Serotonin Receptors Function in the Brain and Mood

Serotonin receptors play an important role in regulating mood, sleep, aggression, sociability, stress, mental functions, memory, learning, hunger, vasoconstriction, and body temperature.

These receptors are also known as 5-HT receptors and they are activated by the neurotransmitter Serotonin.

Serotonin (5-HT, 5-Hydroxytryptamine) is an inhibitory neurotransmitter that is linked to feelings of happiness and contentment. When levels of this neurotransmitter are low, symptoms of depression or anxiety may occur, as well as over-eating, irritation, and poor sleep patterns.

Seven different Serotonin receptor subtypes have been identified. They are numbered 5-HT1 through 5-HT7 and they are distributed throughout the body, intestinal tract, and central nervous system.

Ninety percent of the Serotonin found in the body is located in the enterochromaffin cells in the GI tract. Serotonin receptor locations in the gut are used to regulate digestion and intestinal muscle contractions. However, most Serotonin receptor agonist drugs and supplements target the receptors located in the brain which are involved in mood regulation.

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How It Works:

• Increases Serotonin levels in the brain
• Enhances mood and alleviates stress
• Improves sleep and regulates appetite

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Serotonin Receptors

When Serotonin is released in the brain (or elsewhere in the body), it can bind to Serotonin receptors located on neurons that it comes in contact with.

Depending on the type of receptor it binds to, a different response may occur. There are Serotonin receptor locations in many various parts of the body, and they can have different functions depending on that location.

Serotonin receptors have a number of different functions in the body. This receptor modulates the release of a number of other neurotransmitters, including GABA, glutamate, Dopamine, Acetylcholine, Epinephrine, and Norepinephrine.

It is also involved in modulating the release of certain hormones, including vasopressin, cortisol, oxytocin and prolactin. The activation of Serotonin receptors can also influence mood, anxiety, learning, memory, sleep, and feelings of relaxation and calm.

Serotonin Receptor Modulators: Agonists and Antagonists

As a result of these diverse actions, a number of drugs and supplements are designed to target Serotonin receptors for certain therapeutic effects.

Many drugs prescribed for the treatment of anxiety and depression work by activating these receptors. Drugs for migraine headaches and weight loss supplements may also work by increasing Serotonin receptor activity.

A number of psychedelic drugs, such as LSD and Mescaline, also work by stimulating 5-HT receptors to a very high degree. These compounds are referred to as “serotonin receptor agonists” because they promote a specific physiological response.

In comparison, drugs that block the effects of Serotonin receptors are called “antagonists”. Drugs such as yohimbine, propranolol, and clozapine are Serotonin receptor antagonists for certain subtypes of Serotonin receptors.

Most pharmaceutical agents will only activate specific families of 5-HT receptors, due to biochemical differences in the receptor structures. These are called selective Serotonin receptor agonists; drugs that activate all types are called non-selective agonists.

Effects of Increased Serotonin Activity

There is a lot of research that has gone into cataloging the effects of agonizing or antagonizing certain types of Serotonin receptors. These pathways are quite complex. But generally, we know that increasing levels of Serotonin in the brain can have a relaxing, soothing effect (up to a specific point).

In research studies, higher levels of Serotonin in the brain have been correlated with a reduction in symptoms of depression and anxiety.

Taking a supplement that increases Serotonin activity can improve sleep onset and sleep quality, improve mood, promote appetite suppression and weight loss, alleviate feelings of pain, and reduce migraine occurrence.

How to Boost Serotonin Activity

There are several different ways to increase the activity at Serotonin receptors in the brain.

Doctors may prescribe drugs that can activate these pathways directly, or agents like Selective Serotonin Re-Uptake Inhibitors (SSRIs) that prolong the action of Serotonin once it has been released by a neuron. Examples of SSRIs include Prozac, Zoloft, Paxil, Lexapro, and Celexa.

Another way to affect Serotonin activity levels is by naturally increasing the amount of this neurotransmitter that is available to use in the brain. There is a popular class of Serotonin-boosting supplements designed to achieve this effect.

Two supplements that may increase Serotonin levels are 5-HTP and L-Tryptophan. Both of these are natural compounds that are involved in the synthesis of Serotonin in the brain.

L-Tryptophan and 5-HTP

L-Tryptophan is an amino acid, found in foods such as turkey, chicken, red meats, fish, dairy products, and other high-protein sources. When ingested, some of the L-Tryptophan consumed gets converted into 5-HTP in the liver.

5-HTP (5-Hydroxytryptophan) travels through the bloodstream to the brain, and crosses the blood-brain barrier. Once in the brain, the 5-HTP can then be converted into Serotonin for use within the brain.

Supplementing the diet with additional L-Tryptophan can increase levels of this neurotransmitter and may counteract deficiency. However, supplementing with 5-HTP has been found more reliable for increasing levels of Serotonin.

In research studies, the use of 5-HTP for the alleviation of depression symptoms has demonstrated comparable effects to the use of some SSRI medications. Clinical trials have hypothesized that by increasing the levels of this neurotransmitter available to activate Serotonin receptors, 5-HTP may be able to improve mild forms of depression, anxiety, and improve sleep quality.

Danger and Contraindications

5-HTP is typically sold in 50 to 100 mg capsules or pills. The recommended dosage is between 50 – 600 mg per day. Speak to your doctor to determine the right dose for you to use.

If you have been diagnosed with a medical condition by your doctor and are currently taking SSRIs, MAOIs, or other types of anti-depressant drugs, do not take 5-HTP. This supplement could interact with other 5-HT receptor antagonists or agonists and negatively impact the outcomes of any medications you are currently using.

L-Tryptophan and 5-HTP supplements may interfere with these drugs and cause unsafe reactions or imbalances in mood. Too much Serotonin can cause a condition known as Serotonin Syndrome in which receptors for this neurotransmitter are over-stimulated.

Signs of this condition include twitching, increased heart rate, shivering, excessive sweating, and dilated pupils. This condition can be fatal in serious cases if it is left untreated.

Increasing Serotonin levels may cause interactions with other medications as well, including some drugs prescribed for heart conditions. It is advised to always consult with your doctor before taking any supplements.

5-HTP and other Serotonin supplements are recommended for short term use and should not be used longer than three months. When used at appropriate dosages for short periods of time, the risk of 5-HTP side effects is relatively low.

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