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Pharmacology · single question

Histamine causes all of the following EXCEPT:

  1. Relaxation (dilation) of vascular smooth muscle
  2. Contraction of peripheral striated muscle
  3. Release of secretions from exocrine glands
  4. Contraction of non-vascular smooth muscle (bronchospasm, GI cramps)
Show answer and explanation

Correct answer: B. Contraction of peripheral striated muscle

  • A. Histamine causes VASODILATION (relaxation of vascular smooth muscle) via H1/H2 receptors — leading to the classic 'triple response' (flare, wheal, redness). This IS a histamine effect.
  • B. Histamine does NOT cause contraction of peripheral STRIATED (skeletal) muscle. Striated muscle is controlled by acetylcholine at the neuromuscular junction — histamine has no direct effect on skeletal/striated muscle contraction. This is the EXCEPTION.
  • C. Histamine stimulates gastric acid secretion (H2 receptors on parietal cells) and mucus/exocrine secretion. This IS a histamine effect.
  • D. Histamine causes CONTRACTION of non-vascular smooth muscle via H1 receptors — this includes bronchospasm (asthma-like response), GI cramping, and uterine contraction. This IS a histamine effect.

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