Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The purposes of this study were to perform retrospective studies about epilepsy and idiopathic epilepsy in dogs presented at the Veterinary Neurology Service, University Veterinary Hospital, of Federal University of Santa Maria and use a flexible urethral catheter as an alternative method to measuring intracranial pressure in rabbits with head injury and compare the data with ventriculostomy catheter (conventional method) . In the first paper, 66 records of dogs with presumptive diagnosis of epilepsy were selected. 66.7% of them, were epilepsy idiopatic, 21.2% symptomatic and 12.1% probably symptomatic. The mongrel dogs were the most affected and age-group prevailed was one to 5-year-old. The tonic-clonic seizure was the most observed, the main pre-ictal symptom was to try to catch owner´s attention and compulsive walking in the post-ictal period. In the second paper, 21 dogs with idiopatic epilepsy were included; the median age at onset of seizures was 3.4 years, the median number of seizure before the start of treatment was 25.7 and duration of seizure before treatment was 71 days. The phenobarbital was used as monotherapy with dose from 1.4 to 12 mg kg-1 and the median of serum concentration was 26.41 μg kg-1. There was significant reduction in the frequency of the seizure after start the treatment. 19% of dogs were in remission of seizure. In blood analysis, there was increased serum activities of AP (23,81%) and ALT (14,20%), decreased total protein (42,29%), hypoalbuminemia (9,5%) and it was not increased AST activities. The main secondary lesions were liver disease and hypothyroidism. In the third paper, New Zealand rabbits were randomly distributed into two groups, G1: measuring the ICP with ventriculostomy catheter (n=6) and G2: measuring the ICP with urethral catheter (n=6). Two craniotomy were performed in the right and left parietal region for the implantation of the ventriculostomy catheter and/or flexible urethral catheter and epidural 4F Fogarty arterial embolectomy catheter, respectively. MAP, CPP, HR, RF and RT values were measured before and after craniotomy. The ICP value was mensured after craniotomy, ever five minutes during 40 minutes after the balloon was inflated with 0.3 ml of NaCl 0.9% and more 40 minutes after the balloon was inflated with 0.6 ml. The ICP value increased in both groups, however, the ICP values were lower in the rabbits measured with flexible urethral catheter. The flexible urethral catheter can be used as alternative method to measure ICP values im rabbits with head injury. / Os objetivos deste estudo foram: realizar um estudo retrospectivo sobre epilepsia em cães e outro com epilepsia idiopática atendidos no Serviço de Neurologia Veterinária, do Hospital Veterinário Universitário (HVU) da Universidade Federal de Santa Maria e utilizar a sonda uretral flexível como método alternativo para aferição da pressão intracraniana em coelhos com trauma cranioencefálico induzido pelo cateter de Fogarty 4 Fr (balão epidural) e comparar os dados obtidos com o método convencional de cateter de ventriculostomia. No primeiro artigo, foram selecionados os registros de 66 cães com diagnóstico presuntivo de epilepsia, sendo que 66,7% apresentaram epilepsia primária, 21,2% com sinais clínicos e em 12,1% com prováveis sinais clínicos. Os cães sem raça definida foram os mais acometidos e a faixa etária predominou entre um e cinco anos de idade. A crise epiléptica generalizada tônico-clônica foi a mais observada, a ocorrência maior das crises foram durante a noite; os sinais mais observados foram: a procura pelo tutor no período pré-ictal e o andar compulsivo no período pós-ictal. No segundo artigo, foram incluídos 21 cães com epilepsia idiopática, com média de idade para o início das crises epilépticas de 3,4 anos, apresentando em média 25,7 crises epilépticas antes do início do tratamento e o diagnóstico presuntivo foi determinado em média 71 dias após a primeira crise. Foi utilizada a monoterapia com fenobarbital na maioria dos cães e dose variou entre 1,4 a 12 mg kg-1 e a concentração sérica teve média de 26,41 μg ml-1. Após o início do tratamento houve uma redução significativa das crises epilépticas. 19% dos cães apresentaram remissão das crises epilépticas. Nos exames hematológicos, foi observado aumento da FA em 23,81% e da ALT em 14,29%, diminuição da proteína total em 42,86%, hipoalbuminemia em 9,5% dos cães e não foi observado aumento nos níveis da AST. As principais lesões secundárias observadas foram lesão hepática e hipotireiodismo. No terceiro estudo, coelhos da raça Nova Zelândia foram distribuídos aleatoriamente em dois grupos, denominados G1: mensuração da PIC com cateter de ventriculostomia (n=6) e G2: mensuração com sonda uretral (n=6). Foram realizadas duas craniotomias nas regiões parietal direita e esquerda para a implantação do cateter de ventriculostomia ou da sonda uretral flexível e o balão epidural, respectivamente. Foram mensuradas a PAM, PPC, FC, FR e a TR antes e após a craniotomia. A PIC foi avaliada após a craniotomia e a cada cinco minutos depois do preenchimento do balonete com 0,3 ml de NaCl 0,9% permanecendo por 40 minutos e, com 0,6 ml pelo mesmo período de tempo. A PIC aumentou em ambos os grupos, sendo menores os valores registrados com a sonda uretral flexível. Embora haja a necessidade de outros estudos, a sonda uretral flexível demonstrou ser um método alternativo de mensuração da PIC em coelhos com trauma cranioencefálico.

Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal. / Parmi la multitude de fonctions que le système visuel effectue, la perception du mouvement est l'une des plus importantes. Il a été clairement démontré qu'il existe des sites cérébraux spécifiques pour la détection, l'analyse et l'intégration du mouvement. De façon classique, les mécanismes neurophysiologiques qui sous-tendent ces processus sont attribués aux aires corticales. Le thalamus quant à lui, est généralement considéré comme un « relais passif », c'est à dire qui transmet l'information sensorielle vers le cortex sans modifier le signal entrant. Le but de ce projet sera de préciser les mécanismes nerveux impliqués dans la perception et l'intégration du mouvement et plus précisément, la contribution des régions cérébrales sous-corticales et corticales intimement liés par des connexions réciproques. Ces régions sont: le complexe LP-pulvinar, situé dans le thalamus, l'aire extra-striée postero-médiane suprasylvienne (PMLS) et le cortex ectosylvien visuel antérieur (AEV); deux régions corticales ayant un rôle spécialisé dans l'analyse du mouvement. Les expériences ont été réalisées sur des chats adultes normaux anesthésiés. Une microélectrode d'enregistrement a été descendue dans ces trois sites afin d'enregistrer l'activité des neurones. Les réponses neuronales à des réseaux sinusoïdaux, des patrons texturés (« bruit visuel ») et des « plaids » ont été caractérisé pour étudier les mécanismes qui sous-tendent l'intégration du mouvement au niveau cellulaire. Afin de caractériser d'avantage ce lien, l'influence des aires corticales sur les propriétés thalamiques a été déterminée par inactivation locale réversible (i.e. micro-injection de l'acide y-aminobutyrique; GABA) ou par inactivation permanente plus vaste (i.e. ablation chirurgicale). Les résultats de cette étude se résument comme suit : 1) les propriétés des réponses neuronales du PMLS au bruit visuel sont similaires à celles du LP-pulvinar. Ce résultat suggère que les processus d'analyse impliquant une boucle cortico-thalamique PMLS-LP sont comparables au niveau cortical et sous-cortical. 2) les neurones du PMLS et du LP peuvent coder le mouvement relatif entre un objet et son arrièreplan. De plus, l'inactivation réversible du LP perturbe ces réponses au niveau du PMLS. Ces résultats sont essentiels dans l'établissement d'un lien fonctionnel entre ces deux régions quant à l'analyse de certains aspects du mouvement. 3) certains neurones du complexe LP-pulvinar sont capables d'intégrer l'information directionnelle telle que définie par des « plaids ». Ceci constitue la première démonstration de propriétés de haut-niveau en dehors du cortex. De plus, cette découverte suggère que le LP-pulvinar participe de façon parallèle et en coopération avec le cortex dans l'analyse de scènes visuelles complexes via l'exploitation des boucles cortico-thalamiques. Les résultats de cette étude sont importants non seulement pour appuyer des notions théoriques novatrices sur le rôle du thalamus, mais aussi dans le but de réévaluer et de préciser les mécanismes nerveux qui sous-tendent la perception du mouvement et l'intégration sensorielle en général. / Among the multitude of functions the visual system carries out, the perception of motion is one of the most important. It has been clearly demonstrated that the visual system contains numerous specialised areas implicated in the detection, analysis, and integration of motion. Classically, the neurophysiological mechanisms underlying these processes have been uniquely attributed to regions of the cerebral cortex. The thalamus for its part, has generally been regarded as a passive relay transferring information to the cortex without any modification of the sensory signal. The purpose of this study is to investigate the neurophysiological mechanisms implicated in the perception and integration of motion and more specifically, delineate the contribution of cortical and subcortical structures that are intimately related via reciprocal connections. These areas are: the LP-pulvinar complex; located in the thalamus, and the extrastriate posteromedial lateral suprasylvian (PMLS) and anterior ectosylvian visual (AEV) cortical areas; two regions whose role in motion analysis are well established. Experiments were carried out on normal adult anaesthetised cats. A recording microelectrode was descended in one of the aforementioned areas to record neuronal activity. Neuronal responses to drifting sine-wave gratings, moving texture patterns ("visual noise"), and "plaid patterns" were recorded in order to investigate the mechanisms underlying the integration of motion information at the neuronal level. As a continuation of the study, the influence of cortical motion areas on recorded thalannic responses will be determined by local reversible deactivation (i.e. microinjection of y-aminobutyric acid; GABA) or by irreversible deactivation (i.e. surgical ablation). The results of the study are as follows: 1) Response properties of PMLS neurons to moving texture patterns are similar to those found in the LP-pulvinar connplex. These results suggest that motion processing along both components of the PMLS-LP cortico-thalamic loop is carried out within a similar envelope of analysis. 2) Neurons in both PMLS and LP are able to code the relative motion of an object with respect to its background. Furthermore, reversible deactivation of LP disrupts these responses in PMLS. These results are important in establishing that both these areas are functionally linked in the analysis of specific aspects of motion. 3) The fact that pattern-selective responses to moving plaids can be found in the LP-pulvinar complex suggests that this area is capable of carrying out higher-order motion computations. The importance of this later results is two-fold. First, these findings represent the first demonstration that higher-order properties exists outside extrastriate cortical areas. Second, they further suggest that certain thalamic nuclei, via the establishment of cortico-thalamic loops, participate in parallel and in co-operation with the cortex in the analysis of complex visual scenes. The results of this study are important not only to reinforce current and novel theoretical notions regarding the role of the thalamus, but also in the re-evaluation of the neurophysiological mechanisms involved in motion perception and sensory integration as a whole.