03 - Agonists and Dose Response Curves (pharmacodynamics)

Question 1

Dose response curves are plotted using the log of the agonist dose or concentration. This usually results in:

a) bell curve
b) straight line
c) exponential curve
d) s-curve

Answer 1

d) s-curve

Question 2

Quantal dose-response curves look at…

Answer 2

A population

Question 3

Graded dose-response curves look at…

Answer 3

The response of a specific patient, tissue or system

Question 4

Why plot a dose response curve (3)?

Answer 4

• Allows estimation of E max
• Allows estimation of ED50/EC50
• To determine efficacy and potency

Question 5

In the Two-State Hypothesis, the two states are:

Answer 5

Rested (R) and Activated (R*)

Question 6

In the Two-State Hypothesis, the tendency to form the drug-receptor complex is known as…

Answer 6

Affinity

Question 7

In the Two-State Hypothesis, the tendency towards activation of the drug-receptor complex is known as…

Answer 7

Efficacy

Question 8

Total binding - non-specific binding =

Answer 8

Specific binding

Question 9

Affinity can be calculated by dividing…

Answer 9

K1 / K-1

Question 10

A drug with a higher K1 will tend to…

Answer 10

Bind

Question 11

A drug with a higher K-1 will tend to…

Answer 11

Dissociate

Question 12

KD is the equilibrium…

Answer 12

Dissociation constant

Question 13

KD is equal to the concentration of ligand at which…

Answer 13

50% of available receptors are occupied

Question 14

A lower KD means…

a) higher affinity
b) lower affinity
c) no change to affinity

Answer 14

a) higher affinity

Lower KD means less ligand. If less ligand is required to bind the same number of receptors, a higher proportion of it is binding. So the ligand binds more readily, aka a higher affinity.

Question 15

A graph of agonist concentration against response shows:

a) affinity
b) efficacy
c) potency
d) response mechanism
e) receptor density

Answer 15

c) potency

Response =/= binding

Question 16

If the relationship between the occupation of receptors and the effect is linear, KD is equal to

Answer 16

EC50

Question 17

If the maximum response (E max) occurs without all receptors being occupied a system is said to have…

Answer 17

Spare receptors

Question 18

When considering efficacy, drugs can be divided into (2)…

Answer 18

Full or partial agonists

Question 19

Full agonists produce maximum response while occupying…

Answer 19

A small percentage of receptors

Question 20

When compared to full agonists, partial agonists show a…

Answer 20

Truncated curve (lower max response)

Dose-response curve

Question 21

Name one partial agonist and why this property is useful…

Answer 21

• Varenidine (binds to nicotine receptors, partial response allows smokers to wean off nicotine)
• Tamoxifen (binds to estrogen receptors to treat breast cancer, partial response preserves estrogen receptors because some are still needed)

Question 22

Receptors may sometimes respond to partial agonists as if they were full agonists. Receptors that do this are in…

Answer 22

Flip states

Question 23

An inverse agonist differs from an antagonist in that…

Answer 23

It has an effect in addition to simply stopping agonists from binding to the receptor

Question 24

Benzodiazepines bind to GABA A at the…

Answer 24

Allosteric site

Question 25

Benzodiazepines increase:

a) Efficacy of acetylcholine
b) KA for dopamine
c) Efficacy of GABA
d) Efficacy and KA of GABA
e) Efficacy and KA of seratonin

Answer 25

d) Efficacy and KA of GABA

Question 26

PAM stands for…

Answer 26

Positive Allosteric Modulation

Question 27

NAM stands for…

Answer 27

Negative Allosteric Modulation

Question 28

Positive Allosteric Modulation increases the affinity of the…

Answer 28

Endogenous agonist

Question 29

Desensitisation of the receptors is known as…

Answer 29

Tachyphylaxis

Question 30

Tachyphylaxis may result from (4)…

Answer 30

1. Conformational changes
2. Internalisation of receptors
3. Depletion of mediators
4. Altered drug metabolism