The chemical dopamine is a neurotransmitter, a chemical that transmits information from a neuron (brain cell) to a receptor. Although it was synthesized in 1910, dopamine's role in the brain was not recognized until 1958 by Arvid Carlsson and Nils-Ake Hillarp of Sweden. Carlsson won the 2000 Nobel Prize in Medicine for his work.
Dopamine is made in several places in the brain; the dopamine from the area called the substantia nigra is responsible for the signals controlling movement. When these cells die, production of dopamine decreases, the signals are transmitted more slowly, and coordination is impaired. This is Parkinson's disease (PD).
Parkinson's disease is chronic and progressive. Its symptoms are continuous and become more acute with time. There is no cure, but there are treatments to manage its symptoms.
Roughly one million people in the Unites States live with Parkinson's.
Parkinson's Disease Symptoms
Symptoms of Parkinson's include:
- Trembling of the hands, arms, legs, jaw, and face when at rest
- Stiffness of the arms, legs, and trunk as muscles are unable to relax
- Slowness and incompleteness of movement, which can affect speaking and swallowing.
- Poor balance and coordination.
Symptoms usually become apparent when about 80% of the dopamine-producing cells in the substantia nigra have died.
Causes and Prevention
What causes the cells if the substantia nigra to die is unknown. It is clear that older people are more at risk than younger ones. If you have a parent or sibling with Parkinson's, your risk is elevated by two or three times.
Early-stage Parkinson's is difficult to diagnose accurately, and diagnosis may take several years. Your WellStar neurologist will take a medical history, noting especially your symptoms, and will administer a neurological examination. He/she will observe your expression; whether you have tremors or stiffness, can stand up easily, and walk normally. He/she will test your balance by pulling you backwards.
If Parkinson's is indicated, levadopa, which temporarily restores dopamine in the brain, may be administered.
There is no cure for Parkinson's, but there are many medications that treat its symptoms. Each person with Parkinson's must be evaluated to determine which drug or drugs will work best for him or her.
Since dopamine cannot pass from the blood to the brain, once class of medications is based on levodopa, a chemical that is converted to dopamine by the brain. Levodopa is the most effective medication for Parkinson's. About 70 to 80 percent of those being treated for Parkinson's take levodopa, often with other drugs like carbidopa, which prevents it from being converted to dopamine in the blood.
Another category of medication is dopamine agonists, which stimulate the parts of the brain that normally receive dopamine, in effect substituting for dopamine.
Mild Parkinson's expressed by tremors can be treated with anticholinergics, which decrease the production of another neurotransmitter, balancing the reduced production of dopamine.
MAO-B inhibitors block a brain enzyme that breaks down levodopa, delaying the need for that drug, and enhancing its effect when it is needed.
Finally, COMT inhibitors, taken with levodopa, blocks an enzyme in the stomach lining that breaks down levodopa, allowing more to reach the brain, and providing a steadier supply.
Deep brain stimulation (DBS) is a surgical treatment for Parkinson's. Guided by magnetic resonance imaging (MRI), electrodes are implanted into part of the brain that controls motor function. An impulse generator is put under the collarbone, with a battery that lasts three to five years. The patient is given a controller to check the battery and turn the device on and off. When it is turned on, it delivers electrical stimulation to the brain. DBS is not a cure for Parkinson's, and it does not slow its progression, but it can dramatically relieve some symptoms.