Researchers have in the past shown that exercise results in greater amounts of BDNF, which in turn promotes neurogenesis. Here, this line of research is extended to show that exercise results in an increased release of dopamine, and this benefit depends on BDNF upregulation. Dopamine is important in brain function, but the loss of dopamine that takes place in Parkinson's disease, as dopamine-secreting cells are destroyed, is most likely the primary motivation for this study.
Experts have long understood that regular running raises dopamine activity in the brain and may protect nerve cells from damage. In addition, past research has tied exercise-driven boosts in the dopamine-triggering chemical called brain-derived neurotrophic factor (BDNF) and in dopamine levels to improvements in learning and memory. However, the precise way these three factors interact has until now remained unclear.
A new study showed that mice running on a wheel for 30 days had a 40 percent increase in dopamine release in the dorsal stratium, the part of the brain involved in movement, compared to levels in mice that did not exercise. The runners also showed a nearly 60 percent increase in BDNF levels compared to their non-running counterparts. Notably, the increase in dopamine release remained elevated even after a week of rest. Additionally, when BDNF levels were artificially reduced, running did not lead to additional dopamine release.
For the investigation, researchers provided dozens of male mice with unlimited access to either a freely rotating wheel or a locked wheel that could not move. After one month, the team measured dopamine release and BDNF levels in brain slices. They repeated this same process on a new group of rodents, some of which had been genetically modified to produce half as much BDNF as regular mice. "Our results help us understand why exercise alleviates the symptoms of Parkinson's disease, as well as those of neuropsychiatric disorders such as depression. Now that we know why physical activity helps, we can explore it as a means of augmenting or even replacing the use of dopamine-enhancing drugs in these patients."