New York, May 31 (IANS): US researchers have found an HIV drug that could help reverse memory loss in middle age, in a possible early intervention for dementia.

Human brains rarely record single memories - instead, they store memories into groups so that the recollection of one significant memory triggers the recall of others connected by time. As we age, however, our brains gradually lose this ability to link related memories.

Now, University of California-Los Angeles (UCLA) researchers have discovered a key molecular mechanism behind memory linking. They've also identified a way to restore this brain function in middle-aged mice with an US Food and Drug Administration-approved drug that achieves the same thing.

Maraviroc, which was approved in 2007 for the treatment of HIV infection, was found to suppress a gene in the brains of mice that reduced memory recall.

The finding, published in Nature, suggests that maraviroc could be used off-label to help restore middle-aged memory loss in mice, as well as reverse the cognitive deficits caused by HIV infection.

"When we gave maraviroc to older mice, the drug duplicated the effect of genetically deleting CCR5 from their DNA," said Alcino Silva, Professor of neurobiology and psychiatry at the David Geffen School of Medicine at UCLA.

"The older animals were able to link memories again," he added.

The team focused on a gene called CCR5 that encodes the CCR5 receptor - the same one that HIV hitches a ride on to infect the brain cell and cause memory loss in AIDS patients.

Earlier research had demonstrated that CCR5 expression reduced memory recall.

In the current study, Silva and team found that boosting CCR5 gene expression in the brains of middle-aged mice interfered with memory linking. The animals forgot the connection between the two cages.

When the scientists deleted the CCR5 gene in the animals, the mice were able to link memories that normal mice could not.

"Our next step will be to organise a clinical trial to test maraviroc's influence on early memory loss with the goal of early intervention," said Silva. "Once we fully understand how memory declines, we possess the potential to slow down the process."