This work will investigate three aspects of the role that the immune cells of the brain (microglia) play in stroke — a disease affecting more than 50,000 Canadians every year. First, it will characterize the acute reaction of microglia to low oxygen levels. Second, it will analyze the molecular mechanism by which microglia extend filopodia, thin actin-rich protrusions essential for their role in sensing brain damage. Third, it will examine how microglia, unlike other types of brain cells, can retain their highly dynamic function for several hours in the complete absence of glucose, widely considered as essential for brain energy.