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The alpha-2 (α 2) adrenergic receptor (or adrenoceptor) is a G protein-coupled receptor (GPCR) associated with the G i heterotrimeric G-protein. It consists of three highly homologous subtypes, including α 2A-, α 2B-, and α 2C-adrenergic. Some species other than humans express a fourth α 2D-adrenergic receptor as well. [1]
The adrenergic receptors or adrenoceptors are a class of G protein-coupled receptors that are targets of many catecholamines like norepinephrine (noradrenaline) and epinephrine (adrenaline) produced by the body, but also many medications like beta blockers, beta-2 (β 2) antagonists and alpha-2 (α 2) agonists, which are used to treat high ...
Agonists of alpha-2 receptors in the vascular smooth muscle lead to vasoconstriction. However, in clinical practice drugs applied intravenously that are agonists of alpha-2 receptors such as clonidine lead to powerful vasodilation, which causes a decrease in blood pressure by presynaptic activation of the receptors in the sympathetic ganglia.
The alpha-2 blocker acts on alpha-2 receptors. The alpha-2 receptor is a G-protein coupled receptor as well, which exert its action by Gi function, leading to an inhibition of adenylyl cyclase and thus reducing synthesis of cAMP. [3] It lowers the amount of calcium inside the cell. [3]
The alpha-adrenergic receptor has two subclasses α 1 and α 2. Alpha 2 receptors are associated with sympatholytic properties. Alpha-adrenergic agonists have the opposite function of alpha blockers. Alpha adrenoreceptor ligands mimic the action of epinephrine and norepinephrine signaling in the heart, smooth muscle and central nervous system, with
Major autoreceptor which clinically important are alpha 2(adrenergic receptor subtype 2), H 3(histamine receptor subtype 3), 5 HT 1(serotonin receptor subtype 1). In which respective drugs act are Clonidine on alpha 2 as Agonist used in hypertension which reduce release of norepinephrine and epinephrine from presynaptic neurons.
There are several types of adrenergic receptors which are identified by their differing sensitivities to various drugs. Neurons in the central nervous system contain α1- and α2-adrenergic receptors and β1- and β2-adrenergic receptors. [5] All four kinds of receptors are also found in the various organs of the body aside from the brain.
The binding to these receptors by catecholamines will generally stimulate the sympathetic nervous system, the arm of the autonomic nervous system responsible for the fight-or-flight response. Adrenergic receptor autoantibodies are autoantibodies (antibodies directed against a person's own protein) targeting adrenergic receptors.