Amplificação sináptica e interações não lineares na arborização dendrítica de modelos de motoneurônios

• Autor(a) principal: RODRIGUES, Fábio Barbosa
• Data de Publicação: 2010
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Repositório Institucional da UFG
• Texto Completo: http://repositorio.bc.ufg.br/tede/handle/tde/998
• topic: modelo de motoneurônio; ativação sináptica; não linearidade sináptica; motoneuron model; synaptic activation; synaptic nonlinearity; CNPQ::CIENCIAS EXATAS E DA TERRA::CIENCIA DA COMPUTACAO::SISTEMAS DE COMPUTACAO

From motoneurons models (MN) of complex geometry and structure, able to reproduce the characteristics of a real motoneuron, the aim of this work is to verify the functional differences between proximal and distal synapses, investigating the nonlinearities in passive equivalent dendrites of motoneuron models and to study the influence of persistent calcium channels type L (Cav1.3), present in the dendrites, in the synaptic amplification. The original models developed by Vieira and Kohn (2007), implemented in C++, were expanded. This allowed to accomplish tests in order to verify the functional differences of synapses that occur near the soma and along of the dendrites. Persistent channels of calcium (CaV1.3) were modeled in dendrites and the influence of these channels in the amplification of the synaptic currents along the dendrites was verified. Finally, the nonlinearities of responses degree in the dendritic tree for different synaptic activation was evaluated. In order to verify the functional differences between proximal and distal synapses pure sinusoids were injected in different dendritic compartments of the models. The results showed attenuation at higher frequencies and the cutoff frequency is smaller as we move along the dendrites far from the soma. The influence of persistent calcium channels was verified comparing the functional differences between proximal and distal synapses along of the soma, with and without them. The initial results showed a notable amplification of synaptic activation. Nonlinear interactions were evaluated using sinusoids synaptic inputs with different frequencies in two or more equivalent dendrites in different compartments. The frequency spectrum of the current between the initial segment and the soma was analyzed by comparing the peak amplitude of harmonics and spurious bands with the peak amplitude of the fundamental frequency of smaller amplitude: the smaller these differences were, greater was degree of nonlinearity between synaptic activation in different dendritic segments. The results showed a high degree of nonlinearity between the dendrites. The cases where the synaptic conductance was varied showed greater degree of nonlinearity in relation to the cases in which the synaptic current was varied.