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Pharmacology · single question

Histamine causes all of the following EXCEPT:

  1. Release of secretion from exocrine glands
  2. Contraction of peripheral (non-vascular) striated muscle
  3. Contraction of vascular smooth muscle (vasoconstriction)
  4. Relaxation of vascular smooth muscle (vasodilation)
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Correct answer: B. Contraction of peripheral (non-vascular) striated muscle

  • A. INCORRECT — Histamine increases exocrine secretions (e.g., gastric acid via H2 receptors on parietal cells, mucus secretion) — this IS a correct effect.
  • B. CORRECT (EXCEPTION) — Histamine does NOT cause contraction of non-vascular striated (skeletal) muscle. Histamine acts on H1/H2 receptors on smooth muscle, endothelium, and glands — not on striated/skeletal muscle.
  • C. INCORRECT — Histamine can cause vasoconstriction in some vascular beds (via H1 receptors on larger vessels), though vasodilation predominates in the microcirculation.
  • D. INCORRECT — Histamine causes vasodilation (via H1 and H2 receptors on vascular smooth muscle), which is the basis of the 'triple response' and allergic vascular effects.

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