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AIDS-DEMENTIA LINK STUDY: Patients lack dopamine
  Brookhaven lab's finding notes depletion of brain chemical, offering a possible treatment with drugs
September 21, 2004
Scientists at Brookhaven National Laboratory have identified a biochemical abnormality that might help explain why some people with AIDS develop dementia.
For the first time in living AIDS patients with early signs of dementia, scientists detected depletion of the brain chemical dopamine. Not everyone with AIDS develops dementia. It is more common in the late stages of AIDS. Depletion of dopa- mine is most often associated with Parkinson's, not dementia.
Brain scan studies suggest that AIDS patients with dementia have lost between 12 to 20 percent of their dopamine cells. By contrast, Parkinson's patients lose 80 to 90 percent of the dopamine cells in a key area of the brain that regulates movement before any symptoms develop.
In addition to the tremors and rigidity, many Parkinson's patients can also suffer mild attention and thinking problems and are at high risk for depression.
This may somehow tie into what the Brookhaven scientists have identified in the brain.
The finding, reported in the latest issue of the British journal Brain, provides a window into complaints of attention and memory deficits among some AIDS patients and offers a potential treatment using medicines designed to treat Parkinson's. The main medicines boost dopamine.
However, Dr. Gene-Jack Wang, Brookhaven's lead scientist in the study, said test-tube and animal studies suggest the current dopamine-enhancing Parkinson's medicines, such as L-Dopa, may actually leave the dopamine brain cells more vulnerable to attack from the AIDS virus. Adding antioxidants to the treatment with Parkinson's drugs reduces this risk, he said.
Recent studies on cadaver brains culled from patients with AIDS dementia also found a loss of dopamine cells.
"It is a dementia, but it is very different from Alzheimer's," said Wang, who conducted the study with Dr. Linda Chang. "This is a unique form of dementia. Doctors must appreciate that the treatments will be vastly different from the ones used in Alzheimer's patients."
"It is very important to find out how this type of dementia differs from that of Alzhei- mer's," added Dr. Robert Klitzman, associate professor of clinical psychiatry and co-director of the center for bioethics at Columbia University College of Physicians and Surgeons.
The scientists took brain scans of 15 AIDS patients, some of whom had signs of dementia, and 13 HIV-negative volunteers. They found that the dopamine terminals, the place between two cells where chemical communication takes place, are injured. The scientists suspect that this decrease in dopamine transporters may contribute to the disease process. These transporters recycle dopamine, which is the chemical that sends the message to the neighboring cell.
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