Cholinergic Effects Flashcards
(21 cards)
What are 2 examples of receptor super classes?
Nicotinic + muscarinic
What do muscarinic receptors do?
Mediate response of PNS
What are selective agonists of nicotinic receptors?
Nicotine and labeline
What are selective antagonist of nicotinic receptors?
Tubocurarine, hexamethonium + pancuronium
What are selective agonist of muscarinic receptors?
Muscarine, bethanecol, pilocarpine
What are selective antagonist of muscarinic receptors?
Pirenzepine , ipratropium
What are main parasympathetic effects?
Reduce heart rate
Vasodilation
Increased saliva + gastric acid production
Increased tear formation
Visceral smooth muscle contraction e.g. gut, bladder
Pupil constriction
What does expression of M1,M3,M5 lead to?
Lead to stimulation of phospholipase C
What does expression of M2 and M4 muscarinic receptors lead?
Are negatively coupled to adenylate cyclase
Cardiac effects
In heart, parasympathetic nerve releases Ach + interacts with M2 receptor
M2 receptor is negatively coupled with adenylate cyclase
Less cAMP
less stimulation of funny channel
Less PKA so less stimulation of Ca channel + calcium release
Describe vascular effects- arterial relaxation
Ach will lead to vasodilation
There is no parasympathetic nerves going to arteries
M3 receptors are on endothelial cells
Endothelial cells make gas called nitric oxide which is made by NO synthase from arginine
NO diffuses short distance + leads to relaxation of smooth muscle cell
Describe the contraction of non vascular smooth muscle
Activation of M3 receptors leads to increased activation of phospholipase + calcium release
M3 receptors are on endothelial cells
In particular: GI tract, bladder + airways => M3 receptors are on muscle
Where is M1 receptors found?
CNS
peripheral neurone
Gastric parietal cells
Where is M2 receptors found?
Heart-> atria, SAN , AVN
Where is M3 receptors found?
Visceral smooth muscle
Secretory glands
Endothelial cells
Where is M4 receptors found?
CNS
Where is M5 receptors found?
CNS
What does atropine do?
Blocks muscarinic receptors
What is parasympathomimetic?
Drugs that mimic PNS
What are some clinical uses of parasympathomietics?
Directly acting;
Pilocarpine(mAchR agonist)-used to treat glaucoma and dry mouth
Bethanecol (mAchR agonist)- used to aid bladder / gastric emptying
Succinylcholine (high affinity nAchR) used in surgery for depolarising paralysis
Indirectly acting;
AchE inhibitors such as Tacrine, donepezil or rivastigmine used in dementia
Neuromuscular disease such as myasthesia gravis
What are clinical uses of nicotinic blockers?
Muscle relaxants
Depolarising blockers
