Dopamine

Dopamine is an important neurotransmitter that regulates our emotional responses, movement, pain, and the brain’s pleasure and reward center. Without dopamine, we wouldn’t be able to feel pleasure or motivation; however, it can also play a role in addiction.

Introduction

Dopamine is a neurotransmitter, which is a chemical released by neurons (nerve cells) to send signals to other nerve cells (R).
Dopamine is produced in the dopaminergic neurons in the ventral tegmental area (VTA) of the midbrain, the substantia nigra pars compacta, and the arcuate nucleus of the hypothalamus (R).
There are several distinct dopamine pathways in the brain, one of which plays a major role in reward-motivated behavior (R).
Dopamine levels in the brain is increased by most types of rewards, and dopamine neuronal activity is increased by most addictive drugs (R).
Dopamine has many roles in humans, which include: movement, memory, pleasure and reward, behavior and cognition, attention, inhibition of prolactin production, sleep, mood, and learning (R).
Dysfunctions of the dopamine system causes several important diseases such as Parkinson’s disease, schizophrenia, restless legs syndrome and attention deficit hyperactivity disorder (ADHD) (R).

Benefits of Dopamine

1) Dopamine Helps Movement

The basal ganglia, which is the largest and most important sources of dopamine in the brain, regulates movement (R).
The basal ganglia plays a central role in action selection, or choosing what to do next (R).
Dopamine contributes to the action selection process. In order for the basal ganglia to function well, it requires dopamine to be released at the input nuclei (R).
A certain amount of dopamine is required to function at peak efficiency (R). Hence, the threshold is set by dopamine for initiating action (R).
When an increase in dopamine activity causes an action, the basal ganglia circuit is altered and makes the same response easier to evoke when similar situations arise in the future (R).

2) Dopamine Mediates Pleasure

Dopamine mediates pleasure in the brain (R).
When exposed to a rewarding stimulus, the brain responds by increasing release of dopamine (R).
A wide variety of rewarding events strongly activate dopamine neurons in some brain areas (R).
During these pleasurable situations, dopamine is released and stimulates one to seek out the pleasurable activity (R). This means that many types of pleasurable experiences such as sex, food, games or even drug abuse can increase dopamine release (R).
The brain reward system serves to promote survival of the species by rewarding behaviors necessary for continued survival such as seeking food, reproduction, shelter, drink, etc (R).  These activities that are essential to species survival and activate this pathway are associated with ‘feeling good’ (R).
The reinforcement role of dopamine can also be aided by the addition of histamine (R).
3) Dopamine Helps Memory
Memory is strongly modulated by dopamine activity in the brain (R).
Dopamine is essential for hippocampal long-term memory (R).
Dopamine has an effect on episodic memory that is the part of long-term memory, which leads people to recall actual events (R).
It influences which episodic memories are formed and how they are represented, enabling memory for past experience to support future adaptive behavior (R).

4) Dopamine Increases Your Attention and Decreases Anxiety

Dopamine has a role in focus and attention (R).
Dopamine dysfunction in frontal lobes can cause a decline in attention or even attention deficit disorders (R).
Studies showed that moderate levels of dopamine improve the capacity of individuals to switch attention efficiently between tasks. Furthermore, moderate levels of dopamine direct attention more efficiently to stimuli that are relevant to ongoing tasks (R).
Dopamine can also help reduce anxiety (R).

5) Dopamine Regulates Hormones

Dopamine that is released by the hypothalamus also acts as a hormone in the brain (R).
Dopamine is the main neuroendocrine inhibitor of the secretion of prolactin from the anterior pituitary gland (R).
Some cells produce prolactin in absence of dopamine. Thus dopamine inhibits the release of prolactin (R).

6) Dopamine Prevents Parkinson’s Disease

Dopamine is responsible for the connection between two regions in the brain which are the substantia nigra and the corpus striatum. This is critical to produce smooth, purposeful movement. Loss of dopamine in this circuit results in impaired movement (R).
The nerve cells in this circuit produce dopamine. Parkinson’s disease occurs when these nerve cells become impaired and/or die (R).
When approximately 60 to 80% of the dopamine-producing cells are damaged and do not produce enough dopamine, the motor symptoms of Parkinson’s disease appear (R).
Low dopamine levels contribute to the painful symptoms that frequently occur in Parkinson’s disease (R).

7) Dopamine Regulates Sleep

Dopamine receptors play a part in modulating sleep (R).
When mice were given a D2 dopamine receptor antagonist, their REM was reduced.
Patients suffering from Parkinson’s Disease may also have sleep disturbances. These disturbances result from a low amount of dopamine [R].

8) Dopamine Can Help the Autoimmune System

Dopamine is shown to interact with the immune system.
Dopamine levels are altered in the brain of mouse models of multiple sclerosis, lupus, patients with inflammatory bowel diseases, and rheumatoid arthritis (R).
Dopamine treatment can decrease inflammation and have other therapeutic effects (R).

9) Dopamine Aids the Stomach and Intestines

There are dopamine receptors located in the stomach and intestines.
They can help relieve nausea and vomiting, or even acid reflux (R).
However, dopamine can also cause constipation (R).

10) Dopamine Helps Increase Bone Strength

Dopamine has an effect on calcium metabolism, and can help increase bone strength.
In a study done on mice missing the dopamine transporter gene, they were shown to have weaker bone strength and less bone mass (R).

Cons of Dopamine

1) Excess Dopamine May Cause Schizophrenia

The dopamine hypothesis proposes that schizophrenia is caused by excessive production of dopamine (R).
Studies support the idea that an overactive dopamine system may result in schizophrenia: Medications that block dopamine receptors, specifically D2 receptors, reduce schizophrenia symptoms (R).
Some evidence suggest that the negative symptoms and some of the cognitive deficits of schizophrenia may be related to decreased prefrontal cortex  function which, in turn, based on indirect evidence, may be associated with decreased mesocortical dopamine activity (R).
Thus, some features of negative schizophrenia (social withdrawal, apathy, anhedonia) are thought to be related to a low dopaminergic state in certain areas of the brain (R).
Schizophrenia is characterized by abnormally low prefrontal dopamine activity (causing deficit symptoms) leading to excessive dopamine activity in mesolimbic dopamine neurons (causing positive symptoms) (R).

2) Dopamine Can Fuel Addiction

Narcotics such as cocaine, nicotine, and amphetamines act to increase the rewarding effects of dopamine, giving pleasurable feelings (R).
Cocaine and amphetamines inhibit the re-uptake of dopamine (R).
Cocaine works by blocking reuptake of dopamine, thus competitively inhibits dopamine uptake to increase the presence of dopamine and its effects (R).
Amphetamine increases the concentration of dopamine in the synaptic gap, but by a different mechanism (R).
Amphetamine and dopamine are similar in structure to dopamine and both enter the terminal button via dopamine transporters as well as diffusing through the membrane (R).
By entering, amphetamines force dopamine molecules out of their storage vesicles (R).
By increasing presence of dopamine both these lead to increased pleasurable feelings and addiction (R).

3) Dopamine Might Cause Obesity

Dopamine is involved with the reward and pleasure system in our brains. Because dopamine is released when someone eats food, this could cause overeating.
An imbalance between circuits that motivate behavior can cause the brain to keep releasing dopamine while a person eats. Since their brain seeks more dopamine, it will lead that person to eat more than usual and cause obesity (R).

Changing Your Dopamine Levels

Increasing Dopamine

Decreasing Dopamine

In cases of schizophrenia, dopamine levels can be decreased by using anti-psychotic drugs (R).
Magnesium and Lithium also decreases the effect of dopamine (R, R).

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