adrenergic receptors

ad·re·ner·gic re·cep·tors

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.

Synonym(s): adrenoceptor, adrenoreceptors

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 the sympathetic nervous system. Such receptors can be activated by norepinephrine, epinephrine, and adrenergic drugs; receptor activation results in a change in effector tissue function, such as contraction of arteriolar muscles or relaxation of bronchial muscles.
Synonym(s): adrenoreceptor.

adrenergic receptors 

Receptors which are stimulated by the catecholamines adrenaline (epinephrine) and noradrenaline (norepinephrine). These receptors belong to a family of G protein coupled receptors and are found in the central nervous system and many tissues innervated by the peripheral nervous system. There are two types of adrenergic receptors: (1) α-receptors, which are mainly excitatory to smooth muscles and gland cells but cause relaxation of intestinal smooth muscles; (2) β-receptors of which there are (at least) two types, β₁ and β₂. Generally, stimulation of β-receptors produces an inhibitory response, although in some cases the effect is excitatory (e.g. in the heart). Example: the dilator pupillae muscle contains mainly α-adrenergic receptors and stimulation (e.g. with adrenaline) produces mydriasis. On the other hand, there are drugs that block the effect of catecholamines on α- or β-adrenergic receptors and are called α- or β-blockers (or sympatholytic drugs or adrenergic receptor agonists). Example: the ciliary epithelium contains mainly β-receptors and a β-blocker such as timolol inhibits the secretion of aqueous humour, thus reducing intraocular pressure. Syn. adrenoceptor. See alpha-adrenergic agonists; alpha-adrenergic antagonists; beta-blocker; miotics; mydriatic; sympatholytic drugs; sympathomimetic drugs; autonomic nervous system.

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.
Synonym(s): adrenoceptor.