Agonist: Difference between revisions - PsychonautWiki Archive

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[[File:Efficacy spectrum.png|thumbnail|275px|Efficacy spectrum of receptor ligands]]

[[File:Inverse_agonist_3.svg|thumbnail|275px|Dose response curves of receptor ligands]]

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>{{Citation | title=Definition of AGONIST | url=https://www.merriam-webster.com/dictionary/agonist}}</ref> A substance's ability to affect a given receptor is dependent on the substance's affinity and intrinsic efficacy towards that receptor. The affinity of a substance describes the strength of attraction between it and a given receptor, and consequently its ability to bind to that receptor. A substance with a high affinity for a receptor has a high likelihood of binding to it, while a substance with a low affinity has a lesser degree of attraction towards a receptor.

This contrasts the efficacy of a ~~drug~~, which describes a ~~drug~~'s 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 maximum 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.

This contrasts the efficacy of a substance, which describes a substance's capacity to produce a response when bound to a receptor. A substance with high efficacy will produce a proportionally stronger effect than a substance of lower efficacy occupying the same number of receptors. The maximum efficacy of a substance reflects the greatest attainable response to a particular substance on a receptor set regardless of dose. A substance with a high efficacy may need to occupy fewer receptors to produce maximum effects, meaning it will not produce stronger effects beyond a certain dosage.

In contrast to an agonist, an [[antagonist]] is a chemical that binds to the receptor of a cell without causing a physiological response. Receptor antagonists work by blocking or diminishing the effects produced by endogenous or ~~drug~~-induced agonism of a receptor.

In contrast to an agonist, an [[antagonist]] is a chemical that binds to the receptor of a cell without causing a physiological response. Receptor antagonists work by blocking or diminishing the effects produced by endogenous or substance-induced agonism of a receptor.

==Types of agonists==

[[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. For example, [[serotonin]] is the endogenous agonist of serotonin receptors.

===Agonists===

There are several types of agonist:

*A '''superagonist''' is an agonist that produces a greater effect from the receptor than the endogenous agonist, and therefore has an efficacy of over 100%.

*A '''full agonist''' binds and activates a receptor with an efficacy equal to the endogenous agonist. For example, [[heroin]] mimics the action of endorphins on μ-opioid receptors in the nervous system.

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===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.

===Partial agonists===

A partial agonist is a substance that activates a receptor but only has partial efficacy in comparison to a full agonist. As a result, partial agonists may have unique properties that full agonists or inverse agonists lack. Some partial agonists, such as [[buprenorphine]], have a ceiling effect, where the subjective effects of the substance do not get any stronger past a certain dose. Partial agonists may also behave as an antagonist in the presence of a full agonist. Buprenorphine, a partial agonist of the μ-opioid receptor, behaves as an antagonist in the presence of other opioids such as [[heroin]]. An individual who is dependent on opioids will go into withdrawal if they take buprenorphine while opioids are still in their system due to buprenorphine's antagonistic effects.

==See also==

*[[Responsible use]]

*[[Scientific information]]

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==External links==

*[https://en.wikipedia.org/wiki/Agonist Agonist (Wikipedia)]

==References==

[[Category:Pharmacology]]

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 [[File:Efficacy spectrum.png|thumbnail|275px|Efficacy spectrum of receptor ligands]]
 [[File:Inverse_agonist_3.svg|thumbnail|275px|Dose response curves of receptor ligands]]
-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>{{Citation | title=Definition of AGONIST | url=https://www.merriam-webster.com/dictionary/agonist}}</ref> A substance's ability to affect a given receptor is dependent on the substance's affinity and intrinsic efficacy towards that receptor. The affinity of a substance describes the strength of attraction between it and a given receptor, and consequently its ability to bind to that receptor. A substance with a high affinity for a receptor has a high likelihood of binding to it, while a substance with a low affinity has a lesser degree of attraction towards a receptor.
-This contrasts the efficacy of a drug, which describes a drug's 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 maximum 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.
+This contrasts the efficacy of a substance, which describes a substance's capacity to produce a response when bound to a receptor. A substance with high efficacy will produce a proportionally stronger effect than a substance of lower efficacy occupying the same number of receptors. The maximum efficacy of a substance reflects the greatest attainable response to a particular substance on a receptor set regardless of dose. A substance with a high efficacy may need to occupy fewer receptors to produce maximum effects, meaning it will not produce stronger effects beyond a certain dosage.
-In contrast to an agonist, an [[antagonist]] is a chemical that binds to the receptor of a cell without causing a physiological response. Receptor antagonists work by blocking or diminishing the effects produced by endogenous or drug-induced agonism of a receptor.
+In contrast to an agonist, an [[antagonist]] is a chemical that binds to the receptor of a cell without causing a physiological response. Receptor antagonists work by blocking or diminishing the effects produced by endogenous or substance-induced agonism of a receptor.
 ==Types of agonists==
 [[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. For example, [[serotonin]] is the endogenous agonist of serotonin receptors.
 ===Agonists===
 There are several types of agonist:
 *A '''superagonist''' is an agonist that produces a greater effect from the receptor than the endogenous agonist, and therefore has an efficacy of over 100%.
 *A '''full agonist''' binds and activates a receptor with an efficacy equal to the endogenous agonist. For example, [[heroin]] mimics the action of endorphins on μ-opioid receptors in the nervous system.
@@ Line 20: / Line 21: @@
 ===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.
+===Partial agonists===
+A partial agonist is a substance that activates a receptor but only has partial efficacy in comparison to a full agonist. As a result, partial agonists may have unique properties that full agonists or inverse agonists lack. Some partial agonists, such as [[buprenorphine]], have a ceiling effect, where the subjective effects of the substance do not get any stronger past a certain dose. Partial agonists may also behave as an antagonist in the presence of a full agonist. Buprenorphine, a partial agonist of the μ-opioid receptor, behaves as an antagonist in the presence of other opioids such as [[heroin]]. An individual who is dependent on opioids will go into withdrawal if they take buprenorphine while opioids are still in their system due to buprenorphine's antagonistic effects.
 ==See also==
 *[[Responsible use]]
 *[[Scientific information]]
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 ==External links==
 *[https://en.wikipedia.org/wiki/Agonist Agonist (Wikipedia)]
 ==References==
-<references/>
+<references />
+[[Category:Pharmacology]]
+{{#set:Featured=true}}