Next, Bero showed in younger mice that the high-plaque regions had increased amyloid beta levels. In a third experiment, he found that the greater amyloid beta levels were caused by increased nerve cell communication in the affected regions.
To further prove the relationship between plaque formation and cell communication, scientists trimmed the whiskers on one side of a group of mice and kept them short for one month.
"Because mice are nocturnal and their eyesight is poor, whiskers are an important way for them to sense where they are in their environment," Holtzman explains. "By cutting the whiskers back on one side, we reduced neuronal activity in the region of the brain that senses whisker movement."
Loss of this input resulted in smaller and less numerous plaques on the side of the brain connected to the pruned whiskers. In a separate experiment, when researchers regularly stimulated whiskers with a cotton swab, amyloid beta levels increased.
According to Holtzman, the results demonstrate the direct connection between amyloid plaque formation and growth and changes in brain cell activity levels in various parts of the brain. He plans further investigations of the mechanisms that regulate default brain activity, their connections to phenomena such as sleep, and their potential effects on Alzheimer's disease.
|Contact: Michael C. Purdy|
Washington University School of Medicine