Neuronal coupling and uncoupling in the developing nervous system.

Sensitive new tracers and imaging techniques have revealed that gap junction coupling during brain development is much more pronounced than previously believed. Recent results demonstrate that cell coupling can produce functional neuron assemblies characterized by synchronized fluctuations in the cytosolic Ca2+ concentration. Coupling is especially pronounced before and during the period of synapse formation and initial establishment of neuronal circuits. Thus, communication via gap junctions may generate coordinated electrical or biochemical activity before the onset of synaptic transmission, and thereby provide the outlines of functional architecture in the developing brain.