15 Questions
What is the function of an antagonist?
Blocks the action of the agonist
What is the difference between endogenous agonists and exogenous agonists?
Endogenous agonists are produced by the body, while exogenous agonists are not
What is the characteristic of a full agonist?
Activates a receptor with the maximum response
What is the endogenous agonist for dopamine receptors?
Dopamine
What is the role of co-agonists in NMDA receptor activation?
They are required along with glutamate for NMDA receptor activation
What is the function of biased agonists?
They bind to the receptor without affecting the same signal transduction pathway
What is the role of partial agonists like buprenorphine in opiate dependence treatment?
They are used due to their milder effects and lower abuse potential
What is the unique characteristic of superagonists?
They produce a greater response than the endogenous agonist
What is the mechanism of action of irreversible agonists?
They bind permanently to a receptor through the formation of covalent bonds
What is the significance of functional selectivity in ligands' behavior?
It leads to terms like 'functional selectivity' and 'protean agonism'
What is the function of selective agonists?
They are specific to a certain type of receptor
What is the role of inverse agonists?
They inhibit the constitutive activity of the receptor
What is the effect of agonists on receptors?
They induce a conformational change and activate the receptor
What does the EC50 value measure?
The concentration of agonist needed to elicit half of the maximum biological response
What does the therapeutic index measure?
The margin of safety between the dose needed for the desired effect and the dose that produces unwanted side-effects
Study Notes
Agonist Types and Mechanism of Action
- A drug can act as a full agonist in some tissues and as a partial agonist in others, depending on receptor numbers and differences in receptor coupling.
- NMDA receptor activation requires the binding of both glutamate, glycine, and D-serine co-agonists.
- Selective agonists are specific to a certain type of receptor, such as buspirone for serotonin 5-HT1A.
- Partial agonists like buprenorphine are used to treat opiate dependence due to their milder effects and lower abuse potential.
- Inverse agonists bind to the same receptor site as an agonist and inhibit the constitutive activity of the receptor.
- Superagonists can produce a greater response than the endogenous agonist for the target receptor.
- Irreversible agonists bind permanently to a receptor through the formation of covalent bonds.
- Biased agonists bind to a receptor without affecting the same signal transduction pathway.
- Oliceridine is a µ-opioid receptor agonist described to be functionally selective towards G protein and away from β-arrestin2 pathways.
- Ligands can concurrently behave as agonist and antagonists at the same receptor, leading to terms like "functional selectivity" and "protean agonism".
- Agonists induce a conformational change and activate the receptor, with unique mechanisms of action depending on the receptor activated and the response needed.
- Potency is inversely related to the EC50 value, which measures the concentration of agonist needed to elicit half of the maximum biological response. Therapeutic index measures the margin of safety between the dose needed for the desired effect and the dose that produces unwanted side-effects.
Test your knowledge of agonist types and mechanisms of action with this quiz. Explore the various forms of agonists, from full and partial agonists to biased and superagonists, and understand their roles in pharmacology and drug development.
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