Coordination of vertebrate cellular assemblies by gap junctions

Traditional views of the role of gap junctions in the vertebrate brain are based on synchronization of neuronal electrical activity through electrotonic coupling. It has become increasingly evident, however, that gap junctions may be more significant as pathways for intracellular second messengers than as passive electrical linkages. Calcium imaging experiments in many non-neuronal cells have demonstrated the presence of propagating, regenerative calcium waves, probably mediated by diffusion of inositol trisphosphate, that appear to play important roles in coordinating the behavior of groups of cells. Expriments in the developing brain indicate that similar mechanisms may be at work, perhaps helping to construct the complex functional assemblies seen in the adult brain.