drbin
Forum Guru
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pls explain,,,thanks
actions of ganglion blockers
1) It inhibits the reflex bradycardia when given along with alpha agonist phenylephrine.
2) It inhibits the predominant action either PANS or SANS. so in heart it inhibits bradycardia caused by stimulation of PANS(being predominant) and causes tachycardia.
But it is also said that it will not block bradycardia when Ach directly acts thru M recepter
my doubt is y it doesnt block bradycardia when Ach directly acts on M receptor even though that is the predominant action there?
i feel this doubt sounds childish but pls im really confused.... 
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| drbin
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Topics: 27
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somebody pls explain. thanks
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| doc179
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hexamethonium being a ganglion blocker you see that the effects of the predominant nerve in a particular organ blocked.
and other concept abt ganglion blockers is that that they block all the reflexes but nt the direct effects of the drug..and bradycardia is the direct effect of Ach which is not blocked. and so the reflex bradycardia by phenylephrine is blocked.
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| drbin
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oh so they are two different concepts, ok thank u doc179
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| macintosh
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Ganglion blockers, block the stimulation of receptors on the autonomic ganglia, including muscle end plates. As nicotine is the receptor on the ganglia, ganglion blockers are nicotinic receptor antagonist.
Reflex tachycardia is caused by increased stimulation of the nicotinic receptors present in the ganglia (post synaptic sympathetic). Administration of ganglion blockers block this stimulation and prevent tachycardia. As acetylcholine stimulates both nicotinic and muscarinic receptors, its nicotinic effects are bloacked but the muscarinic effects are preserved. By the way muscarinic stimulation itself cause bradycardia.
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