The MPTP Model of Parkinson's Disease
Parkinson's disease occurs with damage to the substantia nigra in the brain, interfering with production of the neurotransmitter dopamine. Neurotransmitters are chemical substances that carry impulses (messages) between neurons (nerve cells), and a decrease in dopamine impairs transmission of impulses to motor nerves related to movement, resulting in tremors and impaired mobility. MPTP (methyl-4-phenyl-1,2,5,6-tetrahydropyridine) is a drug that can cause a form of Parkinson's disease.
MPPP to MPTP
According to the medical website My Doctor, MPTP is chemically similar to the illicit street drug MPPP, and if a batch of MPPP becomes contaminated or is improperly manufactured, MPTP can result. When MPTP is metabolized (broken down) in the body, it converts to a neurotoxin, which is a potent poison that targets neurons. In this case, MPTP specifically targets dopamine-producing neurons in the substantia nigra.
Symptoms
As MPTP damages the neurons, dopamine levels fall, and the person begins to exhibit the same symptoms as those with idiopathic (cause unknown) Parkinson's disease: tremors, muscle rigidity, slow movement, unstable gait, depression and sometimes increasing cognitive impairment and dementia. The face muscles may be relatively immobile, giving a masklike appearance
Differences
MPTP Parkinson's disease presents differently than ideopathic Parkinson's, which usually manifests slowly over a period of years. MPTP causes rapid damage to the neurons because of the neurotoxin, so onset of symptoms may be within days. Additionally, ideopathic Parkinson's disease usually occurs in those 60 or older, while MPTP Parkinson's affects much younger drug users, many in their 20s.
Treatment
Treatment for MPTP Parkinson's disease is the same as for ideopathic Parkinson's disease. According to the National Institute of Neurological Disorders and Stroke, treatment includes anticholinergic drugs to decrease tremors. Levodopa increases dopamine levels while dopamine agonists mimic dopamine, with both types of drugs improving mobility because they improve transmission of impulses through motor neurons. Other drugs include antidepressants for depression, MAO-inhibitors to prevent the breakdown of dopamine and the antiviral drug amantadine (Symmetrol), usually given with other drugs to reduce involuntary muscle twitching.
Considerations
While symptoms from some forms of drug-induced (haloperidol, chlorpromazine) Parkinson's disease are reversible, the damage to the brain is permanent with MPTP. Other neurotoxins that can cause permanent damage include carbon monoxide, manganese dust and carbon disulfide.
Tags: ideopathic Parkinson, MPTP Parkinson, Parkinson disease, Parkinson disease, dopamine levels