Washington: Researchers have discovered a sleep-promoting circuit located deep in the primitive brainstem that enables us to fall into deep sleep.
Researchers at Harvard School of Medicine and the University at Buffalo School of Medicine and Biomedical Sciences said this is only the second "sleep node" identified in the mammalian brain whose activity appears to be both necessary and sufficient to produce deep sleep.
The study demonstrated that fully half of all of the brain's sleep-promoting activity originates from the parafacial zone (PZ) in the brainstem.
The brainstem is a primordial part of the brain that regulates basic functions necessary for survival, such as breathing, blood pressure, heart rate and body temperature.
"The close association of a sleep centre with other regions that are critical for life highlights the evolutionary importance of sleep in the brain," said Caroline E Bass, assistant professor of Pharmacology and Toxicology in the UB School of Medicine and Biomedical Sciences and a co-author on the paper.
The researchers found that a specific type of neuron in the PZ that makes the neurotransmitter gamma-aminobutyric acid (GABA) is responsible for deep sleep.
They used a set of innovative tools to precisely control these neurons remotely, in essence giving them the ability to turn the neurons on and off at will.
"To get the precision required for these experiments, we introduced a virus into the PZ that expressed a 'designer' receptor on GABA neurons only but didn't otherwise alter brain function," said Patrick Fuller, assistant professor at Harvard and senior author on the paper.
"When we turned on the GABA neurons in the PZ, the animals quickly fell into a deep sleep without the use of sedatives or sleep aids," he said.
How these neurons interact in the brain with other sleep and wake-promoting brain regions still need to be studied, the researchers said, but eventually these findings may translate into new medications for treating sleep disorders, including insomnia, and the development of better and safer anaesthetics.
The study was published in the journal Nature Neuroscience.
