<unk> s are a class of sympathomimetic agents that selectively stimulates<unk>  adrenergic receptors. The<unk> -adrenergic receptor has two subclasses α1 and α2.<unk>  2 receptors are associated with sympatholytic properties.<unk> s have the opposite function of<unk>  blockers.<unk>  adrenoreceptor ligands mimic the action of epinephrine and norepinephrine signaling in the heart, smooth muscle and central nervous system, with norepinephrine being the highest affinity. The activation of α1 stimulates the membrane bound enzyme phospholipase C, and activation of α2 inhibits the enzyme adenylate cyclase. Inactivation of adenylate cyclase in turn leads to the inactivation of the secondary messenger cyclic adenosine monophosphate and induces smooth muscle and blood vessel constriction.
Alpha-adrenergic agonist
Beta-adrenergic agonist
Beta2-adrenergic agonist
Dopamine agonist
Muscarinic antagonist
Norepinephrine–dopamine disinhibitor
Adrenergic release inhibitor
Dopamine antagonist