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Previous issue date: 2014-10-15 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior - CAPES / O ritmo teta consiste em uma oscila??o eletrofisiol?gica hipocampal presente em v?rias esp?cies de mam?feros (4-12 Hz, com varia??es entre esp?cies). Essa oscila??o est? presente durante a vig?lia ativa de ratos e tamb?m ? predominante no PCL desta esp?cie durante o sono de movimento r?pido dos olhos (sono REM). V?rios trabalhos demonstraram que o ritmo teta ? importante em tarefas cognitivas. O septo medial ? uma regi?o importante na gera??o do ritmo teta hipocampal. Possui proje??es colin?rgicas, GABA?rgicas e glutamat?rgicas para o hipocampo, que por sua vez, possui proje??es de feedback para o septo. Al?m do septo, outras regi?es est?o envolvidas na regula??o do teta, formando uma rede complexa de intera??o e coordena??o entre ?reas que resultam no ritmo. A optogen?tica ? uma ferramenta desenvolvida recentemente que tem sido amplamente utilizada em pesquisas de diversas ?reas. Ela nos permite manipular a atividade el?trica de neur?nios atrav?s de estimula??o luminosa. A t?cnica consiste em, atrav?s de um vetor viral, induzir a express?o neuronal de canais i?nicos associados a opsinas (ex.: ChR2), que uma vez infectados passam a ser sens?veis a luz de determinado comprimento de onda. O presente trabalho de pesquisa de mestrado teve como objetivo implantar a optogen?tica em animais em livre comportamento pioneiramente no Brasil, atrav?s de experimentos com implantes cr?nicos de eletrodos e fibras ?ptica em animais infectados com vetor viral para express?o de ChR2. Foram realizadas cirurgias de inje??es de v?rus no septo medial; resultados histol?gicos confirmaram a express?o de ChR2 atrav?s da marca??o da prote?na rep?rter eYFP no septo e tamb?m em processos hipocampais. Al?m disso, foram realizados experimentos agudos com estimula??o luminosa do septo medial e registro de potenciais de campo local (PCL) no pr?prio septo e hipocampo em animais anestesiados. Ainda nesses experimentos foi poss?vel registrar potenciais de a??o no septo. Nesses experimentos observamos aumento da taxa de disparo dos neur?nios septais durante estimula??o luminosa (n=300 est?mulos). Al?m disso, encontramos uma resposta evocada no PCL do hipocampo no in?cio do pulso luminoso. Tamb?m foram realizados experimentos cr?nicos com estimula??o luminosa do septo medial e registro de PCL do hipocampo em animais em livre comportamento. Atrav?s de an?lise do PCL, verificamos se a estimula??o luminosa do septo ? capaz de induzir ritmo teta no hipocampo. / Theta rhythm consists of an electrophysiological hippocampal oscillation present in mammalian species (4-12 Hz with variations across species). This oscillation is present during active waking and is also prevalent in local field potentials (LFP) during rapid eye movement sleep (REM sleep). Several studies have shown that theta rhythm is important in cognitive tasks and that the medial septum is a key region for its occurrence. The septum sends cholinergic, GABAergic and glutamatergic projections to the hippocampus, which in turn projects axons to the septum. Besides the septum, other regions are involved in regulating theta rhythm, forming a complex network of interactions among brain areas that result in theta rhythm. Optogenetics is a recently developed method that has been widely used in various research areas. It allows us to manipulate the electrical activity of neurons through light stimulation. One of the existing techniques consists in using a viral vector to induce the neuronal expression of ion channels associated with the light-sensitive molecule rhodopsin (e.g. ChR2). Once infected, the neurons become sensitive to light of a particular wavelength. The present M. Sc. research aimed to perform luminous stimulation of the brain in anesthetized and freely behaving animals using chronically implanted electrodes and optical fibers in animals infected with a viral vector for ChR2 expression. Surgical viral injections were performed in the medial septum; histological results confirmed the expression of ChR2 by way of the presence of the eYFP reporter protein in the septum and also in hippocampal processes. Moreover, we performed acute experiments with luminous stimulation of the medial septum and LFP recordings of the septum and hippocampus of anesthetized animals. Action potentials were recorded in the septum. In these experiments we observed a significant increase in the firing rates of septal neurons during luminous stimulation (n = 300 trials). Furthermore, we found an early light-evoked response in the hippocampal LFP. Chronic experiments with luminous stimulation of the medial septum and hippocampus in freely behaving animals were also performed in combination with LFP recordings. We found that the luminous stimulation of the septum is able to induce theta rhythm in the hippocampus. Together, the results demonstrate that the luminous stimulation of the medial septum in optogenetically-modified animals causes relevant electrophysiological changes in the septum and the hippocampus.
| Identifer | oai:union.ndltd.org:IBICT/oai:repositorio.ufrn.br:123456789/19333 |
| Date | 15 October 2014 |
| Creators | Souza, Annie da Costa |
| Contributors | 50591797100, http://lattes.cnpq.br/0649912135067700, Queiroz, Cl?udio Marcos Teixeira de, 16256304845, http://lattes.cnpq.br/3384801391828521, Le?o, Emelie Katarina Svahn, 01771638605, http://lattes.cnpq.br/1279823352935722, Cota, Vin?cius Rosa, 03151319696, http://lattes.cnpq.br/6882402886706744, Le?o, Richardson Naves, Ribeiro, Sidarta Tollendal Gomes |
| Publisher | Universidade Federal do Rio Grande do Norte, PROGRAMA DE P?S-GRADUA??O EM NEUROCI?NCIAS, UFRN, Brasil |
| Source Sets | IBICT Brazilian ETDs |
| Language | Portuguese |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, info:eu-repo/semantics/masterThesis |
| Source | reponame:Repositório Institucional da UFRN, instname:Universidade Federal do Rio Grande do Norte, instacron:UFRN |
| Rights | info:eu-repo/semantics/openAccess |
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