histamine

Examples of histamine in the following topics:

• Types of Neurotransmitters by Function

  • Biogenic amines include the catecholamines, such as dopamine, norepinephrine (NE), and epinephrine, as well as indolamines such as serotonin and histamine.
  • Histamine is synthesized from amino acid histidine.
  • NE, dopamine, and histamine can be excitatory or inhibitory depending on the receptor type.

• Gastric Phase

  • Gastric secretion is stimulated chiefly by three chemicals: acetylcholine (ACh), histamine, and gastrin.
  • Histamine is a paracrine secretion from the enteroendocrine cells in the gastric glands.

• Type I (Anaphylactic) Reactions

  • The mast cells and basophils react by releasing inflammatory mediators such as histamine.
  • When anaphylaxis is not caused by in immune response, the reaction is due to an agent that directly damages mast cells and basophils, causing them to release histamine and other substances that are usually associated with an allergic reaction (degranulation).

• Allergic Responses to Drugs

  • This results in the production of histamines.
  • Anaphylaxis is an extremely severe allergic reaction caused when histamines are overproduced leading to severe contraction of bronchial muscles.

• Pathogen Recognition

  • A mast cell is a leukocyte that produces inflammatory molecules, such as histamine, in response to large pathogens.
  • A hypersensitive immune response to harmless antigens, such as in pollen, often involves the release of histamine by basophils and mast cells; this is why many anti-allergy medications are anti-histamines.
  • In response to a cut, mast cells secrete histamines that cause nearby capillaries to dilate.

• Cephalic Phase

  • Cephalic phase causes ECL cells to secrete histamine and increase HCl acid in the stomach.

• Hypersensitivities

  • Upon subsequent exposure to the same allergen, IgE molecules on mast cells bind the antigen via their variable domains, stimulating the mast cell to release the modified amino acids histamine and serotonin.
  • On secondary exposure, the mast cells release histamines and other modulators that affect the symptoms of allergy.

• Inflammation

  • The most common short term mediators are histamine and seratonin from mast cells, but bradykinin, complement proteins, some interleukins, prostaglandins, and TNF-alpha may also trigger inflammation from other types of cells.
  • Circulating mast cells contain toll-like receptors, which can detect pathogen-associated molecular patterns (PAMPS) on the surface of pathogens and release an inflammatory mediator such as histamine in response.

• WBC Function

  • When a pathogen is detected, or when vascular endothelial cells release stress cytokines from injury (such as a cut) leukocytes will release a variety of inflammatory cytokines (such as histamine or TNF-alpha) that cause vasodilation, increased vascular permeability, and promote neutrophil movement to the site of inflammation.

• Ionotropic and Metabotropic Receptors

  • Examples of metabotropic receptors include glutamate receptors, muscarinic acetylcholine receptors, GABAB receptors, most serotonin receptors, and receptors for norepinephrine, epinephrine, histamine, dopamine, neuropeptides, and endocannabinoids.