SNS Antagonist

Question 1

Name and summarise the effects of all the adrenoreceptors

Answer 1

1. Alpha 1 - vasoconstriction and relaxation of the GI tract
2. Alpha 2 - inhibition of transmitter releases and contraction of vascular smooth muscle + CNS action
3. Beta 1 - increased cardiac rate and force, relaxation of GI, renin release
4. Beta 2 - bronchodilation + vasodilation + relaxation of visceral smooth muscle and hepatic glycogenolysis
5. Beta 3 - lipolysis.

Question 2

Name 5 types of adrenoreceptors antagonists

Answer 2

1. Non selective (alpha 1 and beta 1) - carvediol
2. Alpha 1 and 2 - phentolamine
3. Alpha 1 - prazosin
4. Beta 1 and 2 - propanalol
5. Beta 1 - atenolol

Question 3

Describe the role of beta blockers and give 5 examples

Answer 3

Beta blockers decrease HR and FOC, decreasing cardiac output, heart doesnt have to work as hard - reduced BP. Decreased renin secretion, decreased angiotensin II, thus less vasoconstriction and reduced TPR

1. propanalol - beta 1 and 2
2. Atenolol - beta 1 - cardiac selective
3. Carvediol - alpha 1, beta 1 and 2 - more powerful
4. Nebivalor - beta 1 cardio selective but potentiates NO (vasodilator)
5. Sotalol - beta 1 and 2 and inhibits potassium channels

Question 4

Explain the difference between propanalol and atenolol

Answer 4

Atenolol is better because it negates the negative side effects of beta 2 receptor blockade eg bronchoconstriction and decreased liver function

Carvediol is better than both and is most powerful antihypertensive drug

Question 5

Describe the structure of alpha receptors and the effects of alpha receptor blockers and give 2 examples

Answer 5

Alpha 1 (Gq linked) and exits on post synaptic vascular smooth muscle 
Alpha 2 (Gi linked) and exists on presynatoic autoreceptirs inhibiting NA release. 

Alpha blockers

1. Phentolamine - non selective alpha blockers and used to treat phaechromocytoma induced hypertension
2. Prazosin - inhibit the vasoconstrictor activity of NA and have modest BP reducing effects

Question 6

Describe the role of methyldopa in adrenoreceptor blockade

Answer 6

Methyldopa produces false transmitter - used in antihypertensive drug. Methyldopa is taken up by Noradernergic neurones as is converted into a false transmitter. The transmitter is Less active at beta 1 and alpha 1 receptors and is not metabolised by MAO. It is more likely to accumulate and disolace the noradrenaline in the vehicle

Side effects: thick viscous secretion of saliva, vasoconstriction of blood vessels.

Question 7

Describe the drugs used in arrhythmia and describe the different types of angina

Answer 7

Arrhythmia: abnormal and irregular heart beats due to tea age of heart tissue and increased sympathetic drive to heart precipitated by Beta 1. Therefore use propanalol

Stable angina: pain on exertion, increased demand on the heart and is due to fixed narrowing of the coronary vessels eg atheroma

Unstable angina: pain with less and less exertion, culminating with pain at rest, platelet - fibrin thrombus associated with a ruptured athermatous plaque but without complete occlusion of the vessel (risk of infarction).

Variable angina: occurs at rest and caused by artery spasm and associated with athermatous disease

Question 8

Describe the effect of adrenoreceptor blockade in glaucoma

Answer 8

Look at MM