Traditionally, synapses were thought to consist of just two elements, the presynaptic bouton and postsynaptic membrane. In the early 1990s, however, evidence began to emerge that they are in fact tripartite structures, and that glial cells called astrocytes regulate the chemical signals that are transmitted between neurons. Astrocytes are star-shaped cells that were initially thought to fill the extracellular spaces in brain tissue. But it is now clear that they not only respond to neuronal activity but can also produce their own electrical signals, and they synthesize and release a whole host
...more
