Dans le cas des épilepsies focales motrices pour lesquels la chirurgie résective n'est pas indiquée, la stimulation à haute fréquence a été proposée comme une technique alternative. Afin de mieux comprendre le rôle des ganglions de la base (GB) dans ce type de crise, il est tout d'abord nécessaire de déterminer l'impact des décharges néocorticales paroxystiques sur l'ensemble du circuit des GB (le striatum, le pallidum, le NST et la SNr). Pour cela nous avons tout d'abord mis en point un modèle de crises focales chez le primate par injection intra-corticale de pénicilline. Les crises obtenues étaient très focales et avaient une bonne reproductibilité inter et intra individuelle. Durant les périodes interictales, les changements électrophysiologiques n'apparaissaient qu'à la suite des pointes interictales. En effet, aucune différence n'a pu être notée entre l'activité unitaire de l'état de base et durant les périodes interictales exemptes de pointe alors que d'importantes modifications ont pu être observées dans les millièmes de secondes qui suivaient la pointe. Ces pointes interictales induisaient des changements tant au niveau unitaire qu'au niveau des potentiel de champs locaux. L'analyse de ces mêmes activités électrophysiologiques durant les périodes ictales nous a permis de montrer que les modifications n'étaient pas homogènes pour les différentes structures. Ces résultats nous ont amené à envisager l'existence de 2 boucles impliquées de façon différente dans la propagation et le contrôle des crises. La boucle cortico-subthalamo-nigrale serait préférentiellement impliquée dans la propagation des crises alors que la boucle cortico-putamino-pallidale serait peut être impliquée dans le contrôle des crises. Une seconde étude a été faite sur des crises focales prémotrices afin d'évaluer la spécificité des réseaux impliqués en fonction du types de crises. Nous avons ainsi pu montrer que l'implication des structures étaient différentes avec notamment de ce cas là une plus forte implication du noyau caudé et de la SNr. Cette étude a donc permis d'établir l'implication des GB lors de crises focales motrices chez le primate, de mettre en évidence l'existence de plusieurs boucles fonctionnelles pouvant être impliquées dans de ce type de crises.

Glutamate is the essential neurotransmitters in pain pathways. The discovery of the vesicular glutamate transporters (VGLUT1-3) has been a fundamental step on the way to describe glutamate-dependent pain pathways. We used the Cre-lox system to construct conditional knockouts with deficient Vglut2 transmission in specific neuronal populations. We generated a Vglut2f/f;Ht-Pa-Cre line to selectively delete Vglut2 from the peripheral nervous system. These Vglut2 deficient mice showed decreased acute nociceptive responses and were less prone to develop an inflammatory state. They did not develop cold allodynia, or heat hyperalgesia and were less hypersensitive to mechanical stimuli in the PSNL chronic pain model. Further analyses of genes with altered expression after nerve injury, revealed candidates for future studies of chronic pain biomarkers. Interestingly, the Vglut2f/f;Ht-Pa-Cre mice developed an elevated itch behavior. To investigate more specific neuronal populations, we analyzed mice lacking Vglut2 in the Nav1.8 population, as inflammatory hyperalgesia, cold pain, and noxious mechanosensation have been shown to depend upon Nav1.8Cre positive sensory neurons. We showed that deleting Vglut2 in Nav1.8Cre positive neurons abolished thermal hyperalgesia in persistent inflammatory models and responses to noxious mechanical stimuli. We also demonstrated that substance P and VGLUT2-dependent glutamatergic transmission are co-required for the development of formalin-induced inflammatory pain and heat hyperalgesia in persistent inflammatory states. Deletion of Vglut2 in a subpopulation of neurons overlapping with the vanilloid receptor (TRPV1) primary afferents in the dorsal root ganglia resulted in a dramatic increase in itch behavior accompanied by a reduced responsiveness to thermal pain. Substance P signaling and VGLUT2-mediated glutamatergic transmission in TRPV1 neurons was co-required for the development of inflammatory pain states. Analyses of an itch phenotype uncovered the pathway within TRPV1 neurons, with VGLUT2 playing a regulatory role and GRPR neurons, which are to plausible converge the itch signal in the spinal cord. These studies confirmed the essential role of VGLUT2-dependent glutamatergic transmission in acute and persistent pain states and identified the roles of specific subpopulations of primary afferent neurons. Additionally, a novel pain and itch transmission pathway in TRPV1/VGLUT2 positive neurons was identified, which could be part of the gate control of pain.

[Truncated abstract] During development of the visual system, topographic connections between the retina and the superior colliculus are established using guidance molecules. The EphA family of tyrosine kinase receptors and their ephrin-A ligands are important for establishing topography between the temporo-nasal axis of the retina and the rostro-caudal axis of the superior colliculus. After injury to the visual system via unilateral optic nerve transection, adult mammalian retinal ganglion cells fail to regenerate axons spontaneously to their main visual centre, which in rodents, is the superior colliculus. The EphA5 gradient is down-regulated from a temporalhigh to nasallow gradient to a uniform low level in the few surviving retinal ganglion cells, but ephrin-A2 is upregulated back to a significant rostrallow to caudalhigh gradient in the superior colliculus, similar to that seen during development. In this thesis, a number of experiments have been undertaken to investigate further how EphA5 and ephrin-A2 are regulated after injury and how they may play a role once regeneration has been encouraged through surgical intervention. In the first study, targeted unilateral retinal laser lesions were used to ablate either dorso-nasal or ventro-temporal quadrants of the retina. ... Surviving and regenerating retinal ganglion cells in the retina, and axons in the optic nerve, were analysed. The data suggest that metallothionein-I/II increases axonal regeneration through the optic nerve injury site but, at the dose administered, had no neuroprotective effects on retinal ganglion cells. This thesis provides further insight into the response of guidance molecules to injury, and the potential of metallothionein-I/II as a neuroregenerative factor in the adult mammalian visual system. The regulation of both EphA5 and ephrin-A2 through transsynaptic connections may be a response common to other guidance molecules. Such connectivity now needs to be studied further to understand how it may impact on various treatments designed to increase re-connectivity after other brain injuries, including stroke. The ectopic expression of ephrin-A2 at the insertion site of a peripheral nerve graft in the superior colliculus, implicate this guidance molecule in the glial scar for the first time. Therefore, to overcome inhibition by the glial scar, axons must also overcome ephrin-A2 mediated inhibition, potentially by the addition of EphA5 fusion proteins. Metallothionein-I/II?s effect of increasing axonal regeneration through the optic nerve injury site suggests that it could be used to increase the number of regenerating axons reaching their target. Such strategies to increase the absolute number of regenerated axons should enable these axons to better use the EphA5 and ephrin-A2 topographic gradients to optimize regenerative success.

Thesis (Ph.D.)--University of Melbourne, The National Vision Research Institute of Australia and Dept. of Optometry & Vision Sciences, 2007. / Typescript. Includes bibliographical references (leaves 95-111).

Thesis (Ph.D.)--University of Western Australia, 2007.

Thesis (M. Phil.)--University of Hong Kong, 1999. / Includes bibliographical references (leaves 119-154).

No description available.

Les macrophages primitifs envahissent la moelle épinière dès E11.5-12.5 chez l'embryon de souris. Ces cellules interagissent avec les neurites spinaux en croissance des neurones sensoriels des ganglions de la racine dorsale dès E12.5. La microglie est connue pour réguler plusieurs processus développementaux dans le système nerveux central, mais leur rôle dans le développement du système nerveux périphérique reste inconnu. Nous montrons que les macrophages primitifs régulent le développement des neurones sensoriels dans l'embryon de souris. Nous avons d'abord découvert que les macrophages primitifs interagissent avec les neurites périphériques des neurones sensoriels dès E11.5. Nous avons ensuite démontré que l'absence de macrophage chez les souris PU.1KO ou leur ablation immunopharmacologique, entraînait une réduction initiale des neuronaux TrkB+ et TrkC+ à E11.5, suivie d'une augmentation transitoire de leur nombre à E12.5. Cette augmentation est associée à une augmentation transitoire de leur mort développementale ce qui expliquerait pourquoi leur nombre redevient normal à partir de E13.5. Chez les embryons dépourvus de macrophage la mort augmente à nouveau à E15.5 pour les neurones TrkC+ et dès E14.5 pour les neurones TrkB+. Concernant les neurones TrkA+, leur nombre reste déficitaire entre E12.5 et E15.5, bien que leur mort développementale ne soit pas affectée. Nous avons enfin montré que la prolifération cellulaire était diminuée à E12.5 dans les ganglions des souris PU.1KO. Ces résultats sont la première démonstration que les macrophages primitifs et/ou les microglies immatures peuvent aussi réguler le développement embryonnaire du système nerveux périphérique. / The primitive macrophages invade the spinal cord as early as E11.5-12.5 in the mouse embryo. These cells interact with growing spinal neurites of the dorsal root ganglia sensory neurons as early as E12.5. Microglia is known to regulate several developmental processes in the central nervous system, but their role in the development of the peripheral nervous system remains unknown. We show that primitive macrophages regulate the development of sensory neurons in the mouse embryo. We first discovered that primitive macrophages interact with peripheral neurites of sensory neurons as early as E11.5. We then demonstrated that the absence of macrophage in PU.1KO mice or their immunopharmacological ablation resulted in an initial reduction of TrkB+ and TrkC+ neurons at E11.5, followed by a transient increase in their number at E12.5. This increase is associated with a transient increase in their developmental death which would explain why their numbers become normal again from E13.5. In macrophage-free embryos, death increases again to E15.5 for TrkC+ neurons and as early as E14.5 for TrkB+ neurons. Concerning TrkA+ neurons, their number remains deficient between E12.5 and E15.5, although their developmental death is not affected. We have finally shown that cell proliferation was decreased at E12.5 in ganglions of PU.1KO mice. These results are the first demonstration that primitive macrophages and / or immature microglia can also regulate the embryonic development of the peripheral nervous system.

Les horloges circadiennes, permettant l´anticipation des changements environnementaux cycliques, sont synchronisés par la lumière du jour via un signal lumineux à la rétine. Outre les cônes et les bâtonnets, la rétine contient des cellules ganglionnaires intrinsèquement photosensibles (ipRGCs), subdivisées en sous-types distincts exprimant le pigment mélanopsine et impliquées dans l´entrainement de l´horloge biologique à la lumière. Le système circadien est très similaire chez les animaux nocturnes et diurnes. L'objectif de cette thèse était d'étudier les propriétés morphologiques, moléculaires etphysiologiques des ipRGCs de rongeurs nocturnes (souris) et diurnes (Arvicanthis ansorgei). Ce travail révèle des morphologies comparables des différents types d´ipRGCs pour les deux espèces, mais la proportion du type M1 était plus élevée chez Arvicanthis. Des immunomarquages spécifiques des cellules ganglionnaires de la rétine ont révélé que les ipRGCs constituent une population hétérogène. Chez les deux espèces, l'expression de neurofilaments et de Brn3 différait selon le type d´ipRGC. Les propriétés physiologiques des ipRGCs étaient principalement similaires pour les deux espèces. Chez Arvicanthis, les ipRGCs de type I étaient plus sensibles à de courts éclairs lumineux. En conclusion , les ipRGCs des rongeurs nocturnes et diurnes partagent des caractéristiques communes. Cette étude est la première à décrire la sensibilité des ipRGCs a des éclairs de courte durée. De plus, ce travail étend les connaissances sur l'hétérogénéité moléculaire des différents types d´ipRGCs. / Circadian clocks permit anticipation of cyclic environmental changes and are synchronized to solar day through photic input from the retina. Besides rods and cones, the retina contains intrinsically photosensitive retinal ganglion cells (ipRGCs), consisting of distinct sub-types. IpRGCs express the photopigment melanopsin and are implicated in photoentrainment of the biological clock. Light information shapes the animal’s temporal behavior, but the circadian systems of nocturnal and diurnal animals appear to be very similar. The aim of this thesis was to investigate the morphological, molecular and physiologicalproperties of ipRGCs in nocturnal (C57BL/6 mouse) compared to diurnal (Arvicanthis ansorgei) rodents. The morphological analysis revealed comparable characteristics of the different ipRGC types in both species; however the proportion of M1 cells was higher in Arvicanthis than in mouse. Immunostaining patterns using RGC markers revealed that ipRGCs are a heterogeneous population. In both species, Brn3 and neurofilaments expression were partly distinct between the ipRGC types.The physiological properties of ipRGC types were mostly similar between the two species, but type I ipRGCs were more sensitive to short light flashes in Arvicanthis than in mouse. In conclusion, the melanopsin system of nocturnal and diurnal rodents shares many common features. Importantly, this study is the first describing responses of ipRGCs to short light flashes and the observed molecular heterogeneity extends the characterization of individual ipRGC types.

O diabetes pode ocasionar diversas complicações, dentre elas, a neuropatia diabética, que se caracteriza por lesões anatômicas e funcionais dos neurônios autonômicos e somáticos periféricos. O modelo experimental de diabetes mellitus induzido por estreptozotocina tem sido muito utilizado no estudo das diversas complicações do diabetes. Neste sentido, o objetivo do presente estudo foi avaliar, por meio de métodos estereológicos, a microestrutura do gânglio celíaco de ratos diabéticos (Diabetes mellitus) tipo 1 induzidos por estreptozotocina (STZ) submetidos a treinamento físico. Para isto, foram utilizados vinte ratos Wistar adultos, machos, sendo cinco saudáveis sedentários (SS), cinco saudáveis treinados (ST), cinco diabéticos sedentário (DS) e cindo diabéticos treinados (DT). O diabetes foi induzido por uma única injeção de STZ (60 mg/kg, ev). O teste de esforço máximo foi realizado em todos os grupos para verificação da capacidade física. Os grupos saudável treinado e diabético treinado foram submetidos a um protocolo de treinamento físico em esteira ergométrica (1 hora/dia; 5 dias/semana; 10 semanas; 60% da velocidade máxima no teste de esforço). Após as dez semanas, foi implantada uma cânula na artéria femoral em direção ao ventrículo esquerdo, para registro da pressão arterial (PA) e freqüência cardíaca (FC). Vinte e quatro horas após a canalização a PA e a FC foram registradas e processadas em um sistema de aquisição de dados (CODAS, 2KHz). O DS apresentou redução do peso corporal (33%), hiperglicemia (279%) e um prejuízo hemodinâmico com bradicardia (19%) e hipotensão (12%) e redução do número total de neurônios (26%) em relação ao SS. Após o protocolo de treinamento físico, tanto o ST, quanto o DT apresentaram uma melhora na capacidade física (107% e 75%, respectivamente), o DT apesar de não ter apresentado uma melhora metabólica (glicemia), apresentou uma melhora hemodinâmica atenuando a bradicardia (16%) e reverteu a perda neuronal (25%) no DS. Assim, os resultados obtidos no presente estudo sugerem que o treinamento físico tem papel importante no tratamento da neuropatia diabética autonômica. / Diabetes is associated with several complications, among them, diabetic neuropathy, characterized by anatomical and functional injuries of peripheral somatic and autonomic neurons. The experimental model of diabetes induced by streptozotocin has been used in diabetes complication study. In this way, the aim of this study was to evaluate by stereological methods the microstructure of the celiac ganglion in diabetic rats (Diabetes mellitus) type I induced by induced by streptozotocin (STZ) submitted to exercise training. For this, twenty adult male rats were used, five healthy sedentary (HS), five healthy trained (HT), five diabetic sedentary (DS) and five diabetic trained (DT). Diabetes was induced by a single injection of STZ (60 mg/Kg, ev). The maximal exercise test was performed in all groups to check their physical capacity. The healthy trained and diabetic trained groups were submitted to an exercise training protocol on a treadmill (1 hour/day, 5 days/week, 10 weeks, 60% of the maximum speed on a treadmill test). After ten weeks, a cannula was implanted into the femoral artery into the left ventricle to register the arterial blood pressure (BP) and heart rate (HR). Twenty four hours after cannulation BP and HR were recorded and processed in a data acquisition system (codas, 2KHz). The DS group showed a reduction in body weight (33%), hyperglycemia (279%) and bradycardia with hemodynamic impairment (19%) and hypotension (12%) and reduction in the total number of neurons (26%). After the exercise training protocol, the HT and DT presented an improvement in physical capacity (107% and 75% respectively), despite the DT group have not shown a metabolic improvement (glycemia), it presented a hemodynamic improvement attenuating the bradycardia (16%) and reverted the neuronal loss (25%) in the DS. Thus, the results of this study suggest that physical training has an important role in the treatment of the diabetic autonomic neuropathy.