B OH B 6 B HO HO HO. a B B a HC-CH2-NH2 C HC-CH2-NH B HC-CH2-NH OH OL a OH CH3 OH HC-CH内 Norepinephrine Epinephrine laoproterenol CH3 a a 意 a a A.Chemical structure of catecholamines and affinity for 0-and B-receptors Receptor affinity H Catecholamine- O-methyltransferase Penetrability H through I+H Metabolic membrane stability barriers HCc地-N2 OH CH3 (Enteral abeorbability CNS permeability) Monoamine oxidase