Microglia Detection by Enzymatic Histochemistry

Visualization of microglia by means of histochemistry has been for years a reliable method to demonstrate this population of cells in the central nervous system (CNS). Wide range of data on microglia has been published using lectin and enzymatic histochemistry. While at present, in most laboratories, the use of specific antibodies is the first choice, histochemical detection of microglia remains a powerful method as it has certain advantages upon immunohistochemical methods because it is faster, cheaper, and can be used in different species including human. In this chapter we want to present the detailed methodology for microglial staining using the histoenzymatic demonstration of the enzyme nucleoside-diphosphatase (NDPase), a phosphatase found in the plasma membrane of microglia that is absent in the plasma membrane of other glial cells and neurons. With this technique it is possible to visualize amoeboid microglia during development, ramified microglia in the adult brain, and also reactive microglia. As the technique also stains the blood vessels, it allows the analysis of the relationship between microglia and vasculature. This method can be performed in either histological sections or cell cultures for light microscopy analysis. Furthermore, we described how to combine this histochemical method with conventional immunohistochemistry for double labelling using other markers, and finally we give details to perform the procedure not only for optical microscopic studies but also for transmission electron microscopy (TEM).