Fig. 10.

Glial scarring surrounding chronically implanted electrodes. At the culmination of the longitudinal imaging protocol, mice were perfused and stained for neurons (NeuN, blue), astrocytes (GFAP, yellow), and microglia (Iba-1, red). Stained slices from electrode-implanted animals (a) show evidence of extensive glial scarring with increased reactivity of GFAP and Iba-1 in a compact layer around the electrode insertion site (white ovals, $\mathrm{G}8=586\mathrm{dpi}$ and $\mathrm{G}18=491\mathrm{dpi}$), whereas stained slices from window-only implanted animals (b) show normal (sparse) distribution of glial cells and neuronal cell bodies ($\mathrm{G}19=491\mathrm{dpi}$ and $\mathrm{G}23=428\mathrm{dpi}$). White arrows in magnified GFAP images in (a) indicate hypertrophic astrocytes, and blue arrows show intertwining cells. Transgenic YFP signal in window-only animals (green) shows dendrites of L5 cells radially projecting to the dorsal surface. In electrode-implanted animals, some dendrites appear to curve around the electrode insertion site, whereas others appear severed. (Scale bar for image with merged $\text{channels}=200\mu \mathrm{m}$, scale bar for individual $\text{channels}=100\mu \mathrm{m}$).