What is the mechanism of action of tolcapone?

The correct choice highlights that tolcapone acts as a catechol-O-methyltransferase (COMT) inhibitor. This mechanism is crucial in the context of Parkinson's disease treatment, where levodopa is a primary pharmacological therapy.

Once levodopa is administered, it is converted to dopamine in the brain to help alleviate motor symptoms. However, before it can exert its therapeutic effects, levodopa can be metabolized peripherally, primarily by the enzyme COMT. By inhibiting COMT, tolcapone effectively reduces the peripheral conversion of levodopa into inactive metabolites. This action increases the availability of levodopa in the central nervous system, allowing for greater dopaminergic stimulation in the brain. As a result, patients may experience improved symptom control.

In contrast, other mechanisms mentioned in the other choices do not apply to tolcapone. For example, inhibiting dopamine reuptake pertains to other classes of medications that focus on increasing synaptic dopamine levels but is not relevant for tolcapone. Stimulating dopamine receptors refers to drugs that mimic dopamine's effects directly at the receptor level, not through inhibition of COMT. Enhancing acetylcholine activity is related to different neurological mechanisms and does not relate to the