1 - Drug interactions with receptors and ion channels

Question 1

Benzilylcholine mustard

Answer 1

Irreversibly alkylates muscarinic receptor

Question 2

Cholera toxin

Answer 2

ADP ribosylation of a(s)
Inhibits GTPase activity
Sustained activation of adenylyl cyclase

Question 3

Pertussis toxin

Answer 3

ADP ribosylation of a(i)

Prevents activation of Gi in response to receptor stimulation

Question 4

AIF4-

Answer 4

Mimics gamma-phosphate of GTP

Causes persistent activation of G proteins

Question 5

Lithium

Answer 5

Uncompetitively inhibits phosphatases converting IP1 to inositol
Blocks inositol recycling

Question 6

Tyrphostins

Answer 6

Inhibitors of tyrosine kinase

Question 7

Prednisolone

Answer 7

Agonist for glucocorticoid receptors

Question 8

Mifepristone

Answer 8

Antagonist for glucocorticoid receptors

Question 9

Fludrocortisone

Answer 9

Agonist for mineralocorticoid receptors

Question 10

Spironolactone

Answer 10

Antagonist for mineralocorticoid receptors

Question 11

Ethinylestradiol

Answer 11

Agonist for estrogen receptor

Question 12

Tamoxifen

Answer 12

Antagonist for estrogen reveptor

Question 13

Norethisterone

Answer 13

Agonist for progestagen receptor

Question 14

Danazol

Answer 14

Antagonist for progestagen receptor

Question 15

Lidocaine

• 2 main uses
• what fibres does it affect?
• what does it bind to?
• acid or base?
• how does it act in different pHs?

Answer 15

-Local anaesthetic
Antidysrhythmic agent
-Affects c and Adelta fibres
-Binds preferentially to and stabilises inactivated state (Na channels)
-Weak base
-High ph-greater inhibition, lower potency

Question 16

Procaine

• main uses
• what fibres does it affect?
• what does it bind to?

Answer 16

-Local anaesthetic
Antidysrhythmic agent
-Affects c and Adelta fibres
-Binds preferentially to and stabilises inactivated state (Na channels)

Question 17

QX314

Answer 17

Quaternary local anaesthetic
Ineffective outside axon
Potent LA when perfused inside

Question 18

Benzocaine

Answer 18

Local anaesthetic
Uncharged
Extent of block is independent of pH
Faster block - hydrophobic pathway within membrane for uncharged LAs

Question 19

Quinidine

Answer 19

Local anaesthetic
Slow in slow out
Use dependence at low rates of stimulation

Question 20

Tetrodotoxin

TTX

Answer 20

Guanidinium groups
Block Na channels from outside
Do not show use dependence

Question 21

Bay K 8644

Answer 21

Dihydropyridine (DHP)
Calcium agonist
Lipid soluble

Question 22

Nifedipine

Answer 22

Dihydropyridine (DHP)
Lipid soluble
Calcium antagonist

Question 23

Verapamil

Answer 23

Ca channel blocker
Bind to site away from DHP binding site 
Site interact, so reduces DHP binding
Use dependence
Prolonged block
Preferentially cardiac muscle
Antidysrhythmics

Question 24

Diltiazem

Answer 24

Ca channel blocker
Bind to site away from DHP binding site 
Site interact, so enhances DHP binding
Use dependence
Prolonged block
Preferentially cardiac muscle
Antidysrhythmics

Question 25

Diazoxide

Answer 25

K channel opener Hyper polarise cell membrane Relax smooth muscle

Question 26

Minoxidil

Answer 26

K channel opener Hyper polarise cell membrane Relax smooth muscle

Question 27

Nicorandil

Answer 27

K channel opener Hyper polarise cell membrane Relax smooth muscle

Question 28

Tolbutamide | How does it work?

Answer 28

``` Close Katp acting on sulphonylurea receptor Depolarise pancreatic B cell memb Fires VGCa channel Ca influx Insulin release ```

Question 29

Glibenclamide | How does it work?

Answer 29

``` Close Katp acting on sulphonylurea receptor Depolarise pancreatic B cell memb Fires VGCa channel Ca influx Insulin release ```

Question 30

Muscarine

Answer 30

Agonist for muscarinic receptor on smooth muscle

Question 31

Nicotine

Answer 31

Agonist for nicotinic receptor on skeletal muscle

Question 32

Atropine

Answer 32

Antagonist for muscarinic receptor on smooth muscle

Question 33

D-tubocurarine

Answer 33

Antagonist for nicotinic receptors on skeletal muscle

Question 34

Acetyl-B-methylcholine

Answer 34

Cholinergic agonist | Inactive isomer has no affinity

Question 35

Isoprenaline

Answer 35

B-adrenoreceptor agonist | Inactive isomer has affinity

Question 36

Adenosine

Answer 36

?

Question 37

a bungarotoxin

Answer 37

?

Question 38

Lidocaine - how does it cross the membrane and block the channel? - dependence? - what in what out?

Answer 38

``` -Cross membrane in uncharged form Blocks channel best in charged form -Use dependence at high rates of stimulation Voltage dependence -Fast in fast out ```

Question 39

Procaine - acid or base? - how does it act in different pHs? - how does it cross the membrane and block the receptor?

Answer 39

-Weak base -High ph-greater inhibition, lower potency -Cross membrane in uncharged form Blocks channel best in charges form

Question 40

Tolbutamide | What is it and what does it do/treat?

Answer 40

Orally acting hypoglycaemic agent Treat type 2 diabetes Sulphonylurea

Question 41

Glibenclamide | What is it, what does it do/treat?

Answer 41

Orally acting hypoglycaemic agent Treat type 2 diabetes Sulphonylurea