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It has been known for more than one hundred years that an intravenous injection of histamine causes a fall in the blood pressure. [30] The underlying mechanism concerns both vascular hyperpermeability and vasodilation. Histamine binding to endothelial cells causes them to contract, thus increasing vascular leak.
The extent of vasoconstriction may be slight or severe depending on the substance or circumstance. Many vasoconstrictors also cause pupil dilation. Medications that cause vasoconstriction include: antihistamines, decongestants, and stimulants. Severe vasoconstriction may result in symptoms of intermittent claudication. [1]
Vasodilation works to decrease vascular resistance and blood pressure through relaxation of smooth muscle cells in the tunica media layer of large arteries and smaller arterioles. [17] When vasodilation causes systolic blood pressure to fall below 90 mmHg, circulatory shock is observed. [11]
“Histamine is released in the body and enters the gastrointestinal tract, which can cause gas, bloating, nausea, stomach pains and diarrhea.” He notes specific foods that can make seasonal ...
Once released, the histamine can react with local or widespread tissues through histamine receptors. [citation needed] Histamine, acting on H 1-receptors, produces pruritus, vasodilation, hypotension, flushing, headache, bradycardia, bronchoconstriction, increase in vascular permeability and potentiation of pain. [2]
Anaphylactic shock is caused by a severe anaphylactic reaction to an allergen, antigen, drug, or foreign protein causing the release of histamine which causes widespread vasodilation, leading to hypotension and increased capillary permeability. Signs of anaphylaxis Signs typically occur after exposure to an allergen and may include:
Vasodilation and its resulting increased blood flow causes the redness (rubor) and increased heat (calor). Increased permeability of the blood vessels results in an exudation (leakage) of plasma proteins and fluid into the tissue ( edema ), which manifests itself as swelling ( tumor ).
Vasodilation and increased permeability of capillaries are a result of both H1 and H2 receptor types. [33] Stimulation of histamine activates a histamine (H2)-sensitive adenylate cyclase of oxyntic cells, and there is a rapid increase in cellular [cAMP] that is involved in activation of H+ transport and other associated changes of oxyntic cells ...