A landmark study has raised the prospect of a pill that can treat brain diseases such as Alzheimer's by halting the death of neurons.

The research, performed on sick mice, is at a very early stage and it could be a decade or more before any medicine suitable for patients is developed.

Experts said the findings are highly significant and one predicted that they would be judged by future generations as an historic turning point.

One of the lead researchers behind the research told RTÉ's News At One that the breakthrough is scientific rather than medical and gives targets for the development of future treatments.

Professor Giovanna Mulluci from the University of Leicester said the process involved giving a compound which targeted an enzyme in the brain of mice while at the same time protecting brain cells.

She said there was a pretty good similarity between the brains of mice and those of other mammals such as humans.

"I would be confident that the protection that you seen in mouse brains you can see in other mammals."

She cautioned that the mice in the study had developed diabetes and lost weight as the treatment had consequences for the pancreas.

Focus on abnormal proteins

The British Medical Research Council team focused on the root cause of many degenerative brain diseases: abnormally shaped proteins that stick together in clumps and fibres.

When enough misshapen protein builds up in the brain it can trigger a reaction that results in the death of nerve cells.

Other approaches have sought to stop or limit the accumulation of the abnormal protein, the structure of which is folded the wrong way.

Instead, the MRC researchers targeted the harmful way brain cells react to misfolded proteins.

Using a drug injected into the stomachs of mice through a mouth tube, they flipped a cellular switch from "off" to "on" to prevent neurons dying.

Five weeks after treatment one group of mice remained free of symptoms such as memory loss, impaired reflexes and limb dragging.

They also lived longer than untreated animals with the same brain disease.

The scientists stressed that human trials are a long way off and point out that the mice suffered serious side effects, including significant weight loss and raised blood sugar.

But they also believe the research demonstrates in principle the possibility of developing an oral treatment - a pill or swallowed liquid - that can protect the brain from neurodegenerative disease.

The research, reported in the journal Science Translational Medicine, duplicated previous results achieved by the same team by means of genetic engineering.