Lecture 03, 4

• What is the definition of antagonists in pharmacodynamics?

  They bind but do not activate receptors

  
• How do antagonists typically work?

  By preventing agonists from binding to receptors
• What is a competitive reversible antagonist?

  Binds reversibly, can be displaced by agonist
• What happens when a high concentration of agonist is present with a competitive antagonist?

  It can displace the antagonist and activate the receptor
• What is an irreversible antagonist?

  Binds permanently to a receptor
• How does a non-competitive antagonist function?

  Binds at a different site, cannot be overcome
• What is the effect of a competitive antagonist on efficacy?

  It decreases potency without changing efficacy
• How does the addition of atropine affect ACh potency?

  It requires more ACh to achieve the same effect
• How is the dose ratio used to quantify antagonist effectiveness?

  It indicates how much agonist is needed

  
• What does pA2 measure in pharmacology?

  Affinity of an antagonist for a receptor
• What is a Schild plot used for?

  To plot antagonist concentration against dose ratio

  
• What is the role of carvedilol in pharmacodynamics?

  It is a beta1 selective adrenoceptor antagonist
• How does naloxone function in opioid overdose?

  It reverses opioid-induced respiratory depression
• What is the effect of irreversible antagonists on receptors?

  They permanently prevent agonist binding
• What is the function of prasugrel in pharmacology?

  It blocks platelet aggregation as an antithrombotic
• What is the primary action of ketamine?

  It acts as a non-competitive antagonist
• How do competitive antagonists affect agonist potency?

  They require higher agonist concentrations for effect
• What is the IC50 in pharmacology?

  Concentration displacing 50% of radioligand
• What is the difference between IC50 and Ki?

  Ki is an absolute value, IC50 varies
• What are first messengers in cell signaling?

  Extracellular substances like hormones and neurotransmitters
• What role do second messengers play in signaling?

  They trigger physiological changes inside the cell
• What is the function of adenylyl cyclase?

  It converts ATP into cAMP
• How do ligand-gated ion channels function?

  They mediate fast synaptic events
• What is the primary action of tyrosine kinase receptors?

  Transfer phosphate groups from ATP to proteins
• What are the two important signaling transduction pathways?

  Ras/Raf/MAP and Jak/Stat pathways
• What is the role of intracellular receptors?

  They alter protein synthesis inside the cell
• What types of ligands bind to intracellular receptors?

  Steroid hormones, T4, and vitamin D
• What are the four main types of receptors?

  • G-protein coupled receptors
  • Ligand-gated ion channels
  • Tyrosine kinase receptors
  • Intracellular receptors
• How do receptors mediate cellular changes?

  • Receptors bind to ligands
  • Activate signal transduction pathways
  • Result in physiological changes via second messengers
• What is the difference between first and second messengers?

  • First messengers: Extracellular signals (e.g., hormones)
  • Second messengers: Intracellular molecules that amplify signals
• Explain how receptors elicit cellular change via second messengers.

  • First messenger binds to receptor
  • Activates second messenger production
  • Triggers physiological responses (e.g., proliferation, survival)
• What are the physiological changes triggered by second messengers?

  • Proliferation
  • Differentiation
  • Migration
  • Survival
  • Apoptosis
• What is the significance of the Schild plot?

  • Used to analyse antagonist effects
  • Plots log dose ratio against log antagonist concentration
• How do competitive and non-competitive antagonists differ in their effects?

  • Competitive: Decrease potency, efficacy unchanged
  • Non-competitive: Decrease both potency and efficacy

  
• What is the role of G-protein coupled receptors?

  • Largest family of receptors
  • Involved in slow signaling
  • Activate second messengers via G-proteins
• What are the key features of ligand-gated ion channels?

  • Mediate fast synaptic events
  • Allow ions to flow in/out rapidly
  • Example: Acetylcholine nicotinic receptor
• What is the function of tyrosine kinase receptors?

  • Transfer phosphate groups from ATP
  • Involved in cell growth and differentiation
• What are the two important signaling pathways in cell signaling?

  • Ras/Raf/MAP pathway
  • Jak/Stat pathway
• What is the role of intracellular receptors in cellular function?

  • Bind ligands that enter the cell
  • Alter gene expression and protein synthesis
• How do first messengers differ from second messengers?

  • First messengers: Extracellular signals
  • Second messengers: Intracellular signaling molecules