For many years, researchers have known that the movement problems associated with Parkinsons disease result from a loss of neurons that produce a nerve-signaling chemical called dopamine in one part of the brain. A new study suggests that Parkinsons disease (PD) also affects nerve endings that produce a related chemical, norepinephrine, in the heart. The finding improves understanding about how Parkinsons disease develops and may lead to a way of predicting the disorder and possibly even preventing it.
The study also improves understanding of orthostatic hypotension, or a fall in blood pressure when a person stands up, which is a common complication of Parkinsons disease. This condition can cause dizziness, lightheadedness, and fainting.
Using positron emission tomography (PET) scans, researchers at the National Institute of Neurological Disorders and Stroke (NINDS) found that nearly all of the 29 Parkinsons disease patients they studied had decreased numbers of norepinephrine-producing nerve endings in the heart. This finding suggests that Parkinsons is more than just a brain disease and may be caused by an abnormality that affects the peripheral nervous system, which includes the sympathetic nervous system, as well as the brain. The study, and a related editorial, appear in the September 5, 2000, edition of the Annals of Internal Medicine.(1) (2)
The loss of nerve terminals in the heart was not related to whether the patients had taken the drug levodopa, which is converted to dopamine and is commonly prescribed to treat Parkinsons patients, says David S. Goldstein, M.D., Ph.D., Chief of the Clinical Neurocardiology Section at NINDS, who led the study. The extent of loss was also unrelated to the duration or severity of the disease.
Loss of norepinephrine-producing nerves throughout the heart was found in the nine
Parkinsons patients who also had orthostatic hypotension. However, most of the
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NIH/National Institute of Neurological Disorders and Stroke