Chapter 3 - Pathophysiology of Gap Junctions in the Brain

Abstract

Neurons communicate either through chemical synapses, where transmitters released from one neuron bind to the postsynaptic cell membrane, or through direct communication mediated by electrical synapses. Gap junctions, the most predominant type of electrical synapse, directly connect the cytoplasms of two adjacent neurons and allow for direct electrotonic and metabolic cell-to-cell communication. Gap junctions are ubiquitously expressed in the brain and play a pivotal function in brain development including cell differentiation, cell migration, tissue homeostasis and survival. The structural components of gap junction channels are connexin and pannexin proteins. Connexin gap junction channels enable the intercellular, bidirectional transport of ions, metabolites, second messengers and other molecules smaller than 1.5 kDa. More than 20 connexin genes have been found in the human genome. Pannexins, hemichannels and heterocellular communication will be briefly addressed, and the diverse expression and function of connexin gap junctions will be reviewed, with an emphasis on identifying their relevant roles in physiology and pathology in the brain.