What physiological change is caused by cholinergic agents in the respiratory system?

Cholinergic agents, which mimic the effects of the neurotransmitter acetylcholine, activate the parasympathetic nervous system. In the context of the respiratory system, these agents lead to bronchoconstriction. This is due to stimulation of muscarinic receptors located in the bronchial smooth muscle, resulting in contraction and narrowing of the airways.

This bronchoconstriction causes a reduction in airflow, which is relevant for conditions such as asthma where excessive constriction can contribute to difficulty breathing. Thus, cholinergic agents effectively manage certain respiratory conditions by modulating the tone of the bronchial passages.