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amantadine toxicity p. 568
Anti-parkinson medications are used to treat Parkinson’s disease, which is a movement disorder where the dopamine-producing neurons in the substantia nigra of the brain undergo degeneration. It’s a progressive, adult-onset disease, and is more common with age, affecting about 1% of people over 60. The substantia nigra is a part of the basal ganglia, a collection of nuclei in the brain that control movement through their connections with the motor cortex. The substantia nigra actually can be split into two sub-regions. First, there’s the pars reticulata, which receives signals from another part of the basal ganglia called the striatum, and relays messages to the thalamus via neurons rich in the neurotransmitter GABA, also known as gamma-aminobutyric acid. Second, there’s the pars compacta, and this is the part of the substantia nigra affected in Parkinson’s.
The pars compacta sends messages to the striatum via neurons rich in the neurotransmitter dopamine, forming the nigrostriatal pathway, which helps to stimulate the cerebral cortex and initiate movement. In Parkinson’s disease, the neurons in the substantia die, so the individual may experience hypokinesia, which is difficulty initiating movements, and bradykinesia, or slowed movements. The substantia nigra also helps to calibrate and fine tune a person’s movements, which leads to the other clinical features of Parkinson’s, like “pill-rolling” tremor, which is the repetitive, involuntary rubbing of the thumb and index finger, as well as rigidity, stooped posture, and an expressionless, mask-like face. As the neurodegeneration progresses, non-motor dysfunction can appear, including depression, dementia, sleep disturbances, and difficulty smelling.
Parkinson's disease is a neurodegenerative disorder in which there is progressive depletion of dopaminergic neurons in the basal ganglia, especially in the substantia nigra. Anti-Parkinson medications are drugs used in the management of this disorder.
There are a few different classes of medications used to manage Parkinson's Disease. These include dopamine precursors such as levodopa (L-Dopa); dopaminergic drugs such as bromocriptine that increases the amount of dopamine in the brain; monoamine oxidase (MAO)-B inhibitors like rasagiline that blocks an enzyme that breaks down dopamine; and catechol-O-methyltransferase (COMT) inhibitors such as tolcapone which work by stopping an enzyme from breaking down levodopa.
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