DOES ASTROCYTIC GLYCOGEN BENEFIT AXON FUNCTION AND SURVIVAL IN CNS WHITE-MATTER DURING GLUCOSE DEPRIVATION

Axons, the functional elements in CNS white matter, are frequently inj ured by ischemia, especially in the context of stroke. The pathophysio logy of axonal injury induced by energy deprivation has been analyzed in the rat optic nerve and involves excessive calcium influx by way of reverse Na+/Ca2+ exchange and Ca2+ channels. Evidence is presented th at CNS axonal function can be supported in the absence of glucose by i ntrinsic energy reserves provided through the breakdown of astrocytic glycogen. It is argued that energy is transferred from astrocytes to a xons in the form of lactate, which is able to maintain axonal function when substituted for glucose. These observations complement the incre asingly convincing hypothesis that astrocytes and neurons interact met abolically, both in the course of normal activity and under pathologic al conditions such as ischemia. The emerging picture would be no surpr ise to Camillo Golgi, who predicted a close facsimile of this glial-ne uronal interaction more than a century ago. (C) 1997 Wiley-Liss, Inc.