This dissertation explores the role of brainstem structures in the development and expression of generalized tonic-clonic seizures. The functional consequences of brainstem seizures are investigated using the kindling paradigm in order to understand the behavioral and cognitive effects of generalized seizures. <BR><BR> I begin by investigating the general characteristics of brainstem kindling. The first experiment demonstrates that certain brainstem sites are indeed susceptible to kindling and begins to delineate the features that distinguish brainstem seizures from those evoked at other brain regions. Further investigation of the EEG signal features using wavelet analysis reveals that changes in the spectral properties of the electrographic activity during kindling include significant changes to high-frequency activity and organized low-frequency activity. I also identify transitions that include frequency sweeps and abrupt seizure terminations. The changing spectral features are shown to be critically associated with the evolution of the kindled seizures and may have important functional consequences. The surprising responsiveness of some brainstem structures to kindling forces us to reconsider the overall role of these structures in epileptogenesis as well as in the healthy dynamical functioning of the brain. <BR><BR> In order to study the functional consequences, a series of experiments examines the changes in behavior, cognition and affect that follow these brainstem seizures. Although the results show no effects on spatial learning or memory, there are significant and complex effects on anxiety- and depression-like behavior that appear to be related to motivation. In order to further study the cognitive effects, a second set of behavioral experiments considers how context (i.e., the environment) interacts with the behavioral changes. The results indicate that changes in affect may only be apparent when choice between seizure-related and seizure-free contexts is given, suggesting that the environment and choice can play key roles in the behavioral consequences of seizures. This thesis also includes an appendix that applies synchrotron imaging to investigate the anatomical consequences of electrode implantation in kindling and shows that significantly increased iron depositions occur even with purportedly biocompatible electrodes widely used in research and clinical settings. <BR><BR> Examination of the role of brainstem structures in generalized seizures in this dissertation offers new perspectives and insights to epileptogenesis and the behavioral effects of epilepsy. The changes in EEG features, behavior, affect and motivation observed after brainstem seizures and kindling may have important clinical implications. For example, the results suggest a need to reexamine the concept of psychogenic seizures, a potential connection to Sudden Unexplained Death in Epilepsy (SUDEP), and the contribution of environmental factors. It is hoped that these findings will help elucidate the complex issues involved in understanding and improving the quality of life for people with epilepsy.

This dissertation explores the role of brainstem structures in the development and expression of generalized tonic-clonic seizures. The functional consequences of brainstem seizures are investigated using the kindling paradigm in order to understand the behavioral and cognitive effects of generalized seizures. <BR><BR> I begin by investigating the general characteristics of brainstem kindling. The first experiment demonstrates that certain brainstem sites are indeed susceptible to kindling and begins to delineate the features that distinguish brainstem seizures from those evoked at other brain regions. Further investigation of the EEG signal features using wavelet analysis reveals that changes in the spectral properties of the electrographic activity during kindling include significant changes to high-frequency activity and organized low-frequency activity. I also identify transitions that include frequency sweeps and abrupt seizure terminations. The changing spectral features are shown to be critically associated with the evolution of the kindled seizures and may have important functional consequences. The surprising responsiveness of some brainstem structures to kindling forces us to reconsider the overall role of these structures in epileptogenesis as well as in the healthy dynamical functioning of the brain. <BR><BR> In order to study the functional consequences, a series of experiments examines the changes in behavior, cognition and affect that follow these brainstem seizures. Although the results show no effects on spatial learning or memory, there are significant and complex effects on anxiety- and depression-like behavior that appear to be related to motivation. In order to further study the cognitive effects, a second set of behavioral experiments considers how context (i.e., the environment) interacts with the behavioral changes. The results indicate that changes in affect may only be apparent when choice between seizure-related and seizure-free contexts is given, suggesting that the environment and choice can play key roles in the behavioral consequences of seizures. This thesis also includes an appendix that applies synchrotron imaging to investigate the anatomical consequences of electrode implantation in kindling and shows that significantly increased iron depositions occur even with purportedly biocompatible electrodes widely used in research and clinical settings. <BR><BR> Examination of the role of brainstem structures in generalized seizures in this dissertation offers new perspectives and insights to epileptogenesis and the behavioral effects of epilepsy. The changes in EEG features, behavior, affect and motivation observed after brainstem seizures and kindling may have important clinical implications. For example, the results suggest a need to reexamine the concept of psychogenic seizures, a potential connection to Sudden Unexplained Death in Epilepsy (SUDEP), and the contribution of environmental factors. It is hoped that these findings will help elucidate the complex issues involved in understanding and improving the quality of life for people with epilepsy.

Made available in DSpace on 2016-06-02T19:22:50Z (GMT). No. of bitstreams: 1 2381.pdf: 1192808 bytes, checksum: b6bdb4da58bced09244d3a1f38c4a657 (MD5) Previous issue date: 2009-04-24 / Universidade Federal de Sao Carlos / The exposure of animals to aversive situations, such as elevated plus-maze (EPM), activates serotonergic pathways with projections into structures involved in the defense system, such as the amygdala, septum, hypothalamus, hippocampus and periaqueductal grey matter (PAG), producing behavioral changes that can be characterized as anxiety. However the serotonin (5-HT) presents a dual role in this modulation. Thus, while the stimulation of the receptor subtype 5-HT1A and 5-HT2 prosencephalic in structures such as amygdala and hippocampus result in potentiation of responses of anxiety in rodents, the activation of these receptors in the PAG, often tends to reduce behaviors related to anxiety . This study focused the role of 5-HT3 receptors in the PAG in the anxiety in the mice EPM test. In experiments 1 and 2, mice received infusions intra-PAG of ondansetron (0, 0.3, 1.0, 3.0 nmol/0.1 &#956;L) and mCPBG (0, 40, 80 and 160 nmol/0.1 &#956;L), 5-HT3 receptors antagonist and agonist, respectively. As the mCPBG not changed any of the conventional indices (% open-arm entries and % open-arm time) and risk assessment, we investigated in experiment 3 the possibility of interaction between 5-HT3 and 5-HT2 receptors. For this, we perform combined microinfusions of intra-PAG ondansetron and mCPP, an agonist of 5-HT2B/2C receptors, on behavior of maze-naïve mice. The results showed that intra-PAG infusions of ondansetron (3.0 nmol) increased the behavioral indices of anxiety. None of the doses of intra-PAG infusions of mCPBG modified the conventional and ethological indices of anxiety. The anxiolytic-like effect produced by intra-PAG infusions of mCPP (0.03 nmol) was blocked by infusions of ondansetron (1.0 nmol) in the same mesencephalic structure. All effects were observed in the absence of significant changes in locomotor activity (closed-arm entries). Our results indicate that there is a possible interaction between 5-HT3 and 5-HT2B/2C receptors modulation into the PAG of anxiety in mice. / A exposição de animais a situações aversivas, tais como o labirinto em cruz elevado (LCE), ativa vias serotoninérgicas com projeções para estruturas envolvidas no sistema de defesa tais como, amídala, septo, hipotálamo, hipocampo e substância cinzenta periaquedutal (SCP), produzindo alterações comportamentais que podem ser caracterizadas como ansiedade. Entretanto, a serotonina (5-HT) apresenta um papel dual nesta modulação. Assim, enquanto a estimulação de receptores do subtipo 5-HT1A ou 5-HT2 em estruturas prosencefálicas como, amídala e hipocampo resultam na potencialização de respostas de ansiedade em roedores, a ativação dos mesmos receptores na SCP, freqüentemente tende a diminuir comportamentos relacionados à ansiedade. Este estudo investigou o papel dos receptores 5-HT3 da SCP na modulação da ansiedade em camundongos avaliados no LCE. Nos Experimentos 1 e 2, camundongos receberam microinjeções intra-SCP de ondansetron (0, 0,3, 1,0, 3,0 nmol/0,1 &#956;l) e mCPBG (0, 40, 80 e 160 nmol/0,1 &#956;l), antagonista e agonista dos receptores 5-HT3, respectivamente. Como o mCPBG não alterou nenhum dos índices convencionais de ansiedade (porcentagem de entrada e tempo gasto nos braços abertos) e de avaliação de risco, verificamos no experimento 3 a possibilidade de interação entre receptores 5-HT3 e 5-HT2. Para isso, realizamos microinjeções combinadas de ondansetron e mCPP, um agonista dos receptores 5-HT2B/2C. Os resultados mostraram que microinjeções de ondansetron (3,0 nmol) aumentaram os índices convencionais de ansiedade. Nenhuma das doses de mCPBG intra-SCP, alteraram os índices convencionais e etológicos de ansiedade. O efeito ansiolítico produzido pela administração intra-SCP do mCPP (0,03 nmol), foi bloqueado pela infusão de ondansetron (1,0 nmol) na mesma estrutura mesencefálica. Todos os efeitos foram observaA exposição de animais a situações aversivas, tais como o labirinto em cruz elevado (LCE), ativa vias serotoninérgicas com projeções para estruturas envolvidas no sistema de defesa tais como, amídala, septo, hipotálamo, hipocampo e substância cinzenta periaquedutal (SCP), produzindo alterações comportamentais que podem ser caracterizadas como ansiedade. Entretanto, a serotonina (5-HT) apresenta um papel dual nesta modulação. Assim, enquanto a estimulação de receptores do subtipo 5-HT1A ou 5-HT2 em estruturas prosencefálicas como, amídala e hipocampo resultam na potencialização de respostas de ansiedade em roedores, a ativação dos mesmos receptores na SCP, freqüentemente tende a diminuir comportamentos relacionados à ansiedade. Este estudo investigou o papel dos receptores 5-HT3 da SCP na modulação da ansiedade em camundongos avaliados no LCE. Nos Experimentos 1 e 2, camundongos receberam microinjeções intra-SCP de ondansetron (0, 0,3, 1,0, 3,0 nmol/0,1 &#956;l) e mCPBG (0, 40, 80 e 160 nmol/0,1 &#956;l), antagonista e agonista dos receptores 5-HT3, respectivamente. Como o mCPBG não alterou nenhum dos índices convencionais de ansiedade (porcentagem de entrada e tempo gasto nos braços abertos) e de avaliação de risco, verificamos no experimento 3 a possibilidade de interação entre receptores 5-HT3 e 5-HT2. Para isso, realizamos microinjeções combinadas de ondansetron e mCPP, um agonista dos receptores 5-HT2B/2C. Os resultados mostraram que microinjeções de ondansetron (3,0 nmol) aumentaram os índices convencionais de ansiedade. Nenhuma das doses de mCPBG intra-SCP, alteraram os índices convencionais e etológicos de ansiedade. O efeito ansiolítico produzido pela administração intra-SCP do mCPP (0,03 nmol), foi bloqueado pela infusão de ondansetron (1,0 nmol) na mesma estrutura mesencefálica. Todos os efeitos foram observados sem alteração da atividade locomotora (entrada nos braços fechados). Os nossos resultados sugerem uma possível interação entre receptores 5-HT3 e 5-HT2B/2C da SCP na modulação da ansiedade em camundongos.dos sem alteração da atividade locomotora (entrada nos braços fechados). Os nossos resultados sugerem uma possível interação entre receptores 5-HT3 e 5-HT2B/2C da SCP na modulação da ansiedade em camundongos.

Ciliary neurotrophic factor (CNTF) is produced by astrocytes which have been implicated in regulating stress responses. We found that CNTF in the medial amygdala (MeA) promotes despair or passive coping, i.e., immobility in an acute forced swim stress, in female mice, while having no effect in males. Neutralizing CNTF antibody injected into the MeA of wildtype females reduced activation of downstream STAT3 (Y705) 24 and 48 h later. In concert, the antibody reduced immobility in the swim test in females and only after MeA injection, but not when injected in the central or basolateral amygdala. Antibody injected into the male MeA did not affect immobility. These data reveal a unique role of CNTF in female MeA in promoting despair or passive coping behavior. Moreover, 4 weeks of chronic unpredictable stress (CUS) increased immobility in the swim test and reduced sucrose preference in wildtype CNTF+/+, but not CNTF-/- littermate, females. Following CUS, 10 min of restraint stress increased plasma corticosterone levels only in CNTF+/+ females. In males, the CUS effects were present in both genotypes. Further, CUS increased CNTF expression in the MeA of female, but not male, mice. CUS did not alter CNTF in the female hippocampus, hypothalamus and bed nucleus of stria terminalis. This suggests that MeA CNTF has a female-specific role in promoting CUS-induced despair or passive coping, behavioral anhedonia and neuroendocrine responses. Compared to CNTF+/+ mice, CNTF-/- mice did not show differences in CUS-induced anxiety-like behavior and sensorimotor gating function as measured by elevated T-Maze, open field and pre-pulse inhibition of the acoustic startle response. Together, this study reveals a novel CNTF-mediated female-specific mechanism in stress responses and points to opportunities for developing treatments for stress-related disorders in women.