• Enzymatic Degradation of Catecholamines and COMT Inhibition:
• Catechol-O-Methyltransferase (COMT) catalyzes the transfer of a methyl group from S-adenosylmethionine to a hydroxyl group of catecholamines (dopamine, epinephrine, norepinephrine) and levodopa.
• Entacapone (and Tolcapone) is a selective, reversible COMT inhibitor used in neuropharmacology to prevent peripheral breakdown of levodopa, increasing central dopamine availability.
• Selegiline and Rasagiline are MAO-B inhibitors; Clorgyline is a MAO-A inhibitor.
• nalysis:
• (Entacapone): Correct COMT inhibitor.

Correct option: (3) Entacapone

• Central Neurotransmission of Acetylcholine (ACh):
• In the central nervous system, acetylcholine acting on muscarinic receptors ($M_1$ subtype) produces slow, prolonged excitatory postsynaptic potentials (EPSPs).
• The biochemical mechanism involves $G_q$-protein activation, which closes voltage-gated potassium channels (the M-current / $I_M$), causing a decrease in potassium conductance ($g_{K^+}$).
• Decreased outward $K^+$ efflux leads to membrane depolarization and sustained neuronal excitation.
• (GABA and Glycine increase chloride conductance; Dopamine acts through D1/D2 GPCRs).
• nalysis:
• (Acetylcholine): Correct.

Correct option: (4) Acetylcholine

• Robenidine in Poultry Coccidiosis:
• Robenidine hydrochloride: A synthetic guanidine derivative that acts as a coccidiostat by inhibiting ATP synthesis in first- and second-generation schizonts (acting on the 2nd day of the Eimeria life cycle).
• Meat Taint Risk:
• Robenidine residues deposit in broiler muscle and adipose tissues, imparting a sharp, unpleasant chemical/medicinal taste and odor to the cooked poultry meat.
• Statutory regulations mandate a strict minimum 5-day withdrawal period prior to slaughter to clear tissue residues.
• nalysis:
• (Robenidine): Correct.

Correct option: (4) Robenidine