Agonist: Difference between revisions
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An '''agonist''' is a chemical that binds to the [[receptor]] of a cell and activates the receptor to cause a physiological response. An agonist initiates the same reaction typically produced by the binding of an endogenous ligand (such as a hormone or neurotransmitter) with a receptor. <ref>Agonist definition (Merriam-Webster) http://www.merriam-webster.com/dictionary/agonist</ref> A drug’s ability to affect a given receptor is dependent on the drug’s affinity and intrinsic efficacy towards that receptor. The affinity of a drug describes the strength of attraction between it and a given receptor, and consequently its ability to bind to that receptor. A drug with a high affinity for a receptor has a high likelihood of binding to it, while a drug with a low affinity has a lesser degree of attraction towards a receptor. | An '''agonist''' is a chemical that binds to the [[receptor]] of a cell and activates the receptor to cause a physiological response. An agonist initiates the same reaction typically produced by the binding of an endogenous ligand (such as a hormone or neurotransmitter) with a receptor. <ref>Agonist definition (Merriam-Webster) http://www.merriam-webster.com/dictionary/agonist</ref> A drug’s ability to affect a given receptor is dependent on the drug’s affinity and intrinsic efficacy towards that receptor. The '''affinity''' of a drug describes the strength of attraction between it and a given receptor, and consequently its ability to bind to that receptor. A drug with a high affinity for a receptor has a high likelihood of binding to it, while a drug with a low affinity has a lesser degree of attraction towards a receptor. | ||
This contrasts the efficacy of a drug, which describes a drugs capacity to produce a response when bound to a receptor. A drug with high efficacy will produce a proportionally stronger effect than a drug of lower efficacy occupying the same number of receptors. The maximal efficacy of a drug reflects the greatest attainable response to a particular drug on a receptor set regardless of dose. A drug with a high efficacy may need to occupy less receptors to produce maximum effects, meaning it will not produce stronger effects beyond a certain dosage. In contrast, an [[antagonist]] is the opposite of an agonist; it binds to the receptor, but triggers no response. | This contrasts the '''efficacy''' of a drug, which describes a drugs capacity to produce a response when bound to a receptor. A drug with high efficacy will produce a proportionally stronger effect than a drug of lower efficacy occupying the same number of receptors. The maximal efficacy of a drug reflects the greatest attainable response to a particular drug on a receptor set regardless of dose. A drug with a high efficacy may need to occupy less receptors to produce maximum effects, meaning it will not produce stronger effects beyond a certain dosage. In contrast, an [[antagonist]] is the opposite of an agonist; it binds to the receptor, but triggers no response. | ||
==Types of agonist== | ==Types of agonist== | ||
[[Receptors]] can be activated by chemicals produced by the body (endogenous) or chemicals from outside of the body (exogenous). Therefore, an endogenous agonist for a particular receptor is a chemical produced in the body that binds to and activates that receptor. | [[Receptors]] can be activated by chemicals produced by the body (endogenous) or chemicals from outside of the body (exogenous). Therefore, an endogenous agonist for a particular receptor is a chemical produced in the body that binds to and activates that receptor. | ||
Revision as of 21:40, 17 April 2016
An agonist is a chemical that binds to the receptor of a cell and activates the receptor to cause a physiological response. An agonist initiates the same reaction typically produced by the binding of an endogenous ligand (such as a hormone or neurotransmitter) with a receptor. [1] A drug’s ability to affect a given receptor is dependent on the drug’s affinity and intrinsic efficacy towards that receptor. The affinity of a drug describes the strength of attraction between it and a given receptor, and consequently its ability to bind to that receptor. A drug with a high affinity for a receptor has a high likelihood of binding to it, while a drug with a low affinity has a lesser degree of attraction towards a receptor.
This contrasts the efficacy of a drug, which describes a drugs capacity to produce a response when bound to a receptor. A drug with high efficacy will produce a proportionally stronger effect than a drug of lower efficacy occupying the same number of receptors. The maximal efficacy of a drug reflects the greatest attainable response to a particular drug on a receptor set regardless of dose. A drug with a high efficacy may need to occupy less receptors to produce maximum effects, meaning it will not produce stronger effects beyond a certain dosage. In contrast, an antagonist is the opposite of an agonist; it binds to the receptor, but triggers no response.
Types of agonist
Receptors can be activated by chemicals produced by the body (endogenous) or chemicals from outside of the body (exogenous). Therefore, an endogenous agonist for a particular receptor is a chemical produced in the body that binds to and activates that receptor.
Agonists
There are several types of agonist:
- A superagonist is an agonist that produces a greater response from the receptor than the endogenous agonist, and therefore has an efficacy of over 100%.
- A full agonist binds and activates a receptor, and has full efficacy at the receptor.
- A partial agonist binds and activates a receptor, but has only partial efficacy at the receptor.
Inverse agonists
An inverse agonist is an agent that binds to the same receptor binding-site as an agonist for that receptor, but reverses activity of receptors. Inverse agonists exert the opposite pharmacological effect of a receptor agonist.
Allosteric modulators
An allosteric modulator is a substance which indirectly influences (modulates) the effects of an agonist or inverse agonist at a target protein (for example a receptor). Allosteric modulators bind to a site distinct from that of the agonist binding site. Usually they induce a change within the protein structure. A positive allosteric modulator induces an amplification, while a negative modulator induces an attenuation of the effects of the ligand without triggering a functional activity on its own in the absence of the ligand.
See also
References
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http://www.merriam-webster.com/dictionary/agonist
- ↑ Agonist definition (Merriam-Webster) http://www.merriam-webster.com/dictionary/agonist