GABA
Can GABA help keep us young?
Editor's Note: Prior studies indicate that GABA
supplementation can increase our human growth hormone levels which
can promote a wide array of youthful qualities like more lean mass,
reduced fat levels and improved skin tone. GABA has also been shown
to promote reduced stress levels while keeping mental alertness high.
Now GABA may have even more positive impacts as a substance that
can keep us more mentally fit as we age and GABA may even help us
preserve our eyesight!
STUDY ON WORLD’S OLDEST MONKEYS MAY EXPLAIN AGE-RELATED MENTAL
DECLINE, SCIENTISTS SAY [Reduced GABA levels reduce brain level processing]
Scientists may have discovered why the brain’s higher
information-processing center slows down in old age, affecting everything from language,
to vision, to motor skills. The findings may also point toward drugs
for reversing the process.
A brain chemical called GABA helps neurons stay finicky about which
signals they respond to – a must for the brain to function at its peak.
Certain neurons in very old macaque monkeys lose their pickiness,
researchers have found, seemingly because they don’t get enough GABA. These
results appear in the journal Science, published by the American
Association for the Advancement of Science (AAAS).
If a lack of GABA is indeed responsible for the old neurons’
indiscriminate firing, this problem may be simple enough to treat. Existing
drugs, such as Xanax, increase GABA production, according to author Audie
Leventhal of the University of Utah School of Medicine. These drugs
haven’t been carefully tested on the elderly, though.
Leventhal and his colleagues studied visual function in monkeys he
believes are the oldest in the world. The monkeys live in a colony in
Kunming, China, established as part of a Chinese and Russian experimental
program in the 1950s. At 30 years old (around 90 in people years), these
animals have lived around twice as long as they do in the wild.
“They really do sort of look like grandpa. They have thinning hair and
wrinkles,” Leventhal said.
In monkeys, as well as humans, visual function declines with age. While
the eye itself does degenerate, this decline also involves the
vision-related section of the cerebral cortex, which is responsible for many
“higher-order” brain functions.
What the researchers discovered about the visual system likely applies
to age-related declines in other parts of the cerebral cortex,
according to Leventhal,
"If it's going on in the visual cortex, it's probably going on in other
parts of the cortex," he said.
In the visual cortex, each so-called “V1 neuron” responds only to the
sight of objects at a specific orientation or moving in a certain
direction. GABA probably restricts the V1 neurons from responding to any
other types of stimuli. This process helps the brain make sense out of the
vast quantities of visual information coming in through the eyes.
"It’s like New York City or Boston during a blackout,” Leventhal said,
describing what would happen if neurons weren’t restricted to specific
responses. “With all the gating mechanisms like the stoplights out,
you’d think traffic would move faster. But it doesn’t."
The researchers recorded the activity of individual neurons in the
visual cortex of old and young macaque monkeys, while showing the monkeys
various images on a computer screen. The devices that monitored the
neurons also held small glass tubes of substances that could be released
directly onto the neurons. The substances were GABA, a GABA-enhancing
compound called muscimol, and a GABA-blocking compound called bicuculline.
The GABA blocker made the neurons less selective in the young monkeys,
but had no significant effect in old monkeys. Presumably, that’s
because the older neurons had already lost much of their selectivity,
according to the researchers.
GABA and the GABA-enhancer had a relatively small effect in the young
monkeys, moderately increasing the percentage of cells that were
selective for particular orientations and directions. In the old monkeys,
however, GABA and the GABA-enhancer had a much stronger effect,
significantly increasing the percentage of highly selective cells.
Thus, the visual cortex of the older monkeys seemed to function less
effectively, because GABA wasn’t limiting the neurons to specific
responses. Exactly how this change occurred isn’t completely clear. In their
Science paper, the researchers speculate that perhaps GABA production
decreases in older brains.
“It’s absolutely remarkable to me that my lab is the only lab in the
world studying higher brain function in old monkeys. Old monkeys are
rare, but the world is full of old human primates,” Leventhal said.
“Hopefully we can drum up a little interest, and encourage other people who
are trying to figure out how come their kids are smarter than they are
now.”
Leventhal’s co-authors are Youngchang Wang and Mingliang Pu of the
University of Utah School of Medicine, in Salt Lake City, UT; Yifeng Zhou
of the University of Science and Technology of China, in Hefie, China;
and Yuanye Ma of Kunming Institute of Zoology, Chinese Academy of
Science, in Kunming, China. The study was supported by the National Institute
of Aging, National Institutes of Health.
Source: American Association For The Advancement Of Science
Date Posted: 2003-05-02
Web Address:
http://www.sciencedaily.com/releases
|
|
