|The image shows the loss of dopamine in the striatum of a Parkinson's patient.
Since the disease was first described nearly 200 years ago, researchers have come to understand some of the
causes of the disease. It is now known that Parkinson's disease occurs when dopaminergic neurons in the area of the brain
known as the substantia nigra are destroyed. Normally these nerve cells release dopamine, a chemical that transmits signals
between the substantia nigra and the corpus striatum. These signals cause muscles to make smooth, controlled movements. It
is a normal aspect of aging to lose some dopamine-producing neurons however Parkinson's disease sufferers have lost anywhere
from 60 to 100% of their neurons in the substantia nigra. Researchers are currently trying to determine what causes the
loss of these neurons.
Researchers believe the major causes for the loss of these neurons are:
# Genetic Factors: About 15-25% of Parkinson's patients have a close relative with the disease. One study found that having two first
degree relatives with the disease increases an individuals chance of having Parkinsons ten times. When Parkinson's occurs
in families, the pattern of inheritance is difficult to pin down. Genes on chromosomes 4, 5, 6, 7, 8 and 17 have been
linked to Parkinson's. Scientists have also found that the mitochondria of cells in the brain of some Parkinson's disease
patients do not function as efficiently as normal. The majority of Parkinson's disease cases is sporadic however.
# Environmental Factors: People with exposure to herbicides and pesticides are more likely to develop Parkinson's. Certain drugs
like haloperidal, chlorpromazine, metoclopramide, prochlorperazine and valproate have been linked to Parkinson's. Exposure
to the toxins manganese dust and the chemical MPTP may also cause Parkinson's.
Researchers now believe that Parkinson's disease results from a combination of both genetic and environmental