This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: C.N.S, Subject name: Pharmacology
Selegiline acts by: 
Select and explain. 
A. MAO-A inhibition, B. MAO-B inhibition, C. COMT inhibition, D. Dopamine receptor stimulator
B: MAO-B inhibition
Answer: B: MAO-B inhibition 
Explanation: (Ref: Katzung 14th ed. pg. 499)* After release of DA in synaptic cleft, it is metabolized either by MAO-b or by COMT (catechol-ortho methyl transferase)* In order to prevent this metabolism following drugs can be given, which will enhance DA availability:# MAO-b inhibitor: Selegiline, Rasagiline, safinamide# COMT inhibitor: Entacapone, TolcaponeDrugs stimulating DA receptor:* Ergot Derivative: Bromocriptine, Cabergoline* Non-Ergot: Pramipexole, Ropinirole, Rotigotine (available as transdermal patch)