yunuz
Forum Junior
Topics: 17
Posts: 66
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There was a Q where they give acetylcholine to an animal at low dose and it exerts vasodilation but at high dose this cause vasoconstriction.
In the explanation the wrote the following "Because PANS does not innervate the vasculatue, stimulation of PANS does not cause vasodilation.Therefore, the vasodilation is a pharmacological phenomenon and not physiological action.After acectylcholine is given high dose, it exerts a ganglionic stimulating effect and results in vasoconstriction"
I understand that the action of A.choline is via release of NO and EDRF after stimulation of M recepors.Then guanylyl cyclase is activated and relaxation of the smooth vasculature muscle.
But why and how at high dose A.choline exerts a vasoconstrictive action? Any body has a clue
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| new_n_lost
Forum Hero
Topics: 673
Posts: 6,144
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ACh acts on both Muscarinic and Nicotinic receptors. The affinity of ACh for Nicotinic receptors is low which is thereby increased in high doses. Muscarinic receptors when activated induces the parasympathetic response and the Nicotinic receptors when activated induce a sympathetic response. So in normal doses the ACh activates a muscarinic receptor while in high doses both Nicotinic and Muscarinic receptors will be acitvated.
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FORUM RULES-- Those who believe in telekinesis, raise my hand. I get enough exercise just by pushing my luck --P4U World.." The pure and simple truth is rarely pure and never simple."
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| yunuz
Forum Junior
Topics: 17
Posts: 66
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Thank you.I missed this point.This telle me I need to go back to ANS again!
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| new_n_lost
Forum Hero
Topics: 673
Posts: 6,144
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Everyday u will come across something which will make u feel to go back to ur books.  . Happens to me all the time.
___________________
FORUM RULES-- Those who believe in telekinesis, raise my hand. I get enough exercise just by pushing my luck --P4U World.." The pure and simple truth is rarely pure and never simple."
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| alaa_abes2
Forum Newbie
Topics: 3
Posts: 11
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thanks
this ach reversal as ach stimulate adrenal medulla which release adr ,noradr
and st sym ganglia that release noradr
thanks for all
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| yunuz
Forum Junior
Topics: 17
Posts: 66
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Alaa_abes, this is the pointI am missing, coul you elaborate on this please?Thanks
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