Glial Influences on Neuronal Signaling

Abstract

Since their discovery in the late nineteenth century, glial cells have taken a backstage role to neurons in our investigations of the nervous system. Yet, in the mammalian brain, glial cells outnumber neurons and comprise 50% of the brain volume. A number of proteins, including important synthetic enzymes, are located almost exclusively in glia, suggesting that glial cells may serve functions beyond providing structural support. Speculations of more active roles for glial cells in brain function began at the turn of the century, at which time it had been suggested that they serve nutritive functions (Golgi, 1885), insulate nerve fibers (Ramon y Cajal, 1909), phagocytose dying neurons (Marinesco, 1896), secrete fac tors (Achucarro, 1915), and remove neurotransmitters (the substances by which one nerve cell excites another) from the synaptic cleft (Lugaro, 1907). Many of these early hypotheses have subsequently gained experimental support; however, our understanding of glial roles in brain function is still limited. The Neuroscientist 1:123-126, 1995