New research from the University of Copenhagen shows that the stress transmitter noradrenaline causes you to wake up several times during the night. But don’t worry. This is all part of a normal, good night’s sleep and can also mean that you slept well.
What is noradrenaline?
Noradrenaline is a stress hormone and transmitter substance, which, ia, is associated with the body’s fight or flight response. This is related to adrenaline, and levels can rise during times of stress, but it also helps you stay focused.
“You might think that sleep is a steady state in which you are, and then you wake up. But there’s a lot more to sleep than meets the eye. We’ve learned that noradrenaline causes you to wake up more than 100 times a night And it happens during perfectly normal sleep,” says Celia Kjerby, assistant professor at the Center for Translational Neuromedicine, one of the study’s first authors.
Even though noradrenaline technically causes the brain to wake up more than 100 times a night, we don’t think of it as being awake.
“Neurologically, you wake up because your brain activity during these very brief moments is the same as when you’re awake. But the moment is so brief that the sleeper won’t notice,” says Ph.D. student Mee Anderson is the study’s second first author.
Even if the researchers studied rats, their findings could, in all likelihood, be translated to humans because they focused on basic biological mechanisms—that is, mechanisms shared by all mammals.
The stress transmitter noradrenaline affects sleep waves
Professor Macken Nedergaard, who led the study, sees the new discovery as an important piece of the puzzle to understand what happens in the brain when we sleep.
“We have found the essence of the part of sleep that wakes us up comfortably and that enables us to remember what we learned the day before. We have found that the refreshing part of sleep is stimulated by waves of noradrenaline Very short wakefulness is produced by waves of norepinephrine, which are also very important for memory,” says McKean Nedergaard and adds: “You could say that short wakefulness resets the brain so that when you dive back into sleep so it is ready to store memory.”
We will return to the topic of memory shortly.
What did the researchers do?
Microscopic optical fibers made of glass and genetically manipulated ‘light receptors’ were inserted into the brains of test mice. Optical fibers were connected by cable, which also included an LED light source.
Next, the researchers measured the here and now levels of noradrenaline while the animals slept and compared them to the electrical activity in their brains. This is where he noticed higher levels of noradrenaline.
The researchers then performed memory tests using implanted devices to increase the amplitude of noradrenaline waves, improving the animals’ memory.
Previous research has suggested that noradrenaline, associated with stress, is inactive during sleep. So the researchers were surprised to see how active noradrenaline is during sleep.
The new study shows that when we sleep, the level of noradrenaline in the body is continuously increasing and decreasing in a wavy pattern. High noradrenaline levels mean the brain is briefly awake, while low noradrenaline levels mean you are asleep. Your noradrenaline levels and the degree of ‘awakening’ are linked and constantly changing.
“About 30 seconds go from one ‘top’ to the next, which means your noradrenaline levels are constantly changing. Plus, we can tell that the deeper the ‘valley’, that is, the better the sleep. There will be more subsequent tops, and a higher level of awakening,” says Mee Anderson.
“This suggests that you probably don’t need to worry if you wake up in the night. Of course, prolonged sleeplessness is not good, but our study shows that short-term wakefulness is a function of sleep related to memory.” The natural part is phases. It can also mean that you slept well,” says Celia Kjerby.
Mice develop ‘super memory’
It is a well known fact that Sleep is good for us in many ways. It removes waste products, prevents Alzheimer’s and improves our memory.
The latter was also a focus of this study, and the findings suggest that the rats with the deepest noradrenaline basins had the best memory.
“The mice developed a ‘super memory.’ it is said.
First, rats were allowed to smell two identical objects. They were then put to sleep, and after waking they were returned to objects. However, one of the two items was now replaced by a new one. The rats that saw the highest number of noradrenaline basins were more inclined to study the new object, which suggests that they remembered the last time they saw a different object.
New perspectives on the use of noradrenaline in antidepressants
In addition to increasing our knowledge of the engine room of sleep, the new study provides food for thought regarding antidepressants.
“Some types of antidepressants increase the level of noradrenaline in the body, which increases the risk that you’ll see fewer deep sleep gaits. Our study shows this is likely to affect your memory,” says Celia Kjerby. And says: “This is why we need to look at how different types of drugs that regulate noradrenaline levels in the body affect our sleep. In the future, we need to develop such drugs.” Try something that doesn’t affect the noradrenaline waves during sleep.”