Pharmacodynamics 2: Receptor Theory
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Questions and Answers

What is the term used to describe anything a drug interacts with to cause an effect?

  • Ligand
  • Drug Receptor
  • Binding Site
  • Drug Target (correct)
  • Which of these scientists is credited with the development of the "side chain" chemical binding theory from immunology?

  • Clark
  • Ehrlich (correct)
  • Langley
  • Gaddum
  • What is the term for the binding site that an endogenous agonist binds to?

  • Allosteric binding site
  • Orthosteric binding site (correct)
  • Active binding site
  • Secondary binding site
  • What is the term for the ability of a ligand to generate an effect?

    <p>Efficacy</p> Signup and view all the answers

    Which of these is NOT a factor that contributes to the potency of a drug?

    <p>Concentration</p> Signup and view all the answers

    What is the term for the binding site that other ligands bind to, besides the primary agonist?

    <p>Allosteric binding site</p> Signup and view all the answers

    Which of the following scientists established the theory of receptor action through their work with propranolol?

    <p>Black</p> Signup and view all the answers

    What type of conformational change occurs in a receptor upon ligand binding?

    <p>Activation</p> Signup and view all the answers

    What is the x-axis in a concentration-effect curve?

    <p>Log10[Ligand]</p> Signup and view all the answers

    What is the difference between a concentration-effect curve and a dose-response curve?

    <p>A concentration-effect curve measures the effect of a drug at its target site, while a dose-response curve measures the physiological response to a systemically administered drug.</p> Signup and view all the answers

    What does the EC50 represent?

    <p>The concentration of a drug required to produce a half-maximal effect.</p> Signup and view all the answers

    What is the relationship between potency and EC50?

    <p>Potency is inversely proportional to EC50.</p> Signup and view all the answers

    How does a ligand with a higher affinity compare to a ligand with a lower affinity?

    <p>A ligand with a higher affinity will bind to its target with a lower concentration.</p> Signup and view all the answers

    What does efficacy refer to?

    <p>The maximum effect that a ligand can produce.</p> Signup and view all the answers

    What is the difference in efficacy and affinity between ligands A and C in the graph provided?

    <p>Ligand A has higher affinity and lower efficacy than ligand C.</p> Signup and view all the answers

    What does it mean if two ligands have the same efficacy but different affinities?

    <p>The two ligands will produce the same maximum effect but will require different concentrations to achieve it.</p> Signup and view all the answers

    Study Notes

    Receptor Theory

    • Receptor theory is the main scientific theory of pharmacology, dating back to Ehrlich's "side chain" chemical binding theory from immunology.

    Development of Receptor Theory

    • Langley (1878, 1905) proposed a chemical binding theory for all drugs, which was later developed by others, such as Clark and Gaddum (1920s-1930s).
    • The concept of receptors was firmly established by Sir James Black (1965) with the discovery of propranolol.

    Definition of Receptors and Targets

    • A "drug receptor" refers to anything a drug interacts with to cause an effect, but the term "drug target" is preferable.
    • "Receptor" specifically refers to proteins that recognize and respond to endogenous signaling mediators.

    Binding Sites

    • Receptors have an active ("orthosteric") binding site for endogenous, activating ligands (agonists) with high specificity.
    • Ligand binding induces conformational changes to activate the receptor.
    • Receptors may also contain secondary ("allosteric") binding sites for other ligands.

    Affinity and Efficacy

    • Affinity refers to the ability of a ligand to bind to a target.
    • Efficacy refers to the ability of a ligand to generate an effect.
    • Together, affinity and efficacy determine potency, or the ability of a ligand to generate a response.

    Concentration-Effect and Dose-Response Curves

    • Concentration-effect curves measure the effect of a drug at the target site.
    • Dose-response curves measure the physiological response to a systemically administered drug.
    • The x-axis is typically plotted on a logarithmic scale.

    Affinity and Efficacy on D-R Curves

    • Ligands with different affinities or efficacies will have distinct D-R curves.
    • Ligands with the same efficacy but different affinities will have different EC50 values.
    • Ligands with the same affinity but different efficacies will have different Emax values.

    EC50 and Potency

    • EC50 is the concentration at which the effect is half maximal.
    • Potency is the concentration of drug required to cause an effect, measured by EC50.

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    Description

    This quiz covers receptor theory, including concentration-effect curves, agonists, antagonists, and therapeutic range. It's a crucial concept in pharmacology, building on the work of Ehrlich and immunology. Test your knowledge of pharmacodynamics!

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