Figure 3.

Astrocyte tiling under physiological and pathological conditions. (A) Under physiological conditions, individual astrocytes overlap very minimally (purple), creating defined domains (dashed lines). In these spaces of overlap, astrocytes connect with one another via connexins 30 (Cx30) and 43 (Cx43), the latter of which is localized through HepaCAM (inset 1). Within their domains, astrocytes become highly branched and elaborate, sometimes forming connections with their own processes (inset 2). This extensive branching is represented by the lighter overlay around each astrocyte. Astrocytes regulate synapses by wrapping around them and insulating them, taking up excess neurotransmitters such as glutamate, and recycling them (inset 3). Each astrocyte is able to connect with thousands of synapses, a feature which has increased interest in astrocyte domains and networks. (B) After injury or insult, astrocytes can become reactive and undergo morphological changes including thicker processes but do not generally send processes outside of their domains. With nearby or severe insult, reactive astrocytes generate polarized astrocytes which can become palisading. These astrocytes may extend processes towards the injury which can protrude into the domains of neighboring astrocytes.