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Progress towards possible Down’s syndrome treatment

20 November 2009: Medicines that target specific nerve cells in the brain could reverse poor mental function in people with Down’s syndrome, according to new research.

 

A group of scientists in the US researched ways of improving brain function in people with Down’s syndrome. They looked at whether it was possible to use drugs to treat certain brain cells in mice that are responsible for problems with mental ability. The mice were a suitable model because they were bred to have a similar genetic make-up to humans with Down’s syndrome. The study was carried out on mice because the research is at a very early stage and so cannot be done on humans.

People with Down’s syndrome have memory and learning problems. This delays brain development and means they find it difficult to adapt to changes in their environment. In mice these functions are controlled by nerves in a part of the brain called the locus coeruleus. The nerves in the locus coeruleus mainly use a chemical called noradrenaline, also known as norepinephrine, to communicate with each other.

In these specially bred mice, the locus coeruleus starts to break down and the nerves don’t work properly. They also have lower levels of noradrenaline.

The researchers considered whether increasing the concentration of noradrenaline in the brains of these mice could reverse problems with brain function. If so, this could also be effective in humans who have Down’s syndrome.

The scientists found that when the mice were put into an unfamiliar cage they didn’t build nests, something that unaffected mice would do. The mice were then given a drug that increased the level of noradrenaline in their brains. Within a few hours they built nests as competently as unaffected mice. However, the scientists noted that as the levels of noradrenaline fell, the effects of the drug quickly wore off.

This study suggests that increasing the level of noradrenaline in humans with Down’s syndrome could produce an improvement in brain function. If this effect does occur, it may be possible to develop a treatment for the condition.

Bupa International’s medical director, Dr Sneh Khemka, said: “These findings are interesting but have many flaws. For a start the study was done in mice and the effects in humans may be very different. In addition, the drugs that the researchers used have been seen to cause serious side-effects in humans, including headaches, raised blood pressure and hallucinations.

“However, further research into drugs already being used to treat disorders such as depression by targeting noradrenaline is definitely justified. This is especially relevant given that the number of babies with Down’s syndrome is increasing as more women are having children later in life.”

Key facts

  • Down’s syndrome is caused by having an extra chromosome (one of the bundles of DNA found in all the cells of the body).
  • A woman’s chance of having a baby with Down’s syndrome increases as she gets older.
  • A test called an amniocentesis can detect Down’s syndrome in unborn babies. This involves taking a sample of the amniotic fluid that surrounds a baby in the womb.
  • People with Down’s syndrome are at an increased risk of certain medical conditions, including problems with hearing, eyesight and the heart.

  • Read the study

    Salehi A, Faizi M, Colas D, et al. Restoration of norepinephrine-modulated contextual memory in a mouse model of Down Syndrome. Sci Transl Med 2009; 1(7):7-17. doi: 10.1126/scitranslmed.3000258

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