Vivian6
Forum Newbie
Topics: 4
Posts: 12
|
Hey, guys, I'm reading brs physi now. On page36, it says β2receptor mechanism of action is the same as for β1 receptors, which means it also increase the level of cAMP.Then it will cause restriction not dilation. Can anybody explain this to me? Thanks
|
| drpkaur
Forum Guru
Topics: 195
Posts: 808
|
see mechanism of action will be the same for catecholamines(beta1,beta2) but their locations are different as they have clearly mentioned that b1 rec specifically located in heart,b2 rec in vascular smooth muscles in bronchial tract,GI trct....it is not causing any constriction in heart it causes excitation of heart means incr HR,conduction velocity,contractility,renin release...whereas b2 causes relaxation in VSM of the bronchi and GIT...
|
| mildus
Forum Guru
Topics: 19
Posts: 614
|
I agree with drpkaurs's very nice explanation
|
| Vivian6
Forum Newbie
Topics: 4
Posts: 12
|
Hi, drpkaur, thank you for your insight.
I may have different opinion. I think mechanism is decided by the type of receptor not the medicine. Like catecholamine, the mechanisms will be different if it binds to different receptor.
b1 and b2 do have different location, but I think no matter cardiac muscle or smooth muscle, constriction of them are caused by increased intracellular Ca++ and relaxation is related to decreased ca++. At the same time, increased cAMP can cause increased intracellular ca++ and decreased cAMP results in decreased ca++. Thus, increased cAMP causes contraction and decreased cAMP causes relaxation. In this way, the mechanism for b2 receptor should be deactive adenolyte cyclase not to activate it. Activation of adenolyte cyclase is the mechanism of b1 receptor which I understand.
|
| drpkaur
Forum Guru
Topics: 195
Posts: 808
|
well vivian6,
both the b1,b2 are coupled to Gs PROTEINS,so both of them will activate adenylyl cyclase as so far i have read from lippincott's and kaplan notes..u can check in kaplan notes in pharmacodynamics chapter in the signalling mechanisms-g protein coupled receptors ...u will find ur answer there.
|
| Vivian6
Forum Newbie
Topics: 4
Posts: 12
|
ok. Once I get my books, I'll read that chapter. Thanks.
|
|
| |
| | | | | | |
