Dose-Response Curves for Drug BINDING to Receptors

Question 1

% Receptor Occupancy can also by defined as ____.

Answer 1

RD/Rt x 100

Question 2

On a graph of % Receptor Occupancy vs. Drug Concentration, drug concentration is plotted on what type of scale?

Answer 2

• linear

- X-axis: drug concentration on a linear scale

Question 3

Receptor occupancy is also known as ____, and written as what unit?

Answer 3

binding; Percent %.

Question 4

What is a concentration binding curve?

Answer 4

X-axis = drug concentration on a linear scale
Y-axis = receptor occupancy or binding (%)

Question 5

As the line goes up on a concentration binding curve, what happens to saturation?

Answer 5

Saturation increases.

Question 6

Binding curve on a linear x-axis is also referred to as ____.

Answer 6

Hyperbolic

Question 7

T/F. You can never reach 100% saturation.

Answer 7

TRUE, because even at 99% receptors are constantly being detached and reattached. (on and off, on and off)

Question 8

1/10th Kd gives how much occupancy? 100x Kd gives how much receptor occupancy?

Answer 8

1/10th = 9%, 10x = 91%

Question 9

T/F. Binding is linear with drug concentration.

Answer 9

FALSE. It is NOT linear with drug concentration.

- when drug concentration is low, binding is greater than when drug concentration is high.

Question 10

What is affinity? And how is it defined?

Answer 10

• the amount of drug required to BINDS to receptor for a given fractional occupancy
• defined by Kd (concentration of drug that OCCUPIES 50% of the receptors)

Question 11

What is relationship between Affinity vs. Kd

Answer 11

Low Kd value = high affinity = less drug required = more receptor occupancy at lower drug concentrations
High Kd value = low affinity = more drug required = higher drug concentrations needed for same receptor occupancy