Resumo

DUQUE PARRA, JORGE E  e  TAMAYO ORREGO, LUKAS. GLIAL CELL ADAPTATION: AN EVOLUTIONARY PERSPECTIVE. rev.fac.med [online]. 2007, vol.15, n.1, pp.105-109. ISSN 0121-5256.

Glial evolution still remains unknown, although this process should had required adaptations to the internal medium of the nervous system and to functional needs in the neuroaxis of each species. The hypothesis of the functional and adaptive importance of glia, based on the astrocytary functional multiplicity is supported here as the main objective. The number of glial cells increases in parallel with the encephalic complexity due to a possible activation of new genes associated with the formation of different cellular types; the reason for this cellular growth could be, mainly, the expansion of the astrocytary population. A great functional and adaptive importance for glia is therefore inferred, assumption reinforced by the astrocytary functional complexity. The predominance of a neuroglial type depends on the encephalic morphological and physiological features; brains with thicker parenchyma have astrocytary predominance over ependimary glia. There is a direct correlation between the expansion of the neocortex and the number of astrocytes. The best explanation for this is that the high energetic cost of the neurons causes an increase in the astrocytary population; which constitutes an adaptive strategy of the nervous system for its metabolic support. In short, the phylogenic tendency towards the neuronal specialization should have depended on the emergence, growth and adaptation of the number of glial cells, it may possibly due to the inability of neurons to supply their energy needs by themselves. The initial functional divergence should had allowed the neurons to specialize more in the neurotransmission, while the astrocytes adapted to the metabolic demands of the new neuronal functions.

Palavras-chave : adaptation; glia; evolution; ontogeny; phylogeny.

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