Moderate aerobic exercise can physically reshape the nerve cells that help regulate the heart, according to research from the University of Bristol in the UK. In rats, 10 weeks of training produced strikingly different changes in the nerve clusters on the left and right sides of the body—findings that could eventually support more precisely targeted treatments for arrhythmia, angina, chest pain and stress-induced “broken heart” syndrome.
The study was conducted in rats, so further research is needed to determine whether the same changes occur in humans. Even so, it offers a new perspective on how physical activity affects the nervous system that helps maintain heart function.
Exercise changes the heart’s hidden control system
The heart is regulated in part by the autonomic nervous system, a network that automatically manages functions including heartbeat, breathing and digestion. One part of this system helps the heart beat faster when the body needs more oxygen, such as during exercise or stressful situations.
Small clusters of nerve cells called stellate ganglia play an important role in this process. Located on either side of the lower neck and upper chest, these neural hubs send signals that influence heart rate and other aspects of heart function.
New research suggests that regular exercise changes these nerve clusters in ways that scientists had not previously recognized.
Dr Augusto Coppi, lead author of the study and Senior Lecturer in Veterinary Anatomy at the University of Bristol, said: “Our findings show that there is a previously hidden left-right pattern in the body’s ‘autopilot’ system that helps the heart work.”
“We showed that these neural clusters act like dimmer switches in the heart, and that regular, moderate exercise switches them on in a unilaterally specific way. This may help explain why some treatments work better on one side, and could help doctors more accurately and effectively target treatment in the future.”
Ten weeks of exercise produced major changes in the nerves
To examine how exercise affects the neural clusters, researchers studied rats that completed 10 weeks of moderate aerobic training. Aerobic exercise is any activity that raises heart rate and breathing, such as brisk walking, swimming or cycling.
The study involved researchers from University College London (UCL) in the UK, the University of São Paulo (USP) and the Federal University of São Paulo (UNIFESP) in Brazil.
The team examined the neurons using an advanced three-dimensional analysis technique called stereology. This method allows scientists to estimate the number, size and distribution of cells within tissues.
In trained rats, the right cardiovascular neural cluster contained approximately four times as many neurons as the left cluster. This marked imbalance differed from the pattern observed in untrained rats.
The neurons also changed size, but in the opposite direction on each side. Neurons on the left almost doubled in size, while those on the right became slightly smaller.
The findings suggest that exercise does not affect all of the nerves controlling the heart equally. Instead, it may trigger different structural adaptations on each side of the body.
Could the findings lead to more targeted heart treatments?
The discovery could have implications for conditions involving abnormal nerve activity around the heart.
Arrhythmia occurs when the heart beats too fast, too slowly or irregularly. Angina is chest pain or discomfort usually caused by insufficient blood flow to the heart muscle. “Broken heart” syndrome, also known as stress-induced cardiomyopathy, involves a sudden weakening of the heart muscle, often after intense mental or physical stress.
Doctors sometimes treat these conditions by reducing excessive nerve signals reaching the heart. Procedures such as stellate ganglion nerve blocks temporarily stop nerve activity, while denervation blocks specific nerve pathways.
Understanding differences between the left and right nerve groups could eventually help doctors determine which side to target.
Dr Coppi explained: “Irregular heart rhythms known as arrhythmias, stress-induced ‘broken heart’ syndrome, and certain types of chest pain are often treated by suppressing overactive stellate ganglia (a pair of small nerve hubs in the lower neck/upper chest that send ‘go faster’ signals to the heart).”
“By mapping how the left and right ganglia change with exercise, this study provides clues that could one day fine-tune treatments such as nerve blocks or denervation to the side that is most likely to be effective. This finding is in early stages in rats, so clinical studies will need to follow.”
What comes next in exercise and heart research?
Although the structural changes were significant, scientists still need to determine exactly how they affect heart function.
The research team plans to investigate whether differences between the left and right nerve groups influence how the heart operates at rest and during physical activity. The researchers also plan to look for similar patterns in other animal models and eventually in humans.
For human studies, they hope to use non-invasive markers that can provide information about neural activity without surgery or tissue removal.
If the same differences between the left and right sides are found in humans, the findings could help guide more individualized treatments for arrhythmias, difficult-to-treat angina pectoris and stress-induced “broken heart” syndromes.
Dr Coppi added: “Understanding these left-right differences may help personalize treatments for heart rhythm disorders and angina pectoris. Our next step is to test how these structural changes map to function and whether similar patterns emerge in larger animals and humans.”
Source: www.sciencedaily.com