An existing drug already on the market for ALS might help prevent the clouded judgment and fading memory that often comes with advancing age, researchers say.

The drug riluzole has been found to stop age-related memory loss in rats, say scientists from The Rockefeller University and The Icahn School of Medicine at Mount Sinai in New York City.

The onset of dementia often involves altered or lost connections between neurons in the brain, and the rat study with riluzole showed the drug could prompt changes in the brain known to improve connections.

That, in turn, improved communication between neurons in the hippocampus region of the brain.

"By examining the neurological changes that occurred after riluzole treatment, we discovered one way in which the brain's ability to reorganize itself -- its neuroplasticity -- can be marshaled to protect it against some of the deterioration that can accompany old age, at least in rodents," said study author Bruce McEwen.

Connections between neurons create circuits that connect certain areas of the brain, and that connection is due to a chemical signal known as glutamate. Excess glutamate, however, can be a problem, spilling over and damaging connections in other places in the brain, researchers say.

In cognitive decline related to aging, the damage occurs at the synapses, the points where neurons connect, and can lead to neurodegenerative disorders, such as dementia of full Alzheimer's disease.

Riluzole, known to retard the progress of another neurodegenerative disease -- ALS or Lou Gehrig's disease -- was a prime candidate as a potential treatment for this age-related problem because it helps control glutamate release and uptake, averting damaging spillover, the researchers reported in the Proceeding of the National Academy of Sciences.

They began administering the drug to rats at 10 months, considered middle age for the rodent and the points where cognitive decline normally begins to kick in. After 17 weeks on the drug, the rats were tested for their spatial memory and were found to perform better than rats that were not given riluzole.

"Treated aged rats were protected against age-related cognitive decline displayed in nontreated aged animals," the researchers wrote.

Subsequent examination of the rats' brains showed visible changes in the vital glutamate sensing circuitry in the hippocampus, the region of the brain associated with memory.

"We have found that in many cases, aging involves synaptic changes that decrease synaptic strength, the plasticity of synapses, or both," said Mount Sinai researcher John Morrison.

In the case of the rats, their enhancement of memory was linked to an increase in both the strength and the plasticity of neuron synapses, he said.