Drug-receptor interactions

Question 1

What is a drug?

Answer 1

A chemical substance that interacts with a biological substance to produce a physiological effect

Question 2

What are the 4 drug target sites (all proteins)?

Answer 2

Receptors
Ion channels
Transport systems
Enzymes

Question 3

What are receptors?

Answer 3

Proteins within cell membranes that are activated by NT or hormones

Question 4

What are the two types of drugs?

Answer 4

Agonists

Antagonists

Question 5

What are ion channels?

Answer 5

Selective pores that allow transfer of ions down their electrochemical gradient

Question 6

What are the two types of ion channel?

Answer 6

Voltage sensitive

Receptor-linked

Question 7

What are transport systems?

Answer 7

Transport against concentration gradient

Question 8

What does the potency of a drug depend on?

Answer 8

Affinity and efficacy

Question 9

How do agonists work?

Answer 9

They bind to receptors and form agonist/receptor complex which is then able to bind to a transducer to form agonist/receptor/transducer complex which leads to a response

Question 10

How do antagonists work?

Answer 10

They have a high affinity but no efficacy

Question 11

What are the two types of receptor antagonist?

Answer 11

Competitive- same site as agonist, surmountable, shifts D-R curve to the right
Irreversible- binds tightly or at different site and insurmountable

Question 12

Give an example of a competitive inhibitor?

Answer 12

Atropine and propanolol

Question 13

Give an example of an irreversible inhibitor?

Answer 13

Hexamethonium

Question 14

What are the 4 types of drug antagonism?

Answer 14

Receptor blockade
Physiological antagonism- different receptors
Chemical antagonism- interaction in solution
Pharmacokinetic antagonism- Leads to decrease in conc of active drug at site of action, decrease in absorption, increase in metabolism and increase in excretion

Question 15

What is drug tolerance?

Answer 15

Gradual decrease in responsiveness to drug with repeated administration

Question 16

How do pharmacokinetic factors cause drug tolerance?

Answer 16

Increase in rate of metabolism

Question 17

How can receptor changes cause drug tolerance?

Answer 17

You can have either:
Loss of receptors- by membrane endocytosis (receptor “down-regulation”
Change in receptors- receptor desensitisation- conformational change

Question 18

What other factors cause drug tolerance?

Answer 18

Exhaustion of mediator stores

Physiological adaption- homeostatic responses and tolerance to drug side effects

Question 19

What are the 4 receptor families based on?

Answer 19

Molecular structure

Signal transduction systems

Question 20

What are the 4 receptor families?

Answer 20

Type 1- Ion channel linked- fast responses (ms)
Type 2- G protein coupled receptors- slower (s)
Type 3- Kinase linked type- (mins)
Type 4- Intracellular steroid type receptors (hrs)

Question 21

Give examples for each receptor family?

Answer 21

Type 1- nAChR, GABAA
Type 2- Beta1 adrenoceptors
Type 3- Insulin/growth factors
Type 4- Steroid/thyroid hormones