Histamine acts through 4 types of receptors on target cells.
|
Receptor
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Sites
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H1R
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smooth muscle, endothelial cells, central nervous system
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|
H2R
|
gastric parietal cells, myocytes, mast cells, central nervous system
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|
H3R
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presynaptic nerve nerve fibers (affects nocioceptive fibers), myenteric plexus
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|
H4R
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hematopoietic cells
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Clinical effects are mediated by:
(1) smooth muscle contraction
(2) vasodilatation and increased vascular permeability
(3) mucous gland secretion
(4) increased gastric acid secretion
(5) altered CNS functions
(6) hematopoiesis
Signs and symptoms may include:
(1) headache
(2) tachycardia
(3) cardiac arrhythmias
(4) changes in blood pressure (hypertension or hypotension)
(5) dysmenorrhea in females
(6) abdominal cramps
(7) diarrhea
(8) nausea and vomiting
(9) bronchoconstriction/bronchospasm (asthma) and dyspnea
(10) rhinorrhea and nasal congestion
(11) urticaria and pruritis
(12) cutaneous flushing
(13) vertigo
(14) excess gastric acid (peptic ulcer disease, GERD)
