mjl1717
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Can anyone briefly and clearly state how alpha 1 and alpha 2 receptors work?
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| sturge_weber
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well thats what i know
alpha 1 receptors act on the vessels, and cause their vasoconstriction, an effect leading to vasoconstriction, followed by reflex bradycardia... the reflex bradycardia can be corrected by giving the patient hexamethonium or a ganglionic blocker
on the molecular level, alpha 1 acts on the pip2 pathway, and hence leads to activation of phospholipase c and hence production of dag and ip3 both of which activate the ca. this leads to increase in protein kinase c and then the actions
about alpha 2 receptors, they re quite interesting , they act prejunctionally and cause like a negative feedback loop and hence decrease the producton of ne, egs of this re alpha metyl dopa and clonoidine, and both of these re agonists at the alpha 2 receptors, and decrease the ne effects
on the molecular level alpha 2 acts on the adenylate cyclase pathway or the camp pathway, inc camp, then protein kinase a which causes the phosphorylation of proteins
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| Geroo
Forum Guru
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does alpha 2 decrease cAMP?if it does so that should lead to decrease protein kinase level and leads to dephospholylation rather than phosphorylation,right??
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| sturge_weber
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yep geroo, nice question, well both alpha 2 and beta 1 nad beta 2 act on the camp pathway and the Gi pathway, and hence decrease camp, the glucagon is Gs... i dont know about dopamine and serotonin which also at via the camp pathway
tell if u know about serotonin, da and ach
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| cyra
Moderator
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All serotonin receptors are linked to second messenger systems...except 5HT3,which is coupled directly to an ion channel....
For dopamine...D1 rec is linked to Gs...and therefore increases cAMP
D2 rec is linked to Gi...and therefore would bring about a decrease in cAMP
ACh....M1 and M3...Gq linked...increase IP3 and Ca2+
M2....Gi...decrease in cAMP
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| sturge_weber
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hey cyra, thanks for this peice of info, i have been looking for
anyways cyra, long time no see, hows prep going, when is ur exam
all the best...
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