Glial Plasticity.

Abstract

Over the last few decades, our understanding of the roles of glial cells in the central nervous system has been transformed. There is now a clear consensus that all classes of glia (astrocytes, oligodendrocytes, microglia, and various other progenitors and specialized cells) can detect and respond to a wide range of neurotransmitters, hormones, cytokines, and trophic factors and thereby play an active, signaling role in neurophysiology. To date, much of the focus of glial signaling has been on how glia can influence the function of the neuronal network with the associated impact on information processing and, ultimately, behavior. In particular, the contribution of bidirectional communication between neurons and glia to the regulation of synaptic plasticity has been extensively studied. The papers collected in this special issue focus on a related, but distinct, question: can glia themselves exhibit activity-dependent plasticity? The reviews and experimental papers present the evidence that glia do indeed have the capacity to respond dynamically to a wide range of stimuli with persistent changes in signal transduction, morphology, and homeostasis. In " Plasticity of Neuron-Glial Transmission: Equipping Glia for Long-Term Integration of Network Activity, " W. Croft et al. review the current evidence for plasticity in neuron-glial communication and speculate on the implication of differences in induction paradigms from synaptic plasticity for the computational properties of glial signaling. In " Glutamatergic Transmission: A Matter of Three, " Z. Martínez-Lozada and A. Ortega focus on the consequences of glutamate receptor activation for astroglial physiology. By identifying the downstream targets engaged by gluta-matergic signalling, the authors show how neurons can shape transcriptional and translational regulation in glia to tailor transmitter clearance and recycling to meet synaptic demands. Remaining with regulation of intracellular signaling in astrocytes, N. Komin et al. present an analysis of the impact of variation in uptake of calcium into endoplasmic reticulum stores on cytoplasmic calcium oscillations in " Multiscale Modeling Indicates That Temperature Dependent [Ca 2+ ] i Spiking in Astrocytes Is Quantitatively Consistent with Modulated SERCA Activity. " The results of the modelling study illustrate the striking sensitivity of intracellular calcium dynamics to changes in SERCA activity with implications both for interpretation of experimental results at nonphys-iological temperatures and for prediction of calcium signal kinetics in vivo. In " Fractalkine Signaling and Microglia Functions in the Developing Brain, " I. Arnoux and E. Audinat review the effects of fractalkine receptor activation on microglial function. The review …