Agonist
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- For other meanings of 'agonist' or 'agonism', see agonism (disambiguation).
In pharmacology an agonist is a substance that binds to a specific receptor and triggers a response in the cell. It mimics the action of an endogenous ligand (such as hormone or neurotransmitter) that binds to the same receptor.
A partial agonist (such as buspirone, aripiprazole, bifeprunox or norclozapine) activates a receptor, but only produces a partial physiological response compared to a full agonist. An co-agonist works with other co-agonists to produce the desired effect together. An antagonist blocks a receptor from activation by agonists.
Receptors can be activated or inactivated either by endogenous (such as hormones and neurotransmitters) or exogenous (such as drugs) agonists and antagonists, resulting in stimulating or inhibiting the cell. To see how an agonist may activate a receptor see this link.
New findings that broadens the conventional definition of pharmacology demonstrate that ligands can concurrently behave as agonist and antagonists at the same receptor, depending on effector pathways. Terms that describe this phenomen are "functional selectivity" or "protean agonism".[1][2]
[edit] Etymology
From the Greek αγωνιστής (agōnistēs), contestant; champion; rival < αγων (agōn), contest, combat; exertion, struggle < αγω (agō), I lead, lead towards, conduct; drive
[edit] References
- ^ Kenakin T. (2001). Inverse, protean, and ligand-selective agonism: matters of receptor conformation. FASEB J. 15:598-611. PMID 11259378. Fulltext
- ^ Urban J.D. et al. (2007). Functional selectivity and classical concepts of quantitative pharmacology. J. Pharmacol. Exp. Ther. 320:1-13. PMID 16803859.
[edit] See also
- Inverse agonist
- Receptor antagonist
- Allosteric modulator
- Intrinsic activity
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