VPT 321: Veterinary Neuropharmacology (2+1)

HISTAMINE

• Histamine is a tissue amine derived from the word histos meaning “tissue”.
• Histamine is present in animal tissues and certain plants (stinging nettle).
• This autacoid is a mediator of hypersensitivity phenomenon and tissue injury reactions.
• It is stored in storage granules of mast cells (tissue phagocytes) and basophils.
• Tissues rich in histamine are skin, gastric and intestinal mucosa, lungs, liver and placenta.
• Non-mast cell histamine occurs in the brain, epidermis, gastric mucosa and growing region.
• The turnover of mast cell histamine is slow, while that of non-mast cell is fast.
• Histamine is also present in blood, most body secretions, venom and pathological fluids.

Release of histamine

• Histamine is released during the following situations
  • Allergic reactions
  • Cellular injury that may be caused by mechanical, thermal or radiation stimulus
  • Administration of certain drugs / compounds  like morphine, d-tubocurarine, succinylcholine, contrast medium, vancomycin, 48/80 etc.
• Histamine is released from mast cells in response to IgE-mediated allergic reactions secondary to presentation of an antigen and is one of the principal mediators of hay fever, allergic rhinitis, urticaria and angioedema.