Definition of "agonist" []

• One involved in a struggle or competition. (noun)
• Physiology A contracting muscle that is resisted or counteracted by another muscle, the antagonist. (noun)
• Biochemistry A drug or other chemical that can combine with a receptor on a cell to produce a physiologic reaction typical of a naturally occurring substance. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "In Western anatomy, these are called agonist and antagonist muscle groups, but I call them balancing muscle groups."
• "I paid homage in my review to A.J. Clark for his pioneering work in developing receptor theory, I took issue with his hypothesis that response of a tissue to an agonist is proportional to the fraction of receptors occupied by the agonist."
• "For example, I derived theoretical equations to illustrate how removal of the agonist from the region of the receptor by active uptake or enzymatic destruction could markedly alter the slope of"