Many studies have shown that if the human body is stressed by a lack of blood flow for a short period of time, the body develops defenses to make the body more resistant to a future stress from lack of blood flow. This natural defense system is called preconditioning. Finding medications that have a preconditioning effect to protect against damage from loss of blood flow would be of great help in the treatment of diseases such as heart attacks and stroke that occur because of blockages of blood flow.