Agonist
A drug that binds to a receptor of a cell and triggers a response by the cell. An agonist often mimics the action of a naturally occurring substance. An agonist produces an action. It is the opposite of an antagonist which acts against and blocks an action. Agonists and antagonists are key agents in the chemistry of the human body and important players today in pharmacology. For example, in treating Parkinson disease, the long-used drug levodopa can cause uncontrollable, jerky body movements called dyskinesias that can inhibit a person's ability to function. Dopamine agonists mimic the effects of dopamine in the brain by stimulating dopamine receptors with a lower risk of the uncontrollable and irreversible dyskinesias often associated with levodopa therapy. There are agonists now for many of the known hormones. For example, LHRH (luteinizing hormone-releasing hormone) agonists are similar to LHRH in structure and are able to mimic the effects of LHRH, a hormone that controls sex hormones in both men and women. The word "agonist" comes from the Late Latin agnista, contender, from the Greek agnists, contestant, from agn, contest. An agonist is a chemical contestant or contender.
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1. Denoting a muscle in a state of contraction, with reference to its opposing muscle, or antagonist. 2. A drug capable of combining with receptors to initiate drug actions; it possesses affinity and intrinsic activity. [G. agon, a contest]

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ag·o·nist 'ag-ə-nəst n
1) a muscle that on contracting is automatically checked and controlled by the opposing simultaneous contraction of another muscle called also agonist muscle, prime mover compare ANTAGONIST (a), SYNERGIST (2)
2) a chemical substance (as a drug) capable of combining with a receptor on a cell and initiating the same reaction or activity typically produced by the binding of an endogenous substance <binding of adrenergic \agonists> compare ANTAGONIST (b)

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n.
1. (prime mover) a muscle whose active contraction causes movement of a part of the body. Contraction of an agonist is associated with relaxation of its antagonist.
2. a drug or other substance that acts at a cell-receptor site to produce an effect that is the same as, or similar to, that of the body's normal chemical messenger. Cholinergic drugs (see parasympathomimetic) are examples.

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ag·o·nist (agґə-nist) [Gr. agōnistēs combatant] 1. a person or thing involved in a struggle or competition. 2. agonistic muscle. 3. in pharmacology, a drug that has affinity for and stimulates physiologic activity at cell receptors normally stimulated by naturally occurring substances.

Medical dictionary. 2011.

Look at other dictionaries:

  • Agonist — (griechisch αγωνιστής agonistís ‚der Tätige‘, ‚Handelnde‘, ‚Führende‘) bezeichnet: Agonist (Anatomie), ein Muskel oder Teil des Nervensystems, der bei zunehmender Aktivität von seinem Gegenspieler mehr und mehr gehemmt wird Agonist… …   Deutsch Wikipedia

  • agonist — AGONÍST, Ă s.m. şi f. (livr.) Luptător, sportiv; atlet. [< germ. Agonist, cf. gr. agonistes]. Trimis de LauraGellner, 23.10.2004. Sursa: DN  AGONÍST adj., s.m. (Musculatură) care produce o anumită uşurare. [< …   Dicționar Român

  • Agonist — Ag o*nist, n. [Gr. ?.] One who contends for the prize in public games. [R.] [1913 Webster] …   The Collaborative International Dictionary of English

  • Agonist — (griech.), Wettkämpfer; Agonistik, die zum Zweck des Wettkampfes getriebene Gymnastik, s. Agon …   Meyers Großes Konversations-Lexikon

  • Agoníst — (grch.), Wettkämpfer; Agonístik, Kampfkunst …   Kleines Konversations-Lexikon

  • agonist — (n.) 1876, in writings on Greek drama, from Gk. agonistes, lit. combatant in the games (see AGONY (Cf. agony)) …   Etymology dictionary

  • agonist — agònist m DEFINICIJA 1. onaj koji se bori; borac, natjecatelj 2. anat. mišić koji s grupom drugih mišića djeluje na isti zglob 3. kem. kemijska tvar koja pospješuje rezultate izmjene tvari ETIMOLOGIJA vidi agon …   Hrvatski jezični portal

  • agonist — [ag′ə nist΄] n. [back form. < ANTAGONIST] 1. one who takes part in a struggle, as a main character in a drama 2. a muscle whose action on a joint or orifice is opposed by the action of another muscle, the antagonist …   English World dictionary

  • Agonist — For other meanings of agonist or agonism , see agonist (disambiguation). For a primary fictional character in a work, see Protagonist and Antagonist. Agonists …   Wikipedia

  • agonist — noun a) Someone involved in a contest or battle (as in an agon). when bending the elbow the biceps are the agonist b) The muscle that contracts while the other relaxes. acetylcholine is an agonist at the a cholinergic receptor …   Wiktionary

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