dxtxpx
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Atropine produces divergent effects on cardiovascular system, depending on the dose. At low dose, the predominant effect is decreased cardiac rate, this bradycardia is due to:
a) M3 receptor blockage
b) Central activation of vagal efferent outflow
c) MI receptor blockage
d) all of the above
e) none of the above
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| asmi
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its B
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| dxtxpx
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no try again
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| asmi
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Is it not central activation of vagal efferents...at low dose ? :roll:
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| dxtxpx
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Quote from Lippincott Pharmacology 2nd edition; page 47
"Originally thought to be due to central activation of vagal efferent outflow, newer data indicate that the effect results from blockage of M1 receptors on inhibitory pre-junctional neurons, thus permiting increased acetylcholine release"
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| asmi
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thanks i don't have that point,since my edition of lippincott is an old one
Thanks dxtx 
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| asmi
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What about tachycardia at high doses...is it M2 mediated ?
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| dxtxpx
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With higher doses of atropine, the cardiac receptors on the SA node are blocked, and the cardiac rate increases modestly (tachycardia)
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| asmi
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yes, so its M2 in SA node
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| dxtxpx
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yeah i guess so as only muscarinic receptor subtype on cardiac cell is M2
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| medmanparadise
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you two are two peas in a pod. go get married.
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