Histamine
Histamine is produced from the amino acid histidine by a histidine decarboxylase and is metabolised by the combined actions of histamine methyltransferase and MAO.
Histamine exerts its actions by combining with the following histamine receptors (see table).
Histamine exerts its actions by combining with the following histamine receptors (see table).
| Histamine receptor | Location | Function |
|---|---|---|
| H1 | CNS tissue, smooth muscle, and endothelium | Vasodilation, bronchoconstriction, pain and itching from stings |
| H2 | Parietal cells in stomach | Stimulates gastric acid secretion |
| H3 | Central and peripheral nervous tissue | Decreases the release of other neurotransmitters (serotonin, noradrenaline, acetylcholine) |
| H4 | Basophils | Chemotaxis (cellular movement) |
