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Phil Holmes, Associate Professor
of Psychology and Institute for Behavioral Research Fellow, investigates relationships
between neurotransmitter systems in the brain. He asks questions about which
genes are associated with which neurotransmitters, when and how they interact
and what their activities make happen.
Holmes has explored some of the beneficial ways that exercise alters brain
chemistry. Research shows that exercise decreases depression-related behavior
by increasing the activity of norepinephrine, a neurotransmitter, in some parts
of the brain. Research also shows that exercise can enhance learning and memory.
Holmes, in collaboration with Ron Dishman, a UGA professor of exercise science,
designed a study to determine if there was a correlation between these two
relationships. In particular, they wanted to know if the benefits of exercise
on learning also work through a norepinephrine-dependent mechanism.
In order to answer this question, Holmes had to get a picture of which genes
were turned on and where the gene expression was occurring in the brain during
learning and exercise. “The only way to get information about changes
in neurotransmitters is through brain assays,” he explains. Holmes took
samples of blood from rats who had learned a behavior – some after exercise
and some who were sedentary. Assays were prepared for neuroimaging. A radioactive
DNA probe, synthesized to find and bind to a particular gene, served as a marker
for the gene of interest.
Holmes discovered that galanin, a relatively unknown neuropeptide, may be the
key to the enhanced learning effect of exercise. The gene that encodes galanin
appears to be regulated by exercise, and galanin itself seems to modulate the
release of norepinephrine in part of the brain. Galanin appears to work as
an inhibitory regulator that balances norepinephrine release under certain
conditions. These results are the first evidence of galanin involvement in
learning through actions in the norepinephrine system.
“You need just the right amount of norepinephrine to get an enhanced
learning effect,” Holmes explains. “It’s not just a shot
of norepinephrine, but conversely, too much destroys the effect. You need the
lowest optimal dose.” Galanin helps provide the right level.
In spite of these recent findings showing chemically how exercise can affect
learning, Holmes shuns a pharmacological substitute for exercise. “There’s
no magic bullet that can provide the same beneficial effects of exercise for
learners,” he says. “Exercise specifically enhances certain chemicals
in specific brain circuits that are critical for learning, motivation and emotion.
A pill would indiscriminately activate these transmitters in multiple systems,
probably with very undesirable effects.”
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UGA
psychology professor Phil Holmes has found that a brain chemical called galanin
is regulated by exercise and likewise, galanin regulates norepinephrine, a
neurotransmitter that is associated with learning and moods.
