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.

REM Sleep: Introduction

REM is such a huge topic to cover, I’m going to put down some key points and probably revisit them in detail in later entries.

Rapid eye movement (REM) sleep is the stage of sleep we generally associate with dreams, but as we’ve seen in the July 10th entry on slow-wave sleep, there are actually two dream stages. During REM, named for the random darting of the eyes, the body loses muscle tone and an EEG registers quick, low-voltage readings.

Scientists have some theories as to the function of REM sleep, and the most common being taught in psychology is that the brain is trying to process and store information that may not fit into a clear category, and so dreams are very surreal and disjointed because your mind is trying to give structure to the memories. It’s trying to make a story. According to some studies, REM establishes procedural memory, though there have been conflicting studies that would suggest that this is a function of slow-wave sleep (in reference to the repetitive dreams of games that seem to improve performance upon waking).

REM is important not only for humans, but all land mammals and also birds. Evolution has done us a favor by including a mechanism for tonic immobility during this important stage of sleep. At our most vulnerable, can you imagine how easily a predatory would pick us off if we all acted out our dreams? That’s not to say it never happens. Watch any dog dreaming and you’ll probably notice some foot movement; what I like to call “chasing rabbits.” When functioning ideally, this paralysis (REM atonia) is akin to feigning death. When not functioning ideally, it can result in sleep walking, or sleep paralysis if it continues to suppress movement as the person begins to regain awareness.

REM atonia is produced by the release of monoamines (norepinephrine, serotonin, and histamine). Norepinephrine is partially responsible for fight-or-flight response, activating parts of the brain such as the amygdala. This explains why REM dreams are often very emotional, and also why it is so dangerous to try to wake someone who is sleep walking. The synthesis of norepninephrine depends on the amino acid tyrosine (found in meat, nuts, eggs and cheese). Tyrosine can be synthesized by phenylalanine, but you’ve probably heard all sorts of warnings about that. You find it in many diet drinks containing aspartame. Some people are sensitive to phenylalanine and may suffer seizures, but the same natural sources of tyrosine also contain phenylalanine.

A typical night of sleep involves many cycles through the stages of sleep. A cycle is about 90 minutes, and with each consequent cycle the duration of REM increases while slow-wave tapers off. It is sometimes referred to as paradoxical sleep because brain waves are very similar to those of an awake, alert brain. While it has similar brain waves, the body does a poor job of regulating things like temperature and heart rate during this time. It is also the stage of sleep with increased blood flow to genital areas of both sexes (which could total anywhere from 1 to 3.5 hours during sleep).

As I’ve said, REM is such a huge topic, I will be revisiting more specific elements in future entries. Tomorrow, I will be discussing time-lapse video studies, with which I have had some limited personal success.

Slow Wave Sleep

Nothing much to report from last night’s dreams except some unreasonably tiny baby mice.  They had the physical proportions of adult mice, but were small like pinkies.

So today I’ll jump to a study topic: Slow Wave Sleep.

Slow Wave Sleep (SWS) is also known as Stage 3 sleep (previously Stage 3 and Stage 4, but has been combined recently). It precedes REM sleep and is actually much deeper. It is most difficult to wake someone from this stage of sleep. If you’ve ever gotten to bed late and completely missed your alarm clock, you can probably blame this stage. While it is a Non-Rapid Eye Movement (NREM) stage, dreaming still occurs. The nature of the dreams are different from REM in that they are more normal, thought-like, and repetitive. SWS seems to be a way of solidifying skills or patterns you were learning while awake (edit: there is still some disagreement about the processing of procedural memory, and whether it occurs in SWS or REM). This would be the same stage of sleep where you might experience a seemingly endless game of Tetris or Bejeweled, or you might dream that you are at work carrying out your daily tasks. It’s not very restful, and if you are roused from SWS, you may suffer the effects of sleep inertia. This is a period of impaired cognitive ability that could last as long as 30 minutes after waking.

Being awakened consistently during the SWS stage, your body will adjust to compensate. It will sacrifice some REM time to make up time in SWS. This is dangerous, however, in the fact that once you are given the opportunity to catch up on sleep, your body will go into REM rebound. This highly emotional stage could cause you to experience symptoms similar to depression and bipolar disorder. I think it is relevant to point out that sleep deprivation has been used to treat depression, due to a build up of sleep-promoting chemicals in the body (serotonin, for one), but once the patient is allowed to sleep, the depression returns. You can artificially achieve this effect through use of SSRIs (selective serotonin reuptake inhibitors), which will increase the duration of SWS, again at the expense of REM sleep.

Other ways to increase SWS sleep are determined by the period of wakefulness, body heat, physical activity and even heavy ingestion of carbohydrates. These aren’t generally recommended, because REM sleep is vital for rest. The best plan is to get plenty of sleep on as consistent a schedule as possible. Don’t work yourself to death all week on insufficient sleep with the plan to catch up on your days off. That’s a ticket to depression. I’ve been there and it’s not fun. Actually, I blamed the job for my mental state and wasn’t surprised that when I quit the job, I didn’t need the depression/anxiety meds anymore. What I didn’t realize at the time was that my issue could have been REM rebound from an imbalanced sleep schedule.

I don’t want to sell short the benefits of SWS. It is absolutely necessary to the secretion of growth hormones during puberty. It is quite literally possible to have a growth spurt overnight and wake up a new person. Glucose metabolism also increases during this stage due to increased mental activity.

Later this month, I would also like to cover REM sleep and sleep paralysis. If you have a topic of specific interest regarding sleep, leave a comment below.