Re: Chemistry of sleep, what chemical wakes us up?

Area: NeuroScience
Posted By: James Clack, Faculty Biology, Indiana University - Purdue University, Columbus IN
Date: Tue Sep 9 13:05:14 1997
Area of science: NeuroScience
ID: 873792740.Ns

Message:

Chemistry of sleep, what chemical wakes us up?

What brain chemical wakes us up by signaling the brain that it's had 
enough sleep?

ANSWER

Let me answer this by first giving you a little background about the mechanism of sleep itself. There is an area in your brainstem (the elongated area at the bottom of the brain that connects to the spinal cord) known as the Reticular Activating System (RAS). This functional area is responsible for maintaining a state of arousal, that is, keeping you awake (actually, it is thought that the top of the RAS acts to keep you awake, while the bottom acts to put you to sleep). It does so by a fairly complex mechanism that involves randomizing of cerebral electrical activity, so we won't worry about that. Ultimately, it is thought that the activity of the bottom of the RAS acts to inhibit activity of the top of the RAS and induce sleep. There are many hypotheses as to which neurochemicals induce sleep. One hypothesis states that serotonin secretion by cells of the raphe nucleus may induce sleep. Another states that cells of the reticular nuclei secrete another neurotransmitter, Acetylcholine, that induces sleep.

As far as which neurochemical "wakes us up," it is probably a combination of Acetycholine and other stimulatory neurotransmitters that act to "disinhibit," or activate the upper part of the RAS by stimulating it chemically. It is likely that, because we move through different levels of sleep (from wakefullness to Stage 4 sleep), a fortuitous combination of general and/or special sensory stimulation from the environment that occurs while we are in Stage 1 sleep (light sleep) causes us to wake up.

Best Regards,
James W. Clack
Associate Professor of Biology

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