Key takeaways
- Dopamine is a neurotransmitter that supports smooth, controlled movement. In Parkinson’s disease, dopamine drops, causing movement to become shaky, slow, or stiff.
- Symptoms often begin after major dopamine loss, sometimes when 60% to 80% of dopamine-producing cells are gone. Early signs can include poor coordination, trouble concentrating, stooped posture, and loss of smell.
- Parkinson’s treatments aim to raise brain dopamine levels or improve response to dopamine. Treatment options include medications like levodopa and procedures like deep brain stimulation.
Parkinson’s disease is a progressive neurological disorder. It causes issues such as tremor, muscle stiffness, and slow movements. It affects more than 1.1 million people in the United States.
Scientists don’t fully understand Parkinson’s disease. There’s no known cure, and diagnostic tests can’t definitively determine whether a person has it. But researchers do know a fair amount about how the loss of dopamine affects symptoms.
In this article, we’ll discuss what dopamine is and how it’s connected to Parkinson’s disease. You’ll also learn about treatment options that improve dopamine levels.
Dopamine is a chemical that has effects throughout the body, including the brain. It is produced in a part of the brain called the substantia nigra.
Dopamine helps mediate smooth, controlled muscle movements.
Dopamine also plays a role in the body’s motivation and reward mechanism. When you do something good or pleasurable, your brain is flooded with dopamine, which encourages you to take the action again.
Dopamine also has systemic effects, which include regulating blood pressure, heart rate, heart function, digestion, kidney function, blood flow, and immunity.
Your body is capable of producing all the dopamine it needs. It can get the building blocks from the foods you eat and the activities you do.
In people with Parkinson’s disease, dopamine levels drop, and the brain doesn’t have enough of the neurotransmitter to do the important work of sending electrical impulses throughout the brain.
For people with Parkinson’s disease, dopamine levels in the brain are too low. As the dopamine starts to fall, signs and symptoms of Parkinson’s disease will begin to emerge.
That means smooth, controlled body movements may be replaced by symptoms such as tremor or stiffness in the limbs. Fluid motions may become slow, shaky, and halted.
Dopamine levels may be significantly reduced by the time these symptoms are noticeable. Some of the earliest signs of Parkinson’s disease aren’t as obvious, and they may occur years before the more significant motor problems arise.
These symptoms include:
- difficulty concentrating
- poor coordination
- stooped posture
- loss of smell
It’s not clear why people develop Parkinson’s disease, but we do know that a major feature of the disease is shrinking, damage, and destruction of the dopamine-producing cells in the brain.
The cells are located in the brainstem — specifically in an area called the substantia nigra. When the cells shrink or become damaged, they don’t produce adequate amounts of dopamine.
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That means the drop in dopamine may be happening long before symptoms are recognized and your doctor begins trying to determine what’s causing your issues.
Neurotransmitters in the brain send signals rapidly so you can move and react. However, when there’s too much or too little of any neurotransmitters, signs and symptoms may develop.
Dopamine is transported through your brain along specific pathways. These are called dopaminergic pathways, or dopamine pathways.
In people with Parkinson’s disease, two significant dopamine pathways — the mesolimbic pathway and the nigrostriatal pathway — decrease communication with other neurons and parts of the brain.
The dopamine transporter scan (DaTscan) can detect changes consistent with PD, but it can’t distinguish PD from other similar conditions.
During the imaging test, a healthcare professional administers a small amount of radioactive material. This material provides contrast on the DaTscan so they can determine how much dopamine is available in the brain.
This test is not normally used in a clinical setting, but it is sometimes used in research experiments.
Various types of treatments for Parkinson’s disease aim to increase dopamine levels or response to dopamine.
Can dopamine be used to treat Parkinson’s?
Since the symptoms of Parkinson’s disease are caused by a drop in dopamine, it might make sense that replacing that dopamine would stop the symptoms and halt the progression of the disorder. But it’s not that easy.
Dopamine can’t penetrate the blood-brain barrier if it’s taken as an injection or a pill. In fact, dopamine has serious effects outside the brain and can cause significant changes in heart rate and blood pressure, without even having any effect on Parkinson’s disease symptoms. That makes it an ineffective treatment.
An amino acid called levodopa can help increase levels of dopamine in the brain. Levodopa converts to dopamine in the systemic circulation. That can cause serious and dangerous changes in blood pressure, heart rate, and heart function.
When it’s used for treating Parkinson’s disease, levodopa is combined with another molecule called carbidopa. Sinemet, the first-line treatment for Parkinson’s, is a combination of carbidopa and levodopa.
Carbidopa prevents levodopa from being converted to dopamine in the systemic circulation, so it can be converted to dopamine in the brain. This maximizes the effects on Parkinson’s symptoms while minimizing systemic effects such as blood pressure and heart function changes.
Certain medications, such as COMT inhibitors and MAO-B inhibitors, prevent the natural breakdown of dopamine. When people take these drugs alongside Sinemet, it helps the dopamine in the brain last longer.
Parkinson’s disease medications only increase dopamine for a few hours. Once the dopamine level starts to decline, symptoms return. There are long-acting versions of these drugs that may reduce symptoms for up to 12 hours.
Deep brain stimulation
Deep brain stimulation involves placing electrodes on specific parts of the brain and using a generator to send electrical impulses through it.
In people with Parkinson’s disease, these electrical signals can help reduce symptoms like tremor, rigidity, and muscle spasms.
What’s more, deep brain stimulation may increase the level of dopamine in a part of your brain. This, in turn, may reduce symptoms.
Without medication or procedures such as deep brain stimulation, it’s impossible to increase the amount of dopamine in the body in a way that would have any impact on Parkinson’s disease symptoms without medication.
Your body makes dopamine in the substantia nigra, and you also have dopamine receptors in the brain. The problem in Parkinson’s disease is not a lack of dopamine building blocks from the diet. Instead, it’s a deficiency in the dopamine-producing cells as well as a decrease in dopamine receptors in the brain.
No amount of protein from your diet can overcome that deficiency.
Regulating dopamine naturally
Exercise and sleep can help regulate dopamine in the body, which can have a beneficial effect on mood. Natural ways to promote dopamine regulation include:
- Exercise: You may already know that when you exercise, your endorphins rise. But exercise may also help regulate dopamine levels.
- Sleep: Sleep is one of the healthiest things you can do for your body, but it also helps regulate your dopamine levels. People who don’t get enough sleep may have low levels of dopamine. Aim for 7 to 9 hours a night.
Dopamine plays a vital role in the body. It helps regulate movement, and it responds during times of reward and motivation.
A deficiency of dopamine in the brain affects the way your brain controls your movements. Signs and symptoms of the dopamine drop will begin to appear. These include tremor, muscle stiffness, and loss of coordination. This might be an indication that you have PD or another neurological disease.
While you can’t replace the lost dopamine in the brain, many of the medications used to treat Parkinson’s disease consist of molecules that are converted to dopamine or prevent the breakdown of dopamine. Treatment can slow or decrease some of the symptoms of the progressive neurological disorder.