The astrocytic syncytium

Publisher Summary This chapter summarizes the evidence that gap junctions between astrocytes provide a pathway for direct intercellular exchange of ions, nutrients, and signaling molecules. It discusses that this direct intercellular pathway may be a part of the machinery responsible for the delivery of nutrients to neurons, ridding the extracellular space of excess of K + and glutamate, spreading intercellular waves of Ca 2+ , and exchanging cell death signals. Although this intercellular network is not truly syncytial, as it consists entirely of discrete cellular elements, the interconnections extend cellular functions, such as enlarging the buffer volume for dilution of K + and toxins, as well as integrating the cells with different classes of nonjunctional proteins into functional units. The chapter also reviews that new study carefully defining the surfaces of the interactions between individual astrocytes indicates that each has its own private volume, where intercellular communication is limited to the outermost fringes surrounding the autocellular space. Within this space, hundreds of oligodendrocytes may intermingle with fine astrocyte processes and tens of thousands of synapses are surrounded by individual processes of a single astrocyte.