Fresh insights gained from a study of tropical fish could help our understanding of how the nervous system works.

Researchers have uncovered vital clues in zebrafish brains about the way our bodies produce myelin, a fatty sheath that insulates and protects nerve fibres.

Myelin is critical for allowing nerve impulses to be transmitted quickly, enabling us to carry out a range of everyday functions such as walking, speaking and seeing.

The scientists found that individual cells in the brain and central nervous system have only a very short time period in which to generate this protective coating.

It is the first time that scientists have been able to quantify the time frame, which is only a matter of hours.

They hope that the results of their studies may one day help the treatment of myelinrelated conditions such as multiple sclerosis.

The researchers, based at the University of Edinburgh, are now studying how manipulation of genes and the use of drugs might promote myelin formation in zebrafish.

Myelin which is made by specialised cells called oligodendrocytes is crucial for good health. When myelin breaks down, and is not repaired properly, it can cause numbness, loss of vision and dizziness. It also leads to the debilitating symptoms of diseases such as MS.

Although MS patients have an abundance of oligodendrocytes in their brains, these fail to produce sufficient myelin to bring about repair.

The Edinburgh team used zebrafish in the study because they share more than 80 per cent of the genes associated with human diseases. The tiny fish also exhibit responses to drugs that are very similar to those of humans.

Young zebrafish are transparent, which allows researchers to look directly into their living nervous system without surgical or physical intervention.

Dr David Lyons, of the University of Edinburgh's Centre for Neuroregeneration, said: "To enhance myelin repair, we will need to improve either their ability to make myelin during the short time in which they have to do this, or find a way to allow them to produce myelin for a longer period of time."

The study, which is published in Developmental Cell, was carried out in the Centre for Neuroregeneration in collaboration with the MRC Centre for Regenerative Medicine at the University of Edinburgh.

The research was supported by the Biotechnology and Biological Sciences Research Council, the Lister Institute, the Wellcome Trust and an EMBO fellowship.