What is Dopamine

Dopamine is one of the brain’s neurotransmitters—a chemical that ferries information between neurons. Dopamine helps regulate movement, attention, learning, and emotional responses. It also enables us not only to see rewards, but to take action to move toward them. Since dopamine contributes to feelings of pleasures and satisfaction as part of the reward system, the neurotransmitter also plays a part in addiction. 

Neurotransmitters are chemicals made by nerve cells called neurons. They’re used to communicate messages across different parts of the brain and between the brain and the rest of the body.

Dopamine is involved mainly in controlling movement. An insufficient production of dopamine in part of the brain can lead to Parkinson’s disease. Parkinson’s diseases is a noncurable nervous system disorder that affects movement. It may cause stiffness, tremors, shaking, and other symptoms. How Dopamine Works Inside the Brain’s Reward System

Dopamine plays a role in the brain’s reward system, helping to reinforce certain behaviors that result in reward. A surge of dopamine, for instance, is what prompts a laboratory rat to repeatedly press a lever to get a pellet of food, or a human to take a second slice of pizza.

Recently, scientists have shown that dopamine can help with unlearning fearful associations. In a study published in June 2018 in the journal Nature Communications, researchers uncovered the role of dopamine in lessening fearful reactions over time, an important component of therapy for people with anxiety disorders, such as phobias or post-traumatic stress disorder (PTSD).

More on the Brain and Dopamine

Dopamine also helps to aid the flow of information to the brain regions responsible for thought and emotion. According to the National Institute of Mental Health, too little dopamine — or problems in the way the brain uses dopamine — may play a role in disorders such as schizophrenia or attention deficit hyperactivity disorder (ADHD).

Dopamine and the Body’s Stress Response

In other parts of the body, dopamine acts as type of hormone called a catecholamine. Catecholamines are made in the adrenal glands — small hormone production factories that sit on top of the kidneys.

There are three main catecholamines:

    Dopamine

    Epinephrine (adrenaline)

    Norepinephrine

These hormones get released into the bloodstream when the body is physically or mentally stressed. They cause biochemical changes that activate the so-called fight-or-flight response. That’s the body’s natural reaction to a real or perceived stress.

Dopamine has many functions outside the brain. It acts as a vasodilator, helping to widen blood vessels. It helps to increase urine output in the kidneys, and in the pancreas it reduces the production of insulin, a hormone involved in blood sugar regulation.

Dopamine and Digestion

Dopamine also plays a role in the digestive system, helping to make sure the contents of the gastrointestinal tract don’t pass through too quickly. In the immune system, dopamine dampens inflammation, normally helping to prevent the sort of runaway immune response seen in autoimmune diseases.

What Are Dopamine Receptors?

Dopamine receptors are proteins found in the brain and nerves throughout the body. If neurotransmitters are the nerve cells’ chemical messengers, then receptors are the nerve cells’ chemical receivers.

As a dopamine signal approaches a nearby neuron, it attaches to that neuron’s receptor. The receptor and neurotransmitter work like a lock and key. The dopamine attaches to the dopamine receptor, delivering its chemical message by causing changes in the receiving nerve cell.

Why Dopamine Receptors Are Key for Neurological and Physical Functions

Dopamine receptors play an important role in many neurological processes, including movement coordination and fine motor control, pleasure, cognition, memory, and learning.

Abnormally functioning dopamine receptors may play a role in several neurological and psychiatric illnesses. Therefore, dopamine receptors are a natural target for many drug therapies.

Some street drugs, including heroin, cocaine, and methamphetamine, also act on dopamine receptors in the brain. They can cause nerve cells to release too much dopamine or prevent the nervous system from recycling dopamine once it’s done its job, highjacking the brain’s reward system.

Euphoric Effects, Pleasure, and Dopamine

Dopamine creates feelings of pleasure. Certain drugs, such as cocaine, can cause large amounts of dopamine to flood the system, producing euphoric effects or a “high” that leave the user wanting more.

As these drugs are abused over time, dopamine’s pleasurable effects on the brain lessen.

To regain these pleasurable effects, a user must increase the amount of drug taken. This phenomenon is called “tolerance.”

Dopamine Drugs

There are a few classes of medication that work on the dopamine pathways of the brain to treat disease. They include:

Levodopa (L-dopa) Levodopa is a drug used to treat Parkinson’s disease. Symptoms of Parkinson’s disease start to show up when dopamine-producing cells in the brain die. Levodopa, a precursor chemical to dopamine, helps to boost dopamine levels in the brain. Once levodopa reaches the brain, it transforms into dopamine.

Dopamine Agonists Dopamine agonists are a class of drugs that bind to and activate dopamine receptors in the brain. They mimic the action of naturally-occurring dopamine in the brain, causing the neurons to react as they would to dopamine.

Dopamine agonists trick the brain into thinking it’s getting the dopamine it needs.

Dopamine agonists are used to treat low dopamine conditions, including Parkinson’s disease and restless legs syndrome (RLS). RLS is a sleep disorder that causes an unpleasant tingling or twitching sensation in the legs when lying or sitting down, mostly at night, resulting in an irresistible urge to move them, and in insomnia. Like Parkinson’s disease, it too seems to be caused by a dopamine shortage in the brain.

Dopamine agonists also are sometimes used to treat depression and fibromyalgia.

Common dopamine agonist drugs include:

    Mirapex (ramipexole)

    Neupro (rotigotine)

    Requip (ropinirole)

Serious side effects associated with dopamine agonists include low blood pressure, dizziness when standing up, hallucinations, and impulse control disorders, such as pathological gambling, compulsive eating, and hypersexuality.

Dopamine Antagonists Dopamine antagonists are a class of drugs that bind to and block dopamine receptors. Dopamine antagonists turn down dopamine activity, which may be useful for the treatment of psychiatric conditions such as schizophrenia and bipolar disorder, which have been associated with an overactive dopamine system.

Many antipsychotic drugs are dopamine antagonists, working to block dopamine receptors in the brain.

Dopamine antagonists that act on dopamine receptors in the gastrointestinal tract may be used to treat nausea, or as anti-emetics to stop vomiting.

Dopamine antagonist drugs include:

    Thorazine or Largactil (chlorpromazine)

    Reglan (metoclopramide)

    Phenergan (promethazine)

    Invenga (paliperidone)

    Risperdal (risperidone)

    Seroquel (quetiapine)

    Clozaril (clozepine)

Dopamine Supplements and Supplementation

Dopamine is found in many types of food, but dopamine itself can’t cross into the brain from the bloodstream, so eating foods that contain dopamine won’t raise dopamine levels in the brain. But dopamine’s precursor molecule, tyrosine, can cross the blood-brain barrier, according to a review published in November 2015 in the Journal of Psychiatric Research.

Tyrosine is an amino acid found naturally in protein-rich foods, such as cheese, nuts, and meat. Under certain circumstances, tyrosine supplements can help boost dopamine levels in the brain, leading some to believe that tyrosine supplementation could help with neurological and mental health conditions involving low dopamine. In fact, the Parkinson’s disease drug Levodopa was originally synthesized from one form of tyrosine.

But scientific studies have failed to show that this is the case. Tyrosine supplements don’t appear to have much — if any — effect on physiology, thought, or behavior.

  

Dopamine is heavily involved in the motor system. When the brain fails to produce enough dopamine, it can result in Parkinson’s disease. A primary treatment for Parkinson’s disease, therefore, is a drug called L-dopa, which spurs the production of dopamine. Dopamine has also been implicated in schizophrenia and ADHD, but its role is not fully understood. People with low dopamine activity may also be more prone to addiction. The presence of a certain kind of dopamine receptor is associated with sensation-seeking, more commonly known as risk taking.