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Although histamine is small compared to other biological molecules (containing only 17 atoms), it plays an important role in the body. It is known to be involved in 23 different physiological functions. Histamine is known to be involved in many physiological functions because of its chemical properties that allow it to be versatile in binding.
Histamine intolerance is a presumed set of adverse reactions (such as flush, itching, rhinitis, etc.) to ingested histamine in food. The mainstream theory accepts that there may exist adverse reactions to ingested histamine, but does not recognize histamine intolerance as a separate medical condition that can be diagnosed. [1]
The vomiting center in the medulla, called the area postrema, contains high concentrations of substance P and its receptor, in addition to other neurotransmitters such as choline, histamine, dopamine, serotonin, and endogenous opioids. Their activation stimulates the vomiting reflex.
Histamine is a weak base (a compound able to react with a hydrogen ion to form an acid) that can link with acid groups within the granules of the mast cells. [8] The mechanism of the displacement theory. The crux of this theory lies in the assumption that histamine liberators release histamine by displacing it from cells.
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.
Like all histamine receptors, the H 3 receptor is a G-protein coupled receptor. The H 3 receptor is coupled to the G i G-protein , so it leads to inhibition of the formation of cAMP . Also, the β and γ subunits interact with N-type voltage gated calcium channels , to reduce action potential mediated influx of calcium and hence reduce ...
For instance, epinephrine raises arterial pressure through vasoconstriction mediated by A1-adrenergic receptor activation, in contrast to histamine, which lowers arterial pressure. Thus, despite not being true antihistamines because they do not bind to and block the histamine receptor, epinephrine and other such substances are physiological ...
Histidine decarboxylase is the primary biological source of histamine. Histamine is an important biogenic amine that moderates numerous physiologic processes. There are four different histamine receptors, H 1, H 2, H 3, and H 4, [16] each of which carries a different biological significance.