Heterogeneity and function of hippocampal macroglia
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The contribution of glial cells to normal and impaired hippocampal function is increasingly being recognized, although important questions as to the mechanisms that these cells use for their crosstalk with neurons and capillaries are still unanswered or lead to controversy. Astrocytes in the hippocampus are morphologically variable and a single cell contacts with its processes more than 100,000 synapses. They predominantly express inward rectifier K+ channels and transporters serving homeostatic function but may also release gliotransmitters to modify neuronal signaling and brain circulation. Intracellular Ca2+ transients are key events in the interaction of astrocytes with neurons and the vasculature. Hippocampal NG2 glia represent a population of cells with proliferative capacity throughout adulthood. Intriguingly, they receive direct synaptic input from pyramidal neurons and interneurons and express a multitude of ion channels and receptors. Despite in-depth knowledge about the features of these transmembrane proteins, the physiological impact of NG2 glial cells and their synaptic input remain nebulous. Because of the low abundance of oligodendrocytes in the hippocampus, limited information is available about their specific properties. Given the multitude of signaling molecules expressed by the various types of hippocampal glial cells (and because of space constraints), we focus, in this review, on those properties that are considered key for the interaction of the respective cell type with its neighborhood.
KeywordsHippocampus Astrocyte NG2 glia Oligodendrocyte Neuron-glia interaction
The current work of the authors is supported by the European Commission (ERA-NET NEURON project BrIE; ITN project EU-GliaPhD to C.S.) and Deutsche Forschungsgemeinschaft (SPP 1757: SE 774/6 to G.S., STE 552/5 to C.S.). We apologize to all colleagues whose work we could not mention because of space constraints.
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Conflict of interest
The authors declare that they have no conflict of interest.
Research involving human participants and/or animals
This article does not contain any studies performed by any of the authors on human participants or animals.
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