The amyloid plaques associated with Alzheimer's disease may promote the draining of negative ions from memory-forming cells, causing the cells to die much like a car battery, according to researchers.

"Normal cells are negatively charged inside and positively charged on the outside," said Vernon Ingram of the Massachusetts Institute of Technology, adding that the difference in the cell's charge allows it to receive electrical signals from neighboring cells.

Ingram and his colleagues found that when the amyloid plaques touch a cell, positive calcium ions flood the inside of the cell, while negative chloride ions quickly flow out, draining the cell of negative charge.

By adding a special dye to human and rat nerve cell cultures, the researchers were able to measure the flow of icons, observing differences in the flow of negative and positive ions across the cell membrane.

They then added an amyloid compound, and found that the cells became depolarized within minutes.

"If this happens in memory-forming cells, you lose your memory," Ingram said.

But after exposing the depolarized cells to 1,500 known drugs, they found that 10 drugs actually reversed the depolarization and restored the cells to normal state.

Some drugs, they said, worked from the outside, while others worked from the inside, to block depolarization of the cells.

The researchers said their next step would be "to test the drugs on brain slices from mice, and on live mice engineered to develop similar symptoms to Alzheimer's."

Other Sources: New Scientist