.1016/j.nbd.2003.11.010] [Citation(s) in RCA: 109] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2002] [Revised: 10/03/2003] [Accepted: 11/03/2003] [Indexed: 12/24/2022] Open
Abstract
Status epilepticus (SE) is characterized by continual seizure activity that can vary widely in the intensity of convulsions. We induced seizures by applying continuous electrical stimulation to the hippocampus in adult rats to explore the effects of three different SE states on neurogenesis and neuronal death in the hippocampus. Rats exhibiting the most severe SE state (fully convulsive) demonstrated profound increases in cell proliferation in the dentate gyrus (DG) at 1 week post-insult, but the majority of the new neurons had died at 4 weeks. In contrast, rats exhibiting less severe SE states (ambulatory or masticatory, partial convulsive) had the same degree of cell proliferation at 1 week, but most new neurons survived at 4 weeks. As compared to partially convulsive SE rats, fully convulsive SE rats had significantly greater DG pathology. Our data indicate that SE of varying severity triggers similar short-term proliferation of neural progenitors, but that the long-term outcome of neurogenesis is influenced by the degree of insult-induced degeneration in the DG tissue environment.
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Affiliation(s)
- Paul Mohapel
- Section of Restorative Neurology, Wallenberg Neuroscience Center, SE-221 84 Lund, Sweden.
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McNally KA, Blumenfeld H. Focal network involvement in generalized seizures: new insights from electroconvulsive therapy. Epilepsy Behav 2004; 5:3-12. [PMID: 14751200 DOI: 10.1016/j.yebeh.2003.10.020] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Generalized seizures are commonly thought to involve the entire brain homogeneously. However, recent evidence suggests that selective cortical-subcortical networks may be crucial for the initiation, propagation, and behavioral manifestations of generalized seizures, while other brain regions are relatively spared. Here we review previous studies, and describe a new human model system for the investigation of generalized seizures: single-photon emission computed tomography, ictal-interictal difference imaging of generalized tonic-clonic seizures induced by electroconvulsive therapy (ECT). Bitemporal ECT activates focal bilateral frontotemporal and parietal association cortex, sparing other regions; bifrontal ECT activates mainly prefrontal cortex; while in right unilateral ECT the left frontotemporal region is relatively spared. Associated midline subcortical networks are also involved. Focal verbal memory deficits parallel the focal regions involved in these neuroimaging studies. Further studies of this kind may elucidate specific networks in generalized tonic-clonic seizures, providing targets for new therapeutic interventions in epilepsy.
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Affiliation(s)
- Kelly A McNally
- Department of Neurology and Department of Neurobiology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA
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Faingold CL. Emergent properties of CNS neuronal networks as targets for pharmacology: application to anticonvulsant drug action. Prog Neurobiol 2004; 72:55-85. [PMID: 15019176 DOI: 10.1016/j.pneurobio.2003.11.003] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2003] [Accepted: 11/19/2003] [Indexed: 01/13/2023]
Abstract
CNS drugs may act by modifying the emergent properties of complex CNS neuronal networks. Emergent properties are network characteristics that are not predictably based on properties of individual member neurons. Neuronal membership within networks is controlled by several mechanisms, including burst firing, gap junctions, endogenous and exogenous neuroactive substances, extracellular ions, temperature, interneuron activity, astrocytic integration and external stimuli. The effects of many CNS drugs in vivo may critically involve actions on specific brain loci, but this selectivity may be absent when the same neurons are isolated from the network in vitro where emergent properties are lost. Audiogenic seizures (AGS) qualify as an emergent CNS property, since in AGS the acoustic stimulus evokes a non-linear output (motor convulsion), but the identical stimulus evokes minimal behavioral changes normally. The hierarchical neuronal network, subserving AGS in rodents is initiated in inferior colliculus (IC) and progresses to deep layers of superior colliculus (DLSC), pontine reticular formation (PRF) and periaqueductal gray (PAG) in genetic and ethanol withdrawal-induced AGS. In blocking AGS, certain anticonvulsants reduce IC neuronal firing, while other agents act primarily on neurons in other AGS network sites. However, the NMDA receptor channel blocker, MK-801, does not depress neuronal firing in any network site despite potently blocking AGS. Recent findings indicate that MK-801 actually enhances firing in substantia nigra reticulata (SNR) neurons in vivo but not in vitro. Thus, the MK-801-induced firing increases in SNR neurons observed in vivo may involve an indirect effect via disinhibition, involving an action on the emergent properties of this seizure network.
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Affiliation(s)
- Carl L Faingold
- Department of Pharmacology, Southern Illinois University School of Medicine, P.O. Box 19629, Springfield, IL 62794-9629, USA.
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Foster JA, Puchowicz MJ, McIntyre DC, Herkenham M. Activin mRNA induced during amygdala kindling shows a spatiotemporal progression that tracks the spread of seizures. J Comp Neurol 2004; 476:91-102. [PMID: 15236469 DOI: 10.1002/cne.20197] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The progressive development of seizures in rats by amygdala kindling, which models temporal lobe epilepsy, allows the study of molecular regulators of enduring synaptic changes. Neurotrophins play important roles in synaptic plasticity and neuroprotection. Activin, a member of the transforming growth factor-beta superfamily of growth and differentiation factors, has recently been added to the list of candidate synaptic regulators. We mapped the induction of activin betaA mRNA in amygdala and cortex at several stages of seizure development. Strong induction, measured 2 hours after the first stage 2 (partial) seizure, appeared in neurons of the ipsilateral amygdala (confined to the lateral, basal, and posterior cortical nuclei) and insular, piriform, orbital, and infralimbic cortices. Activin betaA mRNA induction, after the first stage 5 (generalized) seizure, had spread to the contralateral amygdala (same nuclear distribution) and cortex, and the induced labeling covered much of the convexity of neocortex as well as piriform, perirhinal, and entorhinal cortices in a nearly bilaterally symmetrical pattern. This pattern had filled in by the sixth stage 5 seizure. Induced labeling in cortical neurons was confined mainly to layer II. A similar temporal and spatial pattern of increased mRNA expression of brain-derived neurotrophic factor (BDNF) was found in the amygdala and cortex. Activin betaA and BDNF expression patterns were similar at 1, 2, and 6 hours after the last seizure, subsiding at 24 hours; in contrast, c-fos mRNA induction appeared only at 1 hour throughout cortex and then subsided. In double-label studies, activin betaA mRNA-positive neurons were also BDNF mRNA positive, and they did not colocalize with GAD67 mRNA (a marker of gamma-aminobutyric acidergic neurons). The data suggest that activin and BDNF transcriptional activities accurately mark excitatory neurons participating in seizure-induced synaptic alterations and may contribute to the enduring changes that underlie the kindled state.
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Affiliation(s)
- Jane A Foster
- Section on Functional Neuroanatomy, National Institute of Mental Health, National Institutes of Health, United States Department of Health and Human Services, Bethesda, Maryland 20892-4070, USA
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Abstract
Model systems are needed for the scientific investigation of consciousness. A good model system should include variable states of consciousness, allowing the relationship between brain activity and consciousness to be investigated. Examples include sleep, anesthesia, focal brain lesions, development, evolution, and epilepsy. One advantage of epilepsy is that changes are dynamic and rapidly reversible. The authors review previous investigations of impaired consciousness in epilepsy and describe new findings that may shed light on both normal and abnormal mechanisms of consciousness. Abnormal increased activity in fronto-parietal association cortex and related subcortical structures is associated with loss of consciousness in generalized seizures. Abnormal decreased activity in these same networks may cause loss of consciousness in complex partial seizures. Thus, abnormally increased or decreased activity in the same networks can cause loss of consciousness. Information flow during normal conscious processing may require a dynamic balance between these two extremes of excitation and inhibition.
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Affiliation(s)
- Hal Blumenfeld
- Department of Neurology, Yale University School of Medicine, New Haven, CT 06520-8018, USA.
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Brandt C, Glien M, Potschka H, Volk H, Löscher W. Epileptogenesis and neuropathology after different types of status epilepticus induced by prolonged electrical stimulation of the basolateral amygdala in rats. Epilepsy Res 2003; 55:83-103. [PMID: 12948619 DOI: 10.1016/s0920-1211(03)00114-1] [Citation(s) in RCA: 106] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
It has previously been shown that prolonged (60-min) low-intensity electrical stimulation of a kindled focus in the basolateral nucleus of the amygdala (BLA) of Wistar rats resulted in the development of self-sustained status epilepticus (SSSE) with predominantly partial seizures and subsequent brain damage in the ipsilateral hemisphere. In the present study, using high-intensity (700 microA) pulsed-train electrical stimulation of the BLA for 25 min, SSSE was induced in both kindled and non-kindled Wistar rats, demonstrating that under these experimental conditions prior kindling is not necessary to induce SSSE. Thus, all subsequent experiments were done in non-kindled rats of different strains (Wistar, Sprague-Dawley) and genders. Three distinct behavioral types of SSSE were observed: (1) continuous partial seizures; (2) continuous partial seizures, repeatedly interrupted by generalized convulsive seizures; and (3) continuous generalized convulsive seizures. These three forms of SSSE were seen in both strains and genders, although the percentage of rats in each strain and gender developing a specific type of SSSE differed. Rats spontaneously recovered from SSSE after between 3 and 8h on average, the SSSE duration depending on SSSE type, rat strain and gender. Following SSSE, rats were monitored with a video- and EEG-recording system for occurrence of spontaneous recurrent seizures (SRS). Overall, about 80% of the rats developed epilepsy with SRS after SSSE, but the proportion of rats developing SRS depended on the type of SSSE. Only 33% of the rats developed SRS after a partial SSSE, compared to >90% in case of either type 2 or type 3 SSSE with generalized convulsive seizures. Interruption of different forms of SSSE with diazepam after 90 min prevented development of epilepsy, while a generalized SSSE duration of 4h consistently produced epilepsy in >90% of rats. Histologic analysis of rat brains after the different SSSE types indicated that neuronal loss after partial SSSE was much more regionally restricted and less severe compared to neuronal damage after SSSE with generalized convulsive seizures, which was similar to the brain damage seen in the kainate and pilocarpine models of temporal lobe epilepsy. These experiments establish that prolonged electrical stimulation of the BLA induces different forms of SSSE that resemble nonconvulsive and convulsive types of SE in humans. These different forms of SSSE induce epilepsy with SRS and brain pathology reminiscent of temporal lobe epilepsy with hippocampal sclerosis. The rat model provides a new tool to mimic different types of SE and investigate the pathogenesis underlying their long-term complications.
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Affiliation(s)
- Claudia Brandt
- Department of Pharmacology, Toxicology, and Pharmacy, School of Veterinary Medicine, Bünteweg 17, D-30559, Hannover, Germany
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Kelly ME, Staines WA, McIntyre DC. Secondary generalization of hippocampal kindled seizures in rats: examining the role of the piriform cortex. Brain Res 2002; 957:152-61. [PMID: 12443991 DOI: 10.1016/s0006-8993(02)03617-x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
A primary feature of epilepsy is the potential for focal seizures to recruit distant structures and generalize into convulsions. Key to understanding generalization is to identify critical structures facilitating the transition from focal to generalized seizures. In kindling, development of a primary site leads progressively to secondarily generalized convulsions. In addition, subsequent kindling of a secondary site results in rapid kindling from that site, presumably because of its facilitated access to the primary kindled network. Here, we investigated the role of the piriform cortex in convulsive generalization from a secondary site kindled in the hippocampus after primary site amygdala kindling. In a necessarily complicated design, rats initially experienced forebrain commissurotomy to lateralize the experiment to one hemisphere. Then the amygdala was kindled and, 3 weeks later, it was electrically-triggered into status epilepticus, which destroyed the ipsilateral piriform cortex. This experience occurred several days before secondary site kindling of the dorsal hippocampus. In rats with complete piriform cortex loss, there was no disruption in kindling or convulsive seizure expression from the hippocampus. However, when damage also involved parts of the perirhinal, insular and entorhinal cortices, convulsive expression was blocked. Although other evidence suggests that piriform lesions affect generalization of primary site kindling, the present study shows that they do not alter secondary site kindling in the dorsal hippocampus. The additional involvement of parahippocampal cortical areas in convulsive expression suggests an important functional association between these cortical regions and the hippocampus in seizure propagation and clinical expression.
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Affiliation(s)
- Mary Ellen Kelly
- Department of Psychology, Life Sciences Research Center, Carleton University, Ontario Ottawa K1S 5B6, Canada
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18
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Abstract
Like normal cerebral function, epileptic seizures involve widespread network interactions between cortical and subcortical structures. Although the cortex is often emphasized as the site of seizure origin, accumulating evidence points to a crucial role for subcortical structures in behavioral manifestations, propagation, and, in some cases, initiation of epileptic seizures. Extensive previous studies have shown the importance of subcortical structures in animal seizure models, but corresponding human studies have been relatively few. We review the existing evidence supporting the importance of the thalamus, basal ganglia, hypothalamus, cerebellum, and brain stem in human epilepsy. We also propose a "network inhibition hypothesis" through which focal cortical seizures disrupt function in subcortical structures (such as the medial diencephalon and pontomesencephalic reticular formation), leading secondarily to widespread inhibition of nonseizing cortical regions, which may in turn be responsible for behavioral manifestations such as loss of consciousness during complex partial seizures.
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Affiliation(s)
- Andrew D. Norden
- Departments of Neurology and Neurobiology, Yale University School of Medicine, 333 Cedar Street, New Haven, 06520-8018, CT, USA
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Scorza FA, Arida RM, Priel MR, Calderazzo L, Cavalheiro EA. Glucose utilisation during status epilepticus in an epilepsy model induced by pilocarpine: a qualitative study. ARQUIVOS DE NEURO-PSIQUIATRIA 2002; 60:198-203. [PMID: 12068345 DOI: 10.1590/s0004-282x2002000200003] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Status epilepticus (SE) is a medical emergency and it is associated to brain damage. 2-deoxy-[14C] glucose (2-DG) procedure has been used to measure the alterations in the functional activity of the brain induced by various pharmacological and toxicological agents. The aim of this study was to determine which changes occur in the seizure anatomic substrates during the SE induced by pilocarpine (PILO) using [14C]-2 deoxyglucose functional mapping technique. Wistar male adult rats were submitted to SE PILO-induced for 6h and received [14C] 2-deoxyglucose injection via jugular vein 45 min before the 6th hour of SE. The control animals were submitted to all procedures but received saline and not pilocarpine. Brain sections were prepared and exposed X-ray film about seven days. The optical density of each region was obtained using a solid state digital analyser. The analysis revealed that 14C-2DG utilisation was pronounced in the SE rats on the areas corresponding to the hippocampal formation (+50.6%), caudate-putamen (+30.6%), frontoparietal cortex (+32.2%), amygdala (+31.7%), entorrinal cortex (+28.2%), thalamic nucleus (+93.5%), pre-tectal area (+50.1%) and substantia nigra (+50.3%) when compared to control. Our results suggest that the different activation levels of the distinct structures may be particularly important for understanding triggering and spreading mechanisms underlying epileptic activity during status epilepticus.
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André V, Ferrandon A, Marescaux C, Nehlig A. The lesional and epileptogenic consequences of lithium-pilocarpine-induced status epilepticus are affected by previous exposure to isolated seizures: effects of amygdala kindling and maximal electroshocks. Neuroscience 2001; 99:469-81. [PMID: 11029539 DOI: 10.1016/s0306-4522(00)00209-8] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
In temporal lobe epilepsy, the occurrence of seizures seems to correlate with the presence of lesions underlying the establishment of a hyperexcitable circuit. However, in the lithium-pilocarpine model of epilepsy, neuronal damage occurs both in the structures belonging to the circuit of initiation and maintenance of the seizures (forebrain limbic system) as in the propagation areas (cortex and thalamus) and in the circuit of remote control of seizures (substantia nigra pars reticulata). To determine whether or not we could protect the brain from lesions and epileptogenesis induced by status epilepticus and identify cerebral structures involved in the genesis of epilepsy, we studied the effects of the chronic exposure to non-deleterious seizures, either focalized with secondary generalization (amygdala kindling, kindled-pilocarpine rats), or primary generalized (ear-clip electroshocks, electroshock-pilocarpine rats) on neuronal damage and epileptogenesis induced by lithium-pilocarpine status epilepticus. These animals were compared to rats subjected to status epilepticus but not pretreated with seizures (sham-kindled-pilocarpine or sham-electroshock-pilocarpine rats). Compared to sham-pilocarpine rats, neuronal damage was prevented in the limbic system of the kindled-pilocarpine rats, except in the hilus of the dentate gyrus and the entorhinal cortex, while it was enhanced in rats pretreated with electroshocks, mainly in the entorhinal and perirhinal cortices. Most sham-kindled- and sham-electroshock-pilocarpine rats (92-100%) developed recurrent seizures after a silent period of 40-54days. Likewise, all kindled-pilocarpine rats developed spontaneous seizures after the same latency as their sham controls, while only two of 10 electroshock-pilocarpine rats became epileptic after a delay of 106-151days. The present data show that the apparent antiepileptic properties of electroshocks correlate with extensive damage in midbrain cortical regions, which may prevent the propagation of seizures from the hippocampus and inhibit their motor expression. Conversely, the extensive neuroprotection of the limbic system but not the hilus and entorhinal cortex provided by amygdala kindling does not prevent epileptogenesis. Thus, the hilus, the entorhinal and/or perirhinal cortex may be key structure(s) for the establishment of epilepsy.
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Affiliation(s)
- V André
- INSERM U398, Faculté de Médecine, Université Louis Pasteur, 67085 Cedex, Strasbourg, France
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21
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Plata-Salamán CR, Ilyin SE, Turrin NP, Gayle D, Flynn MC, Romanovitch AE, Kelly ME, Bureau Y, Anisman H, McIntyre DC. Kindling modulates the IL-1beta system, TNF-alpha, TGF-beta1, and neuropeptide mRNAs in specific brain regions. BRAIN RESEARCH. MOLECULAR BRAIN RESEARCH 2000; 75:248-58. [PMID: 10686345 DOI: 10.1016/s0169-328x(99)00306-x] [Citation(s) in RCA: 156] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Cytokines and neuropeptides may be involved in seizure-associated processes. Following amygdala kindling in rats, we determined alterations of IL-1beta, IL-1 receptor antagonist (IL-1Ra), IL-1 receptor type I (IL-1RI), IL-1 receptor accessory proteins (IL-1R AcPs) I and II, TNF-alpha, TGF-beta1, neuropeptide Y (NPY), glycoprotein 130 (gp 130) and pro-opiomelanocortin (POMC) mRNA levels in the parietal, prefrontal and piriform cortices, amygdala, hippocampus and hypothalamus. Messenger RNAs expression in all brain regions was determined 2 h or 3 weeks following the last generalized convulsive seizure triggered from the ipsilateral kindled amygdala. The same brain region sample was used to assay for changes of all mRNA components. The results show that the 2 h-kindled group exhibited a significant up-regulation of IL-1beta, IL-1RI, TNF-alpha and TGF-beta1 mRNAs in all three cortical brain regions, amygdala and hippocampus. The largest up-regulation occurred in the prefrontal cortex (about 30-fold induction for IL-1beta and TNF-alpha mRNAs). IL-1R AcP I and II mRNA levels were also up-regulated in the cortical regions. No changes in IL-1beta, IL-1RI or TNF-alpha mRNA levels occurred in the 3 week-kindled group. NPY mRNA levels increased in the hippocampus, prefrontal and piriform cortices in the 2 h-kindled group, while IL-1Ra, gp 130, or POMC mRNA levels did not change in any group. The overall profile of mRNA changes shows specificity of transcriptional modulation induced by amygdala kindling. The data support a role of cytokines and NPY in the adaptive mechanisms associated with generalized seizure activity, with implications for neuroprotection, neuronal dysfunction and vulnerability associated with epileptic activity.
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Affiliation(s)
- C R Plata-Salamán
- Division Molecular Biology, School of Life and Health Sciences, University of Delaware, Newark, DE, USA. cplatasa@
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22
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Pereira de Vasconcelos A, Mazarati AM, Wasterlain CG, Nehlig A. Self-sustaining status epilepticus after a brief electrical stimulation of the perforant path: a 2-deoxyglucose study. Brain Res 1999; 838:110-8. [PMID: 10446323 DOI: 10.1016/s0006-8993(99)01729-1] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Status epilepticus remains a life-threatening condition associated with a high mortality. In order to understand the pathophysiological mechanisms underlying sustained seizures, the identification of structures involved in seizure activity allowing to define epileptic networks may be important. Thus, local cerebral metabolic rate for glucose (LCMR(glc)) was measured in a rat model of self-sustaining status epilepticus (SSSE) induced by a brief intermittent perforant path stimulation of 30 min, using the quantitative [(14)C]2-deoxyglucose autoradiographic technique. SSSE induced a generalized bilateral increase in LCMR(glcs) affecting 27 of the 42 structures studied. Largest metabolic increases (>250%) were recorded in the hippocampus, amygdala, entorhinal and piriform cortices, and lateral septum. Marked metabolic activation was also seen in basal ganglia areas such as the substantia nigra, globus pallidus and accumbens nucleus. LCMR(glcs) in brainstem, some midbrain structures, and in the neocortex were not affected by SSSE. In conclusion, a brief stimulation of the hippocampus induced a reproducible limbic SSSE in 100% of the rats, characterized by the metabolic activation of limbic and extralimbic structures, known to be involved in this type of seizures. Therefore, this new model allowing the development of a well-defined SSSE, appears to be particularly suitable for further studies on the mechanisms involved in status epilepticus.
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Kelly ME, Battye RA, McIntyre DC. Cortical spreading depression reversibly disrupts convulsive motor seizure expression in amygdala-kindled rats. Neuroscience 1999; 91:305-13. [PMID: 10336080 DOI: 10.1016/s0306-4522(98)00656-3] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
To determine the role of the frontal cortex in the generalization of limbic seizures, we first produced unilateral cortical spreading depression to reversibly suppress neuronal activity in the motor cortex and then triggered an amygdala-kindled seizure. Three minutes following induction of unilateral spreading depression, stimulation of the ipsilateral kindled amygdala produced only a brief electrographic seizure, and completely failed to produce the bilateral electrographic and clonic convulsive seizures that were normally present during control trials. A very different outcome occurred when unilateral spreading depression was induced in the cortex contralateral to the kindled amygdala. In these cases, the electrographic amygdala seizures were normal and bilateral like control trials, yet the clonic convulsive seizures were lateralized and appeared to be controlled by the non-depressed, kindled hemisphere. These lateralized convulsions were identical to those observed following forebrain commissurotomy, when direct communication between the frontal cortices was permanently severed. The results of the present study further define the pathways of temporal lobe seizure propagation, and highlight the important contribution frontal cortical regions provide to both the electrographic and convulsive expression of amygdala-kindled seizures by amplifying local seizures and projecting them into downstream brainstem and spinal cord circuits.
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Affiliation(s)
- M E Kelly
- Department of Psychology, Institute of Neuroscience, Carleton University, Ottawa, Ontario, Canada
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24
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Smith BN, Dudek FE. Enhanced population responses in the basolateral amygdala of kainate-treated, epileptic rats in vitro. Neurosci Lett 1997; 222:1-4. [PMID: 9121710 DOI: 10.1016/s0304-3940(97)13326-2] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Several lines of evidence suggest that the amygdala is altered functionally in humans with temporal lobe epilepsy, but little is known about neuronal interactions in the amygdala of humans or animals with chronic epilepsy. Using extracellular and intracellular recordings in horizontal slices, we tested the hypothesis that changes in local circuitry in the basolateral amygdala (BLA) permanently enhance neuronal responsiveness in kainate-treated, epileptic rats. Population responses in the BLA to orthodromic stimulation were significantly enhanced, which was at least partly due to a decrease in local inhibition. In the presence of GABA receptor antagonists, population responses were about twice as robust in epileptic versus control rats. We conclude that the enhanced neuronal responsiveness of the BLA in this model of temporal lobe epilepsy involves decreased inhibition, but may also include increased excitation.
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Affiliation(s)
- B N Smith
- Department of Anatomy and Neurobiology, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, USA
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25
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Abstract
Because convulsive seizures develop very rapidly from kindling sites in the anterior perirhinal cortex, we studied perirhinal efferents by using the anterograde tracer Phaseolus vulgaris leucoagglutinin (PhAL). PhAL injections into the anterior perirhinal cortex labelled a prominent network of fibers within the frontal cortex that was most dense within layers I and II and layer VI. As individual PhAL injection sites within the perirhinal cortex were restricted to one or two adjacent laminae, we were able to determine that layer V was the main source of the perirhinofrontal projection. This was confirmed by frontal cortex injections of the retrograde tracer Fluorogold (FG). Other cortical areas with densely labelled fibers following perirhinal PhAL injections included the agranular insular, infralimbic, orbital, parietal, and entorhinal cortices. Moderate to mild fiber labelling was also noted in the posterior piriform, temporal and occipital cortices, and the claustrum. Subcortical labelling was seen in the nucleus accumbens; fundus striati; basal and lateral amygdala nuclei; the "acoustic thalamus"; and the central grey. Several of these cortical and subcortical projections were bilateral. The different laminar origin of these perirhinal efferents is discussed. These results confirmed our prediction of extensive direct projections from the anterior perirhinal cortex to the frontal cortex in the rat. The significance of this projection is discussed with special reference to the anatomical basis of convulsive limbic seizures.
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Affiliation(s)
- D C McIntyre
- Department of Psychology, Institute of Neuroscience, Carleton University, Ottawa, Ontario, Canada
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26
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Mohapel P, Dufresne C, Kelly ME, McIntyre DC. Differential sensitivity of various temporal lobe structures in the rat to kindling and status epilepticus induction. Epilepsy Res 1996; 23:179-87. [PMID: 8739121 DOI: 10.1016/0920-1211(95)00084-4] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Using focal brain stimulation (kindling), discrete seizures can be triggered from many neuroanatomic sites with varying degrees of facility. From several of these sites, protracted seizures or status epilepticus (SE) also can be triggered. To date, no comparison has been made between different brain sites in their sensitivity both to kindling and to SE development. In this report, we have compared the kindling profiles of three amygdala nuclei, namely the basal (BL), central (CE), and medial (ME) nuclei, to the adjacent piriform (PIR) and perirhinal (PRH) cortices. In addition, three weeks following kindling, the susceptibility of each kindled site to status epilepticus (SE) was assessed by exposing the site to 60 min of electrical stimulation. We observed that (a) during the course of daily kindling, the afterdischarge threshold dropped progressively and significantly in all structures, (b) the rate of kindling in the PRH and PIR cortices and the CE amygdala was significantly faster than either the BL or ME amygdala, (c) when discrete convulsions were triggered, the latency to forelimb clonus in the PRH cortex and CE amygdala was significantly shorter than the other three structures, and (d) despite being slower to kindle than most other sites, stimulation of the BL nucleus most readily triggered SE. The kindling data suggest that discharges triggered from the PRH and CE more readily access motor systems supporting limbic convulsions than discharges triggered from the BL, ME nuclei or the PIR cortex. On the other hand, the SE data indicate that the mechanisms and circuits associated with the development of discrete kindled seizures are not identical to those associated with the induction of limbic SE.
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Affiliation(s)
- P Mohapel
- Department of Psychology, Carleton University, Ottawa, Canada
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27
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Araki T, Kato M, Kobayashi T. Limbic seizures originating in the olfactory bulb: an electro-behavioral and glucose metabolism study. Brain Res 1995; 693:207-16. [PMID: 8653410 DOI: 10.1016/0006-8993(95)00626-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
We studied seizures which were induced by a microinjection of kainic acid (KA) into the unilateral olfactory bulb (OB) in the rats. The first epileptiform discharge appeared in the OB, was then propagated to the amygdala and the hippocampus unilaterally, and finally propagated to the unilateral sensori-motor cortex. Consistent graded behavioral changes, almost identical to those of the amygdaloid and hippocampal seizures, occurred during the development of the seizures, and three stages were classified: stage 1 was staring, stage 2 consisted of masticatory movement and stage 3 demonstrated rearing and rearing and falling. Local cerebral glucose utilization (LCGU) measured with the [14C]2-deoxyglucose method revealed a graded propagation of seizure activities at each stage in the unilateral structures. At stage 1, the increased activities propagated from the OB localized in the anterior olfactory nucleus; at stage 2, the endopiriform nucleus, the nucleus accumbens, the entorhinal cortex, the ventral globus pallidus and the globus pallidus were all activated; at stage 3, the thalamic nuclei (mediodorsal, ventrolateral, ventromedial and centromedian nuclei), the substantia nigra pars reticulata, the entopeduncular nucleus and the sensorimotor cortex were also activated. The globus pallidus, which receives afferent fibers from the nucleus accumbens, was the first structure that was activated metabolically among the extralimbic structures. No metabolic activation occurred in the amygdala and the hippocampus in spite of the early propagation of epileptiform discharges to these structures on EEG. These results suggest that OB seizures involve the limbic structures, while the amygdala and the hippocampus have a little contribution to OB seizures. In addition, the nucleus accumbens plays an important role as a functional interface between the limbic and the motor system in OB seizures.
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Affiliation(s)
- T Araki
- Department of Neurology, Faculty of Medicine, Kyushu University, Fukuoka, Japan
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28
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Handforth A, Ackermann RF. Mapping of limbic seizure progressions utilizing the electrogenic status epilepticus model and the 14C-2-deoxyglucose method. BRAIN RESEARCH. BRAIN RESEARCH REVIEWS 1995; 20:1-23. [PMID: 7711764 DOI: 10.1016/0165-0173(94)00003-8] [Citation(s) in RCA: 53] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
We have previously described a model of limbic status epilepticus in which chronic prolonged seizure states of immobile, exploratory, minor convulsive or clonic convulsive behavior are induced by intracerebral electrical stimulation; these states appear to belong to the same behavioral progression as kindled seizures. We postulated that the underlying seizure substrates, as mapped by the 14C-2-deoxyglucose method, should reflect a corresponding anatomic progression of discharge spread. Status epilepticus was induced in rat by pulsed-train current delivered for up to 90 min to one of several subcortical areas. Autoradiographs revealed that most of the observed patterns of seizure-induced metabolic activation comprised a hierarchical sequence, such that progressively more extensive patterns subsumed anatomic territories activated in less extensive patterns, thus allowing inferences as to the progression of discharge spread. In this sequence, the basolateral amygdala ipsilateral to the induction electrode was among the first structures to be activated. In successively larger activation patterns a small unilateral network related to basolateral amygdala was involved; this evolved through a transitional state to a unilateral extensive limbic pattern; which in turn was succeeded by bilateral extensive limbic activation. This hierarchical sequence culminated in a neocortical activation pattern, in which most of the forebrain was involved in intense seizure-induced activation. Seizure behaviors increased in severity in correspondence with the underlying seizure-activated anatomic substrate. In contrast, patterns of seizure activation were observed which did not fit within the early stages of the above sequence, although analysis indicates that the later stages of spread may be shared. The study of these patterns and those reported in the literature indicates that although limbic seizure networks may be anatomically distinct at their origination, further expansion is characterized by overlap; upon assumption of extensive patterns of activation the number of nuclei participating is so vast that the identity of the limbic originator is lost and common convulsive manifestations occur.
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Affiliation(s)
- A Handforth
- Department of Neurology, UCLA School of Medicine, Reed Neurological Research Center 90024, USA
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Handforth A, Treiman DM. A new, non-pharmacologic model of convulsive status epilepticus induced by electrical stimulation: behavioral/electroencephalographic observations and response to phenytoin and phenobarbital. Epilepsy Res 1994; 19:15-25. [PMID: 7813410 DOI: 10.1016/0920-1211(94)90084-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Much remains to be learned about mechanisms underlying entry into, and temporal progression of, status epilepticus (SE). This report describes a non-pharmacologic model of generalized convulsive SE in rat. Pulsed trains of suprathreshold electric current, were administered bilaterally to either of four rostral forebrain sites: orbital cortex, medial precentral cortex, deep prepiriform cortex, or rostral caudate-putamen (n = 8 per site). This induction method resulted in 30/32 animals attaining limb-clonic convulsive SE within a mean of 30-35 min for each forebrain site, with no differences between sites. Subsequent SE proceeded without further interventions, permitting observation of the natural course of progression. A stereotyped behavioral/electrographic sequence occurred, characterized by devolution. Behaviorally, animals progressed from predominantly limb clonus to head clonus, then to subtle twitching, and finally to electrical SE before cessation of spikes. The corresponding electrographic progression was from fast and slow spiking to periodic epileptiform discharges (PEDs). In 20 animals surviving to 48 h, pathologic damage affected mainly limbic sites; damage was related to total convulsive time rather than to clonic activity. High-dose phenobarbital but not phenytoin suppressed SE when given during orbital cortex-induced limb-clonic SE. These findings are compatible with human observations and indicate that this model will enable investigations of generalized SE mechanisms and evaluation of new therapeutic agents for refractory SE.
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Affiliation(s)
- A Handforth
- Department of Veterans Affairs Medical Center, West Los Angeles, CA
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31
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Handforth A, Treiman DM. Effect of an adenosine antagonist and an adenosine agonist on status entry and severity in a model of limbic status epilepticus. Epilepsy Res 1994; 18:29-42. [PMID: 8088255 DOI: 10.1016/0920-1211(94)90031-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Adenosine is an endogenous neuromodulator that suppresses excitatory neurotransmission. We postulated that adenosine-mediated mechanisms resist status epilepticus (SE) entry and limit SE severity. In the first experiment rats were given an adenosine agonist (2-chloroadenosine), an adenosine antagonist (aminophylline), or saline vehicle, prior to SE induction with pulsed-train current delivered to amygdala in successive 5-min current-on sessions. Saline-treated animals entered limbic SE, with predominantly exploratory behavior, after 6.0 +/- 0.9 current-on sessions. Aminophylline increased major convulsive activity during stimulation and resulted in entry into convulsive SE after only 2.1 +/- 0.1 sessions. 2-Chloroadenosine, in contrast, suppressed major convulsive activity during stimulation, and blocked (in 3/7) or delayed (4/7) SE entry, with successes requiring 12.8 +/- 0.9 stimulation sessions. In a second experiment, animals already in exploratory SE were administered a single injection of saline vehicle, aminophylline, or 2-chloroadenosine. Aminophylline converted exploratory SE into lethally severe convulsive SE. 2-Chloroadenosine suppressed SE behaviorally and electrographically, and protected recipients from the seizure-associated cerebral damage seen in saline-administered SE controls. These results support the hypothesis that endogenous adenosine mechanisms resist SE entry, modulate the severity of ongoing SE, and limit the anatomic spread of seizure activity.
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Affiliation(s)
- A Handforth
- Department of Veterans Affairs Medical Center, West Los Angeles, CA
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32
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Kelly ME, McIntyre DC. Hippocampal kindling protects several structures from the neuronal damage resulting from kainic acid-induced status epilepticus. Brain Res 1994; 634:245-56. [PMID: 8131074 DOI: 10.1016/0006-8993(94)91927-5] [Citation(s) in RCA: 114] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
In an attempt to study the effects of piriform cortex damage on kindled seizure propagation, we administered kainic acid (12 mg/kg; i.p.) to rats previously kindled from the dorsal hippocampus. Unexpectedly, the ensuing status epilepticus (SE) in the kindled rats did not result in the piriform cortex damage normally observed in naive rats. As a result of this surprising finding, a more comprehensive investigation was undertaken to compare dorsal hippocampal kindled and control rats on their electrographic and behavioral SE development and subsequent brain damage. The SE induction profile and the pattern of brain damage observed in our control rats was similar to previous reports [Neuroscience, 14 (1985) 375-403; Brain Res., 218 (1981) 299-318]. By contrast, although fewer kindled rats than controls responded to the initial dose of kainic acid with electrographic and behavioral seizures, those many kindled rats that did respond, showed a pattern of SE induction that was different from controls. Kindled rats manifested fewer 'wet dog shakes', more generalized convulsions and a faster development of severe limbic status (SLS) than controls. In addition, without pharmacological intervention, the SLS continued longer in kindled rats than in controls. Histological examination revealed brain damage in kindled rats that was markedly different from controls. Unlike controls, kindled rats had no damage in the piriform cortex or substantia nigra reticulata and minimal hippocampal damage, yet showed midline thalamic and anterior olfactory nuclei damage similar to controls. These differences were observed from 1 to 28 days after kindling. Although the mechanism(s) of this kindling-based neuroprotection is not known, its discovery should add importantly to our understanding of epilepsy-induced alterations of subsequent neuronal function.
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Affiliation(s)
- M E Kelly
- Department of Psychology, Carleton University, Ottawa, Ont., Canada
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McIntyre DC, Plant JR. Long-lasting changes in the origin of spontaneous discharges from amygdala-kindled rats: piriform vs. perirhinal cortex in vitro. Brain Res 1993; 624:268-76. [PMID: 8252399 DOI: 10.1016/0006-8993(93)90086-3] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The origin of spontaneous field potentials in coronal slices of the amygdala-piriform-perirhinal area (A-P area) from amygdala-kindled and control rats was assessed. In Expt. 1, the field potentials initially originated in the perirhinal (PRh) cortex of control tissue while they originated in the piriform (Pir) cortex of amygdala-kindled tissue. In Expt. 2, this kindling-based change was observed in the A-P area ipsilateral but not contralateral to the kindled amygdala. In both experiments, subsequent exposure to perfusion medium containing 0 Mg2+ resulted in the genesis of strong discharges in both control and kindled tissues. After 2-3 h of such treatment, the origin of spontaneous discharges in control tissue changed from the PRh to the Pir area and persisted in a reduced form during reperfusion with medium containing Mg2+. This change in origin of the discharges in control tissue appeared similar to that seen in previously kindled tissue. In Expt. 3, during exposure to 0 Mg2+, the response of the basolateral amygdala (BLA) was compared with the Pir and PRh areas. Independent of the PRh discharge, the BLA discharge closely followed the Pir discharge both in time and morphology. These lasting changes in the ipsilateral A-P area in vitro must be related in vivo to the change which allows the kindled A-P area to participate in the triggering of generalized limbic-kindled convulsions.
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Affiliation(s)
- D C McIntyre
- Department of Psychology, Carleton University, Ottawa, Ontario, Canada
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34
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Abstract
In vitro experiments have indicated that the perirhinal cortex is highly excitable and its relationship to the basolateral amygdala and piriform cortex is altered by previous amygdala or dorsal hippocampal kindling. As a result, we felt it was important to assess the excitability of the perirhinal cortex in vivo by comparing its kindling profile to that of the basal amygdala, piriform cortex or dorsal hippocampus. We observed that the after-discharge (AD) threshold of the perirhinal cortex was higher than the other 3 structures but the AD duration was not different. Subsequently, the perirhinal cortex kindled more rapidly than the other 3 structures, and with extremely short latencies to onset of forelimb clonus. With the view that synchronized discharge in the perirhinal-piriform area provides the critical trigger for limbic kindled convulsions, the relationship of kindling rate and convulsion latencies and durations between the 4 structures was discussed.
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Affiliation(s)
- D C McIntyre
- Department of Psychology, Carleton University, Ottawa, Ont., Canada
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35
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Abstract
We have previously shown that pulsed-train electrical stimulation of the amygdala results, within 60-90 min, in status epilepticus in which one of four behavioral states is predominant: immobile, exploratory, minor convulsive and clonic convulsive. These four states form a hierarchy which appears, on electrographic and behavioral grounds, to belong to the same order of severity as limbic-kindled seizures, but not representing steady-state versions. We tested the hypothesis that it should be possible to induce prolonged seizure states from numerous limbic sites, as is the case with kindled seizures. It was found that electrogenic status epilepticus could be generated at any of 11 extra-amygdala sites, including parts of hippocampal formation, olfactory/limbic cortical areas, and caudate putamen. These four status categories could each be engendered from numerous sites without any site-specific behavioral features. Midline cortical and caudate stimulation was more prone to elicit clonic convulsive status. Such findings provide further evidence that kindled seizures and electrogenic status states belong to the same progression, and share the same underlying anatomic substrates.
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Affiliation(s)
- A Handforth
- Department of Neurology, UCLA School of Medicine 90024
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