Parkinson's disease is named after the English physician James Parkinson who first described it in a detailed way in 1817. It is a degenerative disorder of the central nervous system. Parkinson's disease involves the loss of dopamine releasing nerves. Dopamine binds to a number of receptors in the body. Dopamine receptor D4 is involved in certain diseases such as Parkinson's disease and schizophrenia. It is important to consult a physician for the diagnosis and treatment of Parkinson's disease and other medical conditions.
Mechanism
The exact mechanism leading to Parkinson's disease is unknown. However, it culminates in the loss of nerve cells, called neurons, in a part of the mid-brain called the substantia nigra, pars compacta. These neurons release dopamine, which binds to the D4 dopamine receptor. The progressive loss of these neurons leads to the symptoms of the disease.
Symptoms and Signs
Parkinson's disease leads to a resting tremor and the condition bradykinesia, which means a slowing of movement. Parkinson's disease causes difficulty initiating and maintaining voluntary movements, which require a set level of dopamine binding to D4 receptors. This can even progress to difficulty swallowing. Other problems from the disease can include psychiatric features such as depression.
Risk Factors
Agents in the environment may increase the risk of Parkinson's disease, but this is not confirmed. Environmental risk factors may include heavy metals and certain herbicides and pesticides. The risk is also increased if a family member has the disease, being male, with some anxiety disorders and increasing age.
Diagnosis and Treatment
Parkinson's disease is a clinical diagnosis, meaning it is not established by labs. Instead it is diagnosed by a history and physical exam. Other tests such as imaging may be done to rule out other disorders. There is no cure for the disease, but treatment involves several types of medications. Levodopa enters the brain and is converted by the body into dopamine, which then binds to the D4 receptor. Some other drugs mimic the effects of dopamine by activating the D4 receptor. MAO-B inhibitors decrease the breakdown of dopamine. Deep brain stimulation and surgery are less commonly used.
References
- "Harrison's Principles of Internal Medicine"; Anthony S Fauci, et al.; 17th Ed 2008
- "Neuroscience"; Dale Purves; 4th Ed. 2007
- "Robbins and Cotran Pathologic Basis of Disease"; Vinay Kumar, et al.; 8th Ed 2009
