Astrocyte calcium signaling: the third wave

Abstract

The discovery that transient elevations of calcium concentration occur in astrocytes, and release 'gliotransmitters' which act on neurons and vascular smooth muscle, led to the idea that astrocytes are powerful regulators of neuronal spiking, synaptic plasticity and brain blood flow. These findings were challenged by a second wave of reports that astrocyte calcium transients did not mediate functions attributed to gliotransmitters and were too slow to generate blood flow increases. Remarkably, the tide has now turned again: the most important calcium transients occur in fine astrocyte processes not resolved in earlier studies, and new mechanisms have been discovered by which astrocyte [Ca(2+)]i is raised and exerts its effects. Here we review how this third wave of discoveries has changed our understanding of astrocyte calcium signaling and its consequences for neuronal function.

An improved method for growing neurons: Comparison with standard protocols

“…Therefore, we assume that the uptake of the calcium sensitive dye from both neurons and astrocytes was similar in the three protocols, mainly dependent on the hydrophobicity of the AM -conjugated molecule 40 . However, further investigations are required to explain the role of astrocytes secreted factors in modulation of calcium-mediated neuronal processes 41 . The presence of the differentiating factor B27 leads to an overall increase of the network's electrical activity when compared to what happens in the serum -based medium.…”

Astrocytic glycogen metabolism in the healthy and diseased brain

“…Ca 2+ and cAMP signals -Astrocytic Ca 2+ signals has been researched intensively for the last few decades (49), whereas the other canonical second messenger, cAMP, has received less attention although protein biosensors for detecting cAMP have been available for about two decades (50). We know that both cAMP and Ca 2+ signals may be diffusing across the cytosol, or only be present in discrete micro (or rather, nano) domains within the cell (e.g., as reviewed in 51,52).…”

“…We know that both cAMP and Ca 2+ signals may be diffusing across the cytosol, or only be present in discrete micro (or rather, nano) domains within the cell (e.g., as reviewed in 51,52). Clearly, this spatial compartmentalization of signaling pathways must influence the functional outcomes, and has indeed been shown to do so in different preparations (51) (49,54). We induced storeoperated Ca 2+ entry (SOCE) in cultured astrocytes by depleting the intracellular stores through inhibition of the SERCA pumps in the absence of extracellular Ca 2+ , and then re-introduced extracellular Ca 2+ to provoke SOCE (53).…”

Astroglial calcium signalling in Alzheimer's disease

“…waves [29][30][31][32]. Astroglial calcium signals have been subsequently characterised in in vitro and in vivo settings (see [33][34][35] for details and critical discussion).…”