Parkinson's Disease - What Research is Being Done?
In the last decade research has laid the groundwork for many of today's promising new clinical trials, technologies, and drug treatments. Scientists, physicians, and patients hope that today's progress means tomorrow's cure and prevention.
Parkinson's disease research focuses on many areas. Some investigators are studying the functions and anatomy of the motor system and how it regulates movement and relates to major command centers in the brain. Scientists looking for the cause of Parkinson's disease will continue to search for possible environmental factors, such as toxins that may trigger the disorder, and to study genetic factors to determine if one or many defective genes play a role. Although Parkinson's disease is not directly inherited, it is possible that some people are genetically more or less susceptible to developing it. Other scientists are working to develop new protective drugs that can delay, prevent, or reverse the disease.
Since the accidental discovery that MPTP causes parkinsonian symptoms in humans, scientists have found that by injecting MPTP into laboratory animals, they can reproduce the brain lesions that cause these symptoms. This allows them to study the mechanisms of the disease and helps in the development of new treatments. For instance, it was from animal studies that researchers discovered that the drug selegiline can prevent the toxic effects of MPTP. This discovery helped spark interest in studying selegiline as a preventive treatment in humans.
Scientists are also investigating the role of mitochondria, structures in cells that provide the energy for cellular activity, in Parkinson's disease. Because MPTP interferes with the function of mitochondria within nerve cells, some scientists suspect that similar abnormalities may be involved in Parkinson's disease.
Today, an array of promising research involves studying brain areas other than the substantia nigra that may be involved in the disease. One group of NINDS-supported scientists is studying the consequences of dopamine cell degeneration in the basal ganglia -- brain structures located deep in the forebrain that help control voluntary movement. In laboratory animals, MPTP-induced reduction of dopamine results in overactivity of nerve cells in a region of the brain called the subthalamic nucleus, producing tremors and rigidity and suggesting that these symptoms may be related to excessive activity in this region. Destroying the subthalamic nucleus results in a reversal of parkinsonian symptoms in the animal models.
Scientists supported by the NINDS are also looking for clues to the cause of Parkinson's disease by studying malfunctions in the structures called "dopamine transporters" that carry dopamine in and out of the synapse, or narrow gap between nerve cells. For example, one research group recently found an age-related decrease in the concentration of dopamine transporters in healthy human nerve cells taken from areas of the brain damaged by Parkinson's. This decline in transporter concentration means that any further threat to the remaining dopamine transporters could result in Parkinson's disease.
The search for more effective medications for Parkinson's disease is likely to be aided by the recent isolation of at least five individual brain receptors for dopamine. New information about the unique effects of each individual dopamine receptor on different brain areas has led to new treatment theories and clinical trials.
