Tom Carmichael on drug research to help with stroke recovery
Scientists have discovered a way that drugs could help people recover from strokes, according to a study published in the journal Nature in October 2010.
Tom Carmichael: A stroke is when there’s sudden loss of blood flow to part of the brain.
UCLA neurologist Tom Carmichael is an author of the study. Today, when a person suffers a stroke, it’s a long, hard process to rewire the brain with physical therapy so the person can begin to function more normally again. Carmichael’s research focused on how the brain tries to repair and reorganize itself – which happens naturally in the aftermath of stroke.
Tom Carmichael: We wanted to know what’s happening there. And we found that the threshold to send signals is much higher after stroke in that brain region. It doesn’t fire and send signals quite as easily.
Carmichael’s research team discovered that a stroke triggers a naturally-occurring molecule that blocks – or inhibits – brain signals from firing. It accumulates in areas where brain tissue is damaged. They recreated the effect in mice.
Tom Carmichael: We were then able to go and use specific drugs that block this inhibitory system, and improve the recovery in mice quite dramatically.
Carmichael said early recovery in mice improved by as much as 50 percent. He said these drugs have yet to tested in human clinical trials, but he hopes that patients may one day be able to take a drug to help recover use of language, or limbs affected by stroke. Carmichael summarized the main findings of his study.
Tom Carmichael: There are probably three things that come out of this. The biggest is that stroke puts the brain that recovers in a hypoexcitable state.
Carmichael explained that “hypoexcitable” means that the brain is less excitable. Excitability is what leads a cell to fire off a signal to communicate with the rest of the brain, he said.
Tom Carmichael: The second finding is that this is actually part of a spectrum of how the brain responds to stroke – and this hypoexcitability is initially protective, and then later deleterious to recovery.
He said that means that the molecule that inhibits, or blocks, the brain signals from firing actually limits the damage to brain tissues during the first days after a stroke. But after a stroke, brain cells do not absorb the inhibiting molecule as they did before, and it starts to accumulate and create an imbalance in the brain.
Tom Carmichael: And finally, it starts to begin to set a window of time in which we can start to consider drug therapies to stroke recovery. As you know, right now, stroke recovery is done with physical therapy. There’s no drug that repairs the brain for stroke.
Carmichael said that the type of drug his team worked with in their studies with mice has been developed by pharmaceutical companies, for diseases involving learning and memory, such as Alzheimer’s disease and Attention Deficit Disorder which involve the same inhibitory molecule in the brain, he said. The next step, Carmichael said, is to make sure that this drug works in other organisms that medical researchers use as models for humans.
Tom Carmichael: And then the next step is to try to initiate clinical trials in humans.
Carmichael hopes those trials will one day lead to a drug for stroke.