Adrenergic agonists cause vasoconstriction or dilation???

[ijustwanttopass]

I cannot get this straight.

I thought all adrenergic agonists cause vasoconstriction (like Epi).

But Clonidine is an adrenergic agonist, and it reduces BP.

How?????

[Cowboyardee]

Different adrenergic receptors, different sites of action. Clonidine affects alpha 2 adrenergic receptors especially in the brain stem. Epinephrine affects all major adrenergic receptors (alpha 1 and 2, beta 1, 2, and 3) and contributes to both vasodilation and vasoconstriction at different sites.

Look up the various adrenergic receptors and what they do. They're a good deal more complicated than you appear to have understood so far.