What Is The Role of Dopamine in Parkinson’s Disease?

Imagine that there is one source behind everything you feel, every move you make, and every food you prefer! There is one chemical substance that affects all feelings, including love, lust, hate, and hunger. It also controls your habits, from eating your favorite dessert when you would like to or fulfilling your craving to alcohol at the bar. This chemical substance is called dopamine, and it plays a major role in all these chemical interactions happening inside your brain.

What is Dopamine?

Like a messenger that delivers orders from one point to another, dopamine is a neurotransmitter that our bodies produce. The nervous system uses dopamine to pass nerve impulses between them. 

Your body defuses dopamine into four main pathways in the brain. This chemical substance interferes with almost everything we do in life. Dopamine affects feelings, lust, enthusiasm in addition to logical thinking and the ability to plan. It even plays a major role in triggering movement in the body. 

In some cases, an increase or decrease in the amount of dopamine can lead to several health problems. Some of these can be manageable. However, other diseases can be dangerous, like Parkinson’s disease.

What is Parkinson’s?

Parkinson’s disease PD is a severe movement disorder that damages nerve cells in the brain that are responsible for movement. This damage causes the dopamine-producing neurons to degrade. In its turn, this leads to tremor, slowness, stiffness, and balance problems. 

Parkinson’s disease usually starts with simple hand tremors, which are barely noticeable. But, this disorder develops with time, and eventually affects the nervous system. It can affect both men and women. However, recent research has shown that the risk of developing the disease is 50 percent higher in men than women. Parkinson’s disease is a genetic disease. Yet, it can develop because of non-genetic factors. Currently, there are no blood or laboratory tests to diagnose non-genetic conditions of Parkinson’s disease. Doctors rely on the patient’s medical history, and perform a neurological examination in order to provide diagnosis.

How Does Dopamine Work?

Parkinson’s disease affects numerous chemical systems that exist in the brain. It plays a crucial part in initiating our feelings and actions. Dopamine is not the only neurotransmitter that contributes to Parkinson’s disease if levels vary. However, it’s the most recognized and significant one at the moment. As Dr. Echo Tan, a neurologist in the Cedars-Sinai Movement Disorders Program, says: “The longtime notion is that its dopamine—but it’s a lot more complicated than that, without finding the real reason behind Parkinson’s disease, we can’t find a cure.”

So, let’s start with what we know for sure. Let’s imagine a certain feeling or order happening in the brain cells. As a messenger, dopamine leaves one neuron to slip through the synapse and reach a receptor on the neighboring neuron. It sends a sign to the nerve cell to initiate a chain of orders that translates in the form of actions, feelings, or movement.

Now you can imagine what happens when we have less amount of dopamine in the brain. The movement or feeling order sent by the nerve cells can reach its next point, causing the cardinal symptoms of Parkinson’s disease to appear.

How Does Dopamine Cause Parkinson’s Disease?

Movement control is managed by intricate interactions between nerve cells in the central nervous system. The most significant group of nerve cells is located in the substantia nigra in the ventral midbrain. 

The human brain is made of billions of these neurons. The damage of any nerve cell in the corpus striatum can lead to a decrease in the dopamine amount available for neurotransmission of the corpus striatum. In turn, this decrease causes movement disorders like Parkinson’s disease.

After years of having Parkinson’s disease, the amount of dopamine in the brain progressively decreases, causing symptoms such as tremors and other movement issues.

Researchers are trying to find a way to halt the degeneration of cells that produce dopamine in the brain to slow the progression of Parkinson’s disease.

Dopamine is A Lifesaver

Although dopamine cannot be classified as a treatment for people with Parkinson’s disease, it can be used to cure various conditions. In some medical cases, dopamine can be used as a treatment. These conditions include low blood pressure, poor cardiac output, poor blood flow to vital organs, and septic shock.

Like any other medication, dopamine can cause some complications, such as irregular heartbeat, faster heart rate, trouble breathing, chest pain, headache, nausea, and vomiting. As such, it’s necessary to regularly follow up with doctors after taking such medication.

Why is Dopamine Not Given To People with Parkinson’s?

You may be thinking, if people with Parkinson’s disease already have low dopamine concentrations in their brain, why don’t we give them dopamine as a treatment?

Unfortunately, dopamine can’t enter the brain if it was given directly to people with Parkinson’s disease. So, doctors tend to prescribe other drugs to people with Parkinson’s disease that either act like dopamine or enter the brain border to turn into dopamine. After starting Parkinson’s disease treatment, the patient will feel a noticeable improvement, and the symptoms will become somewhat manageable. However, the effect of drugs will frequently cut back. Thus, researchers are still trying to make a better understanding of the disease. Also, doctors manage the symptoms using medications that can replace dopamine.

Medication to Replace Dopamine

Several medications can act as a replacement for dopamine. These medications cause few unwanted side effects. Yet, they can still reduce unwanted symptoms associated with Parkinson’s disease. Numerous dopamine replacements can be used for patients depending on the nature and severity of their disease. The most common ones are:

Carbidopa-levodopa

One of the most well-known and effective drugs used to replace dopamine is called Carbidopa-levodopa. It’s a natural chemical substance that passes the brain border and converts to dopamine. The drug side effects include nausea or orthostatic hypotension. In addition, as the patient’s symptoms worsen and a higher dose is prescribed, this drug can cause patients to suffer from dyskinesia. Thus, patients must manage their doses properly and follow up with their doctor regularly to ensure the correct dose is being administered.

Duopa

Duopa is a chemical drug usually given to people who suffer from advanced levels of Parkinson’s disease. This type of patient likely responds to carbidopa-levodopa, but they develop a lot of oscillations. Doctors infuse Doupa directly in the blood to keep the two drugs constant in the patient’s system.

Dopamine Agonists

Dopamine agonists are different from Levodopa. This drug is unable to enter the brain border and change to dopamine. Otherwise, it acts very similarly to dopamine. This type of drug is not as effective as Levodopa in treating Parkinson’s disease symptoms. However, one of its strengths is that it lasts longer than Lepedova, and sometimes doctors prescribe it with Lepedova to ease its unwanted side effects.

The side effects of dopamine agonists are similar to carbidopa levodopa’s ones added to sleepiness and sometimes hallucinations. Moreover, some patients can develop compulsive behaviors such as hypersexuality and gambling.

Amantadine

Amantadine is usually prescribed alone to people with Parkinson’s disease to provide short relief of the symptoms in the early stages. Amantadine can also be given with carbidopa-levodopa during the last stages of Parkinson’s disease to control involuntary forced movements like dyskinesia caused by carbidopa-levodopa. Its side effects include hallucinations, purple spots of the skin, and in some cases, ankle swelling.

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