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Questions and Answers
What is the fundamental event that initiates the action of a drug?
What is the fundamental event that initiates the action of a drug?
Which macromolecule is the receptor site primarily composed of?
Which macromolecule is the receptor site primarily composed of?
What must receptors be in their ligand-binding characteristics?
What must receptors be in their ligand-binding characteristics?
What are effectors in the context of drug-receptor interaction?
What are effectors in the context of drug-receptor interaction?
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What does a graded dose-response curve depict?
What does a graded dose-response curve depict?
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What does the EC50 represent?
What does the EC50 represent?
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What determines potency?
What determines potency?
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What is efficacy?
What is efficacy?
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How is binding affinity measured?
How is binding affinity measured?
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What are spare receptors?
What are spare receptors?
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What does a quantal dose-response curve measure?
What does a quantal dose-response curve measure?
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What results in a sigmoid curve in a dose-response relationship?
What results in a sigmoid curve in a dose-response relationship?
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What determines efficacy?
What determines efficacy?
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What does potency refer to?
What does potency refer to?
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What is the measure of the drug's affinity for its receptor?
What is the measure of the drug's affinity for its receptor?
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What does spare receptors' presence indicate?
What does spare receptors' presence indicate?
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Which type of antagonism involves the direct interaction of a chemical antagonist with the drug being antagonized to remove or prevent it from binding to its target?
Which type of antagonism involves the direct interaction of a chemical antagonist with the drug being antagonized to remove or prevent it from binding to its target?
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Which type of receptors affect an intracellular effector molecule without requiring a specialized transmembrane signaling device?
Which type of receptors affect an intracellular effector molecule without requiring a specialized transmembrane signaling device?
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What characteristic lag period is associated with hormones that act by regulating gene expression?
What characteristic lag period is associated with hormones that act by regulating gene expression?
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What do agonist drugs do once they bind to their receptor?
What do agonist drugs do once they bind to their receptor?
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What type of receptors consist of an extracellular hormone-binding domain and a cytoplasmic enzyme domain?
What type of receptors consist of an extracellular hormone-binding domain and a cytoplasmic enzyme domain?
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What is the largest group of drug-receptor interactions involved in?
What is the largest group of drug-receptor interactions involved in?
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Which type of receptors can be mimicked or blocked by some drugs to regulate the flow of ions through plasma membrane channels?
Which type of receptors can be mimicked or blocked by some drugs to regulate the flow of ions through plasma membrane channels?
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What type of receptors are neurotransmitter reuptake transporters?
What type of receptors are neurotransmitter reuptake transporters?
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What type of antagonism occurs when epinephrine antagonizes histamine's bronchoconstrictor action by acting at β adrenoceptors?
What type of antagonism occurs when epinephrine antagonizes histamine's bronchoconstrictor action by acting at β adrenoceptors?
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Which type of antagonism involves glucagon antagonizing the cardiac effects of propranolol overdose by acting at glucagon receptors?
Which type of antagonism involves glucagon antagonizing the cardiac effects of propranolol overdose by acting at glucagon receptors?
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What do chemical antagonists do to the drug being antagonized?
What do chemical antagonists do to the drug being antagonized?
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What do receptors for many drugs act as?
What do receptors for many drugs act as?
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What does the therapeutic index represent?
What does the therapeutic index represent?
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What is the median effective dose (ED50)?
What is the median effective dose (ED50)?
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What do quantal dose-response data provide information about?
What do quantal dose-response data provide information about?
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What is the therapeutic window?
What is the therapeutic window?
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What do full agonists do when they bind to the receptor?
What do full agonists do when they bind to the receptor?
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What do partial agonists produce when they bind to the receptor?
What do partial agonists produce when they bind to the receptor?
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What do inverse agonists do?
What do inverse agonists do?
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What do neutral antagonists do in the absence of an agonist?
What do neutral antagonists do in the absence of an agonist?
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How do competitive antagonists bind to the agonist receptor site?
How do competitive antagonists bind to the agonist receptor site?
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What do irreversible antagonists cause?
What do irreversible antagonists cause?
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What do physiological antagonists bind to?
What do physiological antagonists bind to?
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What does the quantal dose-response curve measure?
What does the quantal dose-response curve measure?
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Which type of receptor causes the opening of the ion channel when bound by acetylcholine?
Which type of receptor causes the opening of the ion channel when bound by acetylcholine?
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What is the primary mediator of various physiological processes such as energy mobilization and heart muscle function?
What is the primary mediator of various physiological processes such as energy mobilization and heart muscle function?
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What is the result of elevated cytoplasmic Ca$^{2+}$ concentration due to IP3-promoted opening of channels?
What is the result of elevated cytoplasmic Ca$^{2+}$ concentration due to IP3-promoted opening of channels?
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How is cyclic guanosine monophosphate (cGMP) produced?
How is cyclic guanosine monophosphate (cGMP) produced?
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What happens to receptors as a result of continuous exposure to agonists?
What happens to receptors as a result of continuous exposure to agonists?
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What leads to the restoration of the full receptor response after continuous exposure to agonists?
What leads to the restoration of the full receptor response after continuous exposure to agonists?
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What is the primary mediator of the release of calcium from intracellular stores?
What is the primary mediator of the release of calcium from intracellular stores?
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What is the fundamental event that initiates the action of a drug?
What is the fundamental event that initiates the action of a drug?
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What must receptors be in their ligand-binding characteristics?
What must receptors be in their ligand-binding characteristics?
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What are effectors in the context of drug-receptor interaction?
What are effectors in the context of drug-receptor interaction?
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What is the receptor site for a drug?
What is the receptor site for a drug?
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How are most receptors primarily composed?
How are most receptors primarily composed?
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What initiates the action of a drug?
What initiates the action of a drug?
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What is the fundamental event that initiates the action of a drug?
What is the fundamental event that initiates the action of a drug?
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What do partial agonists produce when they bind to the receptor?
What do partial agonists produce when they bind to the receptor?
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What does the therapeutic index represent?
What does the therapeutic index represent?
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What does potency refer to?
What does potency refer to?
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What is efficacy?
What is efficacy?
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What type of antagonism occurs when epinephrine antagonizes histamine's bronchoconstrictor action by acting at $β$ adrenoceptors?
What type of antagonism occurs when epinephrine antagonizes histamine's bronchoconstrictor action by acting at $β$ adrenoceptors?
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What does the EC50 represent in a dose-response curve?
What does the EC50 represent in a dose-response curve?
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What is the primary determinant of a drug's potency in pharmacological dose-response relationships?
What is the primary determinant of a drug's potency in pharmacological dose-response relationships?
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What is the measure of the drug's affinity for its receptor?
What is the measure of the drug's affinity for its receptor?
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What is the maximal effect an agonist can produce at high doses known as?
What is the maximal effect an agonist can produce at high doses known as?
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What type of dose-response curve measures the fraction of a population showing a specified response at increasing doses?
What type of dose-response curve measures the fraction of a population showing a specified response at increasing doses?
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What effect do spare receptors have on the sensitivity to the agonist?
What effect do spare receptors have on the sensitivity to the agonist?
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What is the result of elevated cytoplasmic $Ca^{2+}$ concentration due to IP3-promoted opening of channels?
What is the result of elevated cytoplasmic $Ca^{2+}$ concentration due to IP3-promoted opening of channels?
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What does cyclic adenosine monophosphate (cAMP) mediate?
What does cyclic adenosine monophosphate (cAMP) mediate?
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What is the primary mediator of the release of calcium from intracellular stores?
What is the primary mediator of the release of calcium from intracellular stores?
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What does phospholipase C (PLC) split phosphatidylinositol-4,5-bisphosphate (PIP2) into?
What does phospholipase C (PLC) split phosphatidylinositol-4,5-bisphosphate (PIP2) into?
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What does cyclic guanosine monophosphate (cGMP) act by stimulating?
What does cyclic guanosine monophosphate (cGMP) act by stimulating?
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What is the consequence of continuous exposure to agonists?
What is the consequence of continuous exposure to agonists?
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What does the therapeutic index represent?
What does the therapeutic index represent?
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What do irreversible antagonists cause?
What do irreversible antagonists cause?
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What do quantal dose-response data provide information about?
What do quantal dose-response data provide information about?
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What is the median effective dose (ED50)?
What is the median effective dose (ED50)?
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What do full agonists do when they bind to the receptor?
What do full agonists do when they bind to the receptor?
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What does the therapeutic window describe?
What does the therapeutic window describe?
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Study Notes
Pharmacology I Drug Receptors & Pharmacodynamics
- Receptors are specific molecules in a biological system that drugs interact with to produce changes in the system's function.
- Receptors must be selective in their ligand-binding characteristics and modifiable when they bind a drug molecule.
- Most receptors are proteins, and the receptor site for a drug is the specific binding region with high and selective affinity for the drug molecule.
- Effectors translate the drug-receptor interaction into a change in cellular activity and can be enzymes or a part of the receptor molecule.
- Graded dose-response curve graphs increasing response to increasing drug concentration or dose, and the response is continuous and gradual.
- Potency denotes the amount of drug needed to produce a given effect and is determined mainly by the affinity of the receptor for the drug and the number of receptors available.
- Efficacy, or maximal efficacy, is the greatest effect an agonist can produce and is determined mainly by the nature of the drug and the receptor and its associated effector system.
- Graded dose-binding relationship measures the percentage of receptors bound by a drug, and the concentration of drug required to bind 50% of the receptor sites is denoted as Kd.
- Spare receptors exist if the maximal drug response is obtained at less than maximal occupation of the receptors and increase sensitivity to the agonist.
- Quantal dose-response curve graphs the fraction of a population that shows a specified response at progressively increasing doses.
- Median effective dose (ED50) and median toxic dose (TD50) are determined from quantal dose-response curves and provide information about the variation in sensitivity to the drug in a given population.
- The therapeutic index is the ratio of the TD50 (or LD50) to the ED50 and represents an estimate of the safety of a drug, while the therapeutic window describes the dosage range between the minimum effective therapeutic concentration or dose, and the minimum toxic concentration or dose.
Cell Signaling Mechanisms and Receptor Regulation
- Receptors for membrane ion channels can either directly cause the opening of the channel or modify its response to other agents.
- Acetylcholine at the nicotinic receptor causes the opening of the ion channel, leading to Na+ influx and localized excitatory postsynaptic potential.
- G protein-coupled receptors bind to a large number of drugs and are linked to intracellular or membrane-bound effectors.
- When G-coupled receptors bind agonist, the G protein is activated, involving replacement of GDP with GTP and dissociation of the trimeric G protein complex.
- Cyclic adenosine monophosphate (cAMP) mediates various physiological processes such as energy mobilization and heart muscle function.
- Phospholipase C (PLC) splits phosphatidylinositol-4,5-bisphosphate (PIP2) into diacylglycerol (DAG) and inositol-1,4,5-trisphosphate (IP3), leading to calcium release and activation of protein kinase C.
- Elevated cytoplasmic Ca+2 concentration resulting from IP3-promoted opening of channels promotes the binding of Ca+2 to calmodulin, regulating activities of other enzymes.
- IP3 is inactivated by dephosphorylation, DAG is either phosphorylated or deacylated, and Ca+2 is actively removed from the cytoplasm by Ca+2 pumps.
- Cyclic guanosine monophosphate (cGMP) is produced by membrane-bound guanylyl cyclase and acts by stimulating a cGMP-dependent protein kinase.
- Receptors are dynamically regulated in number, location, and sensitivity over short and longer periods.
- Continuous exposure to agonists can result in short-term diminution of the receptor response, due to mechanisms such as intracellular protein blocking access of a G protein and internalization of agonist-bound receptors by endocytosis.
- Removal of the agonist results in the restoration of the full receptor response after a few minutes or hours.
Pharmacological Principles in Drug Response
- Quantal dose-response curve is obtained by plotting the percentage of the population showing a response at each dose versus the log of the dose administered.
- Median effective dose (ED50) is the dose at which 50% of individuals exhibit the specified effect, while the median toxic dose (TD50) is the dose required to produce a toxic effect in 50% of animals.
- The ED50 determined by quantal dose-response measurements has no direct relation to the ED50 determined from graded dose-response curves.
- Quantal dose-response data provide information about the variation in sensitivity to the drug in a given population, with a small variation resulting in a steep curve.
- The therapeutic index is the ratio of the TD50 (or LD50) to the ED50, representing an estimate of the safety of a drug.
- The therapeutic window describes the dosage range between the minimum effective therapeutic concentration or dose, and the minimum toxic concentration or dose.
- Full agonists fully activate the effector system when they bind to the receptor, while partial agonists produce less than the full effect even when saturated.
- Inverse agonists induce a pharmacological response opposite to that of an agonist, and neutral antagonists have no activity in the absence of an agonist but can block the activity of either.
- Competitive antagonists bind to the agonist receptor site in a reversible way without activating the effector system for that receptor.
- Irreversible antagonists cause a downward shift of the maximum effect, with no shift of the curve on the dose axis unless spare receptors are present.
- Physiological antagonists bind to a different receptor molecule, producing an effect opposite to that produced by the drug it antagonizes, differing from pharmacological antagonists.
- Understanding these principles is crucial for determining drug potency, efficacy, and safety, as well as for developing effective pharmacological interventions.
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Description
Test your knowledge of pharmacology with this quiz on drug receptors and pharmacodynamics. Learn about receptors, effectors, dose-response curves, potency, efficacy, and more. Explore cell signaling mechanisms and receptor regulation, including G protein-coupled receptors, cyclic adenosine monophosphate (cAMP), phospholipase C (PLC), and cyclic guanosine monophosphate (cGMP).
