Researchers are looking into yohimbine, a chemical derived from the bark of an African tree, as a treatment for sleep apnea, reports Science Blog.
Previous research had suggested that the hypoglossal neurons that control the tongue are stimulated by a part of the brain known as the pons, located in the brain stem. Two particular groups of neurons in the pons, known as A5 and A7, had been thought to contribute to hypoglossal neuron activation. In experiments performed on rats, the MIT team found that obstructive apnea that is artificially imposed while the animals are not asleep can actually make this A5 and A7 activation of hypoglossal neurons become even stronger, and stay strong long afterward.
“It is as though these neurons can ‘learn’ from the obstructive apnea experience and remain vigilant against it later,” Poon says.
The activity of A5 and A7 usually drops dramatically during sleep, especially REM sleep, and that’s where the problem begins. “It is as if these cells become sleepy and ‘forget’ to do their job,” Poon says, so the researchers sought to find a way to re-activate these neuron groups. They decided to try yohimbine, which is known to inhibit norepinephrine receptors found on these cells that constrain their excitation of hypoglossal neurons. This approach was counterintuitive, Poon says, because the cells’ activity is already suppressed during sleep, and blocking these receptors would be like beating a dead horse.
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