Researchers at the Stanford University School of Medicine have identified a circuit in the brains of mice that regulates their sleep-wake cycle.
As many as 25-30% of Americans suffer from chronic insomnia, the inability to fall asleep or stay asleep through the night (learn more about insomnia here).
Louis de Lecea, PhD., professor of psychiatry and behavioral sciences: “This has potential huge clinical relevance. Insomnia, a multibillion-dollar market for pharmaceutical companies, has traditionally been treated with drugs such as benzodiazepines that nonspecifically shut down the entire brain. Now we see the possibility of developing therapies that, by narrowly targeting this newly identified circuit, could induce much higher-quality sleep.”
The reward system of the brain affects sleep
The VTA (ventral tegmental area) in the brain is the source of many of the nerve fibers that run to different parts of the brain and secrete dopamine, a neurotransmitter that generates feelings of well-being. Some of these fibers go to a part of the brain that generates feelings of pleasure in anticipation of or in response to obtaining a desired objective. It’s known as the reward circuit and it’s how our brains get us to do things and then reward us when we do them.
Scientists in this study used bioengineered male mice so that they could remotely excite, suppress and monitor the activity in the VTA region of their brains. They found that activity in the VTA in mice increased when they woke up and stayed elevated while they were awake. Scientists were able to keep the mice awake when they would ordinarily be sleeping by activating the VTA.
When scientists suppressed activity in the VTA, the mice went to sleep and stayed asleep even in when “tempted” with food, female mice or threats- circumstances that would normally wake and excite the mice. Even when put in an unfamiliar cage, the mice stayed awake only for 45 minutes to build a new nest, but then they went right to sleep. Typically, when mice are put in a new environment will explore their new surroundings energetically. If these same mice were put into a new cage that already had a nest built for them, they would climb into the next and go right to sleep.
The scientists were able to control whether the mice were awake or asleep by either activating or suppressing activity in the VTA.
Implications of this research for humans
The reward systems in the brains of most vertebrates (animals with internal skeletons made of bone) are very similar and all involve dopamine.
Being able to activate and suppress activity in the VTA of humans could allow for targeted drug treatments for insomnia. There may also be potential to treat other neurological conditions such as schizophrenia or bi-polar disorder that are also characterized by sleep-wake cycle disturbances.
Do you or a loved one suffer from insomnia or excessive daytime sleepiness? Talk to your doctor about potential causes and treatments. Do you need a recommendation for a sleep specialist?
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