Mechanism of action of Tolcapone is –
**Core Concept**
Tolcapone is a reversible inhibitor of catechol-O-methyltransferase (COMT), an enzyme involved in the breakdown of catecholamines such as dopamine, epinephrine, and norepinephrine. By inhibiting COMT, tolcapone increases the availability of these neurotransmitters in the synaptic cleft, thereby enhancing their effects.
**Why the Correct Answer is Right**
Tolcapone selectively inhibits the COMT enzyme, which is responsible for the O-methylation of catecholamines. This leads to an increase in the concentration of dopamine, particularly in the striatum, where it plays a crucial role in motor control. The increased dopamine levels contribute to the therapeutic effects of tolcapone in treating Parkinson's disease. The selective inhibition of COMT by tolcapone also reduces the risk of peripheral side effects associated with dopamine agonists.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as it does not accurately describe the mechanism of action of tolcapone. Tolcapone is not a dopamine agonist, and its primary action is not through direct stimulation of dopamine receptors.
**Option B:** This option is incorrect as it is not a mechanism of action associated with tolcapone. Tolcapone does not have a significant effect on the synthesis or release of dopamine.
**Option C:** This option is incorrect as it describes the mechanism of action of selegiline, a monoamine oxidase B (MAO-B) inhibitor, not tolcapone.
**Clinical Pearl / High-Yield Fact**
Tolcapone is a valuable adjunctive therapy in the management of Parkinson's disease, particularly in patients who are experiencing motor fluctuations or dyskinesias. Its mechanism of action as a COMT inhibitor makes it an effective treatment option for improving motor function and reducing the risk of levodopa-induced dyskinesias.
**Correct Answer: C. Inhibits catechol-O-methyltransferase (COMT)**