How does a parasympatholytic drug primarily affect parasympathetic signaling?

• A. Increases acetylcholine release
• B. Inhibits adrenergic receptors
• C. Binding to receptors and blocking release of acetylcholine
• D. Stimulates nicotinic receptors

Answer: (C)

Parasympatholytic drugs blunt parasympathetic signaling by interfering with acetylcholine pathways. They primarily bind to muscarinic receptors, blocking acetylcholine from activating them, which reduces parasympathetic effects on target organs. Some agents also reduce acetylcholine release at the nerve terminal, further diminishing signaling. This combination best captures how parasympatholytics dampen rest-and-digest activities. The other actions described would either raise parasympathetic activity, target the sympathetic system, or stimulate receptors that promote transmission, which does not align with reducing parasympathetic signaling.