PED1003/L11 Drugs acting on PNS Flashcards
What does the autonomic nervous system control?
Smooth muscle and glands
Describe the neurotransmitters in the sympathetic system.
Preganglionic ACh
Postganglionic NA
Describe the neurotransmitters in the parasympathetic system.
Preganglionic & postganglionic ACh
Describe the synthesis of acetylcholine. (2)
Synthesised by CAT from choline and AcCoA
Forms ACh and CoA
What 2 main classes of ACh receptor are actions of ACh mediated by?
Muscarinic
Nicotinic
What are the 3 subtypes of muscarinic receptor?
M1, 2, 3
What are muscarinic receptors coupled to?
G-protein coupled receptor/ metabotropic receptor
Where are muscarinic receptors located?
Postganglionic parasympathetic synapses
What are the 2 main subtypes of nicotinic receptor?
Neuronal type
Muscle-type
Where are nicotinic receptors located?
Brain and autonomic ganglia
Neuromuscular junctions
What are nicotinic receptors coupled to?
Ligand-gated ion channels
Name 2 muscarinic receptor agonists.
Pilocarpine
Carbachol
How does pilocarpine help treat glaucoma?
Local application causes ciliary muscle contraction
Focus on near vision
Allows increase in drainage of aqueous humour
Give a clinical use of muscarinic receptor agonists.
Treatment of xerostomia: dry mouth/reduced saliva secretions
What can cause xerostomia? (3)
Radiation
Antineoplastic drugs
Side effects of many other drugs
Give 3 side effects of pilocarpine. (muscarinic agonist)
Muscarinic-sweating
Nausea
Minimal cardiovascular side effects
What is tropicamide used for? (muscarinic antagonist)
Pupil dilation in eye surgery
2-6 hour duration
What is atropine used for? (muscarinic antagonist)
Resuscitation in bradycardia
Increase HR
What is atropine and glycopyrronium used for? (muscarinic antagonists)
Decrease oral/respiratory secretions before oral procedures as as adjunct to anaesthesia
What is ipratropium used for? (muscarinic antagonist)
Bronchodilation (asthma)
What is hyoscine used for? (muscarinic antagonist)
Motion sickness
Orally decreases gastric motility
Give an example of a nicotinic agonist.
Suxamethonium
Give an example of a nicotinic antagonist.
Tubocurarine
Describe the action of suxamethonium (nicotinic agonist). (3)
Initial depolarisation and muscle fibre contraction
Fibre consistently depolarised
Depolarising block
Describe the action of tubocurarine (nicotinic antagonist) and give a potential use. (4)
Hyperpolarisation
Muscle fibre relaxation
Paralysis for surgery
Non-depolarising blocker
Describe the action of hemicholinium (ACh synthesis). (3)
Blocks choline uptake
Inhibits synthesis
Blocks ACh transmission
Give 2 drugs that inhibit ACh release.
Botulinum toxin
Bungarotoxin
Give 2 drugs that affect cholinergic transmission.
Neostigmine
Organophosphates
Give 2 effects of anticholinesterase on the autonomic nervous system.
Reflect increased transmission
Increase secretions
Bradycardia
Hypotension
Pupil constriction
Give 2 effects of anticholinesterase on the NMJ.
Increased muscle tension and twitching
Large doses can causes depolarising block
Give a use of neostigmine.
Treating myasthenia gravis - autoimmune disease in which circulating antibodies against muscle nicotinic receptors