Scientists have discovered what goes on when the brain mediates in inhibiting the critical breathing muscles during REM (rapid eye movement) when a person is sleeping, a report published in the Journal of Respiratory and Critical Care Medicine revealed.
The authors, from the University of Toronto, Canada, explained that during REM sleep, there is a profound inhibition of muscle activity. This inactivity can affect the breathing muscles and is a cause of snoring and other breathing problems in sleep, as occurs in obstructive sleep apnea.
The researchers say that their findings could pave the way for new treatments for sleep-related breathing problems.
Co-author, Richard Horner, PhD., said "This paralysis affects breathing muscles and is a cause of snoring and other breathing problems in sleep, especially obstructive sleep apnea."
Sleep apnea is a common sleeping disorder, and may increase the risk of strokes, heart attacks, hypertension, diabetes and daytime drowsiness.
Dr. Horner said "The brain mechanism mediating inhibition of the critical breathing muscles in REM sleep was unknown, but a novel and powerful inhibitory mechanism is identified for the first time in our study."
PhD student Kevin Grace performed a study on rats as they went through sleep-wake states.
The tongue must remain relatively active during sleep, because this "breathing muscle" keeps the airspace open so that we can breathe while we sleep. If tongue muscle activity is inhibited during sleep, it can slide backwards and close up the airspace, making breathing harder.
If the airway is blocked the sleeper experiences sleep apnea - episodes of self-suffocation. This resolves rapidly because the sleeper wakes up. In some cases of sleep apnea, there may be hundreds of episodes each night.
The muscle-activating effects of these interventions were greatest during REM sleep and either absent or minimal in other sleep-wake states. The chemical acetylcholine acts on muscarinic receptors and mediates this powerful muscle inhibition during REM. The muscarinic receptors are functionally linked to a particular class of potassium channel.
Dr Horner said:
"Since REM sleep recruits mechanisms that can abolish or suppress tongue muscle activity during periods of REM sleep and cause obstructive sleep apnea, identification of a mechanism mediating this inhibition is a significant discovery."
This newly identified process has fundamental implications for understanding the common and serious problems of snoring and other breathing problems such as obstructive sleep apnea, which are worse in REM sleep. Moreover, identifying the fundamental mechanism responsible for the shutting down of a muscle in sleep that is critical for effective breathing also identifies a rational drug target designed to prevent this inactivity and so prevent obstructive sleep apnea and other sleep-related breathing problems."
Written by Christian Nordvist