Imaging microglia in brain slices and slice cultures.

Here we describe a method for imaging fluorescently labeled parenchymal microglia (MG) in excised neonatal or adult rodent brain tissue slices. Using multichannel confocal or two-photon time-lapse imaging, the approach affords real-time analyses of MG behaviors, including motility, migration, chemotaxis, proliferation, and phagocytosis in live brain tissues. The method is applicable to acutely prepared tissue slices from developing and adult rodents and to slice cultures derived from neonatal rodents, including transgenic and green fluorescent protein reporter mice. A variety of fluorescent tags can be used to study the structure and physiology of MG in these preparations. Moreover, bath application of reagents (such as ATP) can establish spatial and temporal gradients that induce chemokinesis- and chemotaxis-like MG migration in tissue slices. Thus, the approach is useful for dissecting the molecular basis of MG behaviors and testing whether candidate reagents alter MG behavior and function in semi-intact central nervous system tissue preparations.