SNS agonists

Question 1

What categories of Na/A receptors are there?

Answer 1

4 subtypes, a1/2, B1/2 -when choosing drug just need to know what drug acts on where and how
Need to know what tissue is mainly activated by which one, so which drug will give which effects

Question 2

What is the difference between NA and A for SNS agonist?

Answer 2

All receptors can be activated by both
Noradrenaline is a bit more a than B selective
Adrenaline is more B than A selective
But the drugs overall can definitly act on all

Question 3

How is neuradrenaline produced? Where does it act and why does it matter in drugs?

Answer 3

Tyrosine to DOPA, to DA, the NE (in the vescule)-Action potential causes release, followed by reputake/diffusion/metabolism/etc)
Receptors are on post junction, AND prejunction receptor (a2) (on the nerve-acts as negative feedback to SNS-agonist will inhbit SNS)

Question 4

Why is adrenaline used as a drug?

Answer 4

Used in epipens to combat anaphalatic shock (causes airway block, massive hypotension, etc)
Non-selective so acts on all receptors
B2-Bronchodilate
B1-tachycardia
a1- vasoconstriction

Other use-asthma, acute bronchospasm, =>B2
cardioshock, Spinal aneathetic =>B1
(maintain BP), Local (prolongs action constricting) =>a1

Question 5

What are the main unwanted actions of adrenaline (as a drug)

Answer 5

Secretion-reduced and thickened mucus
CNS-not really
CVS-Tachy, palp, artythmias, cold extremities, hypertension (cerebral haemorrhage, oedema)
GIT-Minimal, 
MSK-tremors

Question 6

What is Phenylephrine?

Answer 6

A1 selective agent (but can bind a2 a bit)
Similar to adrenaline, -resistant to COMT (peripheral), but not MAO (central)
Used as decongestants–vasoconstriction (less white cell infiltration)-
Can also be used as Mydriatic-general vasocontriction

Question 7

What is like Clonidine?

Answer 7

a2 selective agent-so actions look like antagonist
Because a2 receptor has negative feedback on SNS
Used in glaucoma
Treat hypertensions (reduce SNS0
Treat migraine-unsure why,
Reduce SNS tons-presynatpic inhbutuion of NA AND-can stop withing CNS firiing

Question 8

What is glaucoma? Why does it relate to SNS agonists

Answer 8

Characterised by increase of intra-occular presure
Usual poor drainage of aqueous-as you older, flow can be interupted and pressure build up-damage nerves/blood vessels
B1 receptors on vessels are important

a2 receptors agonists act like SNS antagonists to reduce B1 activation
a1 could also work as vasoconstrict-because needs fluid to make the fluid

Question 9

What is Isoprenaline

Answer 9

B1/2 specific agonist-B1=B2&raquo_space;»»A1/2
Use mostly for CVS emegrencies-cardiogenic shock, acute heart failure, myocardial infaction
But it has symetrical B1/B2 effect, and B2 cause massive vasodilation-CO might be good, but cant keep up (BP still drops)-can trigger reflex tachy via baroreceptors

Question 10

What is dobutamine?

Answer 10

Same as Isoprenaline BUT only B1 specific agonist

Still for emergency CVS problems

Question 11

What is Salbulatmol?

Answer 11

B2 selective agonist
Relative resistance to breakdown
Binds B2 receptor in lungs, causing hyperpolarisation of cell and muscle relaxation-dilation of airways, u can breath
Used for Asthma, premature labour (relax of SMC)