Explanation

A parasympathetic antagonist, also known as an anticholinergic drug, blocks the action of the parasympathetic nervous system. The parasympathetic nervous system generally acts to conserve body resources and maintain homeostasis, including slowing heart rate and promoting digestion. In the kidneys, parasympathetic activation typically decreases the Glomerular Filtration Rate (GFR) by causing vasoconstriction of the afferent arterioles. Therefore, a parasympathetic antagonist would block this action, leading to vasodilation and an increase in GFR.