adrenergic blockade

blockade /block·ade/ (blok-ād´)

1. the blocking of the effect of a hormone or neurotransmitter at a cell-surface receptor by a pharmacologic antagonist bound to the receptor.

2. in histochemistry, a chemical reaction that modifies certain chemical groups and blocks a specific staining method.

3. regional anesthesia.

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adrenergic blockade  selective inhibition of the response to sympathetic impulses transmitted by epinephrine or norepinephrine at alpha or beta receptor sites of an effector organ or postganglionic adrenergic neuron.

cholinergic blockade  selective inhibition of cholinergic nerve impulses at autonomic ganglionic synapses, postganglionic parasympathetic effectors, or the neuromuscular junction.

ganglionic blockade  inhibition by drugs of nerve impulse transmission at autonomic ganglionic synapses.

narcotic blockade  inhibition of the euphoric effects of narcotic drugs by the use of other drugs, such as methadone, in the treatment of addiction.

neuromuscular blockade  a failure in neuromuscular transmission that can be induced pharmacologically or may result from pathological disturbances at the myoneural junction.

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adrenergic blockade

n.

Selective inhibition by a drug of the responses of effector cells to adrenergic sympathetic nerve impulses and to adrenergic amines.

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adrenergic

1. activated by, characteristic of, or secreting epinephrine or substances with activities similar to those of epinephrine. The term is applied to those nerve fibers of the sympathetic nervous system that release norepinephrine (and possibly small amounts of epinephrine) at a synapse when a nerve impulse passes.

2. an agent that acts like epinephrine. Called also sympathomimetic.

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adrenergic agents

sympathomimetic amines which exert their effects on adrenergic receptors of effector cells innervated by the sympathetic nervous system. The administration of these adrenergic agonists mimics the physiological effects of sympathoadrenal discharge.

adrenergic alpha-blockers, beta-blockers

see adrenergic blockade.

adrenergic amines

these are the sympathomimetic amines. They have similar but not identical structures and actions. Epinephrine, norepinephrine and isoproterenol are catecholamines but differ in their effects. Norepinephrine is primarily an activator of alpha-receptors whereas isoproterenol is a selective beta-receptor agonist. Epinephrine is an active agonist for both alpha- and beta-receptors. Ephedrine is the classical noncatecholamine sympathetic agonist.

adrenergic blockade

adrenergic blocking agents prevent the activation of adrenergic receptors. They may be alpha-blockers, e.g. ergot, or beta-blockers such as propranolol.

adrenergic blocking agent

a drug that blocks the secretion of epinephrine and norepinephrine at the postganglionic nerve endings of the sympathetic nervous system. By blocking these adrenergic substances, which cause constriction of blood vessels and increased cardiac output, adrenergic blocking agents produce a dilatation of the blood vessels and a decrease in cardiac output.

adrenergic nerves

see adrenergic (1) (above).

adrenergic nervous system

see sympathetic nervous system.

adrenergic receptors

class of receptors named after the action of adrenalin(e), the alternative name for epinephrine. Alpha receptors, which are stimulated by norepinephrine and blocked by agents such as phenoxybenzamine, are categorized into two classes, α₁ and α₂, which have different actions. α₁ adrenergic actions include contraction of the iris, decreased motility in the intestine, and potassium and water secretions from the salivary glands. α₂ adrenergic receptors inhibit adenylate cyclase, rather than activating it. Beta receptors, which are stimulated by epinephrine and blocked by agents such as propranolol, are also categorized into two types; β₁ adrenergic receptors, which produce lipolysis and cardiostimulation, and β₂ adrenergic receptors, which produce bronchodilatation and vasodilatation.

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blockade

1. in pharmacology, the blocking of the effect of a neurotransmitter or hormone by a drug.

2. in histochemistry, a chemical reaction that modifies certain chemical groups and blocks a specific staining method.

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adrenergic blockade

see adrenergic blockade.

cholinergic blockade

see cholinergic blockade.

narcotic blockade

inhibition of the euphoric effects of narcotic drugs by the use of other drugs, such as methadone, in the treatment of addiction.

sympathetic blockade

block of nerve impulse transmission between a preganglionic sympathetic fiber and the ganglion cell.