The aging processes in brain cells that are thought to underlie cognitive decline may be reversible, according to research published in The Journal of Neuroscience. Researchers believe they have found a way to regenerate the fibers that receive neural impulses.
Previous rat studies have indicated that a compound known as ampakine can improve age-related cognitive deficits, and that it can boost production of a key growth factor, brain-derived neurotrophic factor (BDNF).
Rodent, monkey and human studies have indicated that dendrites decline over time, starting in middle age. The process is called dendritic retraction. Dendrites are the branch-like fibers that extend from neurons and receive signals from other neurons.
Researchers at the University of California-Irvine wanted to know whether dendritic retraction was already occurring in 13-month-old - or "middle-aged" - rats and, if so, whether ampakine could reverse it.
The team placed 10-month-old male rats in cages with enriched environments and gave them plenty of space, a large running wheel and objects to explore. Every day for 3 months, the researchers gave 11 rats oral ampakine and 12 other rats a placebo.
Healthier dendrites in rats that received ampakine
During the 3 months, the researchers monitored the rats' activity as they explored the new environment. After 3 months, they examined the rats' hippocampi, the part of the brain associated with learning and memory. They compared the results with those of "adolescent" rats aged 2.5 months.
The "middle-aged" rats in the placebo group had shorter dendrites and fewer dendritic branches than the younger rats.
However, both the dendrite lengths and the branching in the rats that received ampakine were almost the same as those in the young rats. They also had significantly more dendritic spines than either the untreated or the young rats.
Dendritic spines are the small projections on dendrites that receive signals from other neurons. Signaling between neurons was also better in the treated rats, suggesting enhanced learning and memory function.
Co-author Gary Lynch notes that the treated rats had developed strategies for exploration, and they demonstrated a better memory of the environment. The effects of aging in the brain had effectively been reversed.
Behavioral testing also highlighted benefits of the treatment.
When rats are put into a new environment, they normally spend a lot of time randomly exploring before settling into predicable patterns of activity. However, the rats that received ampakine had established predictable patterns by the second day in the new arena, while the placebo group continued their random exploration.
"There is a tendency to think that aging is an inexorable process, that it is something in the genes, and there is nothing you can do about it. This paper is saying that may not be true."
Commenting on the research, Carol Barnes, a neuroscientist at the University of Arizona who studies the effects of aging on the brain, stresses the importance of optimizing cognitive function throughout one's life. Barnes would be interested to see the effect of this treatment developed into a clinical option.
However, both Barnes and the researchers emphasize the need for further studies before the drug can be tested on people.
Medical News Today recently reported that the growth factor BDNF may slow cognitive decline.