agonist

noun ag·o·nist \ ˈa-gə-nist \

|Updated on: 25 May 2018

Definition of agonist

1 : one that is engaged in a struggle

[from antagonist]

a : a muscle that is controlled by the action of an antagonist with which it is paired

b : a chemical substance capable of combining with a specific receptor on a cell and initiating the same reaction or activity typically produced by the binding endogenous substance

dopaminergic agonists

— compare antagonist 2b

Recent Examples of agonist from the Web

Other chemicals, called antagonists, shut down the receptors by preventing the agonists from entering.

— jonathon keats, Discover Magazine, "Building a Better Painkiller," 11 May 2018
Buprenorphine is considered a partial agonist, that works similarly to methadone as a replacement medication.

— rita giordano, Philly.com, "Opioid addiction treatment with medicine works best. Why don't more young people get it?," 11 Apr. 2018
There are also gonadotropin-releasing hormone (GnRH) agonists, which can block the production of hormones that stimulate your ovaries and keep you from having a period, Greves explains.

— korin miller, Allure, "This Is What Endometriosis Pain Feels Like — and How to Treat It," 6 Mar. 2018
Many players only train up the easily visible Quadriceps but forget the Hamstrings in the back, leading to an agonist/antagonist imbalance that results in excess strain on the weaker hamstrings.

— SI.com, "Injury Analysis: Everything You Need to Know About Dybala’s Hamstring Injury in 1 Minute," 7 Jan. 2018
Srinivasan studies how prostheses can restore the natural push-pull balance among muscles, called an agonist-antagonist relationship, like when our bicep flexes while our tricep stretches (and vice versa).

— dan robitzski, Popular Mechanics, "To Make Better Prostheses, We Need Better Biology," 19 Dec. 2017
The new treatment approach was tested in obese mice by loading the nanoparticles with one of two compounds − rosiglitazone (Avandia) or beta-adrenergic receptor agonist − known to promote browning in mice but not in humans.

— stephanie toone, ajc, "Study: Skin patch that melts love handles in mice could work on humans," 16 Sep. 2017
GnRH agonists can only be used short-term because of the side effects, including permanent bone loss.

— meghan cleary, Teen Vogue, "Why Having A Hysterectomy to End Endometriosis Might Not Work," 14 Sep. 2017
This agonist-antagonist muscle pair allowed the body to sense the stretch, torque and speed of a muscle in a realistic way, electrical measurements showed, and in theory, would allow more control over a prosthetic limb.

— karen weintraub, Scientific American, "New Approach to Amputation Could Reduce Phantom Pain," 2 June 2017

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'agonist.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

Origin and Etymology of agonist

borrowed from Late Latin agōnista, borrowed from Greek agōnistḗs, from agōnízesthai "to contend, fight" + -istēs ¹-ist — more at agonize

NEW! Time Traveler

First Known Use: 1658

in the meaning defined at sense 1

See Words from the same year

Medical Dictionary

agonist

noun ag·o·nist \ ˈag-ə-nəst \

medical Definition of agonist

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