reactive components of effector tissues, most of which are innervated by adrenergic postganglionic fibers of the sympathetic nervous system. Such receptors can be activated by norepinephrine and/or epinephrine and by various adrenergic drugs; receptor activation results in a change in effector tissue function, such as contraction of arteriolar muscles or relaxation of bronchial muscles; adrenergic receptors are divided into α-receptors and β-receptors, on the basis of their response to various adrenergic activating and blocking agents.
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.
ad·re·ner·gic re·cep·tors(ad'rĕ-nĕr'jik rĕ-sep'tŏrz)
Reactive components of effector tissues, most of which are innervated by adrenergic postganglionic fibers of the sympathetic nervous system. Such receptors can be activated by norepinephrine and/or epinephrine and by various adrenergic drugs.