<p>In Japan, cerebrovascular disease is the third leading cause of death, and ischemic stroke accounts for more than half of all cerebrovascular disease deaths. In the chronic phase of ischemic stroke, treatment is limited to prevention of recurrence and reduction of complications and sequelae, therefore it is important to be able to provide appropriate treatment in the hyperacute and acute phases. The cells in the penumbra region, where blood flow is reduced, are damaged after the infarction but can be saved from cell death with appropriate treatment. The control of tissue inflammation is worth to improve pathological progression at the penumbra, and microglia and related other immune cells are major cellular targets for that purpose. Minocycline, a tetracycline antibiotics, is used in the treatment of infections caused by unconventional bacteria such as mycoplasma pneumonia and chlamydial infections. On the other hand, minocycline is known to inhibit the activation of microglia. In this study, we investigated the effect of minocycline on the pathological progression of ischemic stroke. We used a photothrombotic ischemic stroke model mouse and examined cellular dynamics of microglia and astrocytes. The results indicated that the astrocytes in the minocycline-administered brain have bigger cell body and thicker astrocytic processes, compared with those in the control saline-administered brain. This result indicates a functional relationship between microglia and astrocytes. I would like to discuss the effects and benefits/risks of minocycline on the pathological progression of ischemic stroke.</p>