Increased mucous secretion in acute asthma is primarily caused by the release of which substance?

Correct answer: B. Acetylcholine

• A. ❌ Serotonin is not the primary mediator of mucous hypersecretion in asthma.
• B. ✅ Correct. Acetylcholine stimulates muscarinic receptors (M3) in airway goblet cells and submucosal glands, causing increased mucous secretion AND bronchoconstriction in asthma. Anticholinergic drugs (e.g., ipratropium) are used to counteract this.
• C. ❌ Histamine causes bronchoconstriction and vasodilation, but acetylcholine is the primary mediator of mucous hypersecretion.
• D. ❌ Norepinephrine acts on β2 receptors to cause bronchodilation — the opposite of bronchoconstriction.