Which type of receptors do anticholinergic agents selectively block?

Anticholinergic agents selectively block muscarinic acetylcholine receptors. These receptors are part of the autonomic nervous system and are primarily located in various tissues, including the heart, smooth muscles, and glands. When activated by acetylcholine, muscarinic receptors mediate a range of physiological responses such as increased salivation, bronchoconstriction, and slowed heart rate.

By blocking these receptors, anticholinergic agents inhibit these responses, which can lead to effects such as reduced secretions, dilation of airways, and increased heart rate. This mechanism of action is utilized in various clinical situations, such as treating asthma, overactive bladder, and motion sickness.

The other receptor types listed, such as nicotinic receptors, adrenergic receptors, and serotonin receptors, are not the primary targets of anticholinergic agents. Nicotinic receptors are involved in the transmission at neuromuscular junctions and ganglia. Adrenergic receptors are responsible for responses to norepinephrine and epinephrine in the sympathetic nervous system. Serotonin receptors are involved in numerous functions in the central nervous system and peripheral tissues, which are unrelated to the anticholinergic agents' mechanism of action.