Thesis--Wisconsin. / Vita. Includes bibliographical references (leaves 209-215).

Thesis (M.S.)--Wisconsin. / Includes bibliographical references (leaves 180-185).

Thesis--Wisconsin. / Vita. Includes bibliographical references (leaves 187-191).

Reproduction de : Thèse de doctorat : Physiologie & Neurosciences : Lyon 1 : 2008. / Titre provenant de l'écran titre. Bibliogr. 176-191.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1984. / Typescript. Vita. Includes bibliographical references (leaves 216-223).

Through the use of chronic experimental animal models, the majority of in vitro investigations of temporal lobe epilepsy have demonstrated enhanced network activity within the subdivisions of the hippocampal formation. However, clinical evidence in combination with in vivo and in vitro studies indicates that structures external to the hippocampus contribute to the genesis of seizure activity. To address the effects of limbic network excitation, I have utilized combined hippocampal---entorhinal cortex brain slices from pilocarpine-treated rats that display chronic seizures. / My investigations have focused upon three structures, the subiculum, entorhinal cortex and the insular cortex. The experiments in the pilocarpine-treated subiculum demonstrated increased network excitability that was attributed to a more positive GABAA receptor mediated inhibitory post-synaptic potential (IPSP) reversal point coupled with a reduced IPSP peak conductance. Utilizing RT-PCR analysis and immunohistochemical staining we observed a decline in K+-Cl- cotransporter mRNA expression and a reduced number of parvalbumin-positive, presumptive inhibitory interneurons. My second project assessed the network hyperexcitability in layer V of the lateral entorhinal cortex. This is the first study to report spontaneous bursting, in the absence of epileptogenic agents, in the epileptic entorhinal cortex. We attributed this level of network excitation to reduced GABAA receptor mediated inhibition and increased synaptic sprouting. In the final project, we extended our slice preparation to include the insular cortex, a structure external to the temporal lobe. Our investigations identified a mechanism of NMDA receptor dependent synaptic bursting that masked GABA A receptor mediated conductances.

Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / Behavioral and neurochemical studies were carried out with 21 days-old rats pretreated or not with nimodipine (10 or 30mg/Kg, i.p.) on pilocarpine-induced seizures (400mg/Kg, s.c.) to investigate the mechanism involved in the acute phase of seizures and the effects of nimodipine on seizures. The behavioral studies showed peripheral cholinergic signs, stereotyped movements, convulsions, status epilepticus in all animals and death in less degree after administration of P400, and the pretreatment with nimodipine reduced convulsions, the latency of first convulsion and death. Neurochemical studies in striatum showed levels increased of lipid peroxidation, nitrite and catalase activity, and nimodipine reverted this effect. Biochemical studies showed that striatum cholinergic and dopaminergic receptors in young rats were decreased after observation period, while the Kd values decreased only in D2 dopaminergics receptors. P400 decreased dopamine and serotonin levels and their metabolites DOPAC and 5-HIAA, respectively; otherwise, the dopaminergic HVA metabolite was increased. In this time, the pretreatment with nimodipine decreased dopaminergic metabolite and increased serotonergic, HVA and 5-HIAA, respectively. Our results showed that young animals are sensitive to epileptogenic stimuli, but they are relatively resistant to death, and nimodipine exhibited a protective effect on the pilocarpine-induced seizures. However, the knowledge of seizures physiopathology and effects of nimodipine on seizures should be better investigated. / Estudos comportamentais e neuroquÃmicos foram realizados em ratos com 21 dias de idade, atravÃs do prÃ-tratamento ou nÃo com nimodipina (10 ou 30mg/Kg, i.p.) e administraÃÃo de pilocarpina (400mg/Kg, s.c., P400), a fim de investigar o mecanismo da fase aguda do processo convulsivo e os efeitos da nimodipina nas convulsÃes. Os animais foram observados durante 1h e logo depois sacrificados. Os estudos comportamentais mostraram que P400, produziu sinais colinÃrgicos perifÃricos (SCP), movimentos estereotipados (ME), convulsÃes e estado epilÃptico em todos os animais, todavia o Ãndice de morte foi em torno de 30%. O prÃ-tratamento com nimodipina nÃo alterou os SCP e ME, mas diminuiu o Ãndice de convulsÃes e aumentou as latÃncias da primeira convulsÃo e morte. Os estudos neuroquÃmicos em corpo estriado, apÃs 1h da administraÃÃo de P400, revelaram um aumento nos nÃveis de peroxidaÃÃo lipÃdica, produÃÃo de nitrito e atividade da catalase, e esses efeitos foram revertidos pelo prÃ-tratamento com nimodipina. A densidade dos receptores colinÃrgicos (M1+M2) e dopaminÃrgicos (D1 e D2) apresentou-se diminuÃda, enquanto a constante de dissociaÃÃo (Kd) foi diminuÃda apenas nos receptores D2. P400 reduziu a concentraÃÃo das monoaminas dopamina (DA) e serotonina (5-HT), e de seus respectivos metabÃlitos, 3,4 Ãcido dihidroxifenilacÃtico (DOPAC) e Ãcido 5-hidroxiindolacÃtico (5-HIAA), enquanto nos nÃveis do metabÃlito dopaminÃrgico, Ãcido homovanÃlico (HVA), foi observado um aumento. Por sua vez, o prÃ-tratamento com nimodipina nas convulsÃes com P400 resultou em uma reduÃÃo do metabÃlito dopaminÃrgico e aumento do metabÃlito serotonÃrgico, HVA e 5-HIAA, respectivamente. Nossos estudos mostram que os animais imaturos sÃo susceptÃveis Ãs convulsÃes, mas apresentam uma certa resistÃncia à morte durante o processo convulsivo, e que a nimodipina exerce uma atividade protetora minimizando as convulsÃes induzidas por P400. Contudo, o conhecimento da fisiopatologia da convulsÃo e a identificaÃÃo dos efeitos da nimodipina nas convulsÃes devem ser melhor investigados para facilitar o conhecimento dos fatores inerentes à epilepsia e aÃÃes da nimodipina no processo convulsivo.

No description available.

This study was conducted to characterize cellular changes occurring during the progression of status epilepticus (SE) that could lead to the maintenance of increased membrane excitability. SE was induced by injection of pilocarpine after which rats were monitored both electrographically and behaviorally. After various lengths of time in SE, specific brain regions were isolated for biochemical study. SE resulted in an early maintenance of PKA activity in both cortical homogenate and crude synaptoplasmic membrane (crude SPM) fractions. At subsequent stages of SE there was a significant increase in PKA activity in both homogenate and crude SPM fractions. Wester blot analysis showed that alteration of PKA protein expression was not responsible for the increase in PKA activity. These results show that SE has a significant duration-dependent effect on PKA activity. Combined with other cellular changes these findings, could represent a mechanism for the formation for potentiated seizure states like epilepsy.

The lithium/pilocarpine model of epilepsy mimics mesial temporal lobe epilepsy with hippocampal sclerosis (MTLE-HS) in humans. Systemic injection of pilocarpine in lithium chloride (LiCL) pretreated adult rats results in an acute episode of severe continuous seizure activity (status epilepticus, SE). SE causes a latent period, whereby the animal appears neurologically normal, with subsequent development of spontaneous recurrent seizures (SRSs). Neuropathological changes that occur during the latent period are believed to contribute to the epileptic condition. The present thesis characterized the development of neuronal death and behavioural alterations in rats after SE induced by the repeated low-dose pilocarpine procedure (RLDP), and investigated the causal relationship between these two processes. Our data demonstrated that the RLDP procedure for the induction of SE results in widespread neurodegeneration and behavioural alterations comparable to the pilocarpine and low-dose pilocarpine (LDP) procedures. However, the advantage to using this protocol was strain-dependent as it reduced mortality in Wistar, but not in Long Evans Hooded (LEH), rats. Stereological analysis of neurons (stained for the neuronal specific marker [NeuN]) at various times (1 hr to 3 months) following SE showed that different brain regions within the hippocampus, amygdala, thalamus and piriform cortex exhibited differential rates of neuronal loss, with the majority of SE-induced neuronal death present by 24 hours. SE resulted in decreased exploratory behavior as assessed in the open field test, increased aggression to handling, increased hyperreactivity as assessed in the touch-response test, and anxiolytic effects as measured in the elevated-plus maze. Furthermore, deficits in search strategies used, as well as impaired spatial learning and memory, contributed to poor Morris water maze (MWM) performance. Partial neuroprotection within the hippocampus (by tat-NR2B9c) had no effect on the number of rats developing SRSs or on behavioural alterations; this argues against a causal relationship between neurodegeneration within this region, genesis of SRSs, and behavioural morbidity.