Cholinergic effects Flashcards
What are some cholinergic esterase inhibitors
Neostigmine, physostigmine, edrophonium and parathion
What are nicotinic acetylcholine receptors
Ligand gated ion channels
Where are N1/Nm receptors found
Skeletal muscle
Where are N2/Nn receptors found
Autonomic ganglia/CNA
What are muscarinic acetylcholine receptors
G-coupled receptors
Where are M1 receptors found
CNS, peripheral neurones and gastric parietal cells
Where are M2 receptors found
Atria, SAN and AVN
Where are M3 receptors found
Visceral smooth muscle, secretory glands and endothelial cells
Where are M4 and M5 receptors found
CNS
What are some nicotinic agonists
Nicotine and lobeline
What are some nicotinic antagonists
Tubocararine, hexamhonium and pancuronium
What are some muscarinic agonists
Muscarine, bethanecol (longer lasting) and pilocarpine
What are some muscarinic antagonists
Atropine, hyoscine, pirenzepine and ipratropium
What are some parasympathetic effects
- Reduced heart rate
- Vasodilation
- Increased saliva and gastric acid production
- Increased tear formation
- Visceral smooth muscle contraction
- Pupil constriction
Which muscarinic receptors are G alpha q/11 receptors
M1, M3 and M5
Which muscarinic receptors are G alpha i receptors
M2 and M4
What are some cardiac effects and how are they achieved
Limited parasympathetic innervation to the heart
Stimulated through the vagus to reach the SAN and atria M2 receptors
How does arterial relaxation occur
Stimulated by acetylcholine on M3 receptors situated on endothelial cells on the monolayer in arteries
How does rapid relaxation of smooth muscle cell occur
NO is released which binds to guanylate cyclase and GTP is converted to cGMP
What is a cardiovascular effect
Blood pressure drops however there is no change in heart rate
How is acid production augmented
Acetylcholine from the vagus nerve activates M1 receptors
How are salivary glands activated
M3
How are sweat glands activated
M3 receptors which are under sympathetic control
How is the pupil narrowed
Parasympathetic stimulation of M3 receptors causing contraction of circular muscle
How is the pupil widened
Sympathetic stimulation of alpha 1 receptors causing contraction of radial muscle
What happens in glaucoma
Poor drainage of fluid through the trabecular network, often due to dilated iris
What is pilocarpine and how is it used
A directly acting mAchR agonist that is used to treat glaucoma and dry mouth and its used in sweat tests
What is bethanecol and how is it used
A directly acting mAchR agonist occasionally used to aid bladder/gastric emptying
What is succinylcholine and how is it used
A directly acting high affinity nAChR agonist used in surgery, depolarising paralysis
What are some indirectly acting clinical uses of parasympathetics
Choline esterase inhibitors such as tacrine, donepezil and rivastigmine used in dementia
What are some clinical uses of muscarinic blockers
- 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
What are some clinical uses of cholinergic blockers
- Muscle relaxants, direct nAchR blockers
- Tubocurarine, pancoronium, vecuronium and atarcurium
- Depolarising blockers, direct nAchR agonists
- Suxamethonium
