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Astrocytes in the hippocampus

by Rachel E. Ventura

The cell body of an astrocyte spans 10-20 microns and its processes radiate out for another 20-30 microns, forming the stellate glial cell. The stellate shape of the astrocyte can be appreciated in this light microscopic image.

Astrocytes fill between 4 and 8% of the volume of stratum radiatum in area CA1 of the hippocampus, making them the most predominant glial subtype there. In addition to astrocytes, the hippocampus is home to other glia, including microglia and oligodendrocytes.

An astrocytic presence near synapses seems to be important for synaptic function (see below). In this electron micrograph from rat hippocampus, astrocytes (blue) can be seen closely intermingling with synaptic complexes (arrows). For more on the three-dimensional relationships of astrocytes and synapses in hippocampus click here.

Astrocytes can be identified at the ultrastructural level by a number of key structural features:

Astrocytes, like other glial subtypes, have been commonly thought of as mere support and maintenance cells for the real actors in brain functioning, the neurons. Over the past several years, however, research has indicated a much more central role for astrocytes in non-synaptic as well as synaptic communication.

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