Exercise reduces stress and makes you feel good. This is a mantra which every health-conscious person believes in and advocates. But the real mechanism behind this was not known until recently. Neuroscientists at the University of Georgia have finally solved the puzzle through a series of experiments and also showed that exercise can help combat depression.
This study reveals that a neuropeptide called galanin is necessary for the beneficial effects of exercise to set in. The researchers demonstrated in an animal model that galanin protects neurons from degeneration caused by stress. Rats were made to exercise while their galanin production was blocked and they seemed to be as anxious as they were before the work out. When sedentary rats were given galanin, they showed a complete reversal in their behavior.
The anatomical evidence suggests that galanin contributes to stress resilience by preserving synaptic plasticity, or the way neural connections are strengthened or weakened over time. “We were able to show that stress, just a single exposure to stress, caused a decrease in synapse formation,” said Philip Holmes, the study’s principal investigator and a professor of psychology in the Franklin College of Arts and Sciences. “The hypothesis was that maybe what galanin is doing, and what exercise is doing, is maintaining neuroplasticity in the prefrontal cortex.”
The prefrontal cortex is responsible for complex cognitive behavior such as planning, decision-making, emotion regulation and stress resilience. Interestingly, said Holmes, this region of the brain atrophies during depression. To measure synapse formation, Holmes’ lab counted dendritic spines on neurons in the prefrontal cortex. If dendrites are a neuron’s branches, then these subcellular structures are the twigs on those branches. “We found this protective effect of exercise, but we could block it with the galanin antagonist, so that was really exciting because that told us that galanin was necessary for the beneficial effects of exercise,” said Holmes. “That’s really the key experiment.”
Galanin was known to play some part in cognition, food regulation, moods etc. But now as a stressbuster, this little known neuropeptide may have much more to reveal about its role on the brain. Also, most importantly, the statement ‘exercise reduces stress’ now has a well-defined research to back it up!
The original publication can be accessed here.