PED1003/L12 Drugs acting on SNS

Question 1

Where does noradrenaline act as a neurotransmitter in the PNS?

Answer 1

Postganglionic neurones in the sympathetic nervous system

Question 2

Describe the synthesis of noradrenaline. (3)

Answer 2

Tyrosine precursor -> DOPA via tyrosine hydroxylase
DOPA -> DA via DOPA decarboxylase
DA -> NA via DOPA decarboxylase B-hydroxylase

Question 3

Describe the termination of noradrenaline neurotransmission.

Answer 3

Uptake and recycled or metabolism by monoamine oxidase

Question 4

Where are a1&2, b1, 2&3 noradrenergic receptors located?

Answer 4

Effector tissues of sympathetic system

Question 5

Describe the response of a-noradrenergic receptors. (2)

Answer 5

G-protein coupled/ metabotropic
Slow responses

Question 6

Describe the response of B-noradrenergic receptors. (2)

Answer 6

G-protein coupled receptors
Slow response

Question 7

Give 3 effects mediated by a1-receptors.

Answer 7

Pupil dilation
Vasoconstriction of vessels to visceral organs and skin
Brain activity general alertness

Question 8

How are a2 receptors different from a1 receptors?

Answer 8

a1 are presynaptic receptors

Question 9

Give a sympathetic effect mediated by B1 receptors.

Answer 9

Increased HR and force of contraction

Question 10

Give 3 sympathetic effects mediated by B2 receptors.

Answer 10

Ciliary muscle relaxation
Bronchodilation
Blood vessels to limb muscles dilate

Question 11

Give a sympathetic effect mediated by B3 receptors.

Answer 11

Increased lipolysis

Question 12

What noradrenergic receptors does adrenaline act on?

Answer 12

a1&2
b1&2

Question 13

How does adrenaline act when given subcutaneously? (2)

Answer 13

Prolong and isolate anaesthesia
a1-mediated vasoconstriction

Question 14

How does adrenaline act when given intramuscularly? (4)

Answer 14

Treating anaphylactic shock
a1-mediated vasoconstriction
B1-mediated cardiac stimulation
B2-mediated bronchiole smooth muscle relaxation

Question 15

Describe the action of clonidine. (4)

Answer 15

a2 agonist
Used for hypertension
Decrease NA release
Dampen SNS

Question 16

Give a use of clonidine clinically.

Answer 16

Treating morphine withdrawal symptoms

Question 17

Give a side effect of clonidine. (2)

Answer 17

Nucleus tractus solitarius
Decrease in sympathetic outflow

Question 18

Describe the action of dobutamine.

Answer 18

B1-mediated increased cardiac rate and force

Question 19

Describe the action of salbutamol. (2)

Answer 19

B2-mediated bronchodilation
Used to treat asthma

Question 20

Describe the action of clenbuterol.

Answer 20

B2/3 agonist
B2-mediated bronchodilation
B3-mediated lipolysis/increased metabolism

Question 21

Describe the action of prazosin. (3)

Answer 21

a1 antagonist
Blocks a1-mediated smooth muscle and vasoconstriction
Used to treat hypertension

Question 22

Describe the action of tamsulson. (3)

Answer 22

a1 antagonist
Blocks a1-mediated smooth muscle and vasoconstriction
Used to treat urinary problems and prostate hyperplasia

Question 23

Describe the action of propanolol. (5)

Answer 23

Mixed B1&2 antagonist
Block B1-mediated increased cardiac rate and force
Block B2-medaited bronchodilation
Used to treat hypertension and angina
Contraindicative in asthmatics

Question 24

Describe the action of atenolol. (4)

Answer 24

B1 antagonist
Blocks B1-mediated increased cardiac rate and force
Used for hypertension
Decreases O2 demand

Question 25

Describe the action of timolol. (3)

Answer 25

B2 antagonist
Block B2-mediated ciliary muscle/lens of eye relaxation
Used to treat glaucoma

Question 26

How can synthesis of NA be affected?

Answer 26

Provide false substrate to inhibit enzymatic activity
E.g., methyldopa

Question 27

Describe the action of methylnoradrenaline. (2)

Answer 27

a2 agonist
Decreases NA release

Question 28

Describe the action of reserpine.

Answer 28

Disrupts storage of NA in synaptic vesicles

Question 29

Give 2 examples of NA reuptake inhibitors.

Answer 29

Desipramine - TCA
Reboxetine - SSRI

Question 30

Explain how monoamine oxidase inhibitors (MAOIs) work. (3)

Answer 30

Block MAO
Allow more NA to be recycled
Increases NA neurotransmission

Question 31

What is the ‘cheese reaction’? (2)

Answer 31

Blocking of transulcypramine and other MAOIs results in blocking of metabolism of dietary amines & cold remedies
Results in hypertension