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Most histamine in the body is generated in granules in mast cells and in white blood cells (leukocytes) called basophils. Mast cells are especially numerous at sites of potential injury – the nose, mouth, and feet, internal body surfaces, and blood vessels.
Mast cells are present in most tissues characteristically surrounding blood vessels, nerves and lymphatic vessels, [11] and are especially prominent near the boundaries between the outside world and the internal milieu, such as the skin, mucosa of the lungs, and digestive tract, as well as the mouth, conjunctiva, and nose. [7]
The histamine receptors are a class of G protein–coupled receptors which bind histamine as their primary endogenous ligand. [1] [2] Histamine receptors are proteins that bind with histamine, a neurotransmitter involved in various physiological processes. There are four main types: H1, H2, H3, and H4.
The H 1 receptor is a histamine receptor belonging to the family of rhodopsin-like G-protein-coupled receptors.This receptor is activated by the biogenic amine histamine.It is expressed in smooth muscles, on vascular endothelial cells, in the heart, and in the central nervous system.
Histamine is an organic compound that primarily functions in service of the human body's immune responses as well as for the regulation of many physiological functions. [1] Since their discovery in 1910, [ 2 ] histamines have been known to trigger inflammatory responses such as itching as part of an immune response to foreign pathogens; for ...
The histamine receptor H 2 belongs to the rhodopsin-like family of G protein-coupled receptors. It is an integral membrane protein and stimulates gastric acid secretion. It also regulates gastrointestinal motility and intestinal secretion and is thought to be involved in regulating cell growth and differentiation. [ 6 ]
Histamine makes blood vessels more permeable (vascular permeability), causing fluid to escape from capillaries into tissues, which leads to the classic symptoms of an allergic reaction—a runny nose and watery eyes. Histamine also promotes angiogenesis. [6]
Mouse-models and other research demonstrated that reducing histamine concentration in the H3R causes tics, but adding histamine in the striatum decreases the symptoms. [ 22 ] [ 23 ] [ 24 ] The interaction between histamine (H3-receptor) and dopamine as well as other neurotransmitters is an important underlying mechanism behind the disorder.