Final answer:
Antiparkinsonian medications, such as L-DOPA and selegiline, act to increase dopamine levels in the brain to alleviate symptoms of Parkinson's disease.
Step-by-step explanation:
An example of antiparkinsonian medication is L-DOPA, which is converted into dopamine in the brain to improve dopamine neurotransmission. Another drug selegiline (Emsam), works by inhibiting the enzyme monoamine oxidase, which normally breaks down dopamine, thus increasing its levels. It is important to note that individuals with Parkinson's disease have low levels of dopamine due to the loss of dopaminergic neurons in the substantia nigra, and medications like dopamine agonists are prescribed to mimic the effects of dopamine.