Astrocytes, which constitute the most abundant cell type in mammalian brain, are extensively coupled to one another through gap junctions composed mainly of connexin43. In regions exhibiting high levels of connexin43 expression, tens of astrocytes are labeled following single-cell intracellular injection. Importantly, both the expression and the permeability of gap junctions are tightly regulated. Such long- and short-term regulations indicate that astrocytic networks might be subject to remodeling and to some plasticity. Since evidence for neuro-glial interaction exists, the degree of coupling between astrocytes could participate to set the tone of neuronal activity and to determine the sphere of influenced neurons. Research in this area is still at its early stages and significant progress requires a transition from the understanding of basic properties to the study of function.