METABOLIC TRAFFICKING THROUGH ASTROCYTIC GAP-JUNCTIONS

Astrocytes are interposed between the pericapillary space and neuronal membranes. Consequently, they may represent an important intermediary element between the source of energetic substrates and the main site of energy-consuming elements, respectively, the blood circulation and the neurons. A typical feature of astrocytes is the connections they e stablish between each other by specialized membrane structures, define d as gap junctions. These intercellular junctions allow direct cell-to -cell exchanges of ions and small molecules, including several compoun ds involved in major metabolic pathways occuring in astrocytes. The pe rmeability of astrocytes gap junction channels is controled by several endogeneous compounds released by astrocytes themselves or by other b rain cell types, including neurons and endothelial cells. In primary c ultures of astrocytes, the intercellular diffusion, the utilization an d the uptake of glucose and derivates are modified when gap junctional permeability is inhibited by uncoupling agents. Altogether these obse rvations indicate that intercellular pathways constituted by groups of coupled astrocytes could participate to the metabolism and the distri bution of energetic substrates throughout the brain. (C) 1997 Wiley-Li ss, Inc.