Adrenergic pharmacology

Question 1

Describe neurons in the sympathetic NS.

Answer 1

Short preganglionic axons, long postganglionic axons.

Question 2

Where are beta-adrenoceptors innervated?

Answer 2

Heart, juxtaglomerular apparatus, brown adipose tissue

Question 3

Where are beta-adrenoceptors non innervated?

Answer 3

Bronchial smooth muscle, uterine smooth muscle, skeletal muscle vasculature

Question 4

What neurotransmitter is released at postganglionic sympathetic nerve terminals?

Answer 4

Noradrenaline

Sweat glands have acetylcholine from muscarinic receptors.

Question 5

What are full and partial agonists acting at beta2 adrenoceptors?

Answer 5

full: adrenaline, isoprenaline
partial: prenalterol

Question 6

What are full and partial agonists acting at alpha2 adrenoceptors?

Answer 6

full: noradrenaline
partial: clonidine

Question 7

How are catecholamines synthesised?

Answer 7

Phenylalanine -> tyrosine.
Tyrosine is transported into cell. L Tyrosine -(tyrosine hydroxylase)-> L DOPA -(L amino acid decarboxylase)-> dopamine (transported into vesicle by vmat) -(dopamine beta dehydroxylase)-> noradrenaline -> (in periphery) adrenaline

Question 8

What are some effects of alpha 1 activation?

Answer 8

Constriction of blood vessels
Decrease in GI motility
Contraction of bladder and eye
minor glycogenolysis in liver
Contraction of smooth muscle except in gut

Question 9

What are some effects of alpha 2 activation?

Answer 9

Constriction of blood vessels
Decrease in GI motility
Aggregation of platelets
Decreased NA release

Question 10

What are some effects of beta 1 activation?

Answer 10

Increase in force and rate of heart

Renin release from kidney

Question 11

What are some effects of beta 2 activation?

Answer 11

Dilation of blood vessels and bronchi
Decrease in GI motility
Relaxation of uterine smooth muscle
Tremor of skeletal muscle
Glycogenolysis in liver

Question 12

What are some effects of beta 3 activation?

Answer 12

Relaxation of bladder detrusor

Lipolysis of fat cells

Question 13

What is propranolol?

Answer 13

A beta blocker - a non-cardioselective beta-adrenergic antagonist.
It binds reversibly to β1 and β2 receptors, reduces heart rate, bp, cardiac output, peripheral vasoconstriction so less NA/A binds β1 and β2 causing Gs activation.

Question 14

Name a β2 adrenergic agonist and its use.

Answer 14

Salbutamol is used to treat asthmatic symptoms by causing dilation of bronchial smooth muscle, opening the airways. This prolongs the QT interval of an ECG.
A side effect of Salbutamol may be increased heart rate due to reduced blood pressure.

Question 15

Name a drug that can treat hypertension, Raynauds and frostbite.

Answer 15

Phentolamine, non selective α agonist.

Question 16

What is Timolol used for?

Answer 16

It is prescribed as an antihypertensive, antiarrhythmic, antiangina, and antiglaucoma agent.
It is a non-selective β-adrenergic antagonist (β blocker)

Question 17

What does sympatholytic mean?

Answer 17

a drug antagonistic to or inhibiting the transmission of nerve impulses in the sympathetic nervous system
eg β blockers and α antagonists

Question 18

What is the dominant β receptor in the heart?

Answer 18

β1 receptors

Question 19

Which receptor does clonidine act on?

Answer 19

α1 receptors.

Treats ADHD, high blood pressure, anxiety and migraines.

Question 20

What is ‘adrenaline reversal’?

Answer 20

The fall in blood pressure observed when given adrenaline following blockage of α-adrenergic receptors by an antagonist eg phenoxybenzamine

Question 21

What is the effect of isoprenaline?

Answer 21

Vasodilation of skeletal muscle and other vascular beds causing decrease in blood pressure and reflex tachycardia. Isoprenaline is a very selective agonist for β receptors.

Question 22

What is phenoxybenzamine?

Answer 22

An irreversible non-competitive antagonist binds covalently to α adrenoceptors.
(log-dose response curve would have a reduced slope, and decreased max response to agonist)

Question 23

Which drug can treat nasal stuffiness and why?

Answer 23

Phenylephrine is a selective α1-adrenergic receptor agonist.
Causes activation of postjunctional alpha-adrenergic receptors found on precapillary and postcapillary blood vessels of the nasal mucos, causing vasoconstriction, and shrinkage of nasal tissue.
It also dilates the pupil and increases blood pressure.

Question 24

On which receptors are NA and A more potent?

Answer 24

NA is more potent on α than β, and most on α1.

A is more potent on β receptors.

Question 25

How does reserpine act?

Answer 25

Reserpine inhibits the uptake of norepinephrine into storage vesicles resulting in depletion of catecholamines and serotonin from central and peripheral axon terminals. It has been used as an antihypertensive and an antipsychotic.

Question 26

What is Tetrabenazine?

Answer 26

Tetrabenazine is a short acting noradrenaline and dopamine depletory, which is reversible and is used to treat hyperkinetic movement disorders, such as Huntington’s disease (monoamine depletor)

Question 27

what is another name for the norepeniphrine transporter?

Answer 27

Solute carrier family 6 member 2 (SLC6A2)

sodium:neurotransmitter symport