Narrator: This is Science Today. Over half a million Americans will have a stroke this year -- blockage of blood flow to the brain. Those who don't die risk being permanently disabled. But new drugs are being tested that may prevent brain damage if they're administered in time, by breaking up the blood clot in the brain. Dr. Wade Smith of the University of California, San Francisco says that besides clot-breakers, there's a whole new class of drugs on the way called neuroprotectors.

Smith: Many of them, we know, of the neuroprotective agents directly protect both the neurons of the brain -- the cells responsible for signalling one another -- but also the structural cells around them, the cells called glial cells.

Narrator: Which is essential for preserving the structure of the brain when the blood supply is cut off.

Smith: The beauty of giving drugs like that is that we may be able to give those to patients as soon as they start having symptoms, for example by paramedics in the home.

Narrator: Then clot-breaking drugs can be given in the hospital, preventing major damage from the stroke. For Science Today, I'm Steve Tokar.