Scientists have pinpointed the brain cells responsible for sighing and how it is crucial to proper lung function.
Jack Feldman, a professor of neurobiology at the David Geffen School of Medicine at the University of California-Los Angeles (UCLA), and colleagues publish the details of their discovery in the journal Nature.
According to Feldman, a sigh is a deep breath, but it is not a voluntary one. “It starts out as a normal breath, but before you exhale, you take a second breath on top of it.”
The average person sighs every 5 minutes – equating to around 12 times an hour. This may sound excessive, but we need to sigh this frequently in order for our lungs to function properly.
Sighing is required in order to inflate the alveoli in the lungs – the tiny sacs that enable oxygen and carbon dioxide to move between the lungs and the bloodstream. However, some of these alveoli can collapse.
“When alveoli collapse, they compromise the ability of the lung to exchange oxygen and carbon dioxide,” explains Feldman. “The only way to pop them open again is to sigh, which brings in twice the volume of a normal breath. If you don’t sigh, your lungs will fail over time.”
Two groups of neurons found to control sighing
While sighing is crucial to health, there are situations when it can become a problem.
Sighing can increase in response to psychological stress, meaning people with depression, anxiety disorders and other mental illnesses may experience excessive sighing that becomes debilitating.
There are two groups of around 200 neurons (highlighted) in the brain stem that control sighing.
On the other hand, there are some conditions that make it difficult for a person to sigh, such as respiratory problems, meaning their lung function may be compromised.
For their study, Feldman and colleagues set out to gain a better understanding of what role the brain plays in sighing and breathing rhythm – information that could one day help people who experience debilitating sighs or who have difficulty sighing.
Previous research has identified peptides in the brain – including frog bombesin – that can influence sighing in rodents, though the mechanisms underlying the release of such peptides have been unclear.
With the aim of unraveling this mystery, the researchers analyzed more than 19,000 gene expression patterns in the brain cells of mice, identifying around 200 neurons, or brain cells, in the brain stem that are responsible for the production and release of bombesin-like peptides.
Further investigation revealed that these peptides stimulated another group of 200 neurons that led the breathing muscles of mice to significantly increase the number of sighs produced, from around 40 an hour to more than 400.
“These molecular pathways are critical regulators of sighing and define the core of a sigh-control circuit,” says study coauthor Mark Krasnow, a professor of biochemistry at Stanford University School of Medicine in California. Read More…
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