Special issue on neuron-glia interactions

What is the physiological importance of bidirectional neuron-glia dynamic signaling in the brain? The amazing architecture of the brain consists of hundreds of billions of neurons, as well as trillions of supporting cells called glia which comprise approximately half the volume of the adult mammalian brain. Glial cells, divided into oligodendrocytes, microglia, and astrocytes, are organized into distinct non-overlapping domains whose boundaries are intimately in contact with synapses and cerebrovascular pathways. Since the first systematic studies of the central nervous system, the information communication and processing roles of neurons were clearly recognized, while the electrically non-excitable glial cells were investigated for their contribution to different physiological processes, such as differentiation, proliferation, and neurotrophic support. Astrocytes are now thought to go beyond these contributions, being involved in almost all aspects of the brain function. There is growing evidence that astrocytes are able to partition the extracellular space, altering and influencing the synaptic microenvironment, as well as neurons' growth. Astrocytes can alter the positioning and the diffusion of neuroactive substances, attracting cells able to repair neurons. Moreover, astrocytes synergistically regulate neuronal activities and blood circulation, thus influencing the neuronal metabolism. It is worth mentioning the relationship between astrocytes and several neurological disorders, i.e., epilepsy, stroke, Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis.