Pharmacology · single question
Histamine causes all of the following EXCEPT:
Show answer and explanation
Correct answer: C. Contraction of peripheral striated (skeletal) muscle
Histamine's classic effects are: contraction of non-vascular smooth muscle (e.g., bronchoconstriction, GI contraction), relaxation/dilation of vascular smooth muscle (vasodilation, a hallmark of the flare/wheal response and anaphylaxis), and stimulation of exocrine gland secretion (e.g., gastric acid, mucus). Histamine has no significant direct action on striated (skeletal) muscle — it does not cause skeletal muscle contraction, making that the exception.
- A. Histamine stimulates gastric acid secretion via H2 receptors and increases exocrine secretions — this IS a histamine effect.
- B. Histamine contracts non-vascular smooth muscle (bronchi, intestine) via H1 receptors — this IS a histamine effect.
- C. Correct. Histamine does NOT contract striated (skeletal) muscle. Skeletal muscle contraction is under neuromuscular (acetylcholine/nicotinic receptor) control, not histamine.
- D. Histamine causes vasodilation via H1/H2 receptors on vascular endothelium and smooth muscle — this IS a histamine effect.