JournalNeural Excitability, Synapses, and Glia

Spatial organization of astrocytes in ferret visual cortex

Spatial distribution of astrocyte somata. A: High‐magnification example of double staining for NeuN (left) and S100 (right). B: Example of mosaic images for NeuN and S100 through all cortical layers. C: Example of the cell body locations obtained from the same z‐stack as images in B. The automatically defined layer boundaries (L1–L6) are overlaid on each plot. D: Plot of cell density as a function of cortical depth computed from the data in C. Scale bar = 20 μm in A; 200 μm in B.

Astrocytes form an intricate partnership with neural circuits to influence numerous cellular and synaptic processes. One prominent organizational feature of astrocytes is the “tiling” of the brain with non‐overlapping territories. There are some documented species and brain region–specific astrocyte specializations, but the extent of astrocyte diversity and circuit specificity are still unknown. We quantitatively defined the rules that govern the spatial arrangement of astrocyte somata and territory overlap in ferret visual cortex using a combination of in vivo two‐photon imaging, morphological reconstruction, immunostaining, and model simulations. We found that ferret astrocytes share, on average, half of their territory with other astrocytes. However, a specific class of astrocytes, abundant in thalamo‐recipient cortical layers (“kissing” astrocytes), overlap markedly less. Together, these results demonstrate novel features of astrocyte organization indicating that different classes of astrocytes are arranged in a circuit‐specific manner and that tiling does not apply universally across brain regions and species.

López-Hidalgo, M., Hoover, W.B., and Schummers, J. (2016). Spatial organization of astrocytes in ferret visual cortex. J. Comp. Neurol. 524, 3561–3576.