Gap junction channels provide an intercellular pathway for direct cytoplasm-to-cytoplasm exchanges of ions and small molecules (<1.8 kDa). These channels are widely expressed in the central nervous system, especially in neurons (electrical synapses) and in glial cells (astrocytic networks). Connexins, their molecular constituents, belong to a multigenic family and at least eight of them have being detected in the brain. Their functional and molecular properties set the rules for an intercellular ‘language’ based on electrical and metabolic coupling. Several signaling molecules have been identified to cross these junctional channels and to contribute to important brain functions, such as information processing and ionic and metabolic homeostasis.