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Researchers usually test hypotheses and theories on mouse models before moving on to larger animals and eventually to humans. Although mouse models do not promise the same results in humans, they are a safe starting base in helping scientists understand how different mechanisms and drugs work. Mouse models can also be genetically modified to help make the research more reliable. According to new research, scientists might be able to create a genetically modified rat with human genes, which would make Alzheimer's research better.

The program director at the National Institute of Neurological Disorders and Stroke (NINDS), Roderick Corriveau stated that this kind of research is "a big step forward...the closer the model is to the human condition in representing the disease, the more likely the drug will behave and cure the way it would in humans." NINDS funded part of the research.

Based on previous research, the scientists knew that creating genetic mutations to alter the genes of mice was not going to be easy. After several trials and efforts to get genetic mutations to work, researchers started looking into the groups of rats that were more susceptible to the same health complications that older people suffer from. The researchers used the mutant genes and implanted them into these rats so that similar plaques found in the brains of Alzheimer's patients would develop in these rats as well.

"The big shocker came when we started counting numbers of neurons in their brains. It turns out that they lose up to about 30 or 35 percent of the neurons in brain regions that are classically associated with Alzheimer's disease," said Terrence Town, a physiology and biophysics professor from the University of Southern California.

Not only did the rats develop similar conditions related to Alzheimer's disease, they also started to lose their cognitive functions and could not do mental tasks. As these rats aged, "they perform even worse, much as you would see in a human being that would have these mutations," according to Town. Town has started to test new Alzheimer's drugs on these genetically engineered rats.

The study was published in The Journal of Neuroscience.