Running increases dopamine release and improves coordination

Scientists from NYU Langone Health came to this conclusion in an experiment on middle-aged mice. They say regular aerobic exercise helps restore ease and dexterity of movement, which typically decline with age in humans and animals.

The team investigated how running and other aerobic exercise affects the release of dopamine, a neurotransmitter involved in the regulation of movement, reward systems and memory. The work builds on an earlier study by the same authors, in which young (10-week-old) male mice showed a persistent increase in dopamine release after 30 days of voluntary wheel running.

The new work showed that in 12-month-old mice (a rough analogue to humans at about 50 years of age), the increase in dopamine was as pronounced or even more pronounced.

In addition, the middle-aged "runners":

• descended a vertical pole faster and more dexterously,

• and moved more quickly across the open arena field,

compared to the same-aged animals with the wheel blocked. The grip strength did not change, indicating that the improvements were related to coordination and nervous system function rather than muscle mass growth.

The benefits of movement are not just for the young

"Our results clearly show that the impact of physical activity on brain health and mobility is not limited to young age," notes the study's senior author, Professor Margaret Rice.

"If we move enough, we can increase the release of dopamine and help ourselves to move faster and more easily," she adds.

It was previously known that aerobic exercise (running, swimming, cycling, dancing, etc.) stimulates the release of dopamine and other important brain substances. But exactly how this mechanism works in the aging brain has remained less well understood, especially as the number of dopamine-producing neurons gradually declines in older adults.

Possible clues for Parkinson's disease therapy

The study, published in the journal npj Parkinson's Disease, according to the authors, was the first to show a direct link between increased dopamine signalling from exercise and improved motor skills in aging mice of both sexes (previous work had only studied young males).

Rice emphasises that the results could be important for understanding Parkinson's disease, a neurodegenerative disease in which dopamine neurons die, leading to tremors, slowed movements, impaired balance and other symptoms. It's long been known that physical activity provides relief for these patients, but now comes a neurochemical explanation for why this works.

"These results provide biochemical evidence for why exercise improves everything from memory to movement to mood," says Rice. - All of these functions are affected in people with Parkinson's disease."

The team's next step is to repeat the experiment on genetically modified mice, which are used as a model for Parkinson's disease. Scientists warn that to fully understand the impact of the "dopamine effect" of exercise on the disease, further studies already involving humans are needed.

How the experiment was conducted

In the study, two dozen mice were given unlimited access to either a freely spinning treadmill wheel or a blocked one. After a month, all the animals

• performed tests of mobility, coordination and muscle strength,

• and compared the results of the runners and the sedentary group.

The researchers then measured the release of dopamine in brain slices taken from the striatum, an area associated with movement control and motivation.

It turned out that mice that were given the opportunity to run had about 50 per cent higher dopamine release than sedentary animals. Interestingly, females ran about twice as much as males, but had similar improvements in dopamine levels and motor performance. This suggests that there is a certain threshold of sufficient load: once this threshold is reached, the body no longer provides additional benefits with further increases in training.

The results once again confirm that regular aerobic activity can markedly improve the functioning of the brain's motor circuits even in adulthood - and this is an important argument in favour of movement for people who want to maintain mobility, as well as for those living with neurodegenerative diseases.