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).