An injection of a bile acid could reduce the number of brain cells which die in the wake of a stroke or serious head injury.
A "cascade" of damage follows a stroke
Researchers from the University of Minnesota claim that the substance, extracted from digestive juices, could interrupt a chain reaction of cell death and perhaps reduce disability.
Bile is produced in the liver, and flows into the digestive tract to help the body absorb fats.
The research team took a component of this, an acid called tauroursodeoxycholic acid (TUDCA) and injected it into the artery supplying the brains of rats who had suffered a haemorrhagic stroke.
It's made in our own bodies and causes no significant side effects when given as a drug to animals
Dr Clifford Steer, University of Minnesota
This kind of stroke is caused by a burst blood vessel in the brain - most strokes are caused by a clot lodging and blocking a key brain blood vessel.
In each case, some cells die as a direct result of starvation of the oxygen and glucose in the blood.
However, on the fringes of this "core" of damage, there is a region in which many brain cells appear to "commit suicide".
The stroke, or the proximity to cells killed by the stroke, sets in motion a chain reaction of "apoptosis" - programmed cell death.
If this additional damage was prevented, then it is possible that the disability experienced by stroke and head injury victims would be much reduced.
Better by half
The Minnesota researchers found that rats treated with TUCDA had their apoptosis reduced by 50%, which translated into a reduction of 50% in the area of physical damage compared with untreated rats.
Dr Clifford Steer, who led the project, said: "What's exciting about TUCDA, is that it's made in our own bodies and causes no significant side effects when given as a drug to animals.
"Not only does it cross the blood/brain barrier, but it also induces survival pathways in cells when they are injured and simultaneously inhibits the destructive pathways."
The potential of the bile acid is not just limited to stroke damage - it is also being developed as a possible treatment for Huntington's disease.
Professor David Graham, a professor of neuropathology at the University of Glasgow, said that it was the delay in getting stroke and accident victims to hospital which was the main factor in poor outcomes.
He said: "The brain is a very vulnerable organ - if you deprive it of oxygen and glucose for more than 15 minutes then you will get structural damage.
"If you could deliver a patient quickly to hospital you can actually improve their outcome quite markedly."
The study was published in the journal Proceedings of the National Academy of Sciences.