In der Folge eines Status epilepticus entwickelt sich häufig eine chronische Epilepsie. In der vorliegenden Dissertation wurde die Fragestellung bearbeitet, ob ein Inhibitionsverlust im Gyrus dentatus Grundlage der Epileptogenese nach Status epilepticus ist. Ein selbst-erhaltender Status epilepticus (SSSE) wurde an erwachsenen Ratten durch elektrische Stimulation ausgelöst. Das Auftreten spontaner epileptischer Anfälle wurde im Verlauf von acht Wochen nach Status epilepticus zu drei Zeitpunkten (1, 4 und 8 Wochen) mittels Videoüberwachung erfasst. Zu denselben Zeitpunkten und vor Status epilepticus wurden elektrophysiologische Messungen im Gyrus dentatus durchgeführt. Die Aktivität der Prinzipalzellen des Gyrus dentatus unterliegt unter physiologischen Bedingungen einer ausgeprägten inhibitorischen Kontrolle. Durch Analyse von Doppelreizantworten wurden Veränderungen der Inhibition in dieser für die Epileptogenese relevanten Hirnstruktur beurteilt. Im Verlauf von acht Wochen nach SSSE entwickelte sich bei einem Großteil der Versuchstiere eine chronische Epilepsie. Zum spätesten Beobachtungszeitpunkt traten rekurrente spontane epileptische Anfälle bei 80 Prozent der Tiere auf. Die Inhibition im Gyrus dentatus war eine Woche nach Status epilepticus signifikant reduziert. Vier und acht Wochen nach SSSE zeigte sich eine zunehmende Wiederannäherung an die vor dem Status epilepticus erhobenen Messwerte, so dass von einem transienten Inhibitionsverlust im Gyrus dentatus nach Status epilepticus gesprochen werden kann. Zusammenfassend konnte in der Dissertation gezeigt werden, dass sich in der Folge eines Status epilepticus bei der Mehrzahl der Tiere eine chronische Epilepsie entwickelt. Der Inhibitionsverlust im Gyrus dentatus war zu einem Zeitpunkt am größten, da noch keine spontanen epileptischen Anfälle auftraten. Als sich bei den meisten Tieren eine chronische Epilepsie entwickelt hatte, war die Inhibition komplett wiederhergestellt. Daher ist ein Inhibitionsverlust im Gyrus dentatus nach einem Status epilepticus nicht der führende pathophysiologische Mechanismus für die Entwicklung einer chronischen Epilepsie. / Development of chronic epilepsy as a consequence of status epilepticus is a frequent clinical observation. The aim of this work was to test the hypothesis that epileptogenesis after status epilepticus depends on a loss of inhibitory function in the dentate gyrus. A self-sustaining status epilepticus (SSSE) was induced in rats by continuous electrical stimulation of the perforant path. The occurrence of spontaneous epileptic seizures was assessed by video monitoring 1, 4 and 8 weeks after SSSE. At the same time points and directly before SSSE, inhibition in the dentate gyrus was measured using a paired pulse paradigm. In this region, excitability of principal cells is under physiological conditions effectively controlled by the activity of inhibitory interneurons. In addition, the dentate gyrus is relevant for the process of epileptogenesis due to anatomical properties. In the time course after SSSE, the fraction of animals showing spontaneous epileptic seizures increased steadily reaching 80 % after eight weeks. One week after SSSE, inhibition in the dentate gyrus was significantly reduced. This loss proved to be transient, as inhibition recovered after 4 weeks and reached pre-status values after 8 weeks. In conclusion, the majority of animals developed chronic epilepsy as a consequence of status epilepticus. Loss of inhibition in the dentate gyrus was maximal while spontaneous seizures had not yet developed. Inhibition was normalized when most animals had become epileptic. Thus, loss of inhibition in the dentate gyrus following status epilepticus is not a decisive mechanism in the emergence of spontaneous seizures.

Introdução: A vigabatrina (VGB - Gama-Vinil-GABA) é um fármaco que eleva os níveis de GABA no organismo, por inibição irreversível da GABA transaminase, cuja eficácia foi bem demonstrada no controle dos espasmos epilépticos em lactentes, especialmente na síndrome de West secundária à esclerose tuberosa. Há escassez de estudos clínicos evidenciando um possível papel deste fármaco no controle de crises epilépticas neonatais e pouco se sabe sobre o potencial impacto do seu uso nessa faixa etária, seus possíveis efeitos adversos, ou se sua introdução teria associações positivas com controle mais adequado das crises na evolução e melhor desenvolvimento neuropsicomotor da criança. A VGB foi introduzida em nosso serviço como terapia de adição para o controle de crises neonatais refratárias, há vários anos, instigando nossa impressão sobre a eficácia deste medicamento no período neonatal. Objetivos: Avaliar a efetividade do uso da VGB como adjuvante no controle das crises eletrográficas e eletroclínicas do período neonatal e seus efeitos sobre o padrão do eletroencefalograma (EEG); Avaliar a evolução clínica e eletrográfica das crianças durante seguimento ambulatorial; Pesquisar associação entre \"controle de crises neonatais com introdução de VGB\" e diversas características demográficas, clínicas e evolutivas destes recém nascidos; Quantificar e caracterizar a ocorrência de efeitos adversos precoces e durante o seguimento. Pacientes e métodos: Estudo transversal retrospectivo, envolvendo o levantamento dos prontuários de uma amostra de recém-nascidos que receberam VGB como tratamento para crises neonatais refratárias aos fármacos convencionais e status epilepticus, no período de janeiro de 2007 a março de 2014, no Serviço de Neonatologia e Terapia Intensiva Neonatal do HCFMRP-USP, mantendo seguimento ambulatorial por pelo menos 1 ano. Foram avaliados os dados demográficos, etiologia e semiologia clínico-eletroencefalográfica das crises, esquema terapêutico prescrito, indicação da introdução da VGB, tempo de internação e tempo para atingir o controle das crises, evolução clínica e eletrencefalográfica durante a internação e no seguimento ambulatorial, época da suspensão da VGB, além de seus efeitos adversos. Resultados: De 48 recém-nascidos avaliados, 34 (79,2 %) obtiveram controle de crises eletrográficas e/ou clínicas durante o período neonatal, havendo melhora no padrão eletrográfico após a introdução da VGB em 79%. Quanto aos critérios para sua indicação, 33,3% (16 indivíduos) iniciaram VGB devido a falha terapêutica no controle das crises com fenobarbital e/ou fenitoína; 27,1% (13 recém nascidos), pela presença de estado de mal epilético e, em 12 crianças (25%), por falha terapêutica do midazolam. Ao final do primeiro ano de vida, a atividade de base do EEG mostrou-se desorganizada em 58,1% (18 de 29 pacientes que o realizaram aos 12 meses de vida). No seguimento ambulatorial de 38 pacientes, algum grau de atraso do desenvolvimento neuropsicomotor foi detectado em 20 crianças (52,6%); 19 lactentes (39,5%) mantiveram o uso da VGB em politerapia, tendo 22 crianças (57,9%) evoluído com persistência das crises epilépticas. Já 37,8% (14 pacientes) enquadraram-se em um padrão de encefalopatia epiléptica, que correspondeu à síndrome de West em 13,9% (5 de 36 crianças). Quanto ao EEG realizado em 34 crianças nessa fase, 17,6% (6 casos) demonstraram a presença de hipsarritmia, enquanto anormalidades focais ou multifocais foram detectadas em 50% (17 lactentes). A taxa de óbito ao final do primeiro ano foi de 23,3% (10 de 43 crianças analisadas quanto a este dado). Não foi possível comprovar déficit visual relacionado diretamente ao uso da VGB. A variável \"controle de crises no período neonatal com o uso da VGB\" foi associada aos seguintes desfechos clínicos favoráveis: melhora no padrão eletrográfico (92,1%), proporção menor de crianças evoluindo para síndrome de West e outras encefalopatias epilépticas (71,9% não tiveram tal desfecho); menor frequência de hipsarritmia no EEG (92,9% sem hipsarritmia), maior alcance de desenvolvimento neuropsicomotor normal (56,2% com bom desenvolvimento neurológico), menor índice de óbito neonatal (97,4% vivos nesta fase) e durante os primeiros doze meses de vida (87,9%). Conclusão: Acreditamos que a VGB seja uma opção terapêutica efetiva e com adequada relação custo-benefício, a ser implementada no controle de crises epilépticas neonatais refratárias como fármaco adjuvante aos convencionais. Entretanto, estudos randomizados e controlados são necessários para confirmar sua eficácia quando comparada a outros medicamentos disponíveis para uso nesta população, bem como para avaliar seus possíveis efeitos adversos a longo prazo. / Introduction: Vigabatrin (VGB - Gama-Vinil-GABA) is an antiepileptic drug which increases systemic GABA levels by irreversibly inhibiting GABA transaminase, with well demonstrated efficacy in the control of infantile epileptic spasms, specially related to West syndrome due to tuberous sclerosis. Clinical studies demonstrating a possible role of VGB in the control of neonatal seizures are still very scarce and very little is known on the impact of its use at this early age, as well as on its possible side effects or eventual positive associations from its use with more adequate seizure control or better neuropsychomotor development in the outcome. VGB has been used in our service as an add-on therapy for refractory neonatal seizures arising the impression that this could be an effective antiepileptic medication in the neonatal period. Objectives: To evaluate the use of VGB as an add-on medication regarding its effectiveness for the control of neonatal electrographic and electroclinical seizures, as well as its effects over the EEG pattern; To evaluate clinical and electrographic evolution of the children in follow-up; To estimate VGB efficacy on the control of neonatal seizures in relation to the demographical and clinical characteristics of those newborns; To quantify and characterize the occurrence of early and late side effects of this medication along follow-up. Patients and methods: This is a transverse retrospective study carried out through charts analysis from a sample of newborns who received VGB as add-on medication for seizures and/or status epilepticus refractory to conventional drugs, from January 2007 through March 2014, at the Neonatal Intensive Care Service of HCFMRP-USP, keeping follow-up in our institution for at least 1 year. Demographical and etiological data were analyzed, as well as clinical-electrographical semiology, VGB prescription indication, therapeutic schedule, time to reach seizure control, clinical and electrographical evolution while in hospital and at the follow-up, age at VGB withdrawal, besides adverse effects. Results: Among 48 newborns evaluated, 34 (79.2%) reached control of electrographic and/or clinical seizures during neonatal period, with improvement of the EEG pattern after VGB introduction in 79%. As for drug introduction criteria, 33.3% (16 children) were started on VGB due to therapeutic failure of phenobarbital and/or phenytoin; 27.1% (13 newborns), due to status epilepticus and, in 12 babies (25%), due to therapeutic failure of midazolam. By the end of the first year of life, EEG background activity was disorganized in 58.1% (18 out of 29 children who had EEG registered at 12 month of life). Along the one year follow-up of 38 patients, 20 infants (52.6%) showed some degree of neurodevelopmental delay; 19 children (39.5%) remained on VGB in polytherapy, with seizure persistence in 22 (57.9%). Evolution to an epileptic encephalopathy was found in 14 kids (37.8%), with West Syndrome being characterized in 13.9% (5 out of 36 kids). As for the EEG carried out in 34 children at the follow-up, 17.6% (6 cases) showed hypsarrhythmia while focal or multifocal abnormalities were seen in 50% (17 infants). Up to 12 month of life, the death rate was 23.3% (10 out of 43 children evaluated for such endpoint). Visual deficit directly related to VGB use could not be determined. The variable \"seizure control during the neonatal period after VGB use\" was associated to the following endpoints: improvement of the EEG pattern (92,1% of children with seizure control after VGB), lower proportion of children evolving into West syndrome and other epileptic encephalopathies (71.9% did not show such endpoint), lower frequency of hypsarrhythmia in the EEG (92.9% without hypsarrhythmia), better milestones reached regarding neuropsychomotor development (56.2% with good neurological outcome), lower rate of neonatal death (97.4% alive by the end of neonatal period) and along the first year of life (87.9%). Conclusion: VGB is an effective therapeutic option with adequate cost-benefit relationship which should be implemented for the control of refractory neonatal seizures as add-on therapy to conventional drugs. However, controlled randomized studies are necessary to confirm such efficacy as compared to other drugs available for use in the neonatal period, as well as to evaluate its possible long term side effects.

Bakgrund: Status epilepticus hos barn innebär risk för livshotande tillstånd, mortalitet eller medicinska komplikationer. Behandlingsriktlinjer finns men uppdateras och följs sällan. Forskning kring barnsjuksköterskans upplevelser saknas. Syfte: Syftet var att belysa barnsjuksköterskans upplevelser inom det akut omhändertagande av barn med status epilepticus. Metod: En kvalitativ design med induktiv ansats. Datainsamlingen utgick från semistrukturerade intervjuer med tio barnsjuksköterskor vid åtta regionala- eller universitetssjukhus i mellersta och södra Sverige. Resultat: Utifrån en kvalitativ innehållsanalys framkom fyra kategorier: Flertalet faktorer påverkar det akuta omhändertagandet, Betydelsen av familjecentrerad vård i den akuta situationen, Betydelsen av kompetensutveckling inför den akuta situationen, Betydelsen av följsamhet till behandlingsstrategier i den akuta situationen. Slutsats: Ett välfungerande strukturerat teamarbete med följsamhet till behandlingsriktlinjer möjliggörs genom utbildning. Kompetensutveckling medför ökad trygghet och KASAM för barnsjuksköterskan, vilket bidrar till ökad patientsäkerhet och ett mer optimalt omhändertagande av barnet och dess familj. Fördjupad forskning kring status epilepticus inom omvårdnad, kompetensutveckling, teamträning och följsamhet till behandlingsriktlinjer kan medföra minskade konsekvenser för barnet och kostnader för samhället. / Background: Status epilepticus in children means a risk of life-threatening conditions, mortality or medical complications. Treatment guidelines exist but are rarely updated and followed. Research on pediatric nurses' experiences is lacking. Purpose: The purpose of the study was to highlight the pediatric nurse's experiences in the emergency care of children with status epilepticus. Method: A qualitative design with an inductive approach. Data collection was based on semi structured interviews with ten pediatric nurses at eight regional and university hospitals in central and southern Sweden. Result: Based on a qualitative content analysis, four categories emerged: Several factors that influence emergency care, The importance of family-centered care in the emergency situation, The importance of competence development in the emergency situation and The importance of compliance to treatment strategies in the emergency situation. Conclusion: Efficient structured teamwork with compliance to treatment guidelines is made possible through training. Competence development brings increased security and KASAM for the pediatric nurse, which contributes to increased patient safety and optimal care of the child and its family. In-depth research into status epilepticus in nursing, competence development, team training and adherence to treatment guidelines can lead to reduced consequences for the child and reduced costs for society.

Made available in DSpace on 2016-03-15T19:39:56Z (GMT). No. of bitstreams: 1 Geraldo Henrique Lemos Barbosa.pdf: 744647 bytes, checksum: a447200460fcb4cfbb7a563e03f92252 (MD5) Previous issue date: 2012-08-16 / Fundo Mackenzie de Pesquisa / Epilepsy is a multifactorial disease, multi-faceted, featuring different variations in severity from person to person, characterized by the emergence of spontaneous seizures due to neuronal hyperactivity. Among the epilepsies, temporal lobe epilepsy (TLE) is a very serious and common, comprising about 40% of all cases, often refractory to medication with a substantial impact on cognitive processes and behavior of the affected person. The ELT is characterized by the presence of complex partial seizures with onset in limbic structures, partially attributed to more frequent primary neuropathology, hippocampal sclerosis. This crisis can cause behavioral and cognitive impairments associated with psychiatric disorders, which Disorder Attention Deficit Hyperactivity Disorder (ADHD). In order to evaluate the locomotor activity and exploration in young rats subjected to status epilepticus. Male Wistar rats aged 25 days postnatal, received intraperitoneal injection of pilocarpine (350mg/kg). Control animals received saline. The model induced by pilocarpine was used in this study, given that their histological, biochemical, electrophysiological and behavioral reliably reproduce those found in human TLE. After induction by pilocarpine SE animals underwent behavioral tests that began five days after SE and were completed in 15 days. They were: the open field and elevated plus maze. The present study showed evidence that young animals subjected to status epilepticus exhibit moderate hyperactivity with increased emotionality in a threatening context. Hyperactivity was observed over time, when the animals were reintroduced to an environment with neutral context (open field) or immediately when exposed to a threatening environment (LCE). The results of this study argue for the simultaneous presence of ADHD in the model of TLE. Evidence shows that behavioral changes are manifested early, even before the installation of behavioral seizures. In this respect, it opens a window of opportunity to get early interventions that may minimize the deleterious consequences of seizures. / A epilepsia é uma doença multifatorial, multifacetada, que apresenta diferentes variações de gravidade de pessoa para pessoa, caracterizada pelo surgimento de crises espontâneas devido à hiperatividade neural. Dentre as epilepsias, a epilepsia do lobo temporal (ELT) é uma forma muito grave e comum, que compreende cerca de 40% de todos os casos, comumente refratária à medicação com um impacto substancial no processo cognitivo e no comportamento da pessoa afetada. A ELT é caracterizada pela presença de crises parciais complexas com início nas estruturas límbicas, parcialmente atribuídas à neuropatologia primária mais frequente, a esclerose hipocampal. Essa crise pode causar prejuízos cognitivos e comportamentais, associados a transtornos psiquiátricos, os quais o Transtorno do Déficit de Atenção e Hiperatividade (TDAH). Com objetivo de avaliar a atividade locomotora e exploratória em ratos jovens submetidos ao status epilepticus. Ratos Wistar machos com idade de 25 dias pós-natal, receberam injeção intraperitoneal de pilocarpina (350mg/kg). Animais controle receberam solução salina. O modelo de indução por pilocarpina foi utilizado nessa pesquisa, tendo em vista que suas características histológicas, bioquímicas, eletrofisiológicas e comportamentais reproduzem de forma fidedigna as encontradas na ELT em humanos. Após a indução ao SE por pilocarpina os animais foram submetidos a testes comportamentais que tiveram início 5 dias após o SE e foram concluídos em 15 dias. Foram eles: o campo aberto e o labirinto em cruz elevado. O presente trabalho mostrou evidências que animais jovens submetidos ao status epilepticus apresentam hiperatividade moderada com aumento da emocionalidade em um contexto ameaçador. A hiperatividade foi observada ao longo do tempo, quando os animais foram reapresentados a um ambiente com contexto neutro (campo aberto) ou imediatamente, quando expostos a um ambiente ameaçador (LCE). Os resultados observados neste estudo argumentam a favor da presença concomitante de TDHA no modelo de ELT. Mostra evidências que as alterações comportamentais se manifestam precocemente, antes mesmo da instalação das crises epilépticas comportamentais. Neste aspecto, abre-se uma janela de oportunidades para se buscar intervenções precoces que possam minimizar as consequências deletérias das crises convulsivas.

Made available in DSpace on 2016-03-15T19:40:50Z (GMT). No. of bitstreams: 1 Adelisandra Silva Santos Castelhano.pdf: 492676 bytes, checksum: 6118cc3994884f74daed04e57878c9e4 (MD5) Previous issue date: 2010-01-26 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The Autism Spectrum Disorders (ASD), conditions which affect the brain development, are characterized by impairments in reciprocal social interactions, communicative use of verbal and nonverbal language, and restricted/repetitive behaviors. Despite a wealth of descriptive data obtained from patient histories, imaging techniques, and genetic and molecular studies, the pathogenesis of ASD remains poorly understood. Progress toward understanding the etiology of an acquired neurological disorder, such as ASD, is largely dependent on the degree to which experimental animal models reflect the human condition. Status epilepticus (SE), the condition of ongoing seizures or repetitive seizure activity, is a clinical emergency more common in children than adults, with almost 40-50% of the case occurring in children younger than 2 years of age. Clinical and experimental studies have been showing that despite of immature brain to be more resistant to structural damage when compared with adult brain, it has been demonstrated that neonatal SE may produce learning deficits, memory impairment, and emotional sequels in adulthood, altered GABAergic intracortical and hipocampal circuitries and reduced dopamine levels in the prefrontal cortex. Taking all information together, the aim of the present study was to evaluate a possible social impairment, learning and exploratory deficits after pilocarpine-induced SE in rats of both genders during development. Wistar rats of both gender at PN9 received intraperitoneal injection of pilocarpine (380 mg/kg). Control animals received saline solution instead pilocarpine. Social and exploratory behaviors were assessed between 30-35 postnatal days using paired-exposure paradigm. Learning performance was assessed, at PN90 using skinner Box apparatus, by quantification of the number of sections to acquire bar pressing conditioning. Our results demonstrated that neonatal SE produced social impairment, learning and exploratory deficits. Furthermore, the social impairment was gender-dependent, affecting predominantly male rats. On the other hand, the exploratory behavior was reduced in both genders, however female rats seems to be more affected, since selfgrooming was enhanced in this specific group. Quite interesting, both behaviors are affected by emotionality and environmental context, suggesting that SE was able to affect more severely the emotionality of the female animals. Moreover, it is also important to note that learning deficits were observed in both genders as well. Based on this evidences, we propose that this animal model can be a valuable tool to investigate the neurobiological basis of ASD. / Os Transtornos do Espectro Autista (TEA) são condições que afetam o desenvolvimento cerebral prejudicando a interação social recíproca, a comunicação verbal e não verbal e são acompanhados por comportamentos repetitivos e padrões anormais de interesses e atividades. Apesar da riqueza dos dados obtidos a partir da história dos pacientes, dos exames de neuroimagem, dos estudos genéticos e moleculares, a patogênese do TEA permanece mal compreendida. Modelos animais têm propiciado a ampliação do conhecimento acerca da neurobiologia dos TEA. O Status epilepticus (SE), uma condição aguda caracterizada por convulsões repetitivas ou prolongada, é uma emergência clínica que ocorre mais frequentemente em crianças que em adultos, e em 40-50% dos casos em crianças com idade inferior a dois anos. Estudos clínicos e experimentais indicam que embora o SE produza menos danos estruturais no cérebro imaturo que no cérebro adulto, SE em neonatos leva a prejuízos na aprendizagem, memória, sequelas emocionais na idade adulta, alteração da circuitaria GABAérgica hipocampal e intracortical, e redução dos níveis de dopamina no córtex pré-frontal. Este trabalho teve como objetivo avaliar se o SE em ratos neonatos de ambos os gêneros produz prejuízos na interação social, na cognição e no comportamento exploratório. Ratos wistar de ambos os gêneros com nove dias pós-natal (PN9) receberam injeção intraperitoneal de pilocarpina (380 mg/kg). Animais controles receberam solução salina. Os comportamentos sociais e exploratórios foram avaliados entre PN30-PN35, empregando-se o paradigma de observação por pares. O desempenho cognitivo foi avaliado empregando-se a caixa de Skinner, quantificando-se o número de sessões para aquisição do comportamento de pressão à barra. Os resultados mostraram que o SE no cérebro em desenvolvimento alterou a sociabilidade, a cognição e o comportamento exploratório. Os prejuízos na interação social foram gênero-dependentes, afetando predominantemente os machos. O comportamento exploratório foi reduzido em ambos os gêneros, no entanto, as fêmeas parecem ter sido mais afetadas, desde que paralelamente observou-se aumentou do selfgrooming. Ambos os comportamentos são afetados pela emocionalidade e pelo contexto ambiental, sugerindo que o SE afetou mais severamente a emocionalidade das fêmeas. Os prejuízos cognitivos foram igualmente observados em ambos os gêneros. Baseando-se nestas evidências, sugerimos que este modelo pode ser utilizado para explorar mecanismos neurobiológicos do TEA.

Patients with epilepsy often suffer debilitating cognitive and psycho-affective disorders.In some cases, epilepsy is associated to neurodegenerative processes that are the targetof certain therapeutical agents. Today, erythropoietin is considered as one of the most promising neuroprotective agents. In addition, an increased body of studies provides evidence that enrichment (or complexity) of housing decreases the cerebral vulnerabilityin the context of diverse brain insults. In this thesis, we demonstrate: 1) in a model ofepilepsy with large neuronal lesions, that erythropoietin protects the most vulnerable neuronal populations to excitotoxic injury, at the only condition that neuronal expression of its receptor is optimized prior to the primary insult causing epilepsy; 2) in a model of epilepsy associated with faint neuronal lesions that: i) erythropoietin prevents anxietyand impaired spatial learning and memory, ii) enriched housing in Marlau™ cages is moreefficient than erythropoietin, and iii) erythropoietin treatment abolishes beneficial effectsof enriched housing. These results, obtained in animal models of epilepsies associatedwith cognitive disorders establish that beneficial effects of a potential therapeutic agentmay rely on quality of life / Dans de nombreux cas, les patients avec des épilepsies présentent d’importants troubles cognitifs et psycho-affectifs. Ces épilepsies sont parfois accompagnées de phénomènes neuro-dégénératifs qui sont la cible de certains agents thérapeutiques. Aujourd’hui, l’érythropoïétine apparaît comme l’un des agents neuro-protecteurs les plus prometteurs.En outre, des études de plus en plus nombreuses montrent que l’enrichissement (ou la complexification) des conditions d’hébergement diminue la vulnérabilité cérébrale face à des agressions d’origine différente. Dans cette thèse, nous montrons : 1) dans un modèle d’épilepsie accompagné de vastes lésions neuronales, que l’érythropoïétine protège les populations neuronales les plus vulnérables aux atteintes excitotoxiques, à la condition d’optimiser l’expression neuronale de son récepteur, préalablement à l’agression cérébrale ayant initié l’épilepsie ; 2) dans un modèle d’épilepsie associé à des phénomènes neurodégénératifs très discrets, que : i) l’érythropoïétine bloque le développement de l’anxiété et des troubles de l’apprentissage et de la mémoire spatiale,ii) l’enrichissement du milieu d’hébergement en cages Marlau™ est plus efficace que l’érythropoïétine, et iii) le traitement par l’érythropoïétine annihile les effets bénéfiques de l’enrichissement du milieu d’hébergement. Les résultats de cette thèse, obtenus dans des modèles expérimentaux d’épilepsies associés à des troubles cognitifs, démontrent que les effets bénéfiques d’un potentiel agent thérapeutique peuvent dépendre de la qualité de vie

Febrile seizures are epileptic seizures, arising in connection with febrile conditions in children of prechool age. In adults with epilepsy is often present a history of febrile status epilepticus, seizure whose duration is longer than 20 minutes. To study the role of febrile status epilepticus (FSE) in the development of epilepsy and neuronal damage, it is necessary to have a relevant animal models. This work is focused on the morphological analysis of the new created model of febrile status epilepticus, using a combination of short-term hyperthermia and chemical induced status epilepticus at 10 days old rats. In adulthood, the animals were examined by video/EEG monitoring, and then morphometric analysis. The aim of this study was to determine the importance of short-term hyperthermia during SE for neuropathological changes using stereological measurements of hippocampal volume.

A positive correlation exists between increasing age and the incidence of hippocampal-associated dysfunction and disease. Normal L-glutamate neurotransmission is absolutely critical for hippocampal function, while abnormal glutamate neurotransmission has been implicated in many neurodegenerative diseases. Previous studies, overwhelmingly utilizing ex vivo methods, have filled the literature with contradicting reports about hippocampal glutamate regulation during aging. For our studies, enzyme-based ceramic microelectrode arrays (MEA) were used for rapid (2 Hz) measurements of extracellular glutamate in the hippocampal trisynaptic pathway of young (3-6 months), late-middle aged (18 mo.) and aged (24 mo.) urethane-anesthetized Fischer 344 rats. Compared to young animals, glutamate terminals in cornu ammonis 3 (CA3) showed diminished potassium-evoked glutamate release in aged rats. In late-middle aged animals, terminals in the dentate gyrus (DG) showed increased evoked release compared to young rats. The aged DG demonstrated an increased glutamate clearance capacity, indicating a possible age-related compensation to deal with the increased glutamate release that occurred in late-middle age. To investigate the impact of changes in glutamate regulation on the expression of a disease process, we modified the MEA technology to allow recordings in unanesthetized rats. These studies permitted us to measure glutamate regulation in the hippocampal formation without anesthetic effects, which showed a significant increase in basal glutamatergic tone during aging. Status epilepticus was induced by local application of 4-aminopyridine. Realtime glutamate measurements allowed us to capture never-before-seen spontaneous and highly rhythmic glutamate release events during status epilepticus. A significant correlation between pre-status tonic glutamate and the quantity of status epilepticus-associated convulsions and glutamate release events was determined. Taken together, this body of work identifies the DG and CA3 as the loci of age-associated glutamate dysregulation in the hippocampus, and establishes elevated levels of glutamate as a key factor controlling severity of status epilepticus in aged animals. Based upon the potential ability to discriminate brain areas experiencing seizure (i.e. synchronized spontaneous glutamate release) from areas not, we have initiated the development of a MEA for human use during temporal lobe resection surgery. The final studies presented here document the development and testing of a human microelectrode array prototype in non-human primates.

Status epilepticus (SE) is a type of neurological injury characterized by continuous seizure activity and can lead to molecular and pathophysiological alterations leading to plasticity changes. SE can lead to the development of AE by the process of epileptogenesis, which is a phenomenon that describes the transformation of normal brain tissue into a hyperexcitable neuronal population. It has been demonstrated both in vivo and in vitro that calcium (Ca2+) dynamics are severely altered during and after SE, and these changes play a major role in the progression of epileptogenesis. It has also been reported that preventing the rise in intracellular Ca2+ ([Ca2+]i) immediately following injury (the Ca2+ plateau) prevents the plasticity changes and ultimate development of epilepsy. Currently, there are no treatments available that can be administered following an injury to prevent the development of AE. Therefore it is clinically important to develop a therapy that can be administered after an injury to block epileptogenesis. Hypothermia is a potential therapeutic intervention. Hypothermia is used clinically to provide neuroprotection following various neurological insults such as stroke and traumatic brain injury (TBI). However, no studies have been performed to evaluate the therapeutic potential of hypothermia following SE. Hypothermia provides protection via multiple mechanisms, one of which includes modulating excitotoxic neurotransmission. It is believed to reduce Ca2+ influx by reducing NMDA receptor activation. It is unclear how hypothermia affects Ca2+ through other modes of entry. This dissertation evaluates the effects of hypothermia on the Ca2+ plateau and demonstrates the novel finding that hypothermia induced post-SE blocks the development of the Ca2+ plateau and reduces the development of AE.

Excitotoxic calcium influx and activation of calcium-regulated systems is a common event in several types of neuronal injury. This mechanism has been the focus of intense research, with the hope that a more complete understanding of how neuronal injury affects calcium-regulated systems will provide effective treatment options. This study examines one such calcium-stimulated enzyme, calcineurin, in the context of two common neurological pathologies, status epilepticus and traumatic brain injury.Status epilepticus was induced by pilocarpine injection. NMDA-dependent increases in calcineurin activity were observed in cortical and hippocampal homogenates. Upon closer examination, the most profound increases in activity were found to be present in crude synaptoplasmic membrane fractions isolated from cortex and hippocampus. A concurrent status epilepticus-induced increase in calcineurin concentration was observed in membrane fractions from cortex and hippocampus. Immunohistochemical analysis revealed an increase in calcineurin immunoreactivity in apical dendrites of hippocampal pyramidal neurons. We examined a cellular effect of increased dendritic calcineurin activity by characterizing a calcineurin-dependent loss of dendritic spines. Increased dendritic calcineurin led to increased dephosphorylation and activation of cofilin, an actin-depolymerizing factor. Calcineurin-activated cofilin induced an increase in actin depolymerization, a mechanism shown to cause spine loss in other models. Finally, via Golgi impregnation, we demonstrated that status epilepticus-induced spine loss is blocked by calcineurin inhibitors.To demonstrate that the increase in dendritic calcineurin activity was not model-specific, we examined a moderate fluid-percussion model of brain injury. Calcineurin activity was significantly increased in hippocampal and cortical homogenates. This increased activity persisted for several weeks post-injury, and may be involved in injury-induced neuronal pathologies. Also similar to the SE model, calcineurin immunoreactivity was dramatically increased in synaptoplasmic membrane fractions from cortex and hippocampus, and immunohistochemistry revealed increased calcineurin content in dendrites of hippocampal CA1-3 pyramidal neurons. These changes in calcineurin distribution also persisted for several weeks post-injury.These studies demonstrate a novel, cellular mechanism of calcium-mediated pathology in two models of neuronal injury. Elucidation of cellular events involved in the acute and chronic effects of brain trauma is essential for the development of more effective treatment options.