A
muscarinic receptor antagonist (MRA) is a type of
anticholinergic agent that blocks the activity of the
muscarinic acetylcholine receptor.
Acetylcholine (often abbreviated
ACh) is a neurotransmitter whose receptor is a protein found in
synapses and other cell membranes. Besides responding to their primary neurochemical, neurotransmitter receptors can be sensitive to a variety of other molecules. Acetylcholine receptors are classified into two groups based on this: