What Is A Dopamine Transporter And How Does It Work?
By Sarah Fader
Updated February 25, 2020
Reviewer Jeffrey Craven , MA, LMHC, LPCC, LLC
When dopamine lights up our brains, we feel pleasure, reward, and motivation. Yet, the dopamine couldn't do what it does if it weren't for the dopamine transporter. What is this mysterious thing, and how does it do what it does? More important to most of us, how does it affect our lives?
Components Of The Mesolimbic Dopamine System
Dopamine is the key component of the mesolimbic dopamine system. This system plays a major role in our physical and mental health. When it goes wrong, problems happen that can impair our functioning, not just within our brains, but in our everyday lives as well.
What Is The Mesolimbic System?
The mesolimbic system is composed of a network of brain cells, or neurons, which are sensitive to dopamine. The system receives and processes stimuli and is associated with physical movement and human emotion.
What Is A Neurotransmitter?
Neurotransmitters are chemicals that are secreted by neurons. They carry messages from one brain synapse to another. A synapse is a tiny space between neurons through which messages are transmitted.
Although the description fails to capture the exact mechanism of the transmission, you can think of the neurotransmitter dopamine is involved in the sending of messages. It's a chemical that eases the transmission of a nerve signal as it jumps across neurons to relay the message.
What Is Dopamine?
Dopamine is a neurotransmitter. It's also a catecholamine, meaning that it acts as both a neurotransmitter and a hormone. Dopamine is a part of the brain's internal reward system. When you do something that's satisfying in some way, dopamine is what sends the signal that allows you to feel pleasure about it.
Dopamine pumps up your motivation because you want to feel that pleasurable reward. It also translates the thought of doing it to the action itself. This is related to the movement problems in Parkinson's that are caused by a dopamine deficiency.
What Is A Dopamine Receptor?
Dopamine receptors are the areas of the brain that accept the message delivered via the dopamine system and ended by the dopamine transporters. Certain neurons are sensitive to dopamine, and these are the ones that receive the dopamine transmissions.
What Are Dopamine Transporters?
Dopamine transporter is a protein existing between the neurons in the brain. Dopamine transporters end the process of the transmission of a message. A dopamine transporter reabsorbs the dopamine after it has been released and sent its message. This reuptake of dopamine allows you to stay at a relatively steady emotional and physical level.
How The Dopamine System Works
The dopamine system functions in a process that synthesizes dopamine release it in response to outside stimuli and then returns it to the brain cell. By this process, your brain responds to stimuli by giving you pleasure or the feeling of reward. When the dopaminergic system is working properly, you feel that pleasure, reward, or motivation without disrupting your emotional or physical homeostasis.
How Is Dopamine Made?
Dopamine is made at the end of the nerve using tyrosine that comes across the blood-brain barrier. All catecholamine-secreting cells synthesize dopamine from dopa. The dopamine that is synthesized either function as a neurotransmitter immediately or is converted to norepinephrine or epinephrine.
When Is Dopamine Released?
Dopamine is released when certain outside stimuli are present. Something happens that catches your attention, and the cells respond by releasing dopamine. The dopamine produces a feeling of pleasure or satisfaction. The dopamine is released only when tyrosine is present between and in the brain cells. This happens at a rate determined by the tyrosine level and the effect of the receptors on the process.
What Releases Dopamine?
It is the action of the tyrosine on the receptor cells that release the dopamine. This is a complex process which relies on all parts of the dopamine system, from the cells that release the dopamine to the receptor cells and back as the dopamine is taken up again by the cells.
How Do Dopamine Transporters Work?
After the dopamine is released, the dopamine transporter function ends the process by binding to the dopamine through a chemical reaction. Once that happens, the dopamine moves back into the cell, where it can be used again later on.
Conditions Related To Dopamine Transporter Function
When something goes wrong with the dopamine transporter, the dopamine builds up between the synapses of the brain. This excess dopamine can cause several problems, both physical and psychological.
Dopamine Beta Hydroxylase Deficiency
Dopamine beta-hydroxylase deficiency can happen in infancy. It can cause people to have it to have low blood pressure, vomiting, and dehydration. It can also lower your body temperature or blood sugar. DBH is an enzyme used in the dopamine system.
Parkinson's Disease happens when the brain begins to waste away. This atrophy usually happens late in life. The nerves are affected by Parkinson's to such a degree that you may develop a tremor, muscle rigidity, slow movement, trouble with balance, and begin to walk in a shuffling way.
What does the dopamine transporter have to do with these symptoms? A lack of available dopamine in the brain's nerve cells causes hesitations in your response to stimuli. Your mind knows what you want to do, but your brain has trouble making it happen smoothly.
Standard treatment for Parkinson's has been the drug L-dopa or levodopa. This drug is actually the chemical dopa that is used in your brain to synthesize dopamine.
Yet, the problems of Parkinson's go beyond the simple decrease in dopamine synthesis. The dopamine transporters are affected, causing excess dopamine reuptake. This leaves even less dopamine available for use in sending messages of motivation to the cells in the body that need to move.
When nerve cells are lost through some form of dementia, the function of the dopamine transporters is impaired. They are unable to pass along the messages from one neuron to the next, so memories aren't sent to the areas of the brain where they are accessible.
The connection between bipolar disorder and the dopamine transporters has been identified at the level of the genes. Although it's still unclear just how this all works, evidence shows that there is a strong connection between having a specific genetic variant for the dopamine transporter and having bipolar. The same type of connection is found for people with schizophrenia and depression.
The availability and function of the dopamine transporters may have a profound influence on whether you are depressed or not. Antidepressants seem to relieve depression by changing these factors.
The dopamine is taken up and bound by chemical reactions more readily in depressed people than those who aren't depressed. The depressed people have a higher availability of dopamine transporters. After treatment, there are fewer available transporters, so the dopamine isn't so thoroughly removed from the equation.
It's hard to say exactly what causes ADHD, but its research shows a strong connection between ADHD and increased dopamine transporters.
When you have an overabundance of dopamine transporters, you're going to have less dopamine available in the brain. That's because the transporters end the transmission of the message of pleasure, motivation, or reward. They don't allow the message to move on to the next cell, or at least at a slower rate.
Alcoholism results in a state in which you have low levels of dopamine. This dopamine deficiency may be related to depression or other mental problems. In one study, scientists followed the behavior of rats dependent on alcohol. Both dopamine transporters and dopamine receptors decreased in their brains.
The rats showed behavior that appeared to be alcohol cravings. This makes sense, as the brain and body seek to get back to homeostasis, or a steady state. The brains of deceased alcoholics were also studied, revealing that dopamine transporters and receptors were altered by the alcohol dependence.
Cocaine And Amphetamine Use
Cocaine inhibits the dopamine transporters. When you take it into your body, the dopamine system gives you a sensation of pleasure as the level of dopamine between the cells rises sharply.
Cocaine binds to the dopamine transporter so that it can't end the message properly. While the dopamine chemical process isn't the same for amphetamines, it is similar in that it involves dopamine transporters that are locked up with the drug.
The problem with treating cocaine abuse with something that would keep the dopamine transporter from binding with the cocaine is that the same thing would instead bind with dopamine and decrease dopamine levels in the brain too much.
What Does It All Mean?
The small but significant dopamine transporter, as well as the complete dopamine action, are still not well understood. We do know that too few or too many dopamine transporters lead to instability in your brain and nerves. Whether you're feeling euphoria or depression, a dopamine transporter is involved.
If you feel like your emotions aren't what you would like them to be, talking to a counselor is a good first step to getting to the underlying cause. Licensed mental health counselors are available at BetterHelp.com. You can talk to a counselor when the time is right for you.
You can learn how to release dopamine more steadily and consistently through therapy, medications, or both.
When your dopamine transport system is working at its steady best, you feel happier and better able to manage what life throws your way. Talking it out can set you on a course for overcoming emotional problems, addictions, or even physical disorders. Find your motivation to connect with a counselor, and you can rely on them to help you keep moving forward!