A novel brain mechanism mediating the inhibition of the critical breathing muscles during rapid eye movement (REM) sleep may cause the inhibition of muscle activity that leads to snoring and other breathing problems in sleep, especially obstructive sleep apnea, according to study results published online ahead of print in the American Thoracic Society's American Journal of Respiratory and Critical Care Medicine.
For the study, investigators performed targeted manipulation of the brain region in rats that controls tongue muscles during sleep. They found that backward movement of the tongue and blockage of the airspace were largest during REM sleep and minimal or absent in other sleep-wake states.
According to researchers, the brain chemical mediating this powerful inhibition of breathing muscle activity in REM sleep is acetylcholine, acting via muscarinic receptors that are functionally linked to a particular class of potassium channel.
"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," said Richard Horner, PhD, professor of medicine and physiology at the University of Toronto. "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."
Horner continued, "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."