receptor theory 2: ⇒ agonists and antagonists

Question 1

Demonstrate understanding of the quantitative relationship between drug concentration and effect in a biological system

Answer 1

• concentration effect curves
  
  • n = slope factor = measure of no. molecules that have to bind ot receptor to activate it
  • highest potency = lowest conc to produce maximal result

effect determined by:
- specificity
- interact with a structurally defined site / receptor/ chemical properties/ molecular structure
- affinity
- ability to bind to receptor
- efficacy
- ability to activate receptor 0 < E ≥ 1
- a full agonist has an efficacy of 1
- antagonists have an efficacy of 0

Question 2

Demonstrate understanding of the concept of spare receptors and their impact on the relationship between agonist concentration and response

Answer 2

tissues with a high proportion of spare receptors will respond to agonists at lower concentrations because presence of spare receptors increases the potency of an agonist

Question 3

Describe the use of, create and analyse a Schild Plot

Answer 3

• measures competitive antagonist affinity
• dose ratio = proportional to (conc of added antagonist / affinity conc for antagonist) +1

Question 4

Describe the relationship between pA2 and KD

Answer 4

• pA2 = potency
  
  • measure of potency of an antagonist
• KD = affinity
  a constant that defines affinity of a drug for a receptor
  ⇒ lower if affinity is high