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Battling Down Syndrome Memory Loss

A mouse model suggests a possible treatment for Alzheimer's-like dementia in aging Down syndrome patients.

A new study on mice suggests that there might be a treatment that could reverse dementia in adults with Down syndrome.

Down syndrome is a chromosomal disorder that causes difficulties with contextual learning and memory; it's also the leading cause of mental retardation in children. Approximately 5,000 infants are born with it in the United States each year.

Those with it tend to have lower-than-average cognitive ability from an early age, and those who survive into middle age begin to show Alzheimer's-like dementia by 50 or 60.

The syndrome is characterized by the presence of all or part of a third 21st chromosome in cells, instead of the usual two. William C. Mobley, chair of the Department of Neurosciences at the University of California, San Diego School of Medicine, and colleagues at Stanford University Medical School studied a mouse model that had three copies of mouse chromosome 16, which caused symptoms similar to those exhibited by humans with Down syndrome. One of the symptoms in the mice was the degeneration of a neuron (a cell that conducts nerve impulses) that communicates with regions of the brain that are critical for learning, memory and attention.

The findings show that for Down syndrome in a mouse model, even though the cell-signaling terminals become damaged before the cells themselves, the receptors keep working and looking for signals.

The study revealed some of the dramatic early changes that the disease causes in mice neurons, which might be useful in finding new treatment methods for Down syndrome in human adults. Mosley said in a university press release that the importance of timing and the potential window for treatment of the disease can be underestimated if scientists focus only on cell body damages.

The team found that, in spite of neuron degeneration, they could reverse the conceptual learning failure in the mice by administering a drug called L-DOPS or xamotrol. They are unsure whether the same neuron actually affects contextual learning in humans, but it is affected by other neurodegenerative diseases, such as Alzheimer's.

A form of the drug is currently in clinical trials to treat fibromyalgia in humans. Mobley believes that there is a very real possibility that, if proven safe, the therapy could be an effective treatment for dementia in middle-aged Down patients.

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