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 Ca+2 blockers/vascular mus  



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Author3 Posts
  #1

Effects of Ca+2 channel blockers on Vascular Smooth Muscle:

a) Large effect of Ca+2 channel blockers on receptor-operated channels or on release of Ca+2 from SR
b) Vascular selectivity is seen with the Ca+2 channel blockers
c) increase cardiac afterload
d) Decrease cardiac preload
e) Specific dihydropyridines may exhibit greater potencies in some vascular beds
f) Specific effect tracheal smooth muscle




  #2

b..vascular selectivity


  #3

Yes b and e are both correct

L-type Ca++ channel blockers inhibit L-type voltage-dependent Ca++ channels
T-type Ca++ channel blockers inhibit T-type voltage-dependent Ca++ channels
Little or no effect of Ca++ channel blockers on receptor-operated channels or on release of Ca++ from SR
"Vascular selectivity" is seen with the Ca++ channel blockers
Decreased intracellular Ca++ in arterial smooth muscle results in relaxation (vasodilatation) -> decreased cardiac afterload (aortic pressure)
Little or no effect of Ca++-channel blockers on venous beds -> no effect on cardiac preload (ventricular filling pressure)
Specific dihydropyridines may exhibit greater potencies in some vascular beds (e.g.- nimodipine more selective for cerebral blood vessels, nicardipine for coronary vessels) Little or no effect on nonvascular smooth muscle (e.g. -tracheal smooth muscle)





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