A new imaging study shows that intense exercise boosts two critical neurotransmitters — glutamate and gamma-aminobutyric acid (GABA) — resulting in better mental fitness.
Published in The Journal of Neuroscience, the study’s findings offer new insights into why exercise could become an important part of treating depression and other neuropsychiatric disorders linked with deficiencies in neurotransmitters, which drive communications between the brain cells that regulate physical and emotional health.
“Major depressive disorder is often characterized by depleted glutamate and GABA, which return to normal when mental health is restored,” said lead author Dr. Richard Maddock, a professor in the Department of Psychiatry and Behavioral Sciences at the University of California Davis Health System.
“Our study shows that exercise activates the metabolic pathway that replenishes these neurotransmitters.”
The research also helps solve a question about the brain, an energy-intensive organ that consumes a lot of fuel in the form of glucose and other carbohydrates during exercise, the researcher notes.
“From a metabolic standpoint, vigorous exercise is the most demanding activity the brain encounters, much more intense than calculus or chess, but nobody knows what happens with all that energy,” Maddock said. “Apparently, one of the things it’s doing is making more neurotransmitters.”
To understand how exercise affects the brain, the team studied 38 healthy volunteers. Participants exercised on a stationary bicycle, reaching around 85 percent of their predicted maximum heart rate.
To measure glutamate and GABA, the researchers conducted a series of imaging studies using a powerful 3-tesla MRI to detect nuclear magnetic resonance spectra, which can identify several compounds based on the magnetic behavior of hydrogen atoms in molecules.
The researchers measured GABA and glutamate levels in two different parts of the brain immediately before and after three vigorous exercise sessions lasting between eight and 20 minutes. They also made similar measurements for a control group that did not exercise.
They found that glutamate or GABA levels increased in the participants who exercised, but not among the non-exercisers.
Significant increases were found in the visual cortex, which processes visual information, and the anterior cingulate cortex, which helps regulate heart rate, some cognitive functions, and emotion.
While these gains trailed off over time, there was some evidence of longer-lasting effects, the researchers reported.
“There was a correlation between the resting levels of glutamate in the brain and how much people exercised during the preceding week,” Maddock said. “It’s preliminary information, but it’s very encouraging.”
The findings point to the possibility that exercise could be used as an alternative therapy for depression, he added. This could be especially important for patients under age 25, who sometimes have more side effects from selective serotonin reuptake inhibitors (SSRIs), anti-depressant medications that adjust neurotransmitter levels.
For follow-up studies, Maddock and the research team hope to test whether a less-intense activity, such as walking, offers similar brain benefits. They would also like to use their exercise-plus-imaging method on a study of patients with depression to determine the types of exercise that offer the greatest benefit.
“We are offering another view on why regular physical activity may be important to prevent or treat depression,” Maddock said.
“Not every depressed person who exercises will improve, but many will. It’s possible that we can help identify the patients who would most benefit from an exercise prescription.”