Final answer:
An antagonistic drug that blocks parasympathetic nerve effects would cause a decrease in parasympathetic activity.
Step-by-step explanation:
An antagonistic drug that blocks parasympathetic nerve effects would cause a decrease in parasympathetic activity. Parasympathetic drugs can be classified into those that increase or decrease activity at postganglionic terminals. Drugs that block muscarinic receptors (anticholinergic drugs) would suppress parasympathetic interaction with the organ.