The progression of Parkinson's disease could be slowed or even stopped by a drug commonly used to treat high blood pressure, a study in Nature suggests.
Parkinson's occurs when dopamine neurons in the brain die
Tests on mice at Northwestern University in Chicago showed isradipine can rejuvenate the brain neurons which are dying in Parkinson's patients.
The disease, which mainly affects those aged over 40, leads to tremors and ultimately the inability to walk.
Parkinson's charities welcomed the study but said they were early results.
"It is too early to state with confidence that this drug will be appropriate for the treatment for Parkinson's disease," said Kieran Breen, director of research and development at the Parkinson's Disease Society.
"A significant amount of further research will be required before any definite conclusions can be drawn."
Isradipine is a calcium-blocker which is usually used to tackle high blood pressure, angina and stroke.
But researchers at Northwestern University found mice, who had been engineered to develop a progressive Parkinson's-type disease, did not become ill when their condition was treated with the drug.
Their dopamine neurons - cells which start to die in Parkinson's patients - appeared to revert back to their original, youthful form.
Dopamine is a critical substance which affects the control of movement. When it is lacking, that movement becomes increasingly difficult and uncoordinated.
The team found that when people become older, calcium ions start to enter the dopamine neurons and change how they behave. It is thought that isradipine's ability to stop calcium entering the cells is key to the effectiveness of the treatment.
"Our hope is that this drug will protect dopamine neurons, so that if you begin taking it early enough, you won't get Parkinson's disease, even if you were at risk," said Professor James Surmeier, who led the team.
The drug could also extend the effectiveness of traditional dopamine-boosting medication, potentially doubling or tripling the length of time it worked, he added.
Between 8,000 and 10,000 new cases of Parkinson's are diagnosed in the UK every year, with 95% of cases in those aged over 40.
At any one time, 120,000 people in the UK have the condition.