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quinta-feira, junho 11, 2009

Células dendríticas


O PLoS Computational Biology nos deu um desconto. De U$ 2200 baixaram para U$ 1500. Acho que perceberam o malabarismo que os autores estavam tentando fazer para conseguir a grana. O artigo deve sair logo, imagino.

Durante minha apresentação no Encontro Nacional de Física de Materia Condensada, eu perguntei à platéia se conheciam alguma célula não-neuronal com árvore dendrítica. Ninguém sabia. Hoje localizei algo parecido, as células dendríticas do sistema imunológico. Será que alguém sabe os dendritos dessas células são excitáveis?


Active dendrites enhance neuronal dynamic range
Leonardo L. Gollo,Osame Kinouchi, Mauro Copelli


Most neurons present cellular tree-like extensions known as dendrites, which receive input signals from synapses with other cells. Some neurons have indeed very large and impressive dendritic arbors. What is the function of such elaborate and costly structures? The functional role of dendrites is not obvious because it is known that, if dendrites were an electrical passive medium, then signals from their periphery could not influence the neuron output activity. Dendrites, however, are not passive, but rather active media that amplify and support pulses (dendritic spikes). These voltage pulses do not simply add but can also annihilate each other when they collide. To try to understand the net effect of the complex interactions among dendritic spikes under massive synaptic input, here we examine a computational model of excitable dendritic trees. We show that, in contrast to passive trees, they have a very large dynamic range, which is a quantity that accounts for the capacity of the neuron to distinguish among the widely different intensities of input which it receives. Moreover, we show that the response of the neuron becomes more robust to strong inputs: owing to active dendrites, it is almost independent of the size of the dendritic arbor.

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