antagonist

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antagonist

 [an-tag´o-nist]
antagonistic muscle. (see illustration.)
1. a substance that tends to nullify the action of another, as a drug that binds to a cellular receptor for a hormone, neurotransmitter, or another drug blocking the action of that substance without producing any physiologic effect itself. See also blocking agent.
2. a tooth in one jaw that articulates with one in the other jaw.
α-adrenergic antagonist alpha-adrenergic blocking agent.
β-adrenergic antagonist beta-adrenergic blocking agent.
folic acid antagonist see folic acid antagonist.
H1 receptor antagonist any of a large number of agents that block the action of histamine by competitive binding to the H1 receptor. Such agents also have sedative, anticholinergic, and antiemetic effects, the exact effect varying from drug to drug, and are used for the relief of allergic symptoms and as antiemetics, antivertigo agents, sedatives, and antidyskinetics in parkinsonism. This group is traditionally called the antihistamines.
H2 receptor antagonist an agent that blocks the action of histamine by competitive binding to the H2 receptor; used to inhibit gastric secretion in the treatment of peptic ulcer.

an·tag·o·nist

(an-tag'ŏ-nist),
Something opposing or resisting the action of another; certain structures, agents, diseases, or physiologic processes that tend to neutralize or impede the action or effect of others. Compare: synergist.

antagonist

(ăn-tăg′ə-nĭst)
n.
1. Physiology A muscle that counteracts the action of another muscle, the agonist.
2. A drug or chemical substance that interferes with the physiological action of another, especially by combining with and blocking its receptor.

an·tag′o·nis′tic adj.
an·tag′o·nis′ti·cal·ly adv.

antagonist

Anatomy
A muscle that opposes the movement of agonist muscles and returns a limb to its initial position.

Pharmacology
A substance that partially or completely nullifies the effect of another agent; a chemical entity that is not naturally found in the body which occupies a receptor, produces no physiologic effects and prevents endogenous and exogenous chemicals from producing an effect on that receptor.

an·tag·o·nist

(an-tag'ŏ-nist)
Something opposing or resisting the action of another; any structure, agent, disease, or physiologic process that tends to neutralize or impede some action or effect.
Compare: synergist

antagonist

1. A muscle that acts to oppose the action of another muscle (the agonist).
2. A drug that counteracts or neutralizes the action of another drug. The antonym of antagonist is agonist.

Antagonist

A substance that tends to nullify the action of another.
Mentioned in: Withdrawal Syndromes

antagonist 

1. An antagonistic muscle.
2. A substance (e.g. a drug, hormone or neurotransmitter) that depresses the action of an agonist or binds to a cell receptor without eliciting a physiological response (e.g. excitation or inhibition). Examples: atropine and hyoscine which block the effect of acetylcholine acting on cholinergic receptors and timolol which blocks adrenergic receptors. See agonist.

an·tag·o·nist

(an-tag'ŏ-nist)
Something opposing or resisting the action of another; certain structures, agents, diseases, or physiologic processes that tend to neutralize or impede the action or effect of others.
Compare: synergist
References in periodicals archive ?
''Internally, the North Korean military is already defined as a main enemy and externally it is also described as an enemy,'' Yonhap quoted a South Korean defense official as saying, explaining the decision not to include the ''main enemy'' term in the defense paper.
Iran, whose leader has threatened to wipe Israel off the map, is viewed by Israel as its main enemy. Iran also worries the Saudis and other Sunni-led Arab allies of the US.
Facing eroding support for his Iraq policy, even among Republicans, President Bush on Thursday called al Qaida "the main enemy" in Iraq, an assertion rejected by his administration's senior intelligence analysts.
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We have to give notice to bin Laden that he is our enemy, but we have to fight our main enemy first.
Potentially lethal chip pans are seen as a main enemy to safety and should be destroyed - so the army in York was drafted in to put them out of action once and for all.
Ethiopia's main enemy remains poverty, which the government and people are fighting together.
Whether a drum is used indoors or outdoors, the main enemy of a steel drum is water.
TODAY, THE RUSSIAN ARTIST'S MAIN enemy, the Soviet power, has fled," he said, "but the inner world, where the artist battles with himself, has remained.
China is still officially and overtly a totalitarian Communist dictatorship that openly denounces the United States as its "main enemy," supports terrorist organizations and state sponsors of terrorism, and verbally threatens us with nuclear annihilation.
He said a 'concerted effort' from Western societies meant Islam had now replaced Communism as the main enemy of the West.
In the past 2 years, the Polk County, Florida, Sheriffs Office realized that time represented its main enemy when hiring both officers and civilians.