All You Need to Know about Serotonin Secrets

Serotonin is a neurotransmitter, and some also consider it a hormone. The body uses it to send messages between nerve cells.

Serotonin is the chemical nerve cells produce. It sends signals between your nerve cells. Serotonin is found mostly in the digestive system, although it’s also in blood platelets and throughout the central nervous system.

Many investigations have looked at serotonin and what it does, but there is still a lot to learn.

Function

Serotonin plays an important role in many organs as a peripheral hormone. Most of the body’s serotonin is circulating in the bloodstream, transported by blood platelets and is released upon activation. The functions of serotonin are mediated by members of the 7 known mammalian serotonin receptor subtype classes (15 known subtypes), the serotonin transporter and by covalent binding of serotonin to different effector proteins. Almost all immune cells express at least one serotonin component. As a neurotransmitter, serotonin relays signals between nerve cells and regulates their intensity.

Serotonin plays a role in mood and the central nervous system and affects functions throughout the body. Serotonin makes learning more efficient. New research has uncovered another role played by serotonin: boosting learning speed. Serotonin also helps to regulate sleep and sexual desire.

Serotonin and the Immune System

In recent years, a number of immunoregulatory functions have been ascribed to serotonin. Theoretically, either peripheral—i.e., predominantly platelet-derived—or central—i.e., neuronal—serotonin (or both) could modulate immune responses.

Serotonin concentrations in blood and tissues are normally low because of uptake by platelets.

Although serotonin is largely studied as a neurotransmitter, enterochromaffin cells of the gut produce most of the body’s serotonin. These cells express tryptophan hydroxylase TPH1, a rate-limiting enzyme for serotonin production . A second TPH isoform, TPH2, synthesizes serotonin in CNS, and gut enteric nerves .

Immune cells, however, may encounter serotonin released from enterochromaffin cells in gut mucosa, or from platelets, that accumulate. In turn, platelets can release this stored serotonin at sites of injury and inflammation. Platelet-derived serotonin is important for attracting innate immune cells such as neutrophils to inflamed tissue. In addition to platelets, dendritic cells (professional antigen-presenting cells) and B-lymphocytes express can accumulate and release serotonin.

Interestingly, recent studies indicate that some immune cells are capable of serotonin biosynthesis. Mast cells (tissue-resident-cells) in rodents and humans express TPH1 and levels of serotonin are elevated in patients with mastocytosis, who have greatly elevated mast-cell numbers. Further, T-lymphocytes express TPH1 upon T-cell receptor activation and can synthesize serotonin.

Serotonin regulates inflammation and immunity by acting on serotonin receptors that are differentially expressed on immune cells, both in rodents and humans. Serotonin acts as a potent chemoattractant, recruiting innate immune cells to sites of inflammation. Serotonin also alters production and release of cytokines and cell activation/proliferation. Some immune cells, including mast cells and T-lymphocytes, have the capacity to synthesize and release serotonin, expanding the range of tissues for serotonin signaling.

Depression

Scientists do not know precisely what causes depression, but one theory is that it stems from an imbalance of neurotransmitters in the body.Doctors commonly prescribe selective serotonin reuptake inhibitors (SSRIs) as antidepressants. Normally, the body reabsorbs a neurotransmitter after it has transmitted its neural impulse. SSRIs stop the body from reabsorbing serotonin, leaving higher levels of serotonin to circulate. Many people find SSRIs help relieve their symptoms, although the link between depression and serotonin remains unclear.

Seasonal Depression

Researchers don’t know exactly what causes seasonal depression. The lack of sunlight may trigger the condition in people who are prone to getting it.

Biological clock change theory: When someone has less exposure to sunlight, their biological clock shifts. This internal clock regulates mood, sleep and hormones. When it changes, people may have trouble regulating their moods.

Brain chemical imbalance theory: People at risk of SAD may already have less serotonin activity. Since sunlight helps regulate serotonin, the lack of winter sun can make the situation worse. Serotonin levels can fall further, leading to mood changes.

Vitamin D deficit theory: Serotonin also gets a boost from vitamin D. Since sunlight helps us produce vitamin D, less sun in the winter can lead to a vitamin D deficiency. That change can affect serotonin and mood.

Melatonin boost theory: Melatonin is a chemical that affects sleep patterns. The lack of sunlight may stimulate an overproduction of melatonin in some people. They may feel sluggish and sleepy during the winter.

Other Disorders

Apart from depression, doctors may prescribe drugs that regulate serotonin levels to treat a number of other disorders including: bipolar disorder, post-traumatic stress disorder, bulimia (a psychological eating disorder in which you have episodes of binge eating and consuming a large quantity of food in one sitting), obsessive-compulsive disorder, panic disorders and migraine.

Can Serotonin Levels Be Used to Diagnose Crohn's Disease?

A new treatment may be on the horizon for people with a major form of inflammatory bowel disease (IBD) called Crohn's disease, after a McMaster University-led study identified serotonin as a possible trigger of flare-ups.

Last month, scientists discovered that increased levels of serotonin hormones prevent gut cells from carrying out autophagy, the routine 'housework' of the gut cleaning out damaged or malfunctioning cellular components.

Crohn’s disease is a condition that causes inflammation throughout the digestive system or gastrointestinal tract.

The disease causes ulcers and inflammation to form, and Crohn’s disease can affect any part of the gut including the small intestine, colon, and bowel. Inflammation is usually the body’s reaction to injury or irritation, but in Crohn’s disease doctors do not know the cause of the inflammation.

Serotonin Deficiency Symptoms

Low levels of serotonin can lead to memory problems and a low mood. These are symptoms of depression. When people use certain recreational drugs, such as MDMA (ecstasy), the body releases large amounts of serotonin. This can lead to serotonin depletion and a low mood, confusion, and other symptoms that last several days. Animal studies have suggested that these drugs may damage the nerves that contain serotonin, with possible long-lasting adverse effects.

How to Boost Serotonin Levels

Some natural remedies may help boost serotonin levels in the body. These include practicing meditation, having light treatment, doing regular exercise and consuming foods that are high in tryptophan.

Foods that contain tryptophan could increase serotonin production in the body. Tryptophan is an essential amino acid in many foods, including: salmon, chicken, turkey, eggs, spinach, seeds, milk products, soy products, legumes, leafy greens and nuts (especially almonds).

Scientists have found meals rich in carbohydrates are easier for tryptophan to cross the blood-brain barrier, increasing serotonin levels in the brain.