Chemicals of Sleep

Strange tidbits of dreams are all I remember this week. I remember one night I was back at an old house I used to rent with my ex. It was in even worse shape than I remember, but the weird part was, in the dream, the reason we had moved out before had something to do with water damage to the walls because a river had flooded and there were dolphins swimming by the windows. Then last night I had some dream about too many tomatoes. We had dozens of tomatoes, but we needed “four more” for whatever it was we were making. Maybe it had part to do with the shopping and part to do with a game I’d been playing where I needed just a few more things to craft some armor.

Anyway, today’s topic isn’t tomatoes or dolphins. Today, I’ll be talking about the chemicals of sleep. I mentioned monoamines before and they really play the most significant role in the sleep cycle. Norepinephrine, serotonin and histamine practically dictate when you sleep, how long you sleep, and when you wake up.

Serotonin is one of the feel-good chemicals in your body. It builds up throughout the day. This is the chemical targeted by sleep-deprivation treatments for depression, and certain drugs are prescribed to depression/anxiety sufferers to block the reuptake of serotonin so that more is available in the body (SSRIs and MAOIs). It is essential for feelings of well-being, as well as appetite, memory and learning, and even wound healing. In fact, bleeding signals an increase in the level of serotonin to the site of the wound. Some stinging insects’ venom contains serotonin which tricks the body into thinking it has some bleeding wound, which is why some stings are very painful.

Serotonin has a lot to do with eating also. Ninety percent of the body’s serotonin is stored in the gut, and the amount present gives the body environmental clues about scarcity of resources. This in turn has an effect on libido, since it would be unwise to reproduce in an environment with too little food to support additional offspring. High carbohydrate diets low in protein seem to increase serotonin levels (so there may actually be something to those ads about vegan sex drive).

So what does this have to do with sleep? Serotonin is synthesized by tryptophan. Yes, that stuff in turkey that makes you sleep is the precursor to serotonin. A step later along this line is melatonin. You can get this as a natural supplement to aid in sleep, but what it actually does is regulate your circadian rhythm. Biologically, melatonin is secreted in darkness regardless of what schedule you or any other animal prefers to keep. Nocturnal animals experience melatonin secretions at night just the same as diurnal animals, because the cues are visual. The blue light in the morning is a zeitgeber (literally “time giver”) for the cycle.

When you are sufficiently tired or “feel-good” enough for sleep, and you start to drift off to sleep, another of your monoamines begins to taper off. Histamine is the chemical that regulates the body’s response to foreign material, essentially the allergic reaction. Have you ever had an itch so bad you thought you’d never get to sleep, but somehow you managed to nod off anyway? Your body halts release of histamine during sleep.

Now you’re nearing REM sleep. It’s time for the emotional centers of your brain to light up. Norepinephrine is the chemical responsible for fight-or-flight and during this stage of sleep, you’ve got a lot of it. It is synthesized from tyrosine which becomes dopamine and then norepinephrine. Dopamine is another feel-good chemical released as a thrill or reward. People sensitive to dopamine tend to be risk-takers, thrill seekers and sometimes addicts. Norepinephrine, a product of dopamine, is a stress hormone. An increase results in increased heart rate, release of glucose stores (which are fuel for mental activity), greater bloodflow and brain oxygen levels. These would all be necessary in an actual fight-or-flight situation in order to think and act quickly, but it seems our sleeping brain is focused on practicing hypothetical situations during this stage.

There is another chemical at work while we sleep. If you look at an EEG, you will notice what is called a K-complex. These occur during NREM sleep and are a mechanism for suppressing arousal. The chemical responsible for this suppression is adenosine. Like GABA (gamma-Aminobutyric acid) which prevents movement during sleep, adenosine is an inhibitory neurotransmitter. Like serotonin, it is beneficial to wound repair. I want to talk more about adenosine, but let’s wake up for that.

As we begin to wake from sleep, our histamine levels rise, our stores of serotonin are low, and unless we’ve been interrupted our norepinephrine levels have dropped off by this point. Time to start a new day.

Okay, adenosine is a tricky little thing. Did you know that caffeine bonds with the same receptors as adenosine? Adenosine, which can initiate atrial fibrillation and bronchospasm, can be blocked if the receptors are already occupied by caffeine. A reduction of adenosine results in increase in activity of dopamine (the precursor to norepinephrine) and glutamate (precursor to GABA, and vital to learning and memory just like serotonin). It’s okay to consume caffeine when you want to stay awake!

Did you need caffeine to get through this? Well, maybe tomorrow will be more exciting. I’ll be covering lucid dreaming at the recommendation of several friends.