Dictionary > Agonist

Agonist

Definition
noun, plural: agonists
(pharmacology) A molecule that combines with a receptor on a cell to trigger physiological reaction. An example is an acetylcholine being the agonist that combines with the cholinergic receptor.
(histology) A muscle that contracts while another muscle relaxes, e.g. when bending the elbow the biceps are the agonist.
Supplement
(pharmacology) There are different kinds of agonists:

  • Full agonists have an affinity for and activate a receptor.
  • Partial agonists bind and activate a receptor but have only partial efficacy at the receptor (compared with full agonists).
  • Inverse agonists reverse constitutive activity of receptors.
  • Co-agonists work with other co-agonists to produce the desired effect together.

Word origin: From the Greek αγωνιστής (agōnistēs), contestant; champion; rival < αγων (agōn), contest, combat; exertion, struggle < αγω (agō), I lead, lead towards, conduct; drive.

Related forms: agonistic (adjective).

Related phrases: physiological agonist.

Compare: antagonist.

See also: agonism.


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