Histamine Receptor - Comparison

Comparison

Histamine receptors
Receptor Mechanism Function Antagonists
H1 Gq
  • ileum contraction
  • modulate circadian cycle
  • itching
  • systemic vasodilatation
  • bronchoconstriction (allergy-induced asthma)
  • H1-receptor antagonists
    • Diphenhydramine
    • Loratadine
    • Cetirizine
    • Fexofenadine
H2 Gs
↑ Ca2+
  • speed up sinus rhythm
  • Stimulation of gastric acid secretion
  • Smooth muscle relaxation
  • Inhibit antibody synthesis, T-cell proliferation and cytokine production
  • H2-receptor antagonists
    • Ranitidine
    • Cimetidine
    • Famotidine
    • Nizatidine
H3 Gi
  • Decrease Acetylcholine, Serotonin and Norepinephrine Neurotransmitter release in CNS
  • Presynaptic autoreceptors
  • H3-receptor antagonists
    • ABT-239
    • Ciproxifan
    • Clobenpropit
    • Thioperamide
H4 Gi
  • mediate mast cell chemotaxis.
  • H4-receptor antagonists
    • Thioperamide
    • JNJ 7777120

There are several splice variants of H3 present in various species. Though all of the receptors are 7-transmembrane g protein coupled receptors, H1 and H2 are quite different from H3 and H4 in their activities. H1 causes an increase in PIP2 hydrolysis, H2 stimulates gastric acid secretion, and H3 mediates feedback inhibition of histamine.

Read more about this topic:  Histamine Receptor

Famous quotes containing the word comparison:

    “[Girls] study under the paralyzing idea that their acquirements cannot be brought into practical use. They may subserve the purposes of promoting individual domestic pleasure and social enjoyment in conversation, but what are they in comparison with the grand stimulation of independence and self- reliance, of the capability of contributing to the comfort and happiness of those whom they love as their own souls?”
    —Sarah M. Grimke (1792–1873)

    “The comparison between Coleridge and Johnson is obvious in so far as each held sway chiefly by the power of his tongue. The difference between their methods is so marked that it is tempting, but also unnecessary, to judge one to be inferior to the other. Johnson was robust, combative, and concrete; Coleridge was the opposite. The contrast was perhaps in his mind when he said of Johnson: “his bow-wow manner must have had a good deal to do with the effect produced.””
    —Virginia Woolf (1882–1941)

    “Clay answered the petition by declaring that while he looked on the institution of slavery as an evil, it was ‘nothing in comparison with the far greater evil which would inevitably flow from a sudden and indiscriminate emancipation.’”
    —State of Indiana, U.S. public relief program (1935-1943)