ABSTRACT
Despite the great advances in our knowledge about basic neuroscience, many neurological
diseases still remain refractory to existing treatments and as a consequence, functional
preservation and recovery after insults is unsatisfactory. Most research attempting to
develop an effective therapy has been focused on neurons and oligodendrocytes trying to
prevent their death and restore functions. On the other hand, astrocytes, the most abundant
cell type in the central nervous system (CNS), have been largely ignored. This is
presumably because astrocytes are widely believed to be more resistant to neurological
insults, and also because the roles of astrocytes have been considered less critical for brain
function compared to their more specialized partners. Nevertheless, progress in
understanding astrocyte biology, especially during the last decade, has revealed their
importance in both physiological and pathological states of brain function. The
development of glia is closely correlated with brain evolution. Only 10% of cells in the
fly nervous system are glia whereas glial cells vastly outnumber neurons in human brains
(1). Astrocytes are more expanded and differentiated as brain size gets bigger and neural
circuits become more complicated. From a phylogenic point of view, the primitive role of
glia in intervertebrates is likely to be the insulation of each neural circuit to prevent cross-
talk. But elaborate coordination and plasticity of neural circuits are required for complex
behavior of higher vertebrates and the development of astrocytes may be the result of
evolutionary pressure to establish these functions. Indeed recent findings have supported
this notion (2,3).
