Which statement describes how anticholinergic drugs work?

• A. They inhibit binding of acetylcholine to muscarinic receptors
• B. They enhance acetylcholine in the synapse
• C. They block dopamine receptors
• D. They activate GABA receptors

Answer: (A)

Anticholinergic drugs work by blocking muscarinic acetylcholine receptors, so acetylcholine cannot bind and exert its parasympathetic effects. This receptor antagonism reduces parasympathetic activity, leading to effects like decreased secretions, relaxed smooth muscle in some tissues, pupil dilation, and increased heart rate. Because they prevent acetylcholine from acting at those receptors, they do not increase acetylcholine in the synapse.

The other ideas describe actions outside this mechanism: enhancing acetylcholine would boost parasympathetic activity (opposite of what anticholinergics do), blocking dopamine receptors relates to antipsychotic effects, and activating GABA receptors pertains to certain sedatives or anticonvulsants.