adrenergic receptor(redirected from Alpha2-adrenergic agonists)
Adrenergic ReceptorAny of a family of G protein-coupled cell membrane receptors which receive neuronal impulses from postganglionic adrenergic fibres of the sympathetic nervous system, which are divided into:
(1) Alpha receptors, which evoke an excitatory response of smooth muscle cells to catecholamines. Alpha receptors are divided into alpha1 (Gq) and alpha2 (Gi) coupled receptors.
Selective agonist, alpha receptor Phenylephrine
Alpha receptor effects Vasoconstriction, reduced GI tract motility.
(2) Beta receptors, which dampen the response to catecholamines. Beta receptors are divided into beta1, beta2, beta3, which are linked to Gs, and adenylate cyclase, increasing cAMP, which in turn drives cAMP-dependent protein kinase that mediates intracellular events.
Selective agonist, beta receptor Isoprenaline
Beta receptor effects Increased cardiac output, increased renin secretion from juxtaglomerular cells, increased gastric ghrelin secretion, smooth muscle relaxation resulting in bronchodilation, reduced GI motility, relaxation of detrusor muscle of the bladder, lipolysis, glycogenolysis and gluconeogenesis, increased renin secretion, insulin secretion, vasodilation, anabolism and thermogenesis of skeletal muscle.
Segen's Medical Dictionary. © 2012 Farlex, Inc. All rights reserved.
adrenergic receptorNeurophysiology Any of a family of cell membrane receptors that receive neuronal impulses from postganglionic adrenergic fibers from the sympathetic nervous sytem, which are divided into α receptors, which results in an excitatory response of smooth muscle cells to catecholamines, and β receptors, which result in an inhibitory response to catecholamines; the GI tract is an exception, in that either α or β receptor stimulation results in relaxation
McGraw-Hill Concise Dictionary of Modern Medicine. © 2002 by The McGraw-Hill Companies, Inc.
There are three families of adrenergic receptors, alpha1, alpha2 and beta, and each family contains three distinct subtypes. Each of the nine subtypes are coded by separate genes, and display specific drug specificities and regulatory properties.
Mentioned in: Alpha 1 -Adrenergic Blockers
Gale Encyclopedia of Medicine. Copyright 2008 The Gale Group, Inc. All rights reserved.