“When we used flow-fiber photometry to examine the brains of mice, we observed slow waves of norepinephrine, but also how it worked in synchrony with fluctuations in blood volume,” Hau said. Mr. Grand says.
Each time noradrenaline levels rise, blood vessels in the brain constrict, reducing blood volume. At the same time, contraction increased the volume of the perivascular space, which quickly filled with cerebrospinal fluid.
When norepinephrine levels decrease, this process works in reverse, causing blood vessels to dilate, allowing blood to flow in and cerebrospinal fluid to be pushed out. “What we discovered is that norepinephrine acts like an orchestra conductor, moving blood and cerebrospinal fluid in sync in these slow waves,” Haugland says.
And because the study was designed to monitor this process in freely moving, undisturbed mice, the research team knew exactly when all this was happening. When the mice were awake, norepinephrine levels were much higher but relatively stable. The researchers observed the opposite phenomenon during the REM sleep phase, with consistently lower levels of norepinephrine. Oscillatory behavior was present only during the non-REM sleep phase.
Therefore, the research team wanted to see how glymphatic clearance works when mice were given a sleeping drug called zolpidem. increase Non-REM sleep time. In theory, zolpidem should promote brain cleansing. But instead I turned it off.
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“When we observed the mice after administering zolpidem, we found that they all fell asleep quickly, which was expected. We take zolpidem because it makes it easier to fall asleep. ” says Haugland. “But then we found that the slow fluctuations in norepinephrine, blood volume, and cerebrospinal fluid stopped almost completely.”
