Intracellular labeling of single cortical astrocytes in vivo.

Glial cells have traditionally been considered to play supportive roles in the central nervous system. As recent experimental evidence suggests glial cells' participation in neural information processing, there has been a need to monitor the physiology of glial cells in vivo in the matured brain. Concurrently, identification and classification of the recorded glial cells is essential as there are at least several different kinds of glial cells. Past studies have achieved in vivo intracellular electrophysiological recording of glial cells using sharp glass microelectrodes, however, morphological recovery and identification of the recorded cells have hardly been done, due to technical difficulties. We demonstrate that use of large fragment biotinylated dextran amine (BDA) is an effective way to label a single glial cell recorded with a sharp microelectrode in vivo. Furthermore, the tracer signal amplification was achieved by a combination of avidin biotinylated horseradish peroxidase macromolecular complex (ABC) and tyramide-based methods, making multiple immunohistochemistry feasible. Using the method described in this study, we have successfully recorded and labeled cortical glial cells including astrocytes, oligodendrocytes, and microglia.