Stroke is the third leading cause of death and major cause of long-term disabilities. To date, tissue plasminogen activator (tPA) is the only approved treatment for ischemic stroke for which few patients are eligible. Our laboratory previously established that systemic administration of insulin-like growth factor IGF-I shortly following stroke is neuroprotective in a rat model. The purpose of this project is to study the role of microglia in neuroprotection by IGF-1 in endothelin-induced stroke rats. Furthermore, since ageing is one of the co-morbidity factors, we will investigate whether microglial changes due to ageing affect the efficacy of IGF-1 treatment following stroke.