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This new book extensively explores a range of topics related to astrocyte-neuron interactions under multiple conditions, in both health and disease. These include the types of interactions that occur during development and the establishment of neuronal circuits that underlie learning and memory formation in various animal models as well as humans. Furthermore, the book addresses topics on how these interactions go awry in disease and injury. In addition, the authors propose inspiring new avenues to explore therapeutic approaches using astrocytes as targets. A cadre of international experts presents a broad range of views on the state-of-the-art of astrocyte-neuron interactions.

The present outline of astrocytic metabolic pathways involved in glucose and amino acid metabolism provides detailed information about the enzymatic pathways involved, as well as a description of the basic properties of the enzymes including regulatory mechanisms. Hence, the glycolytic pathway and glycogen metabolism are outlined, followed by a detailed account of pyruvate oxidation and its role as a substrate for the tricarboxylic acid (TCA) cycle. Moreover, a detailed description of the main enzymes involved in glutamate metabolism is provided and the role of the glutamate-glutamine cycle is explained. Since this text is primarily covering astrocytic metabolism, an emphasis has been placed on a discussion of the significance of the astrocyte specific enzymes pyruvate carboxylase and glutamine synthetase, which enable these cells to perform a net synthesis of glutamine, the precursor for synthesis of glutamate and γ-aminobutyrate (GABA), the main neurotransmitters of the brain. With this, we have underlined the fundamental importance of astrocytic metabolism for neuronal function with a particular emphasis on the fact that, without continuous support from the astrocytic partners in synaptic function, glutamatergic and GABAergic neurotransmission would not be possible. It is thought provoking that these neurotransmission processes, which account for the vast majority of synaptic activity in the brain, have been made totally dependent on astrocytic metabolic support, particularly with regard to replenishment of the respective neurotransmitters.

In 1851, Heinrich Müller discovered what he called “radial fibers” and what we now call Müller cells, as the principal glial cells of the vertebrate retina. Later on, other glial cell types were found in the retina, including astrocytes, microglia, and even oligodendrocytes. It turned out that retinal glial cells are essential constituents of the tissue. For instance, Müller cells appear to constitute the “core” of columnar units of clonally and functionally related groups of neurons. Their primary function is to support neuronal functioning by guiding the light towards the photoreceptor cells, removing excess neurotransmitter molecules from extracellular space, and performing efficient clearance of excess extracellular potassium ions. The latter two functions are also crucial for neuronal survival and are coupled to water clearance which is also essential. Müller cells are capable of “sensing” neuronal activity and modifying it by the release of signal substances (gliotransmitters). In cases of retinal injuries the Müller cells become reactive, and all above-mentioned functions are impaired. However, such de-differentiated Müller cells may proliferate, and may even serve as stem cells for the regeneration of a damaged retina. As well as the Müller cells, retinal astrocytes and microglial cells are important players in retinal development and function. This book gives a comprehensive survey of the present knowledge on retinal glia.

Astrocytes can be defined as the 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.