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Previous issue date: 2016-08-30 / A epilepsia do lobo temporal (ELT) ? a forma mais frequente de epilepsia em adultos, caracterizada clinicamente por um quadro progressivo de crises epil?pticas com foco no lobo temporal, em particular no hipocampo. Dentre os modelos animais, os mais utilizados na investiga??o dos mecanismos fisiopatol?gicos desta condi??o geram crises recorrentes espont?neas atrav?s da indu??o inicial de um estado convulsivo sustentado (status epilepticus, SE) ? por administra??o do agonista glutamat?rgico ionotr?pico, ?cido ca?nico (AC) ou do agonista colin?rgico muscar?nico, pilocarpina (PILO). Entretanto, o uso de inje??es sist?micas e a falta de controle preciso sobre a dura??odo SE geram alta mortalidade, morte celular dispersa e grande variabilidade comportamental durante a fase cr?nica da epilepsia, o que difere em v?rios aspectos do quadro humano. A nosso ver, este padr?o decorre da a??o sist?mica da droga e da dificuldade de controlar a atividade eletrogr?fica/tempo de SE a que cada animal ? submetido, influenciando a din?mica da epileptog?nese. Portanto, este projeto teve como objetivo gerar modelos de ELT por infus?o intra-hipocampal de AC e PILO em ratos e analisar seus comportamentos e atividade eletrofisiol?gica durante o SE. Vale ressaltar que ainda n?o h? estudos eletrofisiol?gicos aprofundados sobre o modelo de PILO intra-hipocampal. Para isto, implantamos feixes de microeletrodos bilateralmente no hipocampo e unilateralmente no c?rtex pr?-frontal medial (CPFm), junto a uma c?nula no hipocampo ventral para infus?o de AC ou PILO. Ap?s a indu??o do SE analisamos a progress?o comportamental e eletrofisiol?gica dos animais. O SE foi bloqueado ap?s 2h por um coquetel anti-convulsivante mais potente do que o utilizado na maioria dos estudos atuais e os animais foram acompanhados por registros cont?nuos de v?deo-EEG sincronizado por at? 72h. Sete dias ap?s o SE, os animais foram sacrificados e seus c?rebros retirados para verifica??o histol?gica da posi??o da c?nula e eletrodos. Os registros de v?deo e de EEG foram analisados por inspe??o visual e t?cnicas de an?lise de s?ries temporais. Nossos resultados mostraram que os animais PILO apresentam 1a crise comportamental com menor lat?ncia do que os animais tratados com AC, por?m com severidade mais vari?vel (AC: 90% animais classe 1 vs. PILO: 50% animais ?classe 3, escala de Racine). Animais PILO tamb?m tiveram menor n?mero de comportamentos do tipo wet-dog shakes que os animais AC, associado a um in?cio de SE precoce comparado aos animais AC. Do ponto de vista eletrofisiol?gico, observamos oscila??es de alta frequ?ncia (>150 Hz), comumente observadas na fase cr?nica da epilepsia, logo ap?s a inje??o de ambos convulsivantes (15-40 min antes do in?cio do SE) concomitante ?s primeiras crises eletrogr?ficas. Por fim, identificamos que o SE em ambos modelos exibe uma organiza??o modular da atividade parox?stica com v?rios n?veis de ritmicidade sobrepostos. Nossos resultados indicam uma maior epileptogenicidade da PILO em rela??o ao AC e, que estas drogas produzem SE com din?micas distintas. Pudemos observar uma composi??o com m?dulos de oscila??es sobrepostas repetidos periodicamente, m?dulos de hipersincronia sem oscila??es acopladas e segmentos de atividade ass?ncrona. Nossos dados ressaltam a import?ncia do registro eletrogr?fico durante o SE para melhor controlar as respostas individuais durante este per?odo. / Temporal lobe epilepsy (TLE) is the most common form of epilepsy in adults. It is characterized by a progressive occurrence of epileptic seizures originating in the temporal lobe, particularly in the hippocampal formation (mesial TLE). Among the animal models used to investigate the physiopathological mechanisms of TLE, the most used are those that lead to spontaneous seizures after an initial insult, such as a prolonged convulsive state (status epilepticus, SE). This condition can be induced by the administration of the glutamatergic agonist, kainic acid (KA) or the cholinergic agonist, pilocarpine (PILO). However, the use of systemic injections and the lack of electrophysiological monitoring during SE lead to high mortality rates, widespread cell death and high behavioral variability during the chronic phase of epilepsy, which differs in several aspects from the human condition. These effects are mainly due to the lack of electrographic control of SE duration and the dynamics of the epileptogenesis process during the weeks following SE. Therefore, this project aimed to generate two animal models of TLE by intra-hippocampal injections of KA or PILO, and then, to analyze their behavioral and electrographic progression during SE. It is important to notice that no electrophysiological study has investigated the SE dynamics in animals infused with PILO into hippocampus so far. For that, we implanted two bundles of microelectrodes in the hippocampus bilaterally, one bundle in the medial prefrontal cortex and a cannula above the intermediate hippocampus for KA or PILO infusion. Following SE induction, we analyzed the behavioral and electrophysiological evolution of KA and PILO animals. SE was blocked after 2h by the injection of an anti-convulsant cocktail and the animals were continuously monitored by video-EEG for up to 72h. Seven days after SE, animals underwent euthanasia and had the brains removed for histological localization of cannula and electrodes. Video and EEG recordings were analyzed by visual inspection and spectral decomposition. Our results showed that PILO animals had shorter latency for first behavioral seizure than KA rats after drug injection. However, seizure severity showed higher variability among PILO rats (PILO: 50% animals had class 3 or higher vs. KA: 90% animals had class 1; Racine?s scale). PILO animals had a reduced number of wet-dog shake behaviors and shorter latency to SE onset as compared to KA rats. Electrophysiologically, we observed that high frequency oscillations (>150 Hz) occurred short after the injection of both drugs (15-40min before SE onset), as opposed to what is commonly reported to occur during the chronic phase of epilepsy in rodents. They were usually found within the first electrographic seizures. Finally, we have identified a distinct modular organization of paroxystic activity during the SE in each group, which consisted of blocks of nested rhythms. These findings thus suggest that PILO is more epileptogenic that KA and that these drugs produce distinct SE dynamics, which seem to be organized as periodically repeating modules of nested oscillations, modules of hyper synchrony with no nested oscillations and segments of asynchronous activity. Our data emphasizes the importance to conduct electrophysiological recordings during SE induction in order to better control individual brain responses. This can reduce variability during epileptogenesis and produce a more homogeneous model of chronic epilepsy.
| Identifer | oai:union.ndltd.org:IBICT/oai:repositorio.ufrn.br:123456789/24080 |
| Date | 30 August 2016 |
| Creators | Bessa, Rafael dos Santos de |
| Contributors | 52408493153, Belchior, Hindiael Aeraf, 01465918604, Leite, Jo?o Pereira, 05558830867, Queiroz, Cl?udio Marcos Teixeira de, Pereira, Rodrigo Neves Romcy |
| Publisher | PROGRAMA DE P?S-GRADUA??O EM NEUROCI?NCIAS, UFRN, Brasil |
| Source Sets | IBICT Brazilian ETDs |
| Language | Portuguese |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, info:eu-repo/semantics/masterThesis |
| Source | reponame:Repositório Institucional da UFRN, instname:Universidade Federal do Rio Grande do Norte, instacron:UFRN |
| Rights | info:eu-repo/semantics/openAccess |
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