Dopamine Hormone Guide
Dopamine is a hormone that serves many complex purposes throughout the body, although it is most well-known for its impact on reward and addiction. Dopamine belongs to both the phenethylamine and catacholamine families. Drugs from the phenethylamine family are known for their stimulant effects as well as their psychoactive effects. Catecholamines are hormones which alter the overall activity level of the central nervous system.
How Did Dopamine Get Its Name?
Dopamine gets its name directly from its chemical structure. Dopamine is an amine, meaning that it is a nitrogen-based organic molecule. Dopamine is formed when an L-DOPA molecule loses its carboxyl group. Dopamine is active both in the brain and in the peripheral systems of the body, but Dopamine acts independently as released in both contained systems.
What is the Function of Dopamine in the Brain?
Dopamine is a hormone that sends messages to other parts of the brain, also known as a neurotransmitter. There are a number of areas of the brain that are activated by Dopamine, most notably, the area associated with desire and reward, but the hormone is associated with a wide variety of other physiological actions as well.
The majority of things that we, as humans, find rewarding—delicious food, sex, drugs—cause this dopamine-based reward system to be activated. Things that are addictive have the ability to fire off these pleasure centers to an extent where the body and mind begin to crave further stimulation.
Dopamine is also related to other activities in the brain, however. It stimulates the release of other hormones, and it helps control movement. There are a number of neurological motor disorders associated with Dopamine dysfunction, including Parkinson's disease.
Parkinson's disease is a neurological, degenerative condition which causes the body to shake near-uncontrollably, while also slowly leading to immobility over time. Parkinson's is caused when the substantia nigra no longer produces the Dopamine which helps regulate motor activity.
Although Parkinson's is a chronic, degenerative disorder, it can be treated with drugs which increase the concentration of Dopamine in the brain. These drugs are also known as antipsychotics.
Other conditions which are hypothesized to be associated with dopamine-inhibition are Restless Legs Syndrome and ADHD.
What Is the Function of Dopamine in the Human Body?
Dopamine is highly active in the brain, but it also serves a number of purposes in the peripheral systems of the body, where it acts as a hormonal messenger.
In the cardiovascular system, dopamine blocks the release of norepinephrine, causing the blood vessels to open up.
In the renal system, the hormone encourages urination and the evacuation of sodium.
Dopamine inhibits the production of insulin by the pancreas
In the gastrointestinal system, Dopamine slows down the rate at which foods pass through the system, and it also helps protect the lining of the intestines.
In the immune system, Dopamine slows down the activity of white blood cells.
Aside from the cardiovascular system, all peripheral effects of Dopamine are considered paracrine activity—this means that Dopamine is released in the immediate vicinity of where it is absorbed by nearby cells, exerting its influence.
How do Medications Affect the Release of Dopamine?
Because of the importance of the hormone, there are a variety of drugs available which affect the way that the body secretes or utilizes Dopamine. Bio-Identical Dopamine Injections are a common form of treatment, but Dopamine, when administered intravenously, is incapable of passing through the blood-brain barrier. Dopamine is frequently used as an emergency treatment for patients suffering from shock or heart failure, for example.
Because there is no way to directly deliver Dopamine to the brain, the most effective way to increase Dopamine levels via medication is through the Dopamine precursor, L-DOPA. L-DOPA does have the ability to pass through the blood brain barrier, and is one of the most common treatments for Parkinson's, because it can suppress tremors by providing Dopamine to struggling areas of the brain.
Drugs which stimulate Dopamine are almost always addictive in high quantities, but they are effective at modest doses to alleviate ADHD. Antipsychotics, on the other hand, are medications which suppress the activity of Dopamine in the body. There are similar drugs that suppress Dopamine through other means that are highly effective at treating nausea.
Dopamine and the Brain
The area of the brain that is central to the body's physiological reward system is located in the ventral tegmental area, and nerves in this region secrete dopamine in response to or in preparation of reward. After Dopamine is produced it travels to the prefrontal cortex and the nucleus accumbens.
Dopamine also controls motor ability, but does so through a different mechanism which does not interact directly with the pleasure pathway. In order to help control movement, Dopamine is released by neurons in the substantia nigra, and the hormone travels to the striatum. The striatum is responsible for our mind's ability to control our movements, and it also allows for fine motor function by suppressing the body's minor conscious movements to enhance control. It also plays a role in social inhibition.
Dopamine is a hormone which plays a wide variety of roles. It is a reward mechanism, it stimulates cognition, motivation, arousal, and physical self-control. There are a number of automatic functions that are related to Dopamine as well, such as the sensations of nausea and sexual pleasure, as well as lactation.
Perhaps surprisingly, there aren't a whole lot of neurons in the brain that are dedicated primarily to Dopamine production. In fact, the entire brain only has about 400,000 of these neurons, and they are located in very particular areas of the brain. In spite of their small number, they have a widespread impact on physiological function.
Areas of the Brain Which Release Dopamine
The Substantia Nigra - Dopamine and Fine Motor Control
As we mentioned earlier, Dopamine plays a vital role in the body's ability to control its movements. Dopamine exerts control over motor function through the substantia nigra, which is an area of dark brain tissue that is attached to the basal ganglia. Most of the Dopamine neurons in the substantia nigra are located in an area known as the pars compacta.
The cells which emit Dopamine in this area can become damaged quite easily, and if a large portion of these cells die, it brings about symptoms that are very similar to Parkinson's Disease.
The Ventral Tegmental Area - Dopamine, Motivation, and Reward
Another area of the brain with dense Dopamine activity is the ventral tegmental area. It is this area of the brain that is responsible for providing the psyche with motivation. Researchers have actually noted that the actions of Dopamine in the ventral tegmental area affect psychological motivation in a similar manner that the nucleus accumbens affects the fine control of motor activity. This means that the ventral tegmental area is also responsible for controlling fine cognitive activity as well, including the mind's ability to make decisions.
Dopamine and the Hypothalamus
There are also cells which produce Dopamine which are located in the posterior hypothalamus, which extend into the spinal cord, but medical researchers are not completely sure how Dopamine impacts the body through this route. There is evidence backing the hypothesis that this Dopamine pathway controls the suppression of motor movement in the body, and those with Restless Legs Syndrome suffer from Dopamine Deficiency in this area of the brain. Restless Legs Syndrome makes it hard to sleep, resulting from the unconscious movements of the body, which is most severe in the legs.
Dopamine and Lactation
Dopamine Neurons in the Periventricular Nucleus and the Arcuate Nucleus suppress the release of breast milk, which is encouraged through the release of prolactin. Dopamine produced in this part of the brain flows into the pituitary gland. The body produces Dopamine as a means to prevent lactation, and when mothers prepare to nurse, this pathway suppresses the production of Dopamine, which allows lactation to take place.
When discussed in the context of this system, Dopamine is often referred to by other names, including Prolactostatin, Prolactin-Inhibiting Hormone, or Prolactin-Inhibiting Factor
Dopamine, Puberty, and Sex Hormone Production
This area of the brain is tightly interconnected with the Hypothalamus. In order for the body to produce sex hormones, Dopamine is released from the Zona Incerta into the Hypothalamus, where the hormone encourages the production of Gonadotropin-Releasing Hormone. The number of Dopamine Receptors in the brain increases dramatically during this period, which helps encourage the rapid onset of sexual changes associated with puberty.
Dopamine and Eyesight
Dopamine also plays a role in eyesight. During the day, amacrine cells in the retina produce Dopamine which simultaneously increases the receptivity of cone cells while reducing the influence of rods. This mechanism makes it easier to see during the day. At night, Dopamine production in this area declines, making it easier to see in dim light.
Dopamine Activity In the Body
As Dopamine is unable to cross from the blood stream into the brain, any Dopamine that is produced by the peripheral systems of the body has no direct impact on Dopamine activity within the brain. There is a lot of Dopamine that travels through the circulatory system, but researchers are still learning how Dopamine impacts the physiology of the body via this pathway.
Some Dopamine is absorbed through the diet, but the body converts this Dopamine into a different form that researchers have discovered no use for. This form of Dopamine is eventually released after it is filtered out by the kidneys.
It is believed that an active form of Dopamine is produced by certain organs, including those in the digestive system and those in the sympathetic nervous system. Physiologically active Dopamine can go through a number of processes in the body. It is sometimes converted by the adrenal glands into norepinephrine, an important hormone which regulates fight-or-flight mechanisms. It can also activate receptor sites throughout the body, or can simply be metabolized.
There are numerous receptors for Dopamine in the arteries. Dopamine activity in this area suppresses the production of norepinephrine and opens up the arteries.
Dopamine and the Immune System
Dopamine has a powerful effect upon the immune system, especially upon the circulatory system, bone marrow, and the spleen. Also, Dopamine suppresses the activity of white blood cells. Cells in the immune system have the ability to release Dopamine, so it is believed that Dopamine helps prevent the white blood cells from going into overdrive.
Dopamine and the Renal System
There are a number of locations in the kidneys that react with Dopamine, and Dopamine is actually produced by the kidneys by tubule cells. Dopamine serves a number of purposes in this system. It encourages filtration, helps draw sodium from the blood stream, and enhances blood flow to the organ. If the kidneys lose their ability to effectively produce Dopamine, this can lead to issues such as hypertension and elevated sodium levels.
Dopamine and the Pancreas
Dopamine plays an intricate role in the function of the pancreas. The pancreas has two sections, the endocrine area and the exocrine area. The exocrine section of the pancreas helps control digestion, releasing substances such as enzymes into the digestive tract to help break down and absorb food. Dopamine plays a role in this process, although researchers are not completely sure of its function. Researchers hypothesize that Dopamine both slows down the rate at which the body processes food and also preserves the inner lining of the intestines.
The areas of the pancreas which regulates internal health are known as the islets of Langerhans. This area is responsible for the production of hormones that are released into the blood stream, one of which is insulin. The cells within the islets of Langerhans which produce insulin are known as beta cells, and it is believed that these cells are receptive to the influence of Dopamine, and that Dopamine activation suppresses the production of insulin.
Dopamine and Risk
There is a strong correlation between Dopamine levels in the brain and one's desire and ability to take risks. Individuals with lower levels of Dopamine activity in the brain tend to be more cautious and are less likely to seek out risk, while individuals with high levels of natural Dopamine production are more likely to enjoy and thrive on risk.
Dopamine is the reason why, when we do something that takes effort and risk, it elicits a feeling of satisfaction. Dopamine encourages us to go outside of our comfort zone and do things we normally wouldn't do. It causes one to thrive on risk, experiencing a literal high when they meet their goals. This often causes them to seek out larger and larger risks, as their surmounted risks are no longer as exciting.
The difference in Dopamine levels among different groups of people explains why some people are happy with comfortable lives and are risk averse, while others seem to thrive on the sensations associated with risk.
Part of what controls Dopamine activity in the brain is the existence of what are known as autoreceptors. Autoreceptors bind with Dopamine and reduce their activity in the body. Researchers have found that people that enjoy risk have fewer of these Dopamine inhibitors, which causes them to be more interested in engaging in risk-taking.
Many people are addicted to Adrenaline. This is the sensation that happens when we ride roller coasters or get in dangerous situations. Adrenaline rewards risky behaviors, but it doesn't reward stepping out of one's comfort zone, necessarily. Whereas Adrenaline makes people love driving fast and getting into fights, Dopamine makes people want to engage in pursuits which might deter others. Dopamine doesn't engage the fight-or-flight response, it simply causes a person to downplay risks and be more likely to engage in out-of-the-box activities.
Dopamine and Depression
Dopamine deficiency is associated with an increased incidence of depression. Robin Williams recent passing is perhaps a testament to this connection. After Robin Williams committed suicide, it was revealed by his wife that Robin was struggling with the initial stages of Parkinson's disease. As we've discussed, Parkinson's is a medical disorder which is caused when the motor area of the brain no longer produces enough Dopamine to regulate motor movement, which leads to the tremors and shaking associated with the disorder.
Reduced Dopamine levels also can lead to depression, because the reward system of the brain is not as active. The body and mind simply do not experience pleasure in the same way, and this increases the likelihood of depression. In Williams' case, depression led him to suicide.
Dopamine also controls one's sense of motivation. In many cases when people truly want to do something but can't generate the willpower, this is a result of Dopamine Deficiency.
Parkinson's Disease and Depression are independent disorders, but one is more likely to occur when the other is present. The conditions also play off of each other and can worsen the effects of both for the patient. The combination leads to feelings of intense isolation and anxiety, which can be incredibly difficult to overcome.
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Dopamine Regulates Motivation to Act, Study Shows: