The current treatment to reduce stroke induced brain tissue injury is limited to thrombolytics (clot busters), a therapy useful only if given in the first hours following stroke. One major new approach aims to reduce cell death after stroke by targeting the ongoing tissue loss initiated by the stroke. The tissue can be maintained by interfering with later neurochemical processes that are activated by stroke, potentially through activating natural substances in the brain that help survival and growth of nerve cells ("neurotrophic" factors).