In Parkinson's disease, the nerve cells in the brain that release dopamine degenerate. Dopamine and acetylcholine are used by the nerves as neurotransmitters, or used to send signals from one nerve to another. Normally, dopamine and acetylcholine are in balance, which is necessary for normal movement. This balance is lost with Parkinson's. When dopamine is used as a hormone, it regulates the release of prolactin.
What is Parkinson's Disease?
Parkinson's disease is a disorder where the nerve cells in an area of the brain called the substantia nigra degenerate. Sometimes these nerve cells degenerate because of a gene mutation. In fact, scientists have determined that three of the abnormal genes have proteins that do not properly break down; instead, the proteins build up and become toxic to the nerve cells. Other causes of Parkinson's are still unknown.
Dopamine as a Neurotransmitter
The nerve cells in the substantia nigra area release dopamine, a chemical substance referred to as a neurotransmitter. It is called a neurotransmitter because it is used by the nerves to transmit signals. Thus, because the nerve cells in the substantia nigra degenerate, people with Parkinson's disease have an abnormally low level of dopamine. In one study, it was estimated that the dopamine-related nerve cells decreased by 66 percent in people with Parkinson's disease, as reported in "Adams & Victor's Principles of Neurology" by Allan Ropper, M.D., professor of neurology at Harvard Medical School.
Dopamine as a Hormone
Dopamine is considered to be a hormone when it is released from the hypothalamus part of the brain to enter blood vessels in the pituitary gland. In this case, it is not used by the nerves to send signals. On the contrary, it is there to interfere with the release of the prolactin hormone by the pituitary gland. Functioning as a hormone, dopamine is not associated with Parkinson's disease.
A Low Dopamine Level and Parkinson's
Due to the low level of dopamine that the nerves need to send signals, people with Parkinson's disease no longer have a balance between dopamine and acetylcholine. Acetylcholine is another neurotransmitter; these two neurotransmitters need to be in balance with one another for normal movement. People with Parkinson's have abnormal movements. The disease may begin with a tremor, but slowly progresses to slow movements, a loss of balance, speech problems and stiff muscles.
References
- "Adams & Victor's Principles of Neurology"; Allan Ropper, et al.; 2009
- "Hazzard's Geriatric Medicine and Gerontology"; Jeffrey Halter, M.D., Joseph Ouslander, M.D., Mary Tinetti, et al.; 2009
- MayoClinic.com: Parkinson's Disease
- "Williams Gynecology"; John Schorge, et al.; 2008
