Adrenoceptor
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(preferred to adrenergic receptor) There are three classes, α1-, α2-, and β-adrenoceptors, each with several subtypes. The α1-adrenoceptor subtypes are α1A, α1B, and α1D (note subscript characters); the α2-adrenoceptor subtypes are α2A, α2B, and α2C; the β-adrenoceptor subtypes are β1, β2, and β3.
Oxford Dictionary of Biochemistry:
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adrenoceptor
or adrenergic receptor or adrenoreceptor or adrenotropic receptor
any receptor on an effector cell that is activated by epinephrine or related catecholamines. Structurally, they are all of the 7TM type. Adrenoceptors may be classified phenomenologically into different types according to their sensitivities to agonists and antagonists. α Adrenoceptors have a relative order of agonist potency: epinephrine > norepinephrine > isoprenaline (isoproterenol), and a relative order of antagonist potency: phentolamine >> propranolol. They are associated with stimulatory effects, such as vasoconstriction and contraction of the iris, nictitating membrane, urinary bladder, seminal vesicles, and vas deferens, and with relaxation of propulsive smooth muscle in the gut. In some species, they mediate stimulation of gluconeogenesis and hepatic glycogenolysis. There are two groups, α1 and α2. α1 receptors act through the phosphoinositide/Ca2+ second messenger system and are of four subtypes: α1A, norepinephrine > epinephrine; α1B, norepinephrine = epinephrine; α1C, norepinephrine = epinephrine (different antagonist sensitivity from α1B); α1D. α2A receptors all inhibit the formation of cyclic AMP; they also open K+ channels and inhibit Ca2+ channels. α2B receptors inhibit Ca2+ channels. α2C receptors have no effect on ion channels. β Adrenoceptors have actions that can be ascribed to the activation of adenylate cyclase. They may be divided phenomenologically into three classes: (1) β1 adrenoceptors, in which the relative order of agonist potency is isoprenaline > norepinephrine > epinephrine, and the relative order of antagonist potency is practolol > propranolol. They are associated with cardiac stimulation and glycogenolysis, lipolysis in white adipose tissue, and calorigenesis in brown adipose tissue; (2) β2 adrenoceptors, in which the relative order of agonist potency is isoprenaline > epinephrine > norepinephrine, and the relative order of antagonist potency is propranolol > practolol; they are associated with skeletal muscle glycogenolysis, promotion of secretion of glucagon and insulin, vasodepression and bronchodilation; and (3) β3 adrenoceptors, with agonist potency norepinephrine > epinephrine. See also β-adrenergic receptor kinase, β-arrestin.
any receptor on an effector cell that is activated by epinephrine or related catecholamines. Structurally, they are all of the 7TM type. Adrenoceptors may be classified phenomenologically into different types according to their sensitivities to agonists and antagonists. α Adrenoceptors have a relative order of agonist potency: epinephrine > norepinephrine > isoprenaline (isoproterenol), and a relative order of antagonist potency: phentolamine >> propranolol. They are associated with stimulatory effects, such as vasoconstriction and contraction of the iris, nictitating membrane, urinary bladder, seminal vesicles, and vas deferens, and with relaxation of propulsive smooth muscle in the gut. In some species, they mediate stimulation of gluconeogenesis and hepatic glycogenolysis. There are two groups, α1 and α2. α1 receptors act through the phosphoinositide/Ca2+ second messenger system and are of four subtypes: α1A, norepinephrine > epinephrine; α1B, norepinephrine = epinephrine; α1C, norepinephrine = epinephrine (different antagonist sensitivity from α1B); α1D. α2A receptors all inhibit the formation of cyclic AMP; they also open K+ channels and inhibit Ca2+ channels. α2B receptors inhibit Ca2+ channels. α2C receptors have no effect on ion channels. β Adrenoceptors have actions that can be ascribed to the activation of adenylate cyclase. They may be divided phenomenologically into three classes: (1) β1 adrenoceptors, in which the relative order of agonist potency is isoprenaline > norepinephrine > epinephrine, and the relative order of antagonist potency is practolol > propranolol. They are associated with cardiac stimulation and glycogenolysis, lipolysis in white adipose tissue, and calorigenesis in brown adipose tissue; (2) β2 adrenoceptors, in which the relative order of agonist potency is isoprenaline > epinephrine > norepinephrine, and the relative order of antagonist potency is propranolol > practolol; they are associated with skeletal muscle glycogenolysis, promotion of secretion of glucagon and insulin, vasodepression and bronchodilation; and (3) β3 adrenoceptors, with agonist potency norepinephrine > epinephrine. See also β-adrenergic receptor kinase, β-arrestin.
| adrenergic receptor, adrenergic, adrenalectomy | |
| adrenochrome, adrenocortical, adrenocorticotropic hormone |
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