Visualizing Astrocytes of the Optic Nerve.

Astrocytes make up approximately 30% of all the cells in the mammalian central nervous system. They are not passive, as once thought, but are integral to brain physiology and perform many functions that are important for normal neuronal development and metabolism, synapse formation, synaptic transmission, and in repair following injury/disease. Astrocytes also communicate with neurons, blood vessels, and other types of glial cells. Astrocytes within the optic nerve head region play a key role in glaucomatous axon degeneration. In this chapter, we describe ways in which astrocytes of the optic nerve head can be visualized, beginning with basic immunohistochemical staining methods, to single-cell dye injections and then to transgenic animals. We will also discuss the pros and cons of each method. Many of the methods were initially developed to visualize brain astrocytes; in some cases, the method has translated well to astrocytes of the optic nerve, and in others, it remains unclear.