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Beta-adrenergic agonist
Beta-adrenergic agonists or Beta-agonists are medications that relax muscles of the airways, which widens the airways and results in easier breathing. They are a class of sympathomimetic agents which act upon the beta adrenoceptors. In general, pure beta-adrenergic agonists have the opposite function of beta blockers. Beta adrenoreceptor agonist ligands mimic the action of epinephrine and norepinephrine signaling in the heart, lungs and smooth muscle tissue, with epinephrine being the highest affinity. The activation of β1, β2 and β3 activates the enzyme, Adenylate cyclase. This in turn leads to the activation of the secondary messenger Cyclic adenosine monophosphate and induces smooth muscle relaxation and contraction of the cardiac tissue.
==Function==
Activation of β1 receptors induces positive inotropic, chronotropic output of the cardiac muscle, leading to increased heart rate and blood pressure, secretion of ghrelin from the stomach, and renin release from the kidneys.
Activation of β2 receptors induces smooth muscle relaxation in the lungs, gastrointestinal tract, uterus, and various blood vessels. Increased heart rate and heart muscle contraction is also associated with the β2 receptors. β3 receptors are mainly located in adipose tissue.
Activation of the β3 receptors induces the metabolism of lipids.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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