Receptors and the Effects of Drugs

Question 1

Give an example of an effect of cocaine (on the molecular level).

Answer 1

Blocking the noradrenaline transporter.

Question 2

List 2 ways by which drugs block effects by binding to receptors.

Answer 2

1 - Antagonism.

2 - Desensitisation.

Question 3

Describe the patch-clamp technique to measure ionic currents from a receptor.

Answer 3

1 - A micropipette filled with an electrolyte is brought into contact with the receptor.

2 - An electrode is inserted into the micropipette.

3 - The current is amplified and visualised.

Question 4

What is the effect of a neutral antagonist on a dose / response curve?

Answer 4

A flat line at 0 response.

Question 5

What drugs produce a negative response (on a dose / response curve)?

Answer 5

Inverse agonists.

Question 6

What type of receptor is the GABA-A receptor?

Answer 6

A ligand-gated chloride ion channel.

Question 7

What effect do benzodiazepine agonists have on GABA-A receptors?

Answer 7

They bind to the GABA-A allosteric site to increase the affinity of GABA for GABA-A receptors.

Question 8

List 2 benzodiazepine receptor (GABA-A allosteric site) ligands.

Answer 8

1 - Diazepam.

2 - Lorazepam.

Question 9

Give an example of a class of drug that is an inverse agonist for benzodiazepine receptors (GABA-A allosteric sites).

Answer 9

Beta-carbolines.

Question 10

Give an example of a drug that is an antagonist for benzodiazepine receptors (GABA-A allosteric sites).

Answer 10

Flumazenil.

Question 11

To which receptor does atropine bind?

What is its effect?

Answer 11

• Muscarinic acetylcholine receptors.

- Competitive antagonistic effect.

Question 12

To which receptor does propranolol bind?

What is its effect?

Answer 12

• Beta adrenoceptors.

- Competitive antagonistic effect.

Question 13

What is the effect of a competitive antagonist on a dose / response curve?

Answer 13

A parallel shift to the right.

Question 14

What is the effect of a non-competitive antagonist on a dose / response curve?

Answer 14

Reduces the height (max response) of the curve.

Question 15

To which receptor does phenoxybenzamine bind?

What is its effect?

Answer 15

• Alpha adrenoceptors.

- Irreversible antagonistic effect.

Question 16

List 5 types of antagonism.

Answer 16

1 - Competitive antagonists.

2 - Irreversible antagonists.

3 - Allosteric antagonists.

4 - Channel blockers.

5 - Physiological antagonists.

Question 17

To which receptor does fulvestrant bind?

What is its effect?

Answer 17

• Oestrogen receptors.

- Degrades the receptor.

Question 18

To which receptor does gallamine bind?

What is its effect?

Answer 18

• The muscarinic receptor allosteric site.

- Antagonistic effect.

Question 19

To which receptor does phencyclidine bind?

What is its effect?

Answer 19

• NMDA receptors.

- Block the channel to prevent passage of ions (a channel blocker).

Question 20

How are physiological antagonists different from other conventional antagonists?

Answer 20

They antagonise the physiological effect of some agonists, but are different in that they achieve this via a different mechanism.

Question 21

Why is adrenaline said to be a physiological antagonist?

Answer 21

Because it has anti-histaminergic action despite not being a ligand for the histamine receptor.

Question 22

What are endocrine disruptors?

Give an example of how some might work.

Answer 22

• A class of physiological antagonist.

- Some inhibit conjugation reactions.

Question 23

Define desensitisation.

Answer 23

Where prolonged or repeated exposure to an agonist reduces the response to that drug.

Question 24

What does controls heroin tolerance?

Answer 24

Adenylyl cyclase activity in the brain.

Question 25

What mechanism might occur to cause desensitisation to some stimulants?

Answer 25

Inactivation of nicotinic receptors.