Astrocytes can be defined as glia inhabiting the nervous system with the main function in the maintenance of nervous tissue homeostasis. Classified into several types according to their morphological appearance, many of astrocytes form a reticular structure known as astroglial syncytium, owing to their coupling via intercellular channels organized into gap junctions. Not only do astrocytes establish such homocellular contacts, but they also engage in intimate heterocellular interactions with neurons, most notably at synaptic sites. As synaptic structures house the very core of information transfer and processing in the nervous system, astroglial perisynaptic positioning assures that these glial cells can nourish neurons and establish bidirectional communication with them, functions outlined in the concepts of the astrocytic cradle and multi-partite synapse, respectively. Astrocytes possess a rich assortment of ligand receptors, ion and water channels, and ion and ligand transporters, which collectively contribute to astrocytic control of homeostasis and excitability. Astroglia control glutamate and adenosine homeostasis to exert modulatory actions affecting the real-time operation of synapses. Fluctuations of intracellular calcium can lead to the release of various chemical transmitters from astrocytes through a process termed gliotransmission. Sodium fluctuations are closely associated to those of calcium with both dynamic events interfacing signaling and metabolism. Astrocytes appear fully integrated into the brain cellular circuitry, being an indispensable part of neural networks.
Table of Contents
Astrocytes: General Perspective
Ion Distribution and Membrane Potential
Ionic Signaling in Astroglia
Gliotransmission: Astrocytes as Secretory Cells of the Nervous System
About the Author(s)Alexei Verkhratsky
, University of Manchester
Professor Alexei Verkhratsky, MD, PhD, D.Sc., Member of Academia Europaea, Member of the German National Academy of Sciences Leopoldina, and Member of Real Academia Nacional de Farmacia (Spain), was born in 1961 in Stanislaw, Galicia, Western Ukraine. He graduated from Kiev Medical Institute in 1983 and received his Ph.D. (1986) and D.Sc. (1993) in Physiology from Bogomoletz Institute of Physiology, Kiev, Ukraine. He joined the Division of Neuroscience, School of Biological Sciences in Manchester in September 1999, became a Professor of Neurophysiology in 2002, and served as Head of the Division from 2002 to 2004. From 2007 to 2010 he was appointed as visiting professor/Head of Department of Cellular and Molecular Neurophysiology at the Institute of Experimental Medicine, Academy of Sciences of Czech Republic. In 2010 Prof. Verkhratsky was appointed as a Research Professor of Ikerbasque (the Basque Research Council), in 2011 as an Honorary Visiting Professor at Kyushu University, Fukuoka, Japan, and since 2012 has acted as Adjunct Scientific Director of the Achucarro Basque Centre for Neuroscience (Bilbao, Spain); he is also professor consultant of the Nizni Novgorod University neuroscience Center. Prof. Verkhratsky is a co-editor-in-chief of Cell Calcium (2000), and Membrane Transport & Signaling - Wiley Interdisciplinary Reviews (2009), Receiving Editor of Cell Death & Disease (2009), and a member of editorial boards of numerous scientific journals. Prof. Alexei Verkhratsky is an internationally recognized scholar in the field of cellular neurophysiology. His research is concentrated on the mechanisms of inter- and intracellular signaling in the CNS, being especially focused on two main types of neural cells, neurons and neuroglia. He made important contributions to understanding the chemical and electrical transmission in reciprocal neuronal-glial communications and on the role of intracellular Ca2+ signals in the integrative processes in the nervous system. Many of Prof. Verkhratsky's studies are dedicated to investigations of cellular mechanisms of neurodegeneration. In recent years he studies the glial pathology in Alzheimer disease.Vladimir Parpura
, University of Alabama, Birmingham
Vladimir Parpura, M.D., Ph.D., holds both a medical degree, awarded from the University of Zagreb in Croatia in 1989, and a doctorate in Neuroscience and Zoology from Iowa State University in 1993. He held faculty appointments at the Department of Zoology and Genetics, Iowa State University, and the Department of Cell Biology and Neuroscience, University of California Riverside. He is presently a tenured Associate Professor in the Department of Neurobiology, University of Alabama at Birmingham, U.S.A., as well as a tenured Professor in the Department of Biotechnology, University of Rijeka, Croatia. He was elected as a Member of Academia Europaea (MAE) in 2012. His current research includes: i) studying the modulation of calcium-dependent glutamate release from astrocytes in health and disease; ii) assessing the role of enteric glia in gut functions; iii) visualization of vesicular/receptor trafficking; iv) examination of the nature and energetics of interactions between exocytotic proteins using single molecule detection approaches; v) development of scaffolds and dispersible materials, most notably modified carbon nanotubes, which can be used in repair after brain injury; vi) development of biosensors (e.g., botulinum toxin and nanofabricated carbon-based detectors), and viii) bio-mimetic micro-robotics. It should be noted that the work done in these categories is highly interrelated. He has been interfacing neuroscience with nanoscience/nanotechnology, synthetic biology, and biomedical engineering.