SCIENTISTS DISCOVER A NEW SLEEP NODE IN THE BRAIN
A sleep-promoting
circuit located deep in the primitive brainstem has revealed how we fall into
deep sleep. Discovered by researchers at Harvard School of Medicine and the
University at Buffalo School of Medicine and Biomedical Sciences, 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.
Published online in
August in Nature Neuroscience, the study demonstrates 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 center with other regions that are critical for life
highlights the evolutionary importance of sleep in the brain," says
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.
"These new
molecular approaches allow unprecedented control over brain function at the
cellular level," says Christelle Ancelet, postdoctoral fellow at Harvard
School of Medicine. "Before these tools were developed, we often used
'electrical stimulation' to activate a region, but the problem is that doing so
stimulates everything the electrode touches and even surrounding areas it
didn't. It was a sledgehammer approach, when what we needed was a
scalpel."
"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," explains 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."
How these neurons
interact in the brain with other sleep and wake-promoting brain regions still
need to be studied, the researchers say, but eventually these findings may
translate into new medications for treating sleep disorders, including
insomnia, and the development of better and safer anesthetics.
"We are at a
truly transformative point in neuroscience," says Bass, "where the
use of designer genes gives us unprecedented ability to control the brain. We
can now answer fundamental questions of brain function, which have
traditionally been beyond our reach, including the 'why' of sleep, one of the
more enduring mysteries in the neurosciences."
The work was funded by
the National Institutes of Health.
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