Lépilepsie myoclonique juvénile (EMJ) est un syndrome épileptique très répandu qui appartient aux épilepsies idiopathiques généralisées. Il se caractérise par des secousses myocloniques et des crises tonico-cloniques débutant pendant ladolescence, entre 12 et 18 ans. Son étiologie est génétique et impliquerait linteraction de plusieurs gènes. Des études de liaisons géniques ont permis lindentification, dans un gène localisé en 6p12, de cinq mutations faux-sens co-ségrégées avec le phénotype de EMJ. Ce gène code une nouvelle protéine, dénommée EFHC1, comportant un motif EF-hand, domaine potentiel de liaison au calcium et trois domaines DM10, de fonction inconnue. L'objectif de notre travail consiste à étudier les propriétés biochimiques et fonctionnelles d'EFHC1. Nous avons dabord étudié la localisation subcellulaire dEFHC1 dans différentes lignées cellulaires (HEK-293, HeLa et COS-7) au moyen de deux approches complèmentaires. Dune part nous avons surexprimé la protéine couplée à lEGFP, un marqueur fluorescent permettant se visualisation et dautre part, nous avons étudié la localisation de la protéine endogène au moyen dun anticorps spécifique. Dans les cellules en mitose, EFHC1 montre clairement une association avec le fuseau mitotique, spécialement au niveau des pôles et du corpuscule de Fleming pendant la cytokinèse. EFHC1 co-localise également avec le centrosome dans les cellules en interphase et en mitose. Dans le but de déterminer la région d'EFHC1 impliquée dans lassociation au fuseau mitotique, nous avons effectué des analyses au moyen de différentes formes tronquées de la protéine couplées à lEGFP. Les résultats indiquent que lextrémité N-terminale d'EFHC1, contenant les 45 premiers acides aminés de la protéine est cruciale pour ladressage au fuseau mitotique. Nous avons démontré, au moyen dexpériences dimmunoprécipitations et de co-sédimentation de microtubules, une association directe dEFHC1 avec lα-tubuline, composant des microtubules. Cette interaction est médiée par un nouveau domaine dassociation aux microtubules situé au niveau de lextrémité N-terminale de la protéine, entre les acides aminés 1 et 45. Dautre part, nous avons mis en évidence un rôle important dEFHC1 dans la régulation de la division cellulaire. En effet, la surexpression dune forme tronquée dEFHC1 ne contenant que les 45 premiers acides aminés de la protéine, agissant comme un dominant-négatif, ainsi que linhibition dexpression dEFHC1 par expression de shRNAs induit de façon significative des fuseaux mitotiques anormaux (fuseaux unipolaires, anomalies de condensation des chromosomes au niveau de la plaque équatoriale pendant la métaphase). De plus, nous avons observé que les cellules invalidées en EFHC1 présentaient un défaut de progression mitotique résultant du blocage des cellules en prométaphase anormale, conduisant à une augmentation significative de lindex mitotique (% de cellules en mitose) et à de lapoptose. Enfin, nous avons démontré un rôle dEFHC1 dans la corticogenèse cérébrale. En effet, linvalidation dEFHC1 (shRNAs et dominants-négatifs) dans le néocortex de rat en développement au moyen des techniques délectroporations ex vivo et in utero conduit à un défaut de migration neuronale radiaire. Nous avons montré que celui-ci résultait dune diminution de sortie de cycle cellulaire des cellules progénitrices neuronales conduisant à une accumulation de celles-ci, dune altération de larchitecture des prolongements de la glie radiaire, dune augmentation de la mort cellulaire par apoptose et dun défaut de locomotion des neurones post-mitotiques.

The goal of this thesis was to understand and quantify to what extent plants are used for the treatment of mental and folk illnesses such as susto and mal aire in the Neotropics and to investigate the anxiolytic and antiepileptic potential of previously unstudied Neotropical members of the genera Piper and Peperomia. Firstly, the literature was reviewed and a regression analysis method was used in order to quantitatively determine which plant families are preferred for the treatment of mental, behavioral and neurological health disorders in the Neotropics. This analysis identified Piperaceae, among others, as an important taxonomic group for the treatment of such disorders. Following that lead, a botanical survey was conducted in Peru, where 47 species of Piperaceae and 21 plants traditionally used for folk illnesses by the Yanesha of Peru, an Amazonian ethnic group, were collected. In order to target potential anxiolytic and antiepileptic plants, two high throughput bioassays were used to evaluate the extracts’ in vitro activity on the γ-aminobutyric acid (GABA) system. Plant extracts in general demonstrated moderate to high affinity to the GABA-BZD receptor. Additionally, extracts demonstrated low to moderate activity in the inhibition of the GABA-T enzyme, with a few plants exhibiting promising activity. Plants selected by the Yanesha showed comparable activity to the other Piperaceae plants with Piper cremii being the most active plant in the GABAA assay, and Drymaria cordata in the GABA-T assay. Finally, four phytochemicals from Piper tuerckheimii, a plant regarded as one of the most effective traditional remedy for the treatment of epilepsy and susto by the Q’eqchi’ Maya of Belize presented, were isolated for the first time.

Amygdala kindling is commonly used to study the neural mechanisms of temporal lobe epilepsy and its behavioral consequences. The repetitive seizure activity that occurs during kindling is thought to induce an extensive array of structural and functional modifications within the brain, particularly in the hippocampus and dentate gyrus regions. Some of these changes include the growth or sprouting of new axonal connections as well as the birth and integration of new neurons into hippocampal circuits. Previous work has shown that these changes in structural and functional plasticity are not necessarily beneficial events. For instance, the growth and reorganization of synaptic terminals in the hippocampus and other brain regions might serve as a substrate that enhances hyperexcitability and seizure generation. In addition, although seizures induce the birth of new neurons, many of these newly generated cells migrate and function improperly within the hippocampal networks. Considering the prominent role of the hippocampus in a variety of behaviours, including learning, memory, and mood regulation, it would appear that alterations involving the structural and functional properties of both mature and newly born neurons in this region could impact these hippocampal-dependent functions. However, to date, the role of kindling-induced changes in hippocampal structural plasticity and neurogenesis on behaviour is incomplete, and the molecular mechanisms that govern these pathological events are poorly understood.<p/> The aim of this dissertation is to gain a better understanding of the changes in synaptic plasticity and neurogenesis within the hippocampus that occur after amygdala kindling. In chapter 2, we will examine if kindling alters the expression of synapsin I, a molecular marker of synaptic growth and activity, in both the hippocampus and other brain regions. In addition, we will also set out to determine if changes in synapsin I are related to the development of behavioural impairments associated with kindling. In chapter 3, the effect of kindling on hippocampal neurogenesis will be examined. In addition, we will also evaluate the effect of kindling on the expression of Reelin and Disrupted-in-Schizophrenia 1 (DISC1), two proteins instrumental for mediating proper neuronal migrational and maturation during development. In chapter 4, the effect of altered DISC1 expression in the dentate gyrus after kindling will be examined more extensively. We will examine whether altered DISC1 expression in the dentate contributes to some of the pathological features associated with seizure-induced hippocampal neurogenesis, such as ectopic cell migration and dentate granule cell layer dispersion. Finally, in chapter 5, the impact of aberrant seizure-induced neurogenesis on behaviour will be examined by determining if seizure-generated neurons functionally integrate and participate in hippocampal circuits related to memory processing. The results of this dissertation enhances our understanding of the functional consequences that altered hippocampal synaptic plasticity and neurogenesis may have on the development of epilepsy and emergence of cognitive impairments associated with chronic seizures.<p/>

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.

The goal of this thesis was to understand and quantify to what extent plants are used for the treatment of mental and folk illnesses such as susto and mal aire in the Neotropics and to investigate the anxiolytic and antiepileptic potential of previously unstudied Neotropical members of the genera Piper and Peperomia. Firstly, the literature was reviewed and a regression analysis method was used in order to quantitatively determine which plant families are preferred for the treatment of mental, behavioral and neurological health disorders in the Neotropics. This analysis identified Piperaceae, among others, as an important taxonomic group for the treatment of such disorders. Following that lead, a botanical survey was conducted in Peru, where 47 species of Piperaceae and 21 plants traditionally used for folk illnesses by the Yanesha of Peru, an Amazonian ethnic group, were collected. In order to target potential anxiolytic and antiepileptic plants, two high throughput bioassays were used to evaluate the extracts’ in vitro activity on the γ-aminobutyric acid (GABA) system. Plant extracts in general demonstrated moderate to high affinity to the GABA-BZD receptor. Additionally, extracts demonstrated low to moderate activity in the inhibition of the GABA-T enzyme, with a few plants exhibiting promising activity. Plants selected by the Yanesha showed comparable activity to the other Piperaceae plants with Piper cremii being the most active plant in the GABAA assay, and Drymaria cordata in the GABA-T assay. Finally, four phytochemicals from Piper tuerckheimii, a plant regarded as one of the most effective traditional remedy for the treatment of epilepsy and susto by the Q’eqchi’ Maya of Belize presented, were isolated for the first time.

Amygdala kindling is commonly used to study the neural mechanisms of temporal lobe epilepsy and its behavioral consequences. The repetitive seizure activity that occurs during kindling is thought to induce an extensive array of structural and functional modifications within the brain, particularly in the hippocampus and dentate gyrus regions. Some of these changes include the growth or sprouting of new axonal connections as well as the birth and integration of new neurons into hippocampal circuits. Previous work has shown that these changes in structural and functional plasticity are not necessarily beneficial events. For instance, the growth and reorganization of synaptic terminals in the hippocampus and other brain regions might serve as a substrate that enhances hyperexcitability and seizure generation. In addition, although seizures induce the birth of new neurons, many of these newly generated cells migrate and function improperly within the hippocampal networks. Considering the prominent role of the hippocampus in a variety of behaviours, including learning, memory, and mood regulation, it would appear that alterations involving the structural and functional properties of both mature and newly born neurons in this region could impact these hippocampal-dependent functions. However, to date, the role of kindling-induced changes in hippocampal structural plasticity and neurogenesis on behaviour is incomplete, and the molecular mechanisms that govern these pathological events are poorly understood.<p/> The aim of this dissertation is to gain a better understanding of the changes in synaptic plasticity and neurogenesis within the hippocampus that occur after amygdala kindling. In chapter 2, we will examine if kindling alters the expression of synapsin I, a molecular marker of synaptic growth and activity, in both the hippocampus and other brain regions. In addition, we will also set out to determine if changes in synapsin I are related to the development of behavioural impairments associated with kindling. In chapter 3, the effect of kindling on hippocampal neurogenesis will be examined. In addition, we will also evaluate the effect of kindling on the expression of Reelin and Disrupted-in-Schizophrenia 1 (DISC1), two proteins instrumental for mediating proper neuronal migrational and maturation during development. In chapter 4, the effect of altered DISC1 expression in the dentate gyrus after kindling will be examined more extensively. We will examine whether altered DISC1 expression in the dentate contributes to some of the pathological features associated with seizure-induced hippocampal neurogenesis, such as ectopic cell migration and dentate granule cell layer dispersion. Finally, in chapter 5, the impact of aberrant seizure-induced neurogenesis on behaviour will be examined by determining if seizure-generated neurons functionally integrate and participate in hippocampal circuits related to memory processing. The results of this dissertation enhances our understanding of the functional consequences that altered hippocampal synaptic plasticity and neurogenesis may have on the development of epilepsy and emergence of cognitive impairments associated with chronic seizures.<p/>

Cyclin-dependent kinase-5 (Cdk5) was identified as a serine/threonine kinase that plays an important role in neuronal development. Association with one of the neuronal activators, p35 or p39, is required for Cdk5 to elicit its diverse effects in the nervous system, such as neurite outgrowth. In addition to these, increasing evidence suggests that Cdk5 also plays an important role in cocaine addiction, neurotransmitter release, NMDA receptor phosphorylation. This thesis is divided into three parts which deals with the effects of Cdk5 inhibitor¡Ðroscovitine on the morphine tolerance development, acute inflammatory pain, and pilocarpine-induced seizure respectively. The first part explored the effect of Cdk5 inhibitior¡Ðroscovitine on the morphine antinociceptive tolerance development. Delta FosB activation is involved in morphine tolerance. Cyclin-dependent kinase- 5 (Cdk5) is found to be the downstream target of delta FosB. We examined the effects of the potent selective Cdk5 inhibitor¡Ðroscovitine on the development of antinociceptive tolerance of morphine. Tolerance was induced by continuous infusion of morphine 5 &#x00B5;g/hr intrathecally (i.t.) for 5 days. The effect of co-administration of roscovitine 1 &#x00B5;g/hr i.t. for 5 days was also examined. Roscovitine co-administration enhanced the antinociceptive effect of morphine in morphine tolerant rats. It also shift the morphine antinociceptive dose¡Ðresponse curve to the left during morphine tolerance induction, and reduced the increase in the ED50 of morphine two-fold. Collectively, these findings suggest Cdk5 modulation may be involved in the development of morphine tolerance and its inhibitor will enhance antinociceptive effect. The second part discussed the roscovitine effect on acute inflammatory pain. Formalin injected into the rat hind paw will evoke flinching (consisting of an elevation and shrinking back of the injected paw), a reliable parameter of pain behavior. The nociceptive response to formalin occurs in a biphasic pattern: there isan initial acute period (phase 1), and after a short period of remission, phase 2 begins and consists of a longer period (1 hour) of sustained activity. The initial response was initially attributed to a direct algogenic effect of formalin, whereas phase 2 was associated with the central sensitization. In this study, the Cdk5 inhibitor¡Ðroscovitine was injected intrathecally to elucidate the mechanism of Cdk5 activation during formalin-induced hyperalgesia. The 50 ul of 5% formalin solution was used as the noxious stimulant. The rats were injected with 0, 50, 100, and 200ug roscovitine intrathecally thirty minutes before hind paw formalin injection. Intrathecal 200ug roscovitine injection attenuates the phase I flinch response. And intrathecal 50, 100, and 200ug roscovitine injection suppress phase II flinch response effectively. Roscovitine administration could effectively suppress the formalin-induced flinch behavior. This implies the activation of Cdk5 plays an important role in the sensitization after nociceptive stimulation. The third part focus on the roscovitine effect on the pilocarpine induced seizure. Pilocarpine temporal lobe epilepsy model is widely used. Chronic electroconvulsive therapy could upregulate Cdk5 activity. Cdk5 inhibitor¡Ðroscovitine could suppress NMDA induced long-term potentiation in hippocampal slice. Intracerebroventricular injection of 100£gg roscovitine 30 min before pilocarpine-induced epilepsy could significantly decrease the seizure-induced mortality ( 11% in roscovitine group VS 77% in control group). The escape latency, spatial memory impairment, in the pilocarpine-induced seizure group is significant longer than the roscovitine pretreatment group in the Morris water maze test after one month (p¡Õ0.05). It is concluded Cdk5 may play an important in the pathogenesis of epilepsy. Therefore, Cdk5 inhibition may become another way for the epilepsy treatment.

Absence seizures in Childhood Absence Epilepsy (CAE) are 5 10 second episodes of impaired consciousness that are characterized on electroencephalography (EEG) by frontally-predominant, 3 4 Hz spike and wave discharges (SWD). The aims of this study were to use simultaneous EEG, functional magnetic resonance imaging (fMRI), and behavioral testing to identify the neural networks involved in absence seizures as well as to examine the timecourse of those ictal fMRI changes. It was hypothesized that absence seizures involve wide-reaching neural networks including the areas traditionally associated with normal attention processing and that absence seizures produce fMRI signal changes not only during the seizure, but before and after it as well. In this study, we recorded 88 absence seizures from a cohort of 42 children with pure CAE. These seizures were recorded as subjects participated in simultaneous EEG-fMRI scanning while engaged in a continuous performance task (CPT) of attentional vigilance or a repetitive tapping task (RTT) requiring repetitive motor activity. Using a novel, voxel-based percent fMRI change analysis combined with a volume of interest analysis, the second-by-second fMRI signal timecourse of the absence seizures were examined across numerous brain regions of interest, from 20 seconds before seizure onset through 40 seconds after seizure onset. EEG frequency analysis revealed seizures with a mean duration of 6.6 seconds and an abrupt onset and ending that were comprised of frontally-predominant, 3 4 Hz SWD. Ictal behavioral testing demonstrated abrupt onset of impairments during periods of SWD. These behavioral impairments were typical of CAE absence seizures in that impairments were greater in the CPT of attentional vigilance (omission error rate, OER = 81%) than in RTT testing (OER = 39 %) (p < 0.003). The ictal fMRI changes we observed varied depending upon the method of fMRI signal analysis used. Using the traditional general liner model, and assuming the standard hemodynamic response (HRF) function, this study replicated results consistent with previous ictal absence fMRI studies showing ictal activations primarily in the thalamus and ictal deactivations in traditional default mode areas. Using a more data-driven, novel voxel-based fMRI percentage change analysis to examine the ictal fMRI timecourse on a second-by-second basis, both ictally as well as pre- and post- ictally, this study, however, demonstrated ictal involvement of diverse brain regions before, during, and after the seizure. Activation was demonstrated up to 16 seconds before seizure onset, starting first in the parietal and orbital-medial frontal cortices and progressing to lateral frontal and lateral temporal cortices followed by the occipital and Rolandic cortices and finally the thalamus. Deactivation followed a similar anatomic progression and lasted up to 17 seconds after the end of SWD. These findings reveal a complex and long-lasting sequence of fMRI changes in CAE absence seizures that are not detectable by conventional HRF modeling and are important in the understanding and eventual treatment of absence seizures associated with CAE.

This report provides an overview of the adverse effects of the antiepileptic drug topiramate. Specifically, it evaluates the negative cognitive-communication effects of topiramate on individuals with epilepsy and postulates that treating these deficits is within the scope of practice of speech-language pathologists. It begins with a discussion on epilepsy, description of seizures, and the mechanism of action for antiepileptic drugs. It then provides an overview of cognitive communication deficits caused by antiepileptic drugs, including: memory problems, impairments in attention, and executive dysfunction. The final section provides an outline of potentially beneficial treatments a speech-language pathologist may provide to patients experiencing adverse effects from topiramate and how continued research can expand this area of practice. / text

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