Agonist
As agonist (Greek αγωνιστής, agonistís - the workers, actors, Leading ) is in pharmacology, a substance (ligand ) indicates that activated by occupation of a receptor signal transduction in the corresponding cell. An agonist can be both an endogenous substance (eg, a hormone or a neurotransmitter ) and a non - endogenous compound that mimics or replaces a certain neurotransmitter in its effect. Chemical compounds which, although binding to a receptor but do not activate it, on the other hand is referred to as an antagonist.
Can be made between a full agonist and a partial agonist on the basis of the degree of activation. Inverse agonists that lead to inactivation of a spontaneously active receptor and thus show an opposite effect to full and partial agonists are, however, not associated with the agonist.
The extent of activation of a receptor depends not only on the properties of the ligand, but also on the degree of expression of the receptor in the cells under investigation or in the examined tissue dependent. In addition, some agonists on the same receptor capable of varying degrees to activate various signaling pathways, and therefore - to produce marked effects of different - depending on the surveyed, signal. So you can - depending on the signal surveyed, - at the same time full agonists, partial agonists, antagonists or inverse agonists be silent. Such agonists are also known as Proteus or functionally selective.
Examples
The following table shows examples of receptors and their subtypes and their agonists at the orthosteric binding site.
Further Reading
- Klaus Aktories, Ulrich Förstermann include: General and special pharmacology and toxicology. 10th Edition, Urban & Fischer, 2009, ISBN 3-437-42522-6, pp. 8-13. limited preview on Google Book Search
References and Table Legend
- Agonist ( Pharmacology )
- Biochemistry