Cholinergic effects

Question 1

What are some cholinergic esterase inhibitors

Answer 1

Neostigmine, physostigmine, edrophonium and parathion

Question 2

What are nicotinic acetylcholine receptors

Answer 2

Ligand gated ion channels

Question 3

Where are N1/Nm receptors found

Answer 3

Skeletal muscle

Question 4

Where are N2/Nn receptors found

Answer 4

Autonomic ganglia/CNA

Question 5

What are muscarinic acetylcholine receptors

Answer 5

G-coupled receptors

Question 6

Where are M1 receptors found

Answer 6

CNS, peripheral neurones and gastric parietal cells

Question 7

Where are M2 receptors found

Answer 7

Atria, SAN and AVN

Question 8

Where are M3 receptors found

Answer 8

Visceral smooth muscle, secretory glands and endothelial cells

Question 9

Where are M4 and M5 receptors found

Answer 9

CNS

Question 10

What are some nicotinic agonists

Answer 10

Nicotine and lobeline

Question 11

What are some nicotinic antagonists

Answer 11

Tubocararine, hexamhonium and pancuronium

Question 12

What are some muscarinic agonists

Answer 12

Muscarine, bethanecol (longer lasting) and pilocarpine

Question 13

What are some muscarinic antagonists

Answer 13

Atropine, hyoscine, pirenzepine and ipratropium

Question 14

What are some parasympathetic effects

Answer 14

• Reduced heart rate
• Vasodilation
• Increased saliva and gastric acid production
• Increased tear formation
• Visceral smooth muscle contraction
• Pupil constriction

Question 15

Which muscarinic receptors are G alpha q/11 receptors

Answer 15

M1, M3 and M5

Question 16

Which muscarinic receptors are G alpha i receptors

Answer 16

M2 and M4

Question 17

What are some cardiac effects and how are they achieved

Answer 17

Limited parasympathetic innervation to the heart

Stimulated through the vagus to reach the SAN and atria M2 receptors

Question 18

How does arterial relaxation occur

Answer 18

Stimulated by acetylcholine on M3 receptors situated on endothelial cells on the monolayer in arteries

Question 19

How does rapid relaxation of smooth muscle cell occur

Answer 19

NO is released which binds to guanylate cyclase and GTP is converted to cGMP

Question 20

What is a cardiovascular effect

Answer 20

Blood pressure drops however there is no change in heart rate

Question 21

How is acid production augmented

Answer 21

Acetylcholine from the vagus nerve activates M1 receptors

Question 22

How are salivary glands activated

Answer 22

M3

Question 23

How are sweat glands activated

Answer 23

M3 receptors which are under sympathetic control

Question 24

How is the pupil narrowed

Answer 24

Parasympathetic stimulation of M3 receptors causing contraction of circular muscle

Question 25

How is the pupil widened

Answer 25

Sympathetic stimulation of alpha 1 receptors causing contraction of radial muscle

Question 26

What happens in glaucoma

Answer 26

Poor drainage of fluid through the trabecular network, often due to dilated iris

Question 27

What is pilocarpine and how is it used

Answer 27

A directly acting mAchR agonist that is used to treat glaucoma and dry mouth and its used in sweat tests

Question 28

What is bethanecol and how is it used

Answer 28

A directly acting mAchR agonist occasionally used to aid bladder/gastric emptying

Question 29

What is succinylcholine and how is it used

Answer 29

A directly acting high affinity nAChR agonist used in surgery, depolarising paralysis

Question 30

What are some indirectly acting clinical uses of parasympathetics

Answer 30

Choline esterase inhibitors such as tacrine, donepezil and rivastigmine used in dementia

Question 31

What are some clinical uses of muscarinic blockers

Answer 31

- Dry up secretions before surgery and prevent vagal slowing of the heart - In heart block to increase AV conduction - Ophthalmology to produce mydriasis for examination - Bronchodilatation in COPD - Anti-spasmodic in GI colic - Treatment of anticholinergic poisoning - Motion sickness

Question 32

What are some clinical uses of cholinergic blockers

Answer 32

- Muscle relaxants, direct nAchR blockers - Tubocurarine, pancoronium, vecuronium and atarcurium - Depolarising blockers, direct nAchR agonists - Suxamethonium