Adrenaline works on A1,2 and B1,2 receptors, but...?

Question

A2 doesnt really do much does it/or doesnt do much in responce to adrenaline?

A1- vasoconstrict

B1 - inotropic

B2- Smooth muscle relaxation

So adrenaline causes increase HR (B1) - vasoconstrict (A1) then smooth muscle relax (B2 - which would also cause vasodilation too wouldnt it, <which predominates A1 constrict or B2 dilate?> and what does A2 effect of adrenaline?

Thanks

Answer 1

The alpha-2 receptor mediates some specific effects:

http://en.wikipedia.org/wiki/Alpha-2_adr...

However, in most clinical scenarios where doctors administer adrenaline (cardiogenic shock, severe sepsis, severe allergic reactions, etc), those not-life-and-death effects of alpha-2 simply pale in comparison to the vasoconstrictive and positive inotropic effects mediated by the other receptor types.

http://en.wikipedia.org/wiki/Epinephrine...

After all, there is a difference between pharmacology in the classroom and saving life in the ICU.

For what it&#039;s worth, doctors do know that adrenaline has multiple receptor types.  As a result, they often use other drugs first if they want a more specific effect -- for example, for more selective vasoconstrictive effects, they often use phenylephrine or norepinephrine.  For positive inotropic effects (especially if additional vasoconstriction is undesired), they often go to dobutamine.

http://www.aic.cuhk.edu.hk/web8/inotrope...

Hope this helps.