This is groundbreaking work. While the critical role of astrocytes in buffering glutamate extracellular levels in CNS is well known (reuptake), this studies goe

This is groundbreaking work. While the critical role of astrocytes in buffering glutamate extracellular levels in CNS is well known (reuptake), this studies goes much farther and reveals new cellular and functional complexities and mechanisms. First, there is evidence for approximately nine subclasses of astrocytes within hippocampus of mouse and human. Whether class membership is fixed or plastic is not yet known. Most readers may assume these types are fixed. Don’t. Second, several of these astrocytic types have the capacity to handle glutamate to a much greater degree than others. The type 7 astrocytes win the glutamate processing award. This heterogeneity result looks very solid to me. But again, astrocyte “type” may wander over time and stage. Third, the type 7 cells dynamically release glutamate via vesicular exocytosis and modulate neuronal and presumably also astrocytic function. The speed of exocytosis is not yet well defined but is is not unusually slow even by the standards if some types of neurons (modulators). This is the strongest novel claim of the study. I would love to see transmission electron microscopy of glutamatergic vesicles in these type 7 astrocytes. That would make me even mire comfortable with the claims of this paper. Note—The distinction between neurons and glial cells is a useful heuristic but the more you know about these cells, the blurrier the distinction becomes. Horizontal cells in retina also blur this boundary. Great work.